1999 4.8 Broken rod - piston hitting valve - HELP...

Thanks in Advance for any help in finding my cause:
I have a 1999 silverado 4.8 2 wheel dr. 171,000 miles ran great till one day knocked parked it. I just bought this as indicated from the original owner and never any problems with truck. He went and bought a new one- drove this in and out of driveway 5 times and I drove to put on trailer to get home. Knocked loud tinny sounding knock and ran like crap.
Diagnosis: 0 comp in one cyl. - leak test, air into cyl. exhaust open air in exhaust, same for intake, closed both and hit the air heard clunk- piston went down. Took off oil pan and splash shield rod had broke hitting splash shield only (no block or head gasket damage). piston stayed up in cyl. Took head off yeaterday top of piston and valve appear same as others very little carbon- HOWEVER- it appears that a valve may have been hitting and spinning the piston around in cyl. swirl marks in top of this piston in circular pattern.
Questions:Why broke rod?, did timing go to allow piston to hit valve?, is it possible for ther eto be enough pressure to push the piston up to valves while running?, the cylinder is fine, and I will be able to replace piston,rod,rings,gaskets and be able to go - BUT I want to fix why it happened.. Sorry for long post- tried to give all info. ANY HELP GREATLY APPRECIATED.. Chris

Have you looked at the valve stem keepers yet. Hard to believe but once in a great while a valve stem key may get thrown then the second key goes (could have been the slight ticking noise you were hearing (valve stem keys rattling around under the covers. The valve then drops down and smacks the piston. Then the show is over.

Where was the rod broken? Are the rod bearings wiped out? Sludge can build up in an engine. Starves the rod mains and creates a wiped out bearing. This then causes alot of stress on the rod and it breaks.

Regardless of all the damage, if your into rebuilding engines it might be salvageable. If not then a used motor from the scrap yard around $500-$1000 or better yet if you can afford it a new crate engine. Probably around $4500 and up.

I used to work for GM Powertrain and saw quite a few casualties in my time. The root cause can be very deceiving.

Thanks in Advance for any help in finding my cause:
I have a 1999 silverado 4.8 2 wheel dr. 171,000 miles ran great till one day knocked parked it. I just bought this as indicated from the original owner and never any problems with truck. He went and bought a new one- drove this in and out of driveway 5 times and I drove to put on trailer to get home. Knocked loud tinny sounding knock and ran like crap.
Diagnosis: 0 comp in one cyl. - leak test, air into cyl. exhaust open air in exhaust, same for intake, closed both and hit the air heard clunk- piston went down. Took off oil pan and splash shield rod had broke hitting splash shield only (no block or head gasket damage). piston stayed up in cyl. Took head off yeaterday top of piston and valve appear same as others very little carbon- HOWEVER- it appears that a valve may have been hitting and spinning the piston around in cyl. swirl marks in top of this piston in circular pattern.
Questions:Why broke rod?, did timing go to allow piston to hit valve?, is it possible for ther eto be enough pressure to push the piston up to valves while running?, the cylinder is fine, and I will be able to replace piston,rod,rings,gaskets and be able to go - BUT I want to fix why it happened.. Sorry for long post- tried to give all info. ANY HELP GREATLY APPRECIATED.. Chris
Pistons do not go up unless piston or rod breaks or rod bearings shell out.
But a timing chain break or valve can drop hitting piston.
Even if you figure out what failed.
I would replace it with a new or re-man or used engine.
Actual cheaper than a complete rebuild and better warranty.

Gm parts places have some good new/rebuilt engine with good warranty.

I agree with the others on this ...considering the mileage and unknown useage/maintainence installing a good used engine would be better..with lower mileage..

Since it did run up to the moment the rod broke, for sure the valve must have dropped. See if you can find the valve stem keys loose in the valve train area.

I would like to comment on the responses- AND THANKS ALOT for looking at this- it all helps me to try and diagnose... Keep them coming....
First I know the original owner and he takes truck to dealer for any work and has alll records - there were very min. trip to dealer nothing major and relgiously kept up on oil changes. I know tihs is tru because last nite I got the piston out. The cylinder is in perfect shape same as others- the valves too are very clean no carbon/sludge this engine looks like new still on the inside. Took off both valves in this cyl. the keys/springs were perfect and tight. There is one spot on piston where the intake valve hit and put a 1/32" gouge in top but the valve has no marks where it was hitting. I will attempt to get some pics downloaded.
The rod bearings were in excellent shape too- normal wear and no additional play at crank. I know I am very lucky to have this happen and not ruin a block or crank...
I have checked all injectors with OHM meter and they all read fine.
I need to see if there is a way to check timing? Can you do like the old days with timing light and mark on harmonic balancer?
I cannot afford to replace the engine and since the condition seems ok I am going to proceed with a slight hone and replace piston/rings/rod/bearing/headbolts/gaskets/spark plug on that cyl. I have priced it out at $262.00 plus tax. Also- think I will also change intake valve to be safe.
BUT-- I still want to TRY to find the cause before I fire her up.
My 3 theorys are:
1. Bad injector flooded cyl. caused stress on rod trying to compress fuel and snapped. This plug was soaked and not carbon like others upon removal first time. Appears to be lighter in color and not firing.
2. Timing off - she ran rough in this condition but just not sure if it was running rougher then having only 7 cyl. going - so timing off - hit valve first time and broke rod- then piston was forced up in top of cyl. by pressure in block and the valve kept tapping top of piston to cause it to spin in cyl. and swirrl pattern on top of piston.
3. Stress on rod and it just went. (ever hear of this?)

I am saving my $$ to get parts and will have in a week or so -before I fire it- I will check spark on that coil with all plugs out. Like to check timing but how?

Please let me know your thoughts- Thanks Again.
Chris in Michigan

Love to see someone that wants to rebuild these engines. I think that is the right move.
If the valve keys were in that throws out the valve smacking the piston causing the piston rod to break.
The injector if stuck open could cause a hydrolock condition and stress the rod to where it braeks. (only if it was a defective rod to start with. Hydrolocked cylinders won't normally break a rod.
Is this a zero clearance engine? if so if the timing chain jumps a few teeth (from being old and streatched, then that would cause the piston hit an opened valve. Doing a rebuild I would normally replace the timing chain/belt anyway.
You should be able to see if the timing is on. Rotate the engine where #1 is at Top Dead Center on the compression stroke and see if the timing marks line up i.e. cam gear/Crank Gear The CAM gear timing marks are what you need to focus on. If they are off a few teeth that would do it.

Good Luck
CJ

Also I have documentation from owner on exactly what happened when she went:

It broke at startup. I was on vacation (at home) between Christmas and New Years, so the truck sat a few days in cold temperatures. The night of Dec. 28th I was going to take my truck to the store. When I started it, I immediately heard the loud rod-knock noise and the check engine light came on...so it was never driven.

When I popped the hood, I did smell gas...so maybe you're on to something with your guess #3, but I think #1 is more likely. I saw air bubbles (probably the gas I smelled) coming from a seal/gasket by the front left piston where I thought the noise was coming from. When I showed a neighbor where I saw the air bubbles, he said that was where the exhaust exits the piston. The neighbor isn't a mechanic, so I have no idea if he knows what he was talking about.

Before the issue, the only time the check engine light would come on is if I was running really low on gas...when that happened the check engine light would blink repeatedly until I got gas. Once I got gas, the check engine light would stay on (not blinking) for 20 miles or so. I figured that once the light comes on, it doesn't turn off until the engine error codes clean themselves up.

The truck was driving great before the issue, especially after having new U-joints installed in the summer. I was never concerned about the truck's reliability...I took it up to Manistee in October and November for deer hunting.

Please let me know your thoughts again- can"t add pics from work - will add tonight...

Thanks to everyone
Chris

Yep the way you describe it now sounds like a hydrolocked cylinder. Must've had an injector stuck open.
I've heard of this potential but never experienced it in a regular V engine. Saw it happen on a rotary engine (typical when a quick startup and shutdown) Ends up you gotta pull the spark plug and rotate the engine to free it up. Mazda's poor design.
Anyway's good luck on the rebuild. Sounds like you've done these before so it should be a fun project. It always is for me. Something about hearing it rev back to life after rebuilding it.

Ciao
CJ

Also I have documentation from owner on exactly what happened when she went:

It broke at startup. I was on vacation (at home) between Christmas and New Years, so the truck sat a few days in cold temperatures. The night of Dec. 28th I was going to take my truck to the store. When I started it, I immediately heard the loud rod-knock noise and the check engine light came on...so it was never driven.

When I popped the hood, I did smell gas...so maybe you're on to something with your guess #3, but I think #1 is more likely. I saw air bubbles (probably the gas I smelled) coming from a seal/gasket by the front left piston where I thought the noise was coming from. When I showed a neighbor where I saw the air bubbles, he said that was where the exhaust exits the piston. The neighbor isn't a mechanic, so I have no idea if he knows what he was talking about.

Before the issue, the only time the check engine light would come on is if I was running really low on gas...when that happened the check engine light would blink repeatedly until I got gas. Once I got gas, the check engine light would stay on (not blinking) for 20 miles or so. I figured that once the light comes on, it doesn't turn off until the engine error codes clean themselves up.

The truck was driving great before the issue, especially after having new U-joints installed in the summer. I was never concerned about the truck's reliability...I took it up to Manistee in October and November for deer hunting.

Please let me know your thoughts again- can"t add pics from work - will add tonight...

Thanks to everyone
Chris

with that description I agree it was a problem with the cylinder filling up with something ...then with the cylinder full of liquid it blew..

normally this would be coolant...not fuel ...If fuel were leaking, would have evaporated a bit and leaked down into the crankcase by the rings..after a few days of sitting ..did you have coolant issues...had to add coolant often,,?

Pictures added........
No coolant issues. I inspected the head gasket, block, and head but do not see any signs of blown head gasket.
Again- thank you all for the help- As of right now I am thinking about a bad fuel injector. But still does not tell me why this plug was burning lean and the top ring was stuck into the piston in one area? See pictures..

Thanks
chris
http://i382.photobucket.com/albums/oo264/easygoin4/48LiterStuckTopringandRodHitSkirt.jpg

http://i382.photobucket.com/albums/oo264/easygoin4/48LiterPistonTopSwirlMarks.jpg

http://i382.photobucket.com/albums/oo264/easygoin4/48LiterBrokenRodandPiston.jpg

http://i382.photobucket.com/albums/oo264/easygoin4/48LiterCapBearingandvalves.jpg

[quote=easygoin43;6100112]Pictures added........
No coolant issues. I inspected the head gasket, block, and head but do not see any signs of blown head gasket.
Again- thank you all for the help- As of right now I am thinking about a bad fuel injector. But still does not tell me why this plug was burning lean and the top ring was stuck into the piston in one area? See pictures..

Thanks
chris
http://i382.photobucket.com/albums/oo264/easygoin4/48LiterStuckTopringandRodHitSkirt.jpg

quote:

looking at this picture , the top compression ring looks rusted ...how does this compare to the other pistons ..

I have to agree after looking at picture close your right. Last weekend I proceeded to clean everything- this is what I found. Head looks fine, but I have noticed that this specific cylinder is different on the intake side. the port on head for intake is cleaner then the rest. the only sign of gasket issue is on intake gasket on the intake side of it near bottom, and the intake port is smooth and has a powder like on the walls - not glossy and carbon like all others. ALSO- found tonight- coolant in the back of the intake plentium. I am thinking that since no coolant ports in the intake that it may be coming in from throttle body area - there is a coolant line in the throttle body? does this make sense?
Why the rust on this piston? Remember the truck sat for sometime out in MI. winter then it popped on startup.
What do you think about this- coolant being sucked into intake near throttle body and then since this cyl is close to that it was coming thru intake valve and collecting in cyl.? But what about the stuck fuel injector theory? Hydro lock of some kind? Thanks a million for all the input- I have ordered rings and rod. hope to get back together soon. thoughts?

Man oh man,, knowing that the piston rings appear rusted is not a good sign. Exposure to gas won't do that. Having coolant or moist air would. Possible for a cracked cylinder wall. If your rebuilding this engine absolutely have the block and specifically that cylinder magnafluxed for cracks. Sometimes cracks are so thin that only magna-flux will expose them. The intake valves are normally loaded up with crud and the exhaust would normally be just blackened but clean. With the intakes being the same as the exhaust would suggest a steam clean or some sort while running. This condition may have been there for a while prior to the rod breaking. I still think a hydro-lock condition broke the rod. Great pics though. Amazing how the valve spun the piston around. Not much clearance in this engine from the depth of the eyebrow cut in the piston.

Food for thought.

Looking back a past posts. Ran great. Parked it. Really cold day. Sat for a few days. Started it, loud knock ran terrible and shut down to diagnose.
Think about a crack in the block. Hot engine, cold temps outside. As the engine cools down a cylinder with the intake valve in a slightly open position will cool down first. Hot coolant and cold cylinder cavity. Coolant and vapor bleeds into cylinder. Any H20 would then freeze. Go to start a couple days later and you have either liquid in cylinder that is ready to close the intake valve and go into the compression stroke. Unfortunately there is either alot of coolant or a chunk of ice in the cylinder. Turn it over and bang there goes the rod.

Again, food for thought. Only a thorough investigation of the block and heads will uncover the truth. The culprit is still there.

Oh, by the way have you looked at the injector for the #6 cyl. Was it stuck open?
I never really diagnosed a bad injector so I wouldn't even know how to tell if it is stuck open or not.

CJ

Looking back a past posts. Ran great. Parked it. Really cold day. Sat for a few days. Started it, loud knock ran terrible and shut down to diagnose.
Think about a crack in the block. Hot engine, cold temps outside. As the engine cools down a cylinder with the intake valve in a slightly open position will cool down first. Hot coolant and cold cylinder cavity. Coolant and vapor bleeds into cylinder. Any H20 would then freeze. Go to start a couple days later and you have either liquid in cylinder that is ready to close the intake valve and go into the compression stroke. Unfortunately there is either alot of coolant or a chunk of ice in the cylinder. Turn it over and bang there goes the rod.

Again, food for thought. Only a thorough investigation of the block and heads will uncover the truth. The culprit is still there.

Oh, by the way have you looked at the injector for the #6 cyl. Was it stuck open?
I never really diagnosed a bad injector so I wouldn't even know how to tell if it is stuck open or not.

CJ:smokin:

Looking back a past posts. Ran great. Parked it. Really cold day. Sat for a few days. Started it, loud knock ran terrible and shut down to diagnose.
Think about a crack in the block. Hot engine, cold temps outside. As the engine cools down a cylinder with the intake valve in a slightly open position will cool down first. Hot coolant and cold cylinder cavity. Coolant and vapor bleeds into cylinder. Any H20 would then freeze. Go to start a couple days later and you have either liquid in cylinder that is ready to close the intake valve and go into the compression stroke. Unfortunately there is either alot of coolant or a chunk of ice in the cylinder. Turn it over and bang there goes the rod.

Again, food for thought. Only a thorough investigation of the block and heads will uncover the truth. The culprit is still there.

Oh, by the way have you looked at the injector for the #6 cyl. Was it stuck open?
I never really diagnosed a bad injector so I wouldn't even know how to tell if it is stuck open or not.

CJ:smokin:

I have to agree after looking at picture close your right. Last weekend I proceeded to clean everything- this is what I found. Head looks fine, but I have noticed that this specific cylinder is different on the intake side. the port on head for intake is cleaner then the rest. the only sign of gasket issue is on intake gasket on the intake side of it near bottom, and the intake port is smooth and has a powder like on the walls - not glossy and carbon like all others. ALSO- found tonight- coolant in the back of the intake plentium. I am thinking that since no coolant ports in the intake that it may be coming in from throttle body area - there is a coolant line in the throttle body? does this make sense?
Why the rust on this piston? Remember the truck sat for sometime out in MI. winter then it popped on startup.
What do you think about this- coolant being sucked into intake near throttle body and then since this cyl is close to that it was coming thru intake valve and collecting in cyl.? But what about the stuck fuel injector theory? Hydro lock of some kind? Thanks a million for all the input- I have ordered rings and rod. hope to get back together soon. thoughts?

normally white powder in a cylinder is the coolant...IN the old days spraying a fine mist of water into the intake with engine running at 2,oooRPM was used to remove carbon in the combustion chamber..

I would with air pressure test the throttle body coolant tube..

if this is a coolant leak getting into the combustion chamber you will at the least carefully test out the O2 for proper operation as a little coolant damages these sensors..

First off THANKS CJ- for hanging in there with me and giving me your thoughts. I wish I knew how to check fuel injector other then OHM meter. Guys let me tell you I really cant afford to pull the engine and start having the block checked- STOP let me give you some input where I am coming from.. I am 47 and have 3 kids and my twin 15 yr old boy is loving the experience. If not for anything else at least I have quality time with my son. I already have 2 good running vehicles for my wife and I, this truck ws purchased because I knew the owners brother and I needed a project (my wife said) All along I knew that the engine could be shot. Since money is tight and my youngest is in remission from Cancer, I am trying to do this one as little cost as possible. Granted I know in the long run that it may run for a short time and go again- (well then it sits or we take her back apart and learn some more- I have more time then money). I just ordered today new piston, the rings and other parts due in couple days. I have been online everynite for over a week reasearching this. CJ your theory sounds very logical, and I was kinda bummed out reading everyones comments on cracked block. The engine is still in the truck with only intake,head, & exhaust off. It is 20 degrees here in michigan and not pulling an engine till spring if that is the case. I just wonder how the coolant got into the intake? My thoughts are to still try and find out cause before I put her back together- but if I can't my plan is to change piston,ring,rod,bearing all plugs, 1-fuel injector,gaskets, and check that one coil to be sure it's firing. I will check timing and compression in all cyl. prior to putting in plugs. Thinking about firing it up and see how she runs, shut it down and do compression and inspection again.
Guys again- I know your shaking your heads on this- Please I will respect any more feedback. I guess I am saying a few prayers that I may get lucky on this one... Sorry for long post - hope you understand..
- Chris

J Cat- thanks just.. read your words- Maybe the powder that I felt in the intake on that cyl. was just that, and wondered if water in the intake- would it get sucked into cyl. and freeze. But why water in the intake- I will look closer at the throttle body area coolant lines tonight.

Thanks
Chris

Sorry to hear about all the things that you are going through. You sound like the sort of person that will survive. Our prayers are with you.
Now back to the culprit. I recall using a penetrating dye to look for cracked cylinders when I used to work at a GM Powertrain plant. I believe you can get it at your auto parts shop or order it on-line. It uses a cleaner then a dye and then a developer and wham the cracks pop up in plain view if they are present. I'm sure a dye kit should be under $60. I'd hate to hear that you had to tear it down again after putting it back together. If you get the dye kit also check the heads for cracks. If a head crackes the usual place is between the intake and exhaust seats. In this case you may have a crack somewhere between a valve seat and a water jacket opening. Look for the narrowest cross-section
Keep in mind. If this has Aluminum Heads which I believ it does. You want to have them machined so they are flat. They do tend to warp a bit over time and when you put it back together with new head gaskets and you don't get them milled the gaskets will not seat completely and you will get a head gasket leak. Trust me on this one, I only did a head gasket job once where I did not get the heads re-machined and I ended up doing the job twice to get it right.The spec for flatness is usually within 0.001" overall. A machine shop should be able to do that for you.
If the heads are cast iron you stand a good chance to just clean them up and reinstall with new head gaskets.
Also whenever installing the heads you need to use new head bolts. They torque these to the point where the bolt stretches. We've been doing that since 1996. THe old bolts cannot be used. They may not hold up and deliver the correct clamp load for the head.

Thanks again CJ- I inspected the heads pretty close tonight again and also the cylinder with a bright light. I honestly could not find anything- no different looking cleaner then other areas. I found out the the local store will check for flat for free, I will get that done. Again I looked at intake- that gasket and smooth inside port keep me going towards and intake leak? Throttle body looked good no water leak there. If I could confirm some how that it had a bad intake gasket and it caused this - I would be very happy.
Oh one thing I read somewhere- leak test on cyl. to find cracks!
I did that before I took her apart. both valves closed - and hit the air- the piston got pushed down in cyl. and I had 100psi on her and it held, that has to mean something- even with that sticky ring she held it? I know cold block any crack may be closed up and when hot it would open... Thoughts?

there are spray on products that will coat the metal surface to inspect for cracks..this product when hit with UV lamp will show any cracks in the metal...I used this when inspecting vehicles for stress cracks ...

Definately if the truck is outside and still cold it would be very difficult to pressure check for a leak. From my experience engine cracks can very extremely if not impossible to see with even a magnifying glass. The dye method is probably the least expensive route. The dye penetrates into the crack and when you hit it with the developer you can then see a crack with the naked eye.
Maybe take the heads to the shop that is going to check for flatness and have him check for cracks for a few bucks.
Also, I didn't notice if you were also going to replace the valve that the piston was hitting
By the looks of the pictures it appears only one valve was hitting the piston....Hmmm
Is there a chance that the valve may have stuck in an open position due to the very6 cold temps and possible corrosion on the valve stem? The clearance between valve rod and bushing ID is normally about 0.001" to 0.0015" Once a valve gets smacked it will bend the valve stem and then it won't close entirely. Have you been able to move the valve in and out of the bushing freely now that it's apart?
Anyways, just a thought. If no crack anywhere something caused the valve to contact the piston and I am sure that the valve hitting the piston broke the rod. I have seen incidents of that in the big block V8 (8.1L V8). I just don't know why a valve would stick open unless there was some liquid frozen between the valve and valve seat preventing it from closing all the way.
Was there any coolant in the oil? i.e. a milky look to the oil?
I'm just rambling, sorry, hopefully something here makes sense.

I wish that were the case, that the valve was stuck and broke the rod... BUT I think the valve would be bent. Both valves are near perfect condition- they do not leak any gas that was poured in on the back side to see if they sealed good. Both stems are near perfect and match all others. I think the piston was up spinnning around as valve was hitting it after the rod broke.

I really am interested in getting some of that apray to check for cracks.
What is it called, and where to get it?

I just got a call and rod/rings are in at the parts store- would like to do the spray check before they go in.

Have to take head to shop and check for flat first.
I'll let you know...

Thanks
chris

Try this site looks like the same stuff we used at the engine plant. I am not sure if you have a local store that carries it. A machine tool shop might .


CJ

Flexbar Magnaflux Spotcheck Red Dye Penetrant Crack Detection Kits ... (http://www.penntoolco.com/catalog/products/products.cfm?categoryID=4193)

- 2 visits - 3:47pmReplica, Proofing & Molding Products, Flexbar Magnaflux Spotcheck Red Dye Penetrant Crack Detection Kits.
www.penntoolco.com › ONLINE CATALOG (http://www.google.com/url?q=http://www.penntoolco.com/catalog/&ei=f-VpS_64Es-MlAfFnNGjCA&sa=X&oi=breadcrumbs&resnum=1&ct=result&cd=1&ved=0CA8Q6QUoAA&usg=AFQjCNGuveqjxwP1ES_5gogOCDBW7wIGZA)

Impressive pics. But to me if the valve had been stuck, it would have been bent simply from the difference in inertia between it and the moving piston...the piston would win.

Sounds to me like you have/had an intake gasket leaking coolant into that cylinder causing the hydrolock and subsequent grenading of the rod...I'm amazed the rod end didn't score the walls as well. You can see the original cutout where the valve should be and the circular marks where the valve pushed the piston down and around once it was free of the rod.

Definitely check the head and deck for warpage...bubbling around the exhaust probably meant that coolant was dripping from a crack there down onto the exhaust manifold.

Good luck to you & God bless!

Guys new information- Sorry about this but every night after work I go out and inspect this thing over and over. This is what I found tonight.
IT IS NOT water/coolant in the intake- it is an oily/fuel like liquid. There is only about 1oz if that in the bottom of the plentium when I pick it up on end, very hard to get out with all the cavities in there. Just remember there are no water ports in this style intake all plastic, for air only and the fuel dumps in the injectors right at the end near the head.
Also- Looking at the head gasket real close in the good light- there is surely a difference around this cyl. in 2 small areas, its not shiny like the others around the entire cylinder, it has a little black- dull carbon like look to it..
Could this be the sign of a bad head gasket? Would this cause fuel mixture to be pushed back up into the intake to clean the port on this cylinder only?
Since the top ring was rusty - coolant must be getting into the cylinder- this blackish area on the head gasket was next to a water port.
And if this has been going on for some time - thats why the lean plug? Still wonder about the intake port being clean?
Let me know your thoughts please..

AND Thanks alot for all the help so far- have learned so much from all of you.
Chris

With your last post it appears we are closer than ever. Like in past posts, coolant in the combustion chamber when running tends to steam clean all the areas. Normally intake valves, unless running a good fuel additive all the time, will cake up with gunk inside the head valve chamber (behind the valve face). With this being very clean and having hi mileage you could have been getting coolant in the combustion chamber for a while. It doesn't take much. Now with the areas on the fire ring having carbon deposits does point to a leak on the fire ring. Without a break in the gasket area around a water jacket port nearby I'm not quite sure.
Were you having engine temperature fluctuations prior to the rod breaking? Engine temps going way up then way down is an issue when you get combustion gasses into the waterjacket and an air bubble develops.

Food for thought.

CJ

Were you having engine temperature fluctuations prior to the rod breaking? Engine temps going way up then way down is an issue when you get combustion gasses into the waterjacket and an air bubble develops.

Food for thought.

CJ

with you question of temp fluctuations if so this is most often always the head gasket..

exhaust gases entire the coolant system causing the water pump to pump erraticly..

Since you have the intake off did you remove the valley pan and look at the lifters? Off on a limb here but what if a lifter collapsed and the runner filled up then pumped back up and hydro-locked the cyclinder? Explains the noise from the loose pushrod when it blew up.

I did not remove the valley pan, From what I can see the cam looks ok and nothing caused me to be concerned in there- I did pull 2 lifters on this side (1 in this cyl. and 1 in the next) they appeared ok.
I never had a pushrod noise it was a broke Connecting rod that was banging on the oil splash pan.
I received new piston last nite and now rings not in till Monday so this weekend I do some more investigative work. I need to get it back together before I go crazy thinking about it.. LOL

Question: would you guys use the head bolts over? remember 171K on it, but be honest I will replace if you think I should. It is only $27.00 for bolts - but this little project is nikle/dime to death- I have not done engine work in prob. 15-20yrs and man have the gasket $$ gone thru the roof.

If you think it would help I can take a few close up pics of head gaskets both sides?
I'll try to clean gunk out of intake this weekend too.

Thanks
Chris

I would not reuse the head bolts. Think about how many heat cycles they have gone thru. Plus they might be torque to yield bolts so don't take a chance for $27.

//2000CAYukon

Use new bolts.

Do not use the old head bolts. Since about 1993 or 94 GM as well as the rest have gotten away from a torque only strategy and went to a torque then an angle. i.e. torque to 85 ft lbs then turn the bolt an additional 90 degrees. This ensures that the bolt stretch is attained to get the proper clamp load. Clamp load is what holds the parts together. Torque only can be tricky due to all the other factors like thread integrity, debris on the threads and any other cause of friction which will show up as torque and yield inconsistant resultant clamp loads.

The bolts are designed to stretch.

Whenever I do a head gasket job I always use new bolts irregardless of how old they are. It doesn't cost that much more to make sure it holds correctly. Last thing I want to do is to do the job over a second time.

ok new head bolts it is..
I'll let you know if I find anymore interesting fact today on the old parts.
Thanks
Chris

ok new head bolts it is..
I'll let you know if I find anymore interesting fact today on the old parts.
Thanks
Chris

the GM repair manual states on head removal must use new bolts..
make sure you follow the thread cleaning of the block threads and use the proper thread material / torque proceedures...

Saturday I got her back together - Checked the old coil and it was firing, all new plugs and new injector in that cylinder. Primed the fuel system few times and she fired right up. No miss, no Lights, no noises.. Runs Great..
I will get a few miles on it and change the oil and filter a few times.
Coolant is staying right up there and temp. is perfect.
Crossing my fingers that she keeps running this good.
I did pull the #4 cyl. plug and couple others to check it and seemed to be burning the same as others. I will pull it again every 10-20 miles or so to keep an eye on it.
Thanks a lot for everyones help on this one- Guess I got lucky SO FAR..
Never did really figure out the cause of the broken rod.
Chris