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

[CJ0717]

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

[CJ0717]

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

[j cAT]

Originally Posted by easygoin43

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..

[easygoin43]

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

[easygoin43]

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

[CJ0717]

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.

[easygoin43]

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?

[j cAT]

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 ...

[CJ0717]

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.

[easygoin43]

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

[CJ0717]

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

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[jdmccright]

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!

[easygoin43]

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

[CJ0717]

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

[j cAT]

Originally Posted by CJ0717

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..