Coolant Leak

I have a coolant leak that appears to be located in the oil pump area of my 97 Tahoe, ie the filter threads to the block and I believe the oil pump ( may not be the pump) The housing has two bolts that are on the bottom side of the enhgine an appear to hold this unit in place
Is there a gaskett in this area that may leak coolant?

Thanks

I'll keep an eye on this thread as I believe I've developed the same problem on my '98.

Andy

I would check the back of the intake where it meets the head. Those engines are prone to leakage there. The coolant will run down the back of the engine and onto the transmission usually leaving white streaks as it dies.
The 3 places I start looking for coolant leaks on those engines are the intake, waterpump bleed hole and the threaded fitting (on the intake)for the heater hose.
You can check the freeze plugs above the oil filter adapter for leakage also.

Okay...the coolant leak appears to be coming from a sensor at the back of the engine, just underneath the distributor. I tightened it about 1/4 turn however I still have leaks. Can I unthread this fitting and use a teflon tape to seal the threads? Any suggestions. It's a tough spot to work in.

That is the oil pressure switch...you wont get a coolant leak from that.
Are you having a coolant or oil leak? Everything you are describing says OIL leak but you state its coolant.

Okay...checked again and its not in the area of the oil sensor. I am leaking coolant. In the previous post you mention checking the back of the intake where it meets the head. I assume you mean under the air intake. If indeed this is the area, how is this fixed. Is this a take it to the shop? Is the head gasket prone to leaking in that area. I have 86k on the rig. It leaks after it been run and it sits hot, once cool, the leak stops.

Those intakes are prone to leaks at the 4 corners where the manifold meets the head.
You will need to remove the manifold and replace the gaskets.
Personally, I have not seen any of those engines with blown or leaking head gaskets.
The torque of the intake bolts is critical in the success of the repair.

I had the same problem, it was the intake manifold gasket. Its hard
to see where the coolant is comming from, but its a common problem.

I believe this may be another problem that my tahoe is having.

It started leaking Friday last week. I thought it was coming from the head gasket but from reading this post it seems like everyone is saying that it is coming from the intake manifold.

I followed the leak up from underneath the vehicle. From what I can see from under it it looks like it is coming from the head gasket (back corner drivers side of the engine) but that is all I could see.

Will have to do this myself, unless it is recommended by folks here to have the dealership to do it. I don't feel like shelling out the cash for a repair when the lease is up in April 04.

If I did it myself, what should I torque the intake manifold bolts to?

Thanks in advance for any help you may be able to give me.

I'm in the middle of this repair myself...actually looking for tips before reassembly. The manual says to torque the lower manifold bolts in 3 stages (71 in/lb; 106 in/lb; final 11 ft/lb). Make sure to alternate your tightening sequence too...8 bolts. Criss-cross (like your lug nuts) inner 4 bolts, then the four outer corners.

My question is how much you should clean up the intake manifold and with what? Leave injectors in too?

Thanks, Murph

99 Tahoe LT 5.7L

The gasket mating surfaces should be spotless.
The intake is alumium, so any rough abrasive will take some of the metal away.
I use a 3m product..its a plastic brush on a drill adapter that will remove the gasket material without damaging the metal.
Just use a solvent such as brake clean.
Also apply medium strengh thread locker to the threads of the manifold bolts.

The gasket mating surfaces should be spotless.
The intake is alumium, so any rough abrasive will take some of the metal away.
I use a 3m product..its a plastic brush on a drill adapter that will remove the gasket material without damaging the metal.
Just use a solvent such as brake clean.
Also apply medium strengh thread locker to the threads of the manifold bolts.

I used some liquid gasket remover.

Also I just used carb cleaner on the manifold and cleaned the gunk from the engine (where the push rods are)

The thing that took me FOREVER to do was when I put everything back together the engine wouldn't start. It would turn over but not start.

When I was taking everything apart I forgot to mark the location of the gear on the Electronic Distributor so when I put everything back together the timing was out. It took me about 2 hrs until I got it started again.

But now I get a code P1345 which is the Crankshaft Position Sensor reading. So I suspect that the time is a little off. Not sure how to check it at the point. I may have to take it to the dealer and let them do the timing.

George

I've got a 1997 Tahoe 5.7l with anti-freeze leak. Finally traced it to the intake manifold where I could see the drops forming. Read my Chiltons manual.

MY question; Is it likely to be UPPER manifold or should both UPPER + LOWER be replaced ?

I have heard from a couple of folks and the dealership that it is common for the upper intake manifold gasket to open up and cause the leak.

A test that you can do to try and find out for sure is with the engine off squeeze the radiator hose that goes to the engine. You might be able to hear the leak.

Mine was leaking on the drivers side on the front corner of the engine. There are two bolts at that location. You might want to check and see if they are loose. Mine were, but I had already had most of the stuff off and just decided to continue and replace the whole gasket.

The lower intake is what is leaking....clean the bolt threads and use blue loctite on reassembly...torque to 11 ft/lbs

The lower intake is what is leaking....clean the bolt threads and use blue loctite on reassembly...torque to 11 ft/lbs

I have this leak on our 99 Sub 5.7 ltr LT 2wd. It is sitting in the garage with the plastic air intake off. That's as far as I've gotten because I am not sure how to proceed. (i've got loads of tools and experience but it appears the the dual A/C unit and pipes seem to be in the way. Not to mention the wiring harness criss crosses the engine. So what do I do to get around all the A/C pipes and wiring harness. I also presume you need to pull the valve covers. Help.

If you want to call me I will walk you through it.

Email me.

-George

Ketch,

What you have to do is this:

Take the A/C off. Flip it up and over top of the coolant tank.
That bracket that the A/c was on you have to take the three bolts out and nut off. I think that there are 3 bolts. the nut is behind the bracket on the lower right of the power steering pump. You just have to loosen that nut.

By taking the bolts out of the bracket you can pull the whole bracket forward to get to the intake manifold bolt underneath it. You will have to do the same thing for the left side where the alternator is.

You do not have to take the valve covers off.

The wiring harness has to stay there. I used a bungee cord to hold the harness to the hood.

George

Ketch,

What you have to do is this:

Take the A/C off. Flip it up and over top of the coolant tank.
George

okay, I see what you mean now...four bolts and or nut hold it to its mount - pull those and lift the entire compressor by flipping it up and back towards tank, taking the two perpendicular hoses up with. Just hope those hoses will bend without cracking - they look kind of brittle.

Do I pull the throttle body off separate or does it come up with the intake manifold?

I emailed you.

Just an FYI...

I jsut replaced my Intake Manifold Gaskets last Friday. Took forever tho get everything out of the way, but a pretty much straight forward process.

The Fel-ProGasket kit was great. Cale with upper and lower intake mainifold, Throttle Body, and Fuel Rail gaskets. I would recommend picking up a set of Valve Cover Gaskets aas it is neccesary to loosen them and move them slightly to get the Intake Manifold off. The OEM Valve Cover gaskets should be okay to reuse since they are rubber, but it's good to have a spare set on hand just in case - and you can always return them.

The reason for the gasket relacement is because I was loosing coolant at the rear drivers side of the intake. This is caused by the the back coolant port on each side being blocked off and causing a high pressure area for easy gasket failure. Just make sure you get a good bead of silicon gasket maker on the front and back of the block between the heads as it's a one-shot deal. I used a a razor blade, liquid gasket remover, and a little acetone to clean the manifold and block mounting surfaces.

I did snap the last bolt as I was tightening down (using the above method). I was able to get it out with an Easy Out, but it was a pain as it was the third bolt back on the passenger side. Appeared to be a bad bolt as I was not even giving the 11 ft lbs of torque needed to tighten it.

Anyway, I got everything put together and put the distributor exactly back where I found it. Now I am getting the P1345 - Camshaft sensor(CMP) and Crankshaft sensor (CKP) correlation. I read a few other posts and talked to the dealership. The consensus is that since you cannot "time" a Vortec manually, the CMP has to be exactly lined up to the degree you took it out. I tried adjusting the HVS (Distributor Housing) back and force and "timing" the best I could to no success. The only way to rectify it is to have a Tech 2, Auto X-Ray EZ Link, or similar OBD-II sensor reador available to look at the CMP Offset in degrees and adjust the HVS until it reads 0. I was able to work a deal out with a local dealership to do it for $37.50 if I leave it there for a few hours to do the 1/2 hours worth of work. I figured that would be worth it. Feel free to let me know if you have any more questions on this procedure.

Just an FYI...

I jsut replaced my Intake Manifold Gaskets last Friday. Took forever tho get everything out of the way, but a pretty much straight forward process.

The Fel-ProGasket kit was great. ......


short of the razor and acetone (I used a Lisle scraper and both lacquer thinner and brake cleaner),,,sounds like exactly what I went through. I misread the torque settings big time and broke a bolt ... thought it said ft/lbs but it is in/lbs for first round of tightening...blame it on all that lacquer thinner and a long day. :p

Fortunately I had a left-handed cobalt drill bit that got that sucker out. Hard to believe the Chevy dealer will sell you a $1.50 bolt for $5.50 and keep a straight face... anyway, because the first set of FELs were messed with RTV silicon I figured the risk of trying to reuse them was not worth the $25 so went ahead a bought another set. This may have been for the best because I realized the tube of RTV that came with the FEL kit was puney and may not even have sealed completely. So I bought a big tube of Permatex ultra black RTV (spec for this application) and got a good dose on there so if I smudged it when sliding the manifold back it would not create a hole. Had a real scare once I started her up - there were new drops of coolant on the floor but after a while I figured it was just leftover that had just shook off after I started her. She has not leaked in a week. Man, that gasket seal is just a thin line of rubber so no wonder it fails. I know conspiracy theories always draw fire but you gotta wonder why they took so long to address this considering how many revisions this engine has gone through by now. Anybody know if they have this problem with the 5.3 small block?

I just took it to the dealership yesterday to have the CMP offset fixed, and they were true to there word- only $37.50. She's been running great since then. I had also replaced the coil pack while I had the wiring harness mount off (you have to pull the wiring harness mount, coil pack mount, and then drill out the rivets that hold the OEM coil pack on to replace one). I did a brake job on it, but I have been noticing some play in the front end. I think the power steering gear box is going out just like all GM's do. I had already checked the idler arm hoping that it may be the problem but it looks good.

oh well, maybe I'll just by a new one. The new 100,000 mile tune up/replacement intervals are great until you get there.

Sounds like a lot of work, but unfortunately, I think that I will have to make the same damn repair. I have been fighting this coolant leak for about a year now, on my '98 Tahoe w/90k on it.
I am noticing the same areas as described by others on this post.
What kind of time frame are we looking at for an average "shade tree mechanic"???

I am not sure I am shadetree material, I just fix what I have to. Plus, I'm a perfectionist when it comes to my vehicle. I would say to give your self a good 6 hours to do it. It will require an oil change and a coolant system refill.

Make sure you have an extra set of Fel-Pro vavle cover gaskets handy in case the old ones are bad. The OEM's are rubber, so you can reuse them if the look okay.

Make sure that you mark the distributor body in relationship to the intake manifold and in relationship to the rotor.

A good Haynes manual should you give you all the information you need.

Ok Guys I just came Across this post and i could really use some help. Right now i got evreything off. Now i see what you mean about the bolts for the a/c compressore brace, but how do i get to the ones behind the Power Steering pump without takeing off the pully.

Okay, I had a few issues here as well.

I think there are two or three bolts on the front of the A/C bracket. You should be able to get to all of them with a socket or wrench. There is also one on the back that you have to get to by laying underneath the truck and looking up at the back of the bracket. Also, there is one on the front of the drivers exhaust manifold. Some of these ore recessed into the bracket, so use your fingers to feel around because you might not be able to see them all. Once all these are all off, you should be able to "wiggle" the backet forward far enough to get the intake manifold out. You should only need an inch or two, so don't go any further than you need to.

This is how I did mine anyway, hope this helps.

Ok guys got it all back together now its giveing me a "Catalyst Efficiency Below Threshold" code On both banks. could this be affected by the intake manifold not sealing right???

Ok that was werid i reset the comp and drove 100 miles and code never came back. I just hope i didnt fudge up an o2 sensor with some junk.

I seem to have a similar problem. My 96 Tahoe seems to have a leak on a freeze plug where there is a sensor installed. How easy is it to replace a freeze plug? Do you have to remove the engine?

I had a 98 that was leaking coolant and I thought it was the rear of the intake or a head gasket. It turned out to be the coolant hose on the front top left (standing in front of the truck looking at windshield) of the engine. The connector is made of plastic and when it leaks it runs down the crease of the intake, down the back of the engine and is very hard to follow. Put a pressure tester on it and move that hose at the coupler. You may be pleasantly surprised and so will your wallet.

try retorqueing the manifold first. It worked for mine and saved a buttload of time

try retorqueing the manifold first. It worked for mine and saved a buttload of time

whoa! are you saying you fixed the manifold leak just by retightening the manifold bolts? If that fixes this common leak, how come nobody said this before?

How many others have actually tried this FIRST before pulling the intake manifold?

Trust me retourqing the intake manifolds bolts wont work. The reason the gaskets fail in the first place is because the bolts on the intake manifold were overtorqued from the factory. Ask a few people who have done them, when I took mine off you could see exactly where the gasket has been overtightened. It cracks the plastic-rubber gasket and causes the leak.

Look guys,
All I'm saying is that it worked for me. I don't think this is a miracle fix for this problem. I also don't expect it to last forever. A friend suggested I try it first because it worked for him and got him an extra 40K of driving time. I gave it a shot, and so far no leaks. It's only been three weeks though. I will also point out that I didn't loosen and retorque the bolts. They were already loose so I just went around in the proper pattern to the specified torque values. It took less than an hour. I don't know how they got loose to start with, but they're not the only loose bolts I've found. Before I bought this truck, the only mechanic to touch it was some guy named Mr. Goodwrench.

I have a coolant leak that appears to be located in the oil pump area of my 97 Tahoe, ie the filter threads to the block and I believe the oil pump ( may not be the pump) The housing has two bolts that are on the bottom side of the enhgine an appear to hold this unit in place
Is there a gaskett in this area that may leak coolant?

Thanks


I was loosing coolant also and could not even find the leak. Fearing the worse, I took it too the chevy dealership and it turned out to be the intake gasket. The mechanic was able to show me exactly where it was leaking and said that it was a common problem with the 5.7 Vortec. I also had the connector into the intake replaced because it seemed a little loose. Everything is working fine now.

I would check the back of the intake where it meets the head. Those engines are prone to leakage there. The coolant will run down the back of the engine and onto the transmission usually leaving white streaks as it dies.
The 3 places I start looking for coolant leaks on those engines are the intake, waterpump bleed hole and the threaded fitting (on the intake)for the heater hose.
You can check the freeze plugs above the oil filter adapter for leakage also.

Hey GMMerlin, I have a leak coming from that threaded fitting for the heater hose. Can this be fixed simply by retightening the fitting or do I need to buy a new one?

Hey GMMerlin, I have a leak coming from that threaded fitting for the heater hose. Can this be fixed simply by retightening the fitting or do I need to buy a new one?

You will have to replace it...most likely when you touch it, it will break and leave the threaded part in the intake..
Its a PIA to remove the broken off portion, but you don't have to take the manifold off to do it.

Well, I guess I'll take to the dealer to have it fixed. I cant imagine a repair like this being very expensive would it? If it breaks off, I dont have the tools or the patience to fix it. I definitely know that its leaking from there, but I'm also worried I might have a intake leak also. There is usually a small puddle on the garage floor after the truck sits for a while. Would coolant leak out from that fitting just sitting there? Looks like I might have to find out how good that aftermarket warranty is. Thanks for your help GMMerlin.

To fix it yourself, the only "special" tool you need is an easy out.
1. Unclip heater hose
2. Try to unscrew old fitting out. It will probably break, so use the easy out to unscrew it.
3. Put sealer on threads of new fitting and tighten securely. Do not overtighten.
4. Clip heater hose in and top off w/coolant mixture.

man... this sucks!!! i've had to fix three coolant leaks (water pump, quick disconnect heater hose fitting and heater valve) already and i havn't had the car for a year. i'm not complaining the parts are cheap and it beats the hell out of working on a nissan or honda...it's just now that i found out about this problem with the 5.7L i'm sure i'm gonna get it...lol. at least i know how to fix it if it does go wrong. thanks in advance. oh yeah and that quick disconnect heater hose that goes to the thermostat housing has got to be the dumbest idea chevy has ever had. who needs a quick disconnect fitting on a heater hose. it's not like you can use it to flush out the system...it's just there so it can break.

To fix it yourself, the only "special" tool you need is an easy out.
1. Unclip heater hose
2. Try to unscrew old fitting out. It will probably break, so use the easy out to unscrew it.
3. Put sealer on threads of new fitting and tighten securely. Do not overtighten.
4. Clip heater hose in and top off w/coolant mixture.


I had this happen and posted over in Suburban forum but same engine for 1999. Does anyone know what size and thread count the fitting has? My fitting was fused to the manifold. I had to painstakingly chip it out but now I need to ream out with a tap of the same size and thread count.

1/2" 14tpi SAE pipe thread

I had the dealer replace the gasket on intake manifold on a 1997; I had experience replacing intake on a 1975 350ci but this one sounded tricky and it's my wife's SUV so I wanted it right (not to spend ~8 hours).

Cost just under $700 with new anti-freeze and oil change. I have 9 months without problem, ~10K miles.

NOTE: I tried tightening bolts before replacing gasket. Some were loose but didn't fix problem. The dealer told me the OEM BOLTS are CHEAP and STRECH !!! This would explain looseness. Hopefully they replaced the bolts with better ones.

DIY, I suggest hardened bolts upon replacement

I had the dealer replace the gasket on intake manifold on a 1997; I had experience replacing intake on a 1975 350ci but this one sounded tricky and it's my wife's SUV so I wanted it right (not to spend ~8 hours).

Cost just under $700 with new anti-freeze and oil change. I have 9 months without problem, ~10K miles.

NOTE: I tried tightening bolts before replacing gasket. Some were loose but didn't fix problem. The dealer told me the OEM BOLTS are CHEAP and STRECH !!! This would explain looseness. Hopefully they replaced the bolts with better ones.

DIY, I suggest hardened bolts upon replacement

Bolts are designed to stretch under torque.
The problem is these are low torque gaskets (11ft/lbs to be exact) and when the gaskets are replaced, the bolts and bolt holes should be cleaned and loc-tite added before torqueing

GMMerlin,

Thanks for the clarification. It's surprising it lasted as long as it did, but this design with the thin-wall, RTV sealant for gasket is....not good.

Thanks again.

G

I have a 99 Tahoe Z71 with two coolant leaks. the first is the pipe fitting on the front of the manifold the fitting aprox. 2" long quick connector is made from a pot metal and as coolant gets old it will start to break down and eat, yes I said EAT metal ! so make sure you change this every 30,000 to 40,000 mls. So the replacement is better quality. My part broke off in my hands. Just take your time and pick out the pieces while running a vacuum next to the hole. once you have all or most of it out chase the threads with a tap 1/2" 14tpi SAE pipe thread. Prlace the part and fill with new coolant.

The second was the drivers side rear lower intake manifold. You CANNOT retorque the bolts and be done if it is leakingthe gasket is compromised and you may have exsesive pitting in the manifold and or heads. The gaskets blow by and to tighten the bolts may help for a short while but the damage is done and it must be repaired.

A repair to the pitted aluminum mainfold I am using is to sand flat the surface, clean good and use a film of JB WELD let it harden sand again and this will fill the pits caused by corrosive fluid. This should work for years to come.

This job is quoted for an automotive shop at 4 hours. At home it may be a full day or two depending.