Coolant Leak

[rkmurphy]

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

[aharper]

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

Andy

[GMMerlin]

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.

[rkmurphy]

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.

[GMMerlin]

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.

[rkmurphy]

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.

[GMMerlin]

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.

[iauthor]

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.

[Geo99M6z]

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.

[drusplanet]

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

[GMMerlin]

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.

[Geo99M6z]

Originally Posted by GMMerlin

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

[glenncof]

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 ?

[Geo99M6z]

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.

[GMMerlin]

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