coolant leak

[2000oldsilh]

I am experiencing coolant leak which has become worse recently.

It is leaking between the transmission and engine beside the fly wheel. I cannot locate the exact location. I did check for the leak around the engine but everything there is dry.

Where is the transmission cooler located?

Or is it possible that it might leak from the freeze plug?

It gets worse when the engine is running.

I thought it was the LIM but it's all dry around there. Maybe the head gasket...but the vehicle is not over heating and the engine oil seems to be fine.

Any ideas? Thanks,

[Airjer_]

No signs of coolant right under the throttle body?

[rockwood84]

also check the heater hoses right behind the throttle body left of the brake booster.there are two hoses that are close together and g.m. used a sort of onion bag stuff to go on the hoses to stop them from rubbing together. as the hoses rub they rub thru this and rub on each other until you have a leak.if you have a hole in the heater hose they will want to sell you one for $8.00 and $20.00 for the quick connect.dealer wants $230.00 for the heater hose .you can fix it for $2.00 by getting a piece of 5/8 heater hose 8" long and a #10 hose clamp. take a small flat screwdriver and work the quickconnect loose and take the rear hose clamp loose and take old hose off. take a pair of diaganal pliers and peel the outside of the factory crimp on the quickconnect. take the old hose off the quickconnect and push the new hose on the quickconnect and tighten the new hose clamp. now using the new hose with quickconect on it measure where you need to cut the new hose by holding it where the old hose was without pushing the quickconnect on hold it just above the pipe and leaving enough to put on the fitting at rear hook up.the trans cooler is on one side off the radiator.take a light and look right below the thermastat housing for coolant laying

[2000oldsilh]

No . There is no leek under throttle body . I dont see any leek from the top on any side of the engine . When I go under the van I see the leek somewhere around flywheel and is dripping alone trany fluid cover. I cant trace it upwords to see where the leek comes from ?. I filled over flow tank last evening and i took for a ride this morning and coolant was gone. I also open the rad and inside the neck I found some kind grease deposit.All hoses that I can see and touch show no wet spots. Thanks

[merc81]

There is a coolant pipe which is impossible to see or even touch down under the air intake. Its between the engine and the tranny, just behind the exhaust manifold crossover pipe. This pipe is inserted into the intake manifold and uses an O ring to seal at that location. It is held in place by the bracket that supports the fuel lines and is bolted down underneath the EGR valve. It connects via one of those quick connect fittings to the heater hose mess behind the EGR valve.

When that O rings fails and leaks, the coolant will run out over the tranny pan just as you describe. Its possible to see the coolant dripping down onto the engine, but you need good lighting, and know where to look.

The gunk in the coolant you mention is typical for the engine as the LIM gasket wears out. If you don't yet need a LIM gasket, you will soon and at that time you should replace the O ring I'm describing.
If you want to try to replace just the O ring, or at least check it for leaks, you will need to remove most of the stuff above the exhaust crossover pipe and best to even remove the pipe as well.
John

[2000oldsilh]

You were right . I took the intake boot off and few other parts and I took closer look at the places You mention and I found the leek under that pipe. I replace the o-ring , but no luck. The o-ring wasnt original ,I foud something similar. I thougt I would get away with it. What is the GM part number for that o-ring ?. I didnt mention before ,my LIM was replace 2years ago. Thanks

[merc81]

I can't find that part number anywhere!
I used an O ring from freon system of the air conditioner. If you purchase a selection of O rings at the parts store intended for the air conditioner seals there are several of the perfect size to fit that pipe. Even though the O ring was the right size, I also painted the pipe & O ring with permatex gasket sealant because its SO hard to get into the area where the pipe installs I didn't ever want it to leak again!

Glad you were able to get to yours. Did you have to remove the exhaust crossover pipe? If you do take that off the job becomes trival.
John

[Airjer_]

Call your local GM dealer and tell them you need a heater tube o-ring.

[rockwood84]

there are two small i think 3/8" hoses that the heater hose the black metal one that runs from the water pump over across the front of the motor . the metal heater pipe slips into these right under the throttle body. as i remember they are about 2" long ..the only "o" ring i remember on the black heater pipe is on top of the waterpump.as the quickconnect is on the other end that goes to the heater hose..and the other return heaterhose connects on the backside of the intake by another quick connect that has a 90 in it. are you sure it is not the quick connect leaking?

[Airjer_]

The older 3.1 used a quick connect for the heater pipe to manifold connection. The newer engines 3.1/3.4 got rid of the quick connect and replaced it with an o-ring. The heater pipe goes directly into the manifold and is secured by the same nut that the secures the fuel line bracket.

[rockwood84]

on my '99 the only "o" ring on the heater hose system i have seen was the one that goes into the top of the waterpump. and on the end of the metal heater pipe that connects to the heater hose by the booster there is a quick connect. and on the heater hose that goes back to the manifold is a 90 degree quick connect. not saying there isn't one but i haven't seen it yet..i did say yet.

[Airjer_]

Just for you rockwood!

Old style with quick connect


New style no quick connect

[merc81]

I can't see the pipe in your 2nd picture Airjer_. It should be below the pipe you are showing and behind the exhaust pipe.
I don't know the size of the correct O ring but I can tell you that it fits just perfectly over the top of one of the 4 bolts that secure the engine mount bracket to the body just over the radiator - - that's where I kept putting all the O rings as I tried each one out from my box to get one that fit!

[rockwood84]

airjer thanks for the pics . haven't had to mess with that leak yet.hey does that pipe that the "o" ring goes on go to a heater hose with a 90 degree quick connect .it will be the heater hose on the left in the mess of them by the brake booster.as from the pics it looks like it might.when the old lady gets the van back i 'll have to feel around and see.the pipe looks like 1/2 " but haven't seen the "o" ring .i"ll bet its one of the thin ones if it slips into a hole.but thanks for the info as i might need it one day.knock on wood.

[merc81]

Yup, that's the pipe; right angle quick connect on the end to heater hose, about half inch pipe and has bracket that connects to same bolt that holds down fuel line clamp. Its a real bear to even touch it without pulling off tons of stuff, let along get a look at it.