Where is my Coolant going?

[2840Ryan]

I have a 1995 Oldsmobile Cutlass Supreme with a 3.4 DOHC with 152,000 miles on it. I have to add coolant about twice a month. When I bought the car, it had green coolant in it, so that's what I’ve been adding. The coolant looks good in the radiator, no gunk that I can see. There is also a significant oil leak coming from somewhere. I plan to investigate that shortly. I've thought about the lower intake manifold gasket leaking, but the engine idles fine with no issues other than a slight stumble from a stop light. I'm guessing that's because I need to replace the throttle position sensor. Any Ideas of what I need to do from here?

Thanks!

[Schurkey]

Are you adding coolant to the radiator, or to the overflow bottle on the fender?

Oil leak? Typically the O-ring on the oil pump drive (what used to be the distributor) A distributor gasket from a Chevy V-8 can be cut and installed under the flange; with a little sealer it'll dry up the leak.

HOW do you know that the TPS needs to be replaced?

[2840Ryan]

Schurkey:
- I'm adding coolant to both the radiator and the overflow tank on the fender. The overflow tank is always empty when I go to fill it up and the radiator is usually 1/4 to 1/2 quart low on coolant.

- That was my guess on the oil leak. Do I have to take the lower intake off to get to that oil pump drive?

- I'm guessing its TPS because it hesitates/stumbles at a certain accelerator position (guessing around 15%), then I give it a little more pedal and it picks right up and goes. I have not ohmed it out and moved the TPS yet to confirm that's the issue.

[Schurkey]

Schurkey:
- I'm adding coolant to both the radiator and the overflow tank on the fender. The overflow tank is always empty when I go to fill it up and the radiator is usually 1/4 to 1/2 quart low on coolant.

Pressure test the system. That should make the leak obvious. Might want to pull the spark plugs, and crank the engine afterward so you know if any got into the cylinders. Any smell of coolant in the passenger compartment? (heater core) Any puddles under the car after it's been sitting?

The quick-disconnect heater fitting on these and other GM vehicles is a known weak point. Having those rot away is common as dirt; but should show signs of external leakage.

- That was my guess on the oil leak. Do I have to take the lower intake off to get to that oil pump drive?

I did, because I wanted to check the gaskets anyway. I'm kinda thinking that only the upper has to come out; and the oil pump drive will only lift about 3/8 inch or less due to interference with the rear head--which is why the gasket is split and then glued back together with gasket sealer.

- I'm guessing its TPS because it hesitates/stumbles at a certain accelerator position (guessing around 15%), then I give it a little more pedal and it picks right up and goes. I have not ohmed it out and moved the TPS yet to confirm that's the issue.

Ohmmeter or scan tool. I'd verify that the TPS is the actual problem.

[95SleeperAcheiva]

When you pull those spark plugs keep track of them. Look for 1 or 2 that is really clean. If you have a small head leak the coolant will be washing the carbon off the plugs and pistons.
Also there is this neat little kit, $19.95, that has a glass vial and stoppers on it. You put this blue liquid in the vial, attach vial to radiator, and if any exhaust/fuel vapors are in the cooling system the blue liquid turns yellow and indicates blown head of cracked block. Great little cheap tool for verifying blown heads. Parts stores call it a block checker.

[TGP37]

When cold, open radiator and idle engine. If you see bubbles, head gasket leak.

If you have a mayo like light colored crap under your oil fill cap, LIM gasket.

Check under the water pump for a weeping of coolant.

Condensation on the front windsheild interior with sweet smell, heater core leak.

Dirty or failing radiator cap, will not hold pressure. Remove over fill hose and rev engine briefly. If water spits at rev decel, bad cap. (in theory I never tried that yet)

It is possible the hose nipples from the radiator neck or the over tank is cracked. That I found once solved a friends problem. Hard to find but over flow water was leaking out and air was getting pulled back in. Even a weak seal for that hose will add air to the system. A pressure check won't easily reveal that as the leak is after the pressure seal.

[mrl390]

x2 on checking the weep hole on the water pump. Mine was leaking and I was losing alot of coolant. I never saw any puddles under the car because it only leaked with the engine running. Its hard to see under the water pump but if you get the right angle you can see where it runs down the front of the motor (if its leaking).

[TGP37]

And with the car well warmed up...probably after a spirited drive....hold up dry paper 1" from the exhaust tail pipe. If the coolant is going into the combustion chamber the paper will get wet.

[supercoop]

i had a leak on my 94 OCS 3.4 awhile back . the molded rubber heater hose at the firewall blewout. there are 2 short L shaped molded rubber hoses hiding back there . just left of the brake booster behind the upper intake. the one that was leaking looked like 5/8 hose that had been expanded over a 3/4 metal line. it was cracked an rotted. also there is a small piece of hose thats a coolant line for the upper intake under the throttle body area .thats prone to leak . and ive heard mention that the metal heater line that runs around the passenger side lower engine area rust out an develop pin hole leaks. thanks for the other tips folks ill have to
try them on my olds..

[jmgtp]

If you have a mayo like light colored crap under your oil fill cap, LIM gasket.

Failure of the LIM gasket with resulting 'mayo' in the oil is more applicable to the 60v6 pushrod motors, where oil/coolant both touch the LIM. However, in the case of the dohc oil doesnt go anywhere near the LIM - but coolant does flow through it. That said, LIM gasket failure isn't all that uncommon on the dohc motors but the result is usually a vacuum leak on a cold motor that leads to a high revving idle until things warm up enough to expand and seal off the vacuum leak.

As others have suggested, with the car being a 95 and of fairly high mileage there are plenty of hoses that could have degraded. Look for tell tale signs of moisture in the engine bay and on the ground. If you can't find that, then its safe to assume that the water is either in the engine oil or out the exhaust. Either case likely pointing to a failed head gasket.

As far as the engine stumble, that could be almost anything. Spark plugs, wires, injectors, coils, ICM, etc - tons of variables.

[TGP37]

jmgtp, I see, thanks.