3.4 L using coolant

[zehner2004]

Hey -

1996 Grand Prix GTP using about a cup of coolant every 30 miles - No visible leaks, Oil is fine - not contaminated or frothy. The cooling system does not loose pressure (maybe a wee bit after an hour or so) under pressure test. No visible emissions from exhaust, steam, smoke or anything. Pulled front 3 plugs and they look fine.

Whats next? Do I pull the back three plugs (not fun)....any other tests I can do? I add coolant everyday and am worried that this motor is not long for this world. Please help!

Paul

[email protected]

[GTP Dad]

You really should check the rear plugs. If you find nothing wrong there then look at the heater core area, hose connections to the radiator, and make sure the coolant recovery hose does not have a leak allowing the coolant to go onto the ground rather than into the recovery tank.

[zehner2004]

I will pull the rear plugs this weekend - what does that entail? Do I need gaskets to replace the part of the intake I remove?

As for leaking - after sitting on the pressure tester for 3 hours there was no visible evidence of any coolant leaking out of the car. It has to be going somewhere...... Help pls....

[StevePT]

Not sure about the 3.4L motor, but on my 97 GP w/ 3.1L, the lower intake manifold gaskets were cracked around the coolant crossover seals and letting coolant out and into the rocker valley.

I don't think the coolant was leaking fast enough that it drained down into the crankcase and raised the oil level, but it did puddle in some low spots in the casting and must have been evaporating with engine block heat.

[richtazz]

I would suspect the head gaskets. Do you have a lot of moisture coming from the tailpipe and/or a sweet smell from the exhaust? If so, you have a cracked head or blown head gasket.

[rbsteve]

when i had my car inspected prior to buying it, my mechanic told me that coolant leaks inside the engine were very common on the 3.4 and 3.1 engines due to head gasket failure. luckily i have the 3.8

if you are losing that much coolant per day, and there is no visible sign of a leak on or under the engine, the only logical explanation is that its leaking into the engine.

[zehner2004]

No sweet smell or steam or smoke from exhaust...This is reall pissing me off

[richtazz]

the only other thing I can think of is the water pump is leaking out the weep hole as you drive. The coolant can get slung around and you'll never see it drip on the ground. Take the serp belt and off and see if you can wiggle the water pump pulley indicating a bad pump bearing. Take the pulley off and see if you can see evidence of coolant leaking out the hole in the casting near the bearing. IF so, you need a water pump.

[SUERED]

Good replies it seems to me. This last Saturday I borrowed a coworkers coolant pressure tester to confirm a leak in the top corner of the radiator in my sister in laws '95 GP 3.1--obvious stain and wetness and large loss of fluid noted on the radiator. I had bought stop leak to use on it and decided to confirm that was the problem--even thought of buying a new radiator. I did not expect any revelations or surprises. In one minute of testing I observe that the leak is coming from the water pump area instead! You cannot see the water pump body because it is completely hidden by the belt guide cover disc (looks like a huge oversized hockey puck) which is mounted to the pump flange. OK --I choose to buy the pump $15 (pretty cheap) and see it is a simple mount with 5 small bolts. The hardest part of the job is taking that "hockey puck" off to access the pump. Turns out (per excellent observation of the parts guy when I returned the core)--the pump was going bad so fluid was running out of the weep hole (which you cannot see unless you are a contortionist capable of wiggling into confined areas). The fluid strikes the running belt and hits the radiator to the front--what deception. I also replaced the lower hose and that turned out to be easy as well because the plastic tank has a plastic nipple mount. The old hose was not welded onto the radiator nipple as is usually been my experience in these cases. My boss had told me last week that many coolant leaks can be tricky when the engine is running because the fluid escapes as a vapor and virtually leaves no trail sometimes. Without the tester, I would have never found this pump as the source. If this leak isn't found soon, the leak could have also ruined the belt. The lower hose cost as much as the pump--wild.

[Franks 04 GTP]

I have had soooo many head gasket failures on my cars. 97 caddy STS with the northstar (pos engine!) and my toyota supra turbo. Go to an auto parts store and get a test kit for the head gasket. what happens is combustion gases will get in your cooling system and turn the coolant more acid. This is a simple test if the color turns you know you are getting blow by! and it is always a head gasket. Use this test on other cars that you know are good so you can compare. GOODLUCK