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Mystery Coolant leak - '92 Burb


nsaP
07-05-2005, 05:01 PM
Did a little searching, didn't find what I was looking for so I decided to post.

Car info:

1992 Chevy Suburban (duh)
~120,000 miles
5.7 liter gas motor

On a drive home a week ago or so the car started to lose coolant. My mother was driving, and continued to even after she smelled it because the temp guage wasn't reading abnormally. We later explained to her that if there's no coolant, there's nothing to read, but I digress.

The car makes it back allright, minus a gallon plus of coolant. Over the next day or so 2 puddles form underneath the car, both coolant and water, but because of all the undercarriage plastic I couldn't tell exactly where it was leaking from. My dad and I filled it up a bit and started her up.

We're pretty sure there was close to the normal amount in there, as there was coolant in the overflow. We let it run for a bit, but there were no obvious leaks. We took it out and drove it around for 5-10 minutes, came back, and there were still no obvious leaks. Hmm.

Something was definitely wrong, as we were missing more than a gallon of coolant. Our problem is finding out what exactly was wrong. The water pump seemed to be functioning normally, and nothing seemed to be coming from that, so we are stumped.

Did this generation of Suburbans have any known problems with this so we would at least have somewhere to start? Or is there someone here who can tell me more about the cooling system to help diagnose this?

All we can figure right now is whatever was leaking didn't have any flow to it when we took it for the short drive again, but it came up to running temp and we were blasting the A/C and keeping it a gear low just to give it a work out. It seems that all of the cooling system would be used, but I admittedly have little knowledge about the 5.7 liter (LT1 is it?).

Thanks for any help.

GMMerlin
07-05-2005, 06:23 PM
2 ways to go about this
1. Have the cooling system pressure tested, the cooling system is under pressure and any leaks will show up
OR
2. add some leak detection dye to the cooling system and run the engine for a while then look for leaks with a leak detection light..this works well for difficult to find leaks or leaks that only happen when the engine is heating up or cooling down.

94century
07-07-2005, 10:53 PM
one thing is that if it's just water it is probably just from the A/C. Also check the upper and lower hoses when the system builds pressure. I have an 85 GMC S-15 that would only leak when pressure built up, it was a leak in the bottom radiator hose.

Blitzburrgh
07-08-2005, 02:46 PM
My 94 did almost the same thing.. but I never had puddles. Anywhere from a day to a week, I was adding coolant, anywhere from a gallon or so. When I did my intake manifold/valve cover gasket change, the quick disconnect fitting at the rear of the intake was rotted and leaking. If this is your problem, use caution taking it out. I had to heat up the intake where the fitting screwed in a bit to take it out. These break very easily, then your off to a machinist.

Have a look around the rear of the intake, see if you have leakage there.

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