1999 GMC C1500 Losing Coolant

ARMSTR2

MEMBER
1999 GMC C1500
V8
2WD
AUTOMATIC
90,000 MILES

I recenly noticed that I'm losing coolant (about 2 quarts per month for the past 3 months), but there are no noticable leaks on the engine or on the garage flloor. The engine doesn't smoke, and there is no water mixing in the engine oil (or oil in the cooling water).

Any ideas where the water could be going?

5 Replies

ARMYAVIATOR

MEMBER
7 POSTS

Greetings from Alabama.

I have a 2000 GMC 5.3L 4x4; same issue. I did find a tiny seep @ water pump about 4 months ago. Fixed that but didnt fix problem. Here's where I am now: there is a gasket on the throttle body. At least one.I am told. Looking for another. I too do not have any water in my oil or coolant on my floor. If you resolve anything, please let me know. I can best be reached @ bryant. Fontenot@us. Army. Mil

--Bryant

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Thursday, October 9th, 2008 AT 3:56 AM

RACEFAN966

MECHANIC
5,029 POSTS

Sound like the intake gasket. This is a very common problem with these gm's. I have had to replace alot of them. They do not leak outward they leak inward and the engine burns the antifreeze you get a little extra steam out the exhaust.

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Thursday, October 9th, 2008 AT 8:38 AM

ARMYAVIATOR

MEMBER
7 POSTS

Thank you, Racefan. I did look into that; was told my not a few GM techs that the intake manifold of the 5.3L is "dry"; no coolant paths up there.

Was told by Jack in here that it could be a head gasket that is not leaking coolant into the oil but into the combustion chamber. Now wondering if I am hurting my engine? I hate the use of coolant like that, but I dunno if a head job is worth it.

--Bryant

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Thursday, October 9th, 2008 AT 8:47 AM

RACEFAN966

MECHANIC
5,029 POSTS

Now I am not refering to the upper intake or plenum I am refuring to the lower intake. If you do have a head leak then you should go to a radiator shop there is a leak detect they can do. They put this fluid in this tube and put in place of the radiator cap and the fluid changes color if it is a head leak. If the head is leaking however then you should have alot of pressure on the radiator too. See if it can pull coolant into the cylinder the compression can get into the radiator. But this leak detect can see that. Hope this Helps.

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Thursday, October 9th, 2008 AT 8:56 AM

ARMYAVIATOR

MEMBER
7 POSTS

. So go to a radiator shop. Will do.

But, in the mean time, am I hurting my engine? I thank you for your explanation about the pressure in the radiator; just wondering if I am hurting my engine.

--Bryant