I can’t figure out where my coolant is going

[Elkins45]

1998 Chevy K1500, 5.7L V8. This vehicle has a whole bunch of issues even though it only has 56k miles so I’m not willing to sink much more into it than I have already. I can smell the coolant when it's running and I have to keep adding to the reservoir but I can’t see where it’s going. There aren’t any visible drips or wet spots when it’s running. I added UV dye and still can’t find the leak. There’s no white exhaust to indicate that it’s being burned.

Is it possible it’s just a small head gasket leak and that it’s being burned slowly enough it won’t show up in the exhaust? As I said it’s more of an academic question than a practical one at this point because the engine and transmission are about the only things still working.

 

[ctechbob]

Aren't those the engines that the intake gaskets need replaced on because of coolant leaks?

 

[clinebarger]

Intake gaskets most likely, As crappy as Fel-Pro is...Their rubber over steel Vortec intake gaskets are really good!

These gaskets like to leak internally as much as externally.

 

[Hirev]

My bet would be the intake gasket.... it was a big problem in that era on the 5.7.

 

[Lubener]

An oil analysis would confirm internal leakage and could possibly save you from an unnecessary repair.

 

[GON]

Any chance it's a failed heater core and that is what you are smelling, coolant entering your interior?

 

[Elkins45]

Any chance it's a failed heater core and that is what you are smelling, coolant entering your interior?

The smell is outside the vehicle, and there's no moisture inside.

 

[billt460]

Any visible steam coming out of the exhaust on a cold start?

 

[ka9mnx]

Any visible steam coming out of the exhaust on a cold start?

Intake gasket leak usually isn't bad enough to show steam from the exhaust. Look for milky oil at the oil fill hole. Pressure test the coolant system

 

[Cujet]

Just an FYI, if coolant drips on to something hot, it will evaporate and not reach the ground. I had a leaking water pump on my Jaguar, and never saw any evidence on the concrete. It would sit on the transmission and evaporate over time.

 

[Astro14]

I’m in the “small head gasket leak” camp - not enough to see steam - but enough to cause a loss.

 

[CarbonToast]

Try some AC Delco Leak Tracer Dye and a blacklight. The evaporated coolant should leave dye residual.

https://a.co/d/aZIzxdN

 

[PontiacHO]

Get the engine hot with pressure on the system. That helps with locating an external leak. Check the underside of the oil fill cap for milky “pudding”. That would indicate internal leak (intake gasket). Avoid getting burnt but remove spark plugs with engine warm and pressure on the cooling system. A pressure tester is preferable. Have someone spin the engine over while you watch each bank of cylinders. You’ll see steam or slight moisture escaping the spark plug holes if coolant is leaking into a cylinder. That can indicate a cracked head or bad head gasket.

 

[Geekhead]

Get the engine hot with pressure on the system. That helps with locating an external leak. Check the underside of the oil fill cap for milky “pudding”. That would indicate internal leak (intake gasket). Avoid getting burnt but remove spark plugs with engine warm and pressure on the cooling system. A pressure tester is preferable. Have someone spin the engine over while you watch each bank of cylinders. You’ll see steam or slight moisture escaping the spark plug holes if coolant is leaking into a cylinder. That can indicate a cracked head or bad head gasket.

The plug will also be steam cleaned and look different from all the others

 

[Elkins45]

Try some AC Delco Leak Tracer Dye and a blacklight. The evaporated coolant should leave dye residual.

https://a.co/d/aZIzxdN

I’ve already done that. I can’t see a glow anywhere. Does the dye lose its fluorescence when it’s passed through the combustion chamber?

 

[Devo242]

Radiators for this model year with the 350ci list ports for engine oil and auto transmission oil coolers integrated into it. Any signs of the coolant in either of those oils from a leak inside the radiator?

 

[Elkins45]

Radiators for this model year with the 350ci list ports for engine oil and auto transmission oil coolers integrated into it. Any signs of the coolant in either of those oils from a leak inside the radiator?

No, neither looks milky at all.