We have been looking at a 1998 Suburban with a 5.7 that drops its coolant level by about 6 inches and stops. Or it gets so slow we cannot see it.

Anyone?

 

Fill the cooling system full. Using a coolant system pressure tester, pressurize the cooling system. You should then be able to see the leak. They are bad about the intake manifold gaskets leaking coolant, but I would make sure its not a hose, radiator or front or rear heater core. Is your front passenger floor wet?

 

We will look, Thanks!

 

intake, or the heater core plug on the passenger side of the intake is common for that. check weap hole in the water pump also.

 

I just want to throw my 2 cents in, the waterpump gaskets and the heater core line into the passenger side head have always been trouble on my k1500.

 

I'll also jump in with the rest for the intake gaskets and/or the heater pipe connector (or whatever it's called).

When the water pump on my 98 K1500 started spraying out of the weephole, it would run itself dry after a few hours. Otherwise the intake gaskets would drop it down to a certain level and remain there, as you have described.

Luckily, my intake gaskets were leaking externally, which is why it wasn't harming the engine or loosing coolant at a consistent rate.

 

Hmmmm, my dads 99 burb is doing the same thing , we are chasing loosing coolant , he had the updated gaskets put on bout 60 k ago, .

A tech recommended to make sure his rad cap was good , cheap to try so we got a new one and are going to see if it helps , seems to wet time to time around the rad core support , rad is not that old.