1991 Chevrolet K1500 keeps overheating.?

Question

I've replaced the fan clutch, flushed the system, replaced the thermostat with a low temp one, replaced the radiator cap, and made sure it was full of water and there is no air. With the cap off I can see coolant flowing and there's no coolant in the oil, but it only goes about 5 minutes, and then the gauge goes up and it really starts boiling in the recovery tank. Any ideas?

Answer 1

Unfortunately, it sounds like you are now at the point that you will need to have the system looked at for cylinder head gaskets or a cracked head or block. Do you ever see white smoke from the tailpipe? This is an indication of burning antifreeze. You may want to investigate the water pump, because in some instances, it will require replacement if flow isn't enough, but I think you are into more serious engine issues.

Answer 2

This will sound stupid, but I've seen it a bunch of times with these trucks. Remove the upper part of the rad shroud and look down in the area between the rad and the AC condenser. If there is a coating of bacteria or it's covered in mud and debris, apply a suitable cleaner and wash this entire area off and do it well. If you don't see anything in here and you can see light when looking through both of the cores, you have some other problem. If water flows through the motor well without the thermostat in, I would think the rad core is plugging up. You will get flow, but not enough. Good luck.

Answer 3

could be be as simple as the thermostat in backwards? they only flow one way. Anther is a plugged rad. At this age look for a lot of buildup. Just my 2 cents worth.

Answer 4

If the rubber air dam below the bumper is missing that could be the problem.

Answer 5

blown head gasket or cracked block

Answer 6

i had the same trouble , change the water pump