1994 gmc stepside overheating. Replaced manifold gasket, no more leaking, but still overheated. Thought thermostat was stuck on open changed it, but inow water is still going up and down in radiator?

SOURCE: 2000 GMC Safari Overheating

double check the pump the impeller inside can be rotted away and it will still pump some but not enough to cool it at 65 mph , you can remove the pump and take off the plate on the back and look at it easily? second get a tech to loan you his infared thermometer and double check the temp it can pinpoint the problem ? good luck [email protected]

SOURCE: I have a 1990 gmc 1500 5 speed that is overheating

It sounds like you have covered the basics. I will provide a list of some of the more major things. I would recommend having the coolant system pressure tested, as well as a compression test on the cylinders. At this point, it could be one of the following. 1: The bypass hose (This connects from the intake to the water pump) 2: Leaking freeze plug or plugs 3: Leaking intake manifold gasket or cracked intake 4: Bad head gasket or cracked head 5: Cracked block Having the coolant system pressure tested should expose any external leaks. Having the cylinders compression tested may tell of any internal problems.

SOURCE: i have a 1990 gmc 1500 5 speed

check and make sure the bolt holding your water pump are on good and check the hoses

SOURCE: my 93 gmc safarie had

you may had overheated you head gasket check your oil, to see if there is any oil in there also check your water pump if not check your water lines one by one to see where is the leak coming from