GMC Repair: Coolant System, coolant system, radiator cap

Question
Hi i have a 1995 gmc sierra with a 350, my question is that the engine keeps overheating and i dont know why. I know im leaking coolant from somewhere but im not sure where. The engine will stay cool on the highway at a constant speed but in town it overheats. its kinda like the thermostat sticks shut and then finally opens. I just replaced it last year so i dont know what the deal is. Thanks in advance for any help you can give me.

Answer
Did you TEST the thermostat BEFORE you installed it ?. Just because it is NEW does NOT mean it works.

Did you test the fan clutch (if applicable to your vehicle)?.


OK, IF the thermostat and the fan clutch is NOT your problem, The most overlooked item is the radiator.

Yes, You can physically SEE the coolant flowing thru the vanes if you remove the radiator cap.

However, You cannot see the middle and lower vanes. In 8 out of 10 cases that when a vehicle has close to or in excess of 100,000 miles, REPLACEMENT of the radiator with a NEW one is the cure.

I said a NEW radiator. NOT a CLEANED and FLUSHED or a REBUILT radiator, I said a NEW radiator.

I have learned, The hard way, That CLEANING, FLUSHING and or having it REBUILT is NOT reliable in my professional opinion.

I have seen to many that were CLEANED, FLUSHED and or REBUILT and the overheat problem was NOT resolved. Installation of a NEW radiator was the solution.