Overheating 1995 Blazer
 

I'm having problems with overheating. About two to three years ago I replaced the radiator, thermosat, and hoses. At that time everything seemed to be okay. Now lately I've notice that it seems to overheat when its warm outside 85-95. Normally the engine runs around 210 then if stuck in traffic, going up hills, or AC on for long time with traffic it will almost get into the red. The warning light comes on the dash "check gauages". If I shut off the AC and turn the heater to hot and max fan it will help to cool it down? It does boil over into the reserve tank then goes back in the morning? I'm not sure if the clutching fan is working. I do know that in the morning the fan will race until the clutch lets go (but only notice noise when its cool not hot). Do you think there could be air in the system? If so how could it suck the coolant back in? Any thoughts. Thanks

Having the same problem
 

If you figure it out let me know if i figure it out I'll let you know.

Well.... Flush your radiator. Clean out your system. Replace your water pump if it has never been done. Get a new thermostat just in case. (get a 180 degree thermostat to keep the truck cooler) And mainly, check for leaks in your hoses. This is all pretty cheap.

Water pump - $35
Thermostat - $10
Hoses (if applicable) - $10-20

And the installation is pretty simple. Try it, im sure that will cure your issues.

Have you checked to see if the AC condensor and radiator are clean. Not full of bugs, leaves etc.? From what you describe it sounds like you are not getting enough air through the radiator due to bugs etc. or the clutch fan is not working properly. When the engine gets that hot the fan should hook up and be quite loud pulling air through the radiator. Or the radiator may be plugged inside. Is the coolant clean? Drain some coolant out and see what the inside of the radiator liooks like through where the cap goes.

Water pumps almost never cause over heating unless the belt is loose or glazed & slipping. Your thermostat does not sound like it is bad or it would overheat at other times. If it is old it would not hurt to replace the thermostat though.

From what you have said I suspect the fan is bad assuming the radiator is clean inside & out side.

To check the fan Grab the fan blade at the top it is ok if you can push the tip of the blade front to back up to 1/4".
A small amount of fluid leakage from the fan clutch is normal.

Then with the engine cold. Spin the fan by hand if the fan freewheels it should be replaced. It should have a slight drag.

Start the engine and set it at 2,000 rpm. Turn the AC on with heater off. During the 1st 15-60 seconds it is normal for the fan to engage and be noisy like you describe in the morning, but then it should quiet down. Block the radiator with cardboard etc. As the coolant temp goes past normal 200-210 the fan should kick in and get loud well before it gets to the red on the gauge. Do not let it get into the red and pull the cardboard, turn off the AC, turn heat on high and run at 1,500 rpm to cool the engine down. If necessary spray the radiator with a hose while running to keep it from getting to the red area.

If the fan did kick in as the engine got hot it should dis-engage and quiet down as the engine cools off.