90 K5 Overheating - What's The Cause?

[CUCV2]

The back story on this is that it has been sitting for 4 years. It was started occasionally. Replaced the easy stuff like the thermostat and radiator cap. Double checked the temps with a thermal gun to confirm that it is actually overheating and it is. There is no anti-freeze in the oil or vice versa. It is not using anti-freeze that I can tell. A friend mentioned the MAP sensor could cause it. Just wondering if there were any other ideas. Pic of said offender.

 

[K85 Octane]

lower hose gone to sh1t and collapsing?
rust in the cooling system

 

[sleepymarks]

Maybe it just needs to be burped?

 

[CUCV2]

lower hose gone to sh1t and collapsing?
rust in the cooling system

I'll check it out.

Maybe it just needs to be burped?

I have heard there could be an air pocket. I parked it on as steep a bank as I could find and let it run for a couple of minutes. Is there another way to do it?

 

[jeff in co]

New radiator??

 

[scottsdale86]

water pump

 

[4xcrazy]

Really could use some more info.

Radiator corroded, plugged. Fan clutch not operating correctly, lack of fan shroud or someone installed the wrong fan blade design for a TBI motor, I have personally seen this happen, a friend was chasing down a sever overheat problem, I saw that he had installed a reverse rotation fan on a standard rotating motor.

even some new t-stats dont work right new. As for air pockets in the motor, they eventually work their way out, the radiator cap is the highest part of the cooling system.

My old dually would overheat the longer i drove it due to a lack of a fan shroud.

Is it overheating while idling, driving?

 

[6.2Blazer]

Just as 4xcrazy stated above, you really need to provide more information. There are many reasons an engine may overheat and you can start narrowing it down by knowing when it overheats.

If it does it only while driving, and gets worse the faster you drive, it's generally the radiator plugged (either mud on the outside or rust on the inside). What does the coolant look like?

Overheat at idle or slow speeds usually leads to a bad cooling fan and/or fan clutch.

Overheating all the time, whether driving down the highway or sitting the driveway? Thermostat, water pump, etc...

These are not definites by any means, just the direction I start looking.

 

[CUCV2]

Thanks for the replies. It overheats while driving or just idling. It does have a fan shroud. I will have to check the fan to see if it is reverse flow or not. Is there a way to test the water pump to see if it is good? Otherwise the plan is to pull out the radiator and have it flushed. The water pump and lower rad hose will be replaced at the same time.

 

[6.2Blazer]

If it overheats while cruising down the highway it shouldn't be the fan.