hi i have a 99 s-10 blazer ls and i replaced rad cap, thermostat and the temp sensor but im still having an weird problem and that is any time im on the highway doing about 65 to 70 the temp rises on the engine also replaced fan clutch cause i thought it might be that, but the problem is still there and yes i took it in and had it pressure tested everything checked out no idea whats caused this please help

 

Have you cleaned the exterior of the radiator and A/C condenser?

 

yes i did fulled of the grill and cleaned the ac condensor and removed rad cleaned inside and out with no luck

 

I'm beginning to think its an unfixable "quirk" with these cars...there are so many threads on here about the same problem and people are trying fan clutch, radiator, flush and fills, new thermostats, new water pumps, cleaning radiator, etc.. and I have yet to hear of any permanent resolution. seems to be mostly when its over 90 degree's outside and the ac is on in the car and driving in stop and go traffic...wish I know how to fix it other that turn my heat on full blast and roll down my windows to keep the thing from overheating...

 

hahaha i know i live in az and my ac doesnt even work its when i hit about 60 it starts heating up

 

Have you flushed the engine & done a very thorough cleaning of the radiator (inside and out -requires removal of the radiator)? You could be experiencing a restriction to flow in the radiator due to buildup.

 

do you have all the covers under the front end to force air thru radiator and shroud in place

 

which covers i know all the fan shrouds are there

 

you may have to take the top of the radiator shroud off and check between ac condenser and radiator for blockage dirt grease leaves
spray degreaser and rinse with water only when engine is cool try that or radiator is pluged on the in side they make a thicker core radiator for this truck this is what i am going to replace mine with when it fails the company is called jagsthatrun.com and they say you can run a smaller fan less drag on engine the radiator costs 155.00 but i know its going to cost you at least that for a stock one check it out that should solve it

 

ok guys i think i found the problem when i started pulling off the fan shroud i noticed a pile of burnt on coolant on the rad next the top hose next to the fins which i suspect is a small leak causing things not to pressure-rise and on top of that the fan clutch is failing its not kicking in so this weekend will be fun lol