I have a 1998 Blazer 4x4 4 door, 130,000 miles, when on the freeway only the engine runs hot (after awhile the temp gauge gets to the 3/4 bar but doesn't go past it). I put a new thermostat and coolant in and it still does it. The coolant is clean and no sludge or anything. I don't want to just start throwing parts at it. Any suggestions?

 

Might be the clutch to the fan is dieing, but then again that would cause issues at slower speeds i would think. Now you say this happens only on the freeway right?

 

With the summertime temps we've all been having lately, this topic has come up in quite a few other threads. Some of them still on the first page of a few of the forum sections.

#1 thing I would recommend is to clean your condenser and radiator exteriors. Anything that restricts the airflow from going through the radiator will cause higher temps.

#2 Are all of the shields in place under the truck, especially the splash shield under the radiator that has the oil filter door in it? A secondary function of this shield is to deflect air down under the vehicle essentially creating a lower pressure area in the engine compartment to aid the fan in pulling air through the radiator. I have seen this type of behavior on some vehicles that have either broken or otherwise lost this shield.

#3 Does it do this with and without the A/C in use?

 

I'll check the cleanliness of the condenser and radiator, the lower shields are all there, the lower platic piece of the bumper itself (where the tow hooks are), the left corner of it is broken off, I don't know if that could cause a problem with the air coming in being in the lower left corner. A/C usage does not matter, at city speeds the temp is fine with the A/C on or off, but on the freeway, it just heats up faster with the A/C on. The engine doesn't fully "overheat", the temp just stays higher than it should which still cant be good.

 

From what I've read on other posts, im going to flush the heater core seperately, as well as the rest of the coolant, replace the radiator cap and clean the exterior of the radiator and condensor in case of any debris/blockage, then see what happens.

Will report back once completed.

 

could be the rad cap not holding the pressure.......quick easy fix possibly