Kooshball1500

5.7l, k1500 1998 suburban is my dedicated beach cruiser. In the middle of the winter I had her overheat and through a series of experiments ended up with a new ACDelco factory thermostat, replacement fan clutch and new radiator cap.

I don't recall having any temp issues last summer so it was surprising yesterday when in 70f air temps, the engine temp slowly rose to slightly above 210 while on the beach. It quickly returned to 180/185 once I got back on the road in 2wd and got the vehicle speed up.

It didn't come close to overheating but obviously couldn't cool to the thermostat set point and it is only spring.

The water pump was replaced 20-30k miles ago by the previous owner and I have a new belt on it...no noises or visible leeks coming from the pump; any chance it has failed in some other way and isn't moving the correct amount of fluid? Coolant is new btw as the intake gasket was recently replaced.

Radiator was also replaced 30k miles ago.

I am not sure why I keep having this issue but are there some simple things that I can do to improve airflow? is there a fan clutch that can engage sooner, or aftermarket fan blade setup that will flow more air? To be honest, I don't recall hearing the fan roaring when the engine temp got up above 210; what is the chance that my CarQuest clutch was bad from the start?

THX

oldchevy

One possible cause could be a partially clogged radiator or engine block. May be a good flush would help.

Kooshball1500

That is a good idea but I am not sure how likely...the motor was replaced with a GM crate motor about 25,000 miles ago..

in2pro

How is the condition of the antifreeze to water mix?

Too much air in the system can cause problems

Radiator cap being defective will prevent proper pressurization

Is the over flow tank and hose in good working order?

Kooshball1500

The anti-freeze is new and perfectly clean . The radiator cap is also new and the hose connecting it to the reservoir are new. I took great care to purge the system of air when I changed the thermostat; I'm confident that it is clear of any air bubbles

in2pro

Does the engine smell like it's getting hot (overheating)?

It's possible the temp sending unit might be flaky and you are getting false info if the system is truly in sound shape.

Make sure both upper and lower radiator hoses are routed properly, and all bends are smooth with no hard kinks. Even though the coolant can flow, hard bends can slow the flow down, though not likely cavitation is plausible...

SWHouston

I just got a suspicion that with all the work you've done, air is remaining in the system and prohibiting efficient cooling. If you don't have a means to remove it, a good radiator shop can vacuum it out for you.

Also, make sure you have the ability to get a good flow of air. Get a Drop Light and put it behind (in engine compartment) and make sure you see light toward the front of the radiator and condenser. Mud/debris may be clogging the fins.

It's pretty easy to verify actual temp to what's reading via the gauge. You need a A/C Stick Thermometer. When cool, remove Radiator Cap and crank up. You may need to catch some of the coolant as it expands. Stick the thermometer in to coolant thru the cap access hole, and let run long enough where you can see maximum temps, and compare as you go to what is showing inside.

Kooshball1500

Thanks for all the replies!

At this point, it is getting hot but not actually overheating as I either get it back up to speed or shut it down well ahead of an issue. I do think that if I let it go, that it would overheat. The temp sensor is likely good as it did boil over (with the bad cap) into the resivour during the first incident.

Is there a DIY vacuum setup that could work to eliminate the potential air? The radiators look good, but I will check for debris and kinks in the hoses.

SWHouston

There probably is, but, I wonder if purchasing one would be justified for only one use.