banner1124

Hi all. I have an '03 chevy express 1500. The issue I've been dealing with for a while now is that it drives to hot at highway speeds. It's not uncommon for the needle to be at the 3/4 mark. It never overheats, but I've been driving these vans for 20 years and have never had one where the gauge goes past half way when operating properly. I just had work done at the dealer and they flushed the cooling system for me. They say that radiator is good and that the system is keeping adequate pressure. A while back I also had the thermostat and water pump replaced (the water pump happened because of damage to a bolt getting the old t-stat off). Not at all sure what the issue could be (fan clutch mabye??). Any advice y'all have would be greatly appreciated. I want to take it in to the dealer again but would like to have an idea of what might be happening just in case there's something else I could attempt before another wallet busting dealer trip.

canucklehead

Running hot while cruising at 2300 rpm with 100 km wind blowing through the rad is almost impossible unless something is really wrong mechanically. I am betting on an electrical fault. Bad coolant sensor, or other issue.

banner1124

My thoughts exactly. Replaced the coolant sensor but that didn't change anything. How likely is it that the guage itself is bad? Personally I've not seen that very often if at all.

Could a bad fan clutch cause the issue I'm seeing? It's about the only part of the system (other than hoses) that i haven't touched so far

canucklehead

You can hear the fan while its running. Its very loud. If it is not running, then that will tell you that its not the engine that is hot.
Also, you could pick up a cheap mechanical gauge and check the coolant temp for certain.

tech2

a clutch fan or electric fan contributes nothing additional to incoming airflow at speeds over 40mph.
are all the fan shrouds in place?
put a scan tool on it and report the actual temp the ect sensor is reading. halfway or 3/4 up a gauge means nothing to me.

cleveland63b

you in dirty areas much? I have seen tons of radiators clogged externally that cause those symptoms but they're usually farm/ranch vehicles. Otherwise x2 on the checking shrouds

banner1124

Thanks for the replies everyone. Haven't responded in a bit because I've been out of town for work and the van has been parked at the airport parking lot. I just got back. I do know that all fan shrouds are in place. I also don't go into dirty areas at all. I'll see how soon I can get actual temp readings and report back.

canucklehead

Here is a thought.
When you are adding fresh coolant after a flush, you cannot put the rad cap on till the engine is warm. It won't suck in from the overflow if the system has air stuck in it.
Take of your rad cap when the engine is cold. It the coolant right up or is there space to add some?
With the cap off, start and full warm up the engine until warm air blows from the heater and the upper rad hose feels a bit warm.......make sure the coolant is topped up then put the cap on.
I know that is basic stuff, but you never know.

canucklehead

Also a mechanical gauge is cheap.....you could hook one up to be sure.

banner1124

I actually had a flush and fill done at the dealer a bit ago, hoping that would address the problem but with no luck. I hooked a scan gauge up to it and took it out. Normal around town driving the temp stays anywhere between 205 and 211. Once you get it up to highway speeds (i got on the freeway and drove for a good 20 minutes with the cruise at 75) it stays around 230. For what it's worth those temps at least tell me my instrument cluster gauge is accurate. So, it's definitely running too high a temp at highway speeds. Now I need to go about figuring out what the root cause is.