Trailblazer Still Overheating

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Nick1994

Nick1994

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Well in June the 2002 Chevy Trailblazer was starting to run pretty warm. It has 105k miles.

It has:
Fresh 50/50 Dexcool/Distilled water mix
New water pump last year
Brand new radiator
Brand new OEM thermostat

I had more issues with a Stant thermostat (had a 10% smaller opening than OEM) and an OEM made a big difference, but a drive yesterday made it run warm.

I took it for a 250 mile highway drive yesterday, there was quite a bit of long mountain passes. It got a little warm (1/2 between 1/2 & 3/4) with slight hills but on long pulls uphill it got to the tip of 3/4 of the way up.

It seems it only overheats now with a load on the engine, when going downhill it cooled right off, and RPMs being high didn't necessarily make it run warm, driving up hills with 1/2 throttle without it kicking down a gear it still ran warm. At 80 mph it was pretty warm, but when I slowed to 65 mph it cooled off.

I know the fan clutches (being part electric) of this year are very troublesome. But what I've read is that when they fail they are stuck on (this one definitely is not) or won't engage (it does seem to spool up).

Anybody else have any ideas? It does need new radiator hoses as they have minor cracks (original).

Here's a picture of the highest temperature it got.

I used a scan tool to check and the gauge is correct.

976suh.jpg
 
I don't see any problem. Look, when it's pushed on a hot day, it has more heat to reject, so the temp climbs a bit above normal. On a cold day, with cold air running through it, when pushed, it will be more able to transfer heat to the colder air and the temp will be more steady.

What was your air temp yesterday? 110? And you're running it hard uphill with the AC on, right? It's gonna get warm under those conditions...that's normal.

You're used to idiot lights posing as gauges...despite variations in the actual temperature, the gauge stays steady in the middle. But this is an actual gauge, and it's showing what's actually happening, not filtered, dumbed-down information.
 
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Originally Posted By: Astro14
I don't see any problem. Look, when it's pushed on a hot day, it has more heat to reject, so the temp climbs a bit above normal. On a cold day, with cold air running through it, when pushed, it will be more able to transfer heat to the colder air and the temp will be more steady.

You're used to idiot lights posing as gauges...despite variations in the actual temperature, the gauge stays steady in the middle. But this is an actual gauge, and it's showing what's actually happening, not filtered, dumbed-down information.
I was under the impression that since it isn't towing a big trailer that the temperature shouldn't fluctuate, so this is still a safe range of temperature?
 
Originally Posted By: Chris142
You should hear the fan roaring at that temp.if not its not working for whatever reason.im seeing lots of newer trucks that must be reflashed to make the fan clutch work
Yeah at that temp in the mountains when I was pretty heavy on the throttle and at over 3,500 RPMs it wasn't roaring.
 
I have an 03 Trailblazer, live in Tucson, and have never seen my temp gage that high. Several years ago it was reading low in the winter and setting a DTC, I don't remember the number, for the coolant not heating up rapidly enough from a cold start. I replaced the thermostat and was still having problems. I noticed that the temperature readout was somewhat erratic and replaced the temperature sensor on a hunch. That cleared up the problem.

Why did you replace the radiator? That might be the problem if it isn't a good match for the OEM.
 
What kind of radiator is in it? OEM, Delphi or something cheap?

I wouldn't *think* the fan clutch would come into play on the highway.
 
Originally Posted By: dishdude
What kind of radiator is in it? OEM, Delphi or something cheap?

I wouldn't *think* the fan clutch would come into play on the highway.


I don't know if the trail blazer has one, but that's where I would look with all of the other stuff that has been replaced.

Even on my little Cherokee, if I'm climbing a hill at 40 or so (I have larger tires), I can hear the fan start to roar
 
I would change out the hoses. The bottom could be sucking partly closed not allowing correct coolant flow. +1 on bad clutch or switch. Also, are you sure you "burped" the system to get all the air out?
 
Did you the check the coolant level after driving the vehicle around a bit after having the radiator and t-stat replaced? You may also have air in the system.
 
I don't see why it is moving around so much. On a healthy cooling system it would be rock solid in one spot. It should NOT matter if you are going up hill, are in the mountains or coasting down a hill. With adequate cooling capacity, the thermostat will modulate the flow to the radiator, resulting in a stable temperature. You have something wrong just not sure what.
 
A few things:

1. Your vehicle is programmed not to engage that fan clutch over 45mph. It would never do any good.

2. While not out of safe operating range, your temps are too high.

3. I live in one of the hottest parts of the country and never saw temps that high on my old Trailblazer, even towing uphill at 80mph.

That you are having these problems at speed leads me to believe that either your water pump has had some sort of failure, you have a bad catalytic converter, or some sort of blockage in the cooling circuit. Since your problem is definitely worse under load points me to the exhaust more than anything.

These trucks are hard to airlock if filled correctly, but check that anyway. Open the cap, and run your truck up to temp with the heater on. Allow it to cool with the cap on, and see if the level has changed. If it has, refill and repeat.
 
Fan should sound like a mack truck at those temps, even at freeway speeds unless the computer won't engage it above some speed. It would for sure if was a purely mechanincal clutch. If not, something between the temp sender, the computer, and the fan clutch isn't working correctly. Loosing any coolant somewhere?

That being said, some rise in temp is to be expected - thinking it will be rock solid is a product of deadening the sensitivity of the temperature gauge at operating temps. My last vehicle that didn't deaden the gauge (a Jeep Cherokee) definitely moved in response to usage. The scangauge on my F150 and Explorer shows that water temp variation of over 20 degrees and the temp guage will never move in either vehicle. The system doesn't operate in perfect temp control - it fluctuates in response to thermal loads and the capability to remove them.

Even accepting that the water temps should rise, I'd be concerned with those temps, particularly not hearing the fan roar.
 
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If hot only when loading RPM and cooler downhill, Im going tho throw this out there... have you checked the converter? maybe its partially clogged which I have seen/heard on these makes them run hot under load conditions.

Also I believe there was a reflash for the fan clutch as well.
 
air in the system and/or you didnt top it off after the thermostat opened when you filled it.
 
I'll burp it out tomorrow, it should be good though.

Coolant level is perfect and hasn't moved at all.

I thought with a bad catalytic converter it would be low on power? It has plenty of power.

I'll also get a new radiator cap and do the hoses.

Radiator is aftermarket, not sure the brand but it was overheating before the radiator was replaced, we replaced it trying to fix the overheating.
 
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