Chevy Trailblazer Overheating

[Nick1994]

Well my grandmother's 2002 Chevy Trailblazer LTZ 4.2L I6 is overheating. It isn't getting crazy hot but it's just under 3/4 which it had NEVER done before, even in the summer. I noticed it 2 days ago when I drove it to the store.

It has just gotten another new thermostat and radiator yesterday and all seemed well when I drove it today, driving it VERY hard on the freeway and on city streets with A/C on. Then on my way back from a 30-35 mile drive today I got off the freeway and the temperature was just barely under 210 (half). Then I drove on surface streets at about 35 mph and then it got almost to 3/4. Then at idle it cooled back down.

I know the electric fan clutches are known to be bad on these, but it IS working properly.

Any other thoughts as to what it could be?

Thanks.

 

[Clevy]

Well my guess is the radiator. At higher speed it stays cool but at low speed it gets hotter on the gauge.
So it's either radiator or water pump. Can you inspect the rad for scale?

 

[PandaBear]

Did you burp the cooling system after the t stat replacement? My guess is you haven't burp it right and it has air inside.

Or you have a bad head gasket (that symptom matches my integra when the head warp).

 

[901Memphis]

You replaced the radiator and it's still doing it? Might need to get a new oem radiator for that Phoenix heat.

 

[Nick1994]

Just replaced the radiator and thermostat. It also got a water pump last year cause it had play in the shaft, no leaks though.

My mechanic did all the work, so I'm pretty sure he burped it all out.

 

[Nick1994]

He's gonna run a pressure test to check the head gasket.

Anybody know if these are known for head gaskets going bad? Only 104,700 miles.

 

[OVERKILL]

Could it be the temp sensor? Have you verified the temperature with a scan tool?

 

[Nick1994]

Originally Posted By: OVERKILL
Could it be the temp sensor? Have you verified the temperature with a scan tool?
Yes my mechanic plugged his scan tool in and it's spot on with the gauge.

He used to work as a Cadillac mechanic at a local dealership, he's a good mechanic. Just trying to get more ideas here to help him figure it out.

 

[Warstud]

Have you checked the coolant level...in the radiator and the overflow tank? When those fan clutches fail...there usually engaged causing it to run cool.

 

[spasm3]

How many miles on it? Water pumps have been know to wear off the vanes and not pump well.

 

[Rand]

Originally Posted By: Nick1994


He used to work as a Cadillac mechanic at a local dealership, he's a good mechanic.


If hes good he will figure it out. Since it runs cooler on highway than city driving I'd think something with the fans or radiator... but then you said it cools down idling..... hmmm.

 

[Chris142]

Whats the actual temp its running?

 

[Nick1994]

Ok he took it for another test drive and it seems to run hotter with the A/C on than off, so he pressure washed the condensor cause it was pretty dirty and we'll see if that helps.

Has 104,700 miles.

I don't know the exact temperature it is when hot but it gets to just under 3/4, this picture isn't at its hottest point. I took this picture 2 days ago.

Also it was running hot on the freeway too with A/C on, it seems really intermittent.

When the temperature gauge goes up it seems pretty fast.

 

[Quest]

If temp still climbs up during highway (with lots of air rushing through radiator to cool), my take would be something coolant regulation or flow related.

Thermostat OE or aftermarket? Water pump OE or aftermarket? coolant up to level? air trapped?

Q.

 

[Nick1994]

Originally Posted By: Quest
If temp still climbs up during highway (with lots of air rushing through radiator to cool), my take would be something coolant regulation or flow related.

Thermostat OE or aftermarket? Water pump OE or aftermarket? coolant up to level? air trapped?

Q.
They're aftermarket parts and coolant is full in radiator and overflow.

It didn't do this 1-2 months ago when I last drove it a lot. But it also wasn't 115 outside like it is now.

 

[Quest]

just like me critising those inquiries RE: car requires higher viscosity than spec'ed when running/operating in florida; granted that there's no clogs and your coolant flow (to/from radiator) is functioning properly, 115 outside should never be an issue to begin with when you are flying down the highway.

Remember this: engine coolant is around 200F, whereas your outside ambient temp is @ 115F. YOu still have 85F difference where the air inrush @ 65mph would have very significant cooling impact through radiator fins.

that's 85F temp difference for cooling your engine!!!

Look deeper....

Q.

 

[CBR.worm]

Slightly lean? Restricted exhaust? An aerodynamic change drawing air away from or around radiator at speed? Mechanical drag? How is the gas mileage - any change?

 

[Nick1994]

Originally Posted By: CBR.worm
Slightly lean? Restricted exhaust? An aerodynamic change drawing air away from or around radiator at speed? Mechanical drag? How is the gas mileage - any change?
Gas mileage has been great as it usually is. I thought about the exhaust but it has tons of power so it should be flowing good. The car is totally stock and no missing shrouds.

I was supposed to be driving it out of town tomorrow but I don't trust it right now, so I'll have 4 people crammed in the Beetle

 

[jeepman3071]

How is the fan clutch? They are a wear item, and I believe the 4.2L has one.

 

[Nick1994]

Originally Posted By: jeepman3071
How is the fan clutch? They are a wear item, and I believe the 4.2L has one.
Yeah it's an electric fan clutch, looks like it's working, when revving up it roars good but isn't stuck on.