02 Blazer overheats when heater on

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Bob Chappuis - 28 Dec 2005 18:59 GMT

My stepson claims his 2002 Blazer overheats only when the heater is turned on.
So far I have flushed the heater core, it did not appear to be clogged up at
all.. My Clymer Manual is no help.

Last winter I drained, flushed system at about 80,000 due to heater not working
and the dex-cool looked gummy. Flushed the heater core and solved problem.
Replaced with fresh Dex-cool. This time the dex-cool looks ok.

Any ideas what the problem might be?

Thanks

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NickySantoro - 28 Dec 2005 21:51 GMT

>My stepson claims his 2002 Blazer overheats only when the heater is turned on.
>So far I have flushed the heater core, it did not appear to be clogged up at
[quoted text clipped - 7 lines]
>
>Thanks

I doubt the heater being on causes an overheat situation. Usually it
is the opposite. It was probably coincidental. I'd check the
thermostat then verify that the water pump is operating. I've heard
of some with plastic impellers that had the impellers shear off
internally and thus not pump. If this problem is intermittent, I'd
concentrate on the thermostat.
FWIW
YMMV

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notMe - 30 Dec 2005 00:22 GMT

>>My stepson claims his 2002 Blazer overheats only when the heater is turned on.
>>So far I have flushed the heater core, it did not appear to be clogged up at
[quoted text clipped - 15 lines]
>FWIW
>YMMV

I agree. The boy says the temperature has been fine since 12/25 since
he stopped usibg the heater. I will try to test drive it Saturday.
Thanks for your reply

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Big Al - 30 Dec 2005 14:57 GMT

> >>My stepson claims his 2002 Blazer overheats only when the heater is turned on.
> >>So far I have flushed the heater core, it did not appear to be clogged up at
[quoted text clipped - 18 lines]
> he stopped usibg the heater. I will try to test drive it Saturday.
> Thanks for your reply

Does the gauge go up instantly when the heater blower goes on?

Al

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Adam - 30 Dec 2005 15:00 GMT

I wouldnt have put dexcool back in the truck, I would have filled it with
green but thats just me... I saw what dexcool did to my hoses, made the
insides of them get all nasty and gummy feeling.

>> >>My stepson claims his 2002 Blazer overheats only when the heater is
> turned on.
[quoted text clipped - 26 lines]
>
> Al

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Hairy - 31 Dec 2005 18:44 GMT

> I wouldnt have put dexcool back in the truck, I would have filled it with
> green but thats just me... I saw what dexcool did to my hoses, made the
> insides of them get all nasty and gummy feeling.

Which is generally a sign of poor maintenance.

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Dave in Columbus - 29 Dec 2005 05:33 GMT

>My stepson claims his 2002 Blazer overheats only when the heater is turned on.
>So far I have flushed the heater core, it did not appear to be clogged up at
[quoted text clipped - 7 lines]
>
>Thanks

Is the gauge saying the engine is overheating or does he have any
indication from the engine/radiator that the engine is overheating?

The only way I can figure this complaint is that some how the gauge is
misreading the actual engine temperature.

Signature

Dave in Columbus

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notMe - 30 Dec 2005 00:30 GMT

>>My stepson claims his 2002 Blazer overheats only when the heater is turned on.
>>So far I have flushed the heater core, it did not appear to be clogged up at
[quoted text clipped - 13 lines]
>The only way I can figure this complaint is that some how the gauge is
>misreading the actual engine temperature.

The story is that the gauge went almost to the red and some coolant
overflowed evidenced by the smell of coolant burning. Some type of
discharge ? came out of the vents, the heater was turned off and
temperature gauge returned to normal. Guage has been showing normal
since then (12/25) with the heater on off. If the heater core is
leaking the passenger floor would be wet, right? I will work on it
Saturday. I plan to flush the Dex-Cool and replace with green stuff.
Thanks for your reply.

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Adam - 30 Dec 2005 15:07 GMT

Check this out.

http://www.girardgibbs.com/dexcool.html

> My stepson claims his 2002 Blazer overheats only when the heater is turned
> on.
[quoted text clipped - 10 lines]
>
> Thanks

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