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Discussion Starter #1
My 2000 deville has been over heating. I have changed the radiator, water pump, cap & thermostat. Now it only overheats when I am driving it. I can let it idle in the driveway for half an hour and it never goes past half way. Is there anything that you can think of that would cause this?
I would also like to know how much of a flow I should be getting from the purge line.
Thanks in advance for all your help.
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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19,270 Posts
Re: Strange over heating issue

My 2000 deville has been over heating. I have changed the radiator, water pump, cap & thermostat. Now it only overheats when I am driving it. I can let it idle in the driveway for half an hour and it never goes past half way. Is there anything that you can think of that would cause this?
I would also like to know how much of a flow I should be getting from the purge line.
Thanks in advance for all your help.
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Now it only overheats when I am driving it.

I can let it idle in the driveway for half an hour
and it never goes past half way.

idling puts no load/strain on the engine -
so it doesn't take much to cool it -

Is there anything that you can think of that would cause this?
blocked airflow -
if the AC condenser is dirty -
it could be restricting airflow -

at speeds below 30 -
the electric cooling fans deliver the airflow -
be sure they are working properly -

if neither the condenser or cooling fans are the problem -
do a BLOCK TEST -
to - HOPEFULLY - rule out a failed head gasket -


I would also like to know
how much of a flow I should be getting from the purge line.

should just be a constant - gentle flow -
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,449 Posts
Re: Strange over heating issue

Please go to the Engines; Northstar forum and study the several sticky threads pertaining to head gasket faults, cooling systems, fan operation and gauge indications.

Lots of insight there. You might also want to study the entire Cadillac Technical Archive way up ^^^ in the top black bar.
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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I agree with Bass. As long as you have flow from the purge line, it is fine. The amount is irrelevant.
Probably time for a bock test right after the next overheat episode.
 

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Discussion Starter #5
Ya. I am thinking that the head is gonna be the issue too. I am worried about doing the head gasket and having the bottom half of the motor start going after a couple months. I know this is common in regular old Chevys and such, but not sure if this is the case with the north star. Any thoughts on that? Also wondering if the fact that I need an a/c low side pressure switch could have anything to do with this.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Posts 2, 3, 4.

The Northstar lower end is practically bulletproof and long-life. No, A/C pressures have no bearing on your perceived overheat problems - diagnosis will tell.
 
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