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Eldorado and DeVille
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Discussion Starter #1
Hi I Bought a sweet 2000 Cadillac DeVille, Saturday. I was Told it had head Gasket Problem. So I check for PCM codes( none!). I drove car home 60 miles but never put the pedal to the metal and she ran fine all the way home; just cruised at 55 up hills and down. Check computer for readiness status and it was up and running. So I took her in for California smog check. She Passed!
But here is the problem I am Having. I use the heater on high to check if it is running out of water. When I pull up to a stop light after she has been running for a while (15min) it starts blowing cool air out? But when I accelerate back up to 35 mph the heater blows hot Air out again? if the temps start rising to about 2/3 of gauge heat starts blowing cool air I pull over shut car off. wait 5 min and start and drive again no problem heater works great again and temp is back at middle bar again. I think it is the water pump or thermostat problem.
Does the 4.6l NorthStar dump exhaust gasses into the water-pump area and causing no water flow?
I have not added any coolant since I have bought the car. the car is still full of coolant..
If the car needs Head Gasket repair, I have all the tools including GM Time-Serts and timing chain tools.
Got any Ideals on what's going on??
:unsure:
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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The heater circuit is full flow at all times - cabin air temp is controlled by hot/cold air blend, not coolant flow rate.

The coolant purge line is probably clogged. Check coolant level cold. 1/2 - 3/4 full.

Clean out the hollow bolt/nipple as well as the entire purge line itself.

Follow the line from the water crossover bolt/nipple -

Water crossover assembled.gif
Deville 2000 reservoir tankside.jpg
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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Does the 4.6l NorthStar dump exhaust gasses into the water-pump area and causing no water flow?
Technically, the answer to "does it dump exhaust gasses into the water-pump area" is no.
If a HG has failed, it will put exhaust gasses into the cooling system at the heads, which will then make it's way to the WP (and heater core) causing no flow.
 

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Eldorado and DeVille
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Discussion Starter #4
I checked the purge line (Pee tube) when she is cold. the car has great flow when you squeeze upper and lower radiator hoses. I do not know if blend doors change when driving because heat is restored at higher RPM. But when it Idles 650 RPM loss of Heat. When I drove the Deville home. I noticed the heat changes driving through deferent city's. I never changed the temps inside of car. I will Clean the purge line and see if that makes a difference. I will also check the blend doors for codes and report back. Thank Submariner409 from Psycho Joe's Cadillac Ranch.
 

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2000 Deville base 2019 Corvette Gran Sport
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998 Posts
The first thing to go on my 2000 Deville was the heat when the head gaskets started to go bad. I had the exact same symptoms of your car. Why don't you do a block test to either definitely confirm or exclude bad head gaskets.
 

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Eldorado and DeVille
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Discussion Starter #6
Technically, the answer to "does it dump exhaust gasses into the water-pump area" is no.
If a HG has failed, it will put exhaust gasses into the cooling system at the heads, which will then make it's way to the WP (and heater core) causing no flow.
Well cause and effect then answer is yes. But remember no coolant loss! pressure equal to coolant loss, radiator cap pressure is equal to coolant loss. Rise in pressure pushes coolant out over flow tube! no losses in coolant so far.
 

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2004 Deville
2004 Deville, Silver, Gone, but not forgotten, 1972 Eldorado, 1974 eldorado, 1975 CDV
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When my head gasket blew in my 04 last winter the heat worked fine, never had a problem. But the car was belching greyish-white steam that stunk of antifreeze out the exhaust pipes.
Do a block test to be sure.
 

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im baffled why you would buy a 20yrold car especially when you were told it had bad head gaskets??
 

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Eldorado and DeVille
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Discussion Starter #9
im baffled why you would buy a 20yrold car especially when you were told it had bad head gaskets??
Simple, There Great! I am very mechanically inclined and the car surpassed, all my standers for buying a Cadillac. the only car's I will drive is Cadillac because of my age, style, and comfort. Head Gasket is a simple task because mechanical skills. The Computer has 487 miles on it. No water pushing out overflow tank and so thanking blown head gasket is the wrong Diagnosis. I will do a block test on it but the car is not leaking a drop of coolant. I am ordering the 2000 Deville Service Manuals and take it from there. Ho yea; I only spent $600; and you should see the car after her first wax job. The only has 98,000 miles, I am looking forward to the time spent with my new ride. Thanks for the responses.
 

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Discussion Starter #10
When my head gasket blew in my 04 last winter the heat worked fine, never had a problem. But the car was belching greyish-white steam that stunk of antifreeze out the exhaust pipes.
Do a block test to be sure.
Remember I just passed California smog test, toughest in the world. Thanks for your input and sorry about your Baby
 

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Discussion Starter #11
When my head gasket blew in my 04 last winter the heat worked fine, never had a problem. But the car was belching greyish-white steam that stunk of antifreeze out the exhaust pipes.
Do a block test to be sure.
I am going to do a block test when it stop raining here, I like being safe; but I notice when driving around town the fan is not coming on. I turn on AC and get only one fan running at low speed. I thought after 1998 and up it has a code for the engine fan not working. Now I will Drive car with AC on and see what happens. I think mid gauge is 210 deg, second line past middle is 227 Deg and both fans should be blowing. Just not sure.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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2000 Deville - both fans work at the same speed at the same time.

Our cars use the same temp sender so the gauge ticks and bars are the same.

Yellow S and red F are SLOW and FAST - 224 and 236 degrees.

Temp gauge - my numbers.jpg
Fan control circuit-2000+.gif
 

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Discussion Starter #13
Thank you Submariner409. I check fan power on driver side positive 12V. not spinning I will be getting both fans ordered tomorrow. Thank you for all your help. I cleaned the purge line tube today like you suggested; in between rain showers today. The gauge never left dead middle on test drive with only one fan working. Some time the best advice given Works Great. Thank you Submariner409(y)
 

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Discussion Starter #14
I am thanking everyone who posted something in helping Diagnosis my Sweet Cadillac Deville. I am fallowing up on posting codes C (Current) H (History) :{ Dim 1536 H}, {IPC 1000 H}, {IPM B0429 H, IPM 1004 H}, {IRC B1016 H, B 1064 H}, and {SDM B 0065 H, U1040 H}
I think the codes are from someone unplugging different module's in attempt to fix heater problem and gave bad head Gasket Problem. But I am just a paranoid phantom of the Opera. But I am glad I will not be the person singing my Blue's. I used Mac Mentor to pull current codes to double check codes and the only codes found Was SDM B0065 Left front Pretensioner Deployment Loop Open, and U1040 Loss of communication with ABS system. My scanner will pull all current codes and there is no current codes.
 

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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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I am thanking everyone who posted something in helping Diagnosis my Sweet Cadillac Deville. I am fallowing up on posting codes C (Current) H (History) :{ Dim 1536 H}, {IPC 1000 H}, {IPM B0429 H, IPM 1004 H}, {IRC B1016 H, B 1064 H}, and {SDM B 0065 H, U1040 H}
I think the codes are from someone unplugging different module's in attempt to fix heater problem and gave bad head Gasket Problem. But I am just a paranoid phantom of the Opera. But I am glad I will not be the person singing my Blue's. I used Mac Mentor to pull current codes to double check codes and the only codes found Was SDM B0065 Left front Pretensioner Deployment Loop Open, and U1040 Loss of communication with ABS system. My scanner will pull all current codes and there is no current codes.
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regarding codes -
the on-board scanner is superior to hand-held units
and will display ALL stored codes - EXCEPT specific cylinder misfires -

codes consist of a letter -
B-Body
C-Chassis
P-Powertrain
U - network
followed by 4 numbers -
and will include either Current or History -

when posting/discussing codes -
we ask that you include the complete code - whether it is H-History or C-Current -
AND their DEFINITIONS - as listed here: CTS-CTS-V FAQ: Cadillac On-Board Diagnostic Trouble Codes (OBD-II) -

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regarding your erratic heat -
it MIGHT be the cabin temp sensor supplying erroneous information to the climate control module -

locate the 1" square grill to the RIGHT of the steering column -
use a flat-blade screwdriver on the right side of the grill and GENTLY pry it off -

behind the grill is a tiny thermistor - heat sensing unit -
further inside is a tiny squirrel-cage fan -
the fan is supposed to draw cabin air past the thermistor - and sent the cabin temp to the module -

with the ignition OFF - use a flashlight and inspect the area behind the grill -

if the thermistor is coated with dust/debris
it is actually insulated and can't report accurate temp -

ALSO - if the squirrel-cage fan is clogged up -
it can't draw cabin air past the thermistor -

use several short blasts of LOW-PRESSURE compressed air to clear the thermistor and fan -
IF you use too high pressure - you'll destroy the fan -

when finished - re-inspect the area with a flashlight to be sure it is clean -

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Discussion Starter #16 (Edited by Moderator)
regarding your erratic heat -
it MIGHT be the cabin temp sensor supplying erroneous information to the climate control module -


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Thank You Basscat: I will clean and use air in a can to Clean area as instructed. I will let you know how it turns out. Thanks again(y)(y)
 

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Discussion Starter #17
I did block test today and stayed nice and blue. We ( the Forum) figured out the heater problem; blend door out of time so makes a clunk sound when you first start car. I will pull off blend door module tomorrow and retime, and heater should work.:coffee: :cool: psycho Joe Cadillac man. Thanks for all the help(y)(y)(y)(y)(y)
 

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Discussion Starter #18
I installed two new radiator fans and time the heater blend door actuator today and car drives Great; heater work with no loss of heat. Now I will head out to the Chumash Casino because, I must be on a lucky roll. Now I feel like I am the proud owner of a beautiful red Cadillac Deville. Thank you Submariner409 for all the service pictures and guidance and for information you posted on other threads. The Deville just went 35 mile to beach, shopping and back with no codes present in IPM module. I am Glad I did the Block test that everyone suggested, because it really takes the heat off!
 
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