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Discussion Starter #1 (Edited)
Recently as the cold weather has started to come upon us i have noticed that my heat in my 2002 9-5 Linear has not been working correctly. I have tried to find fault codes with no results. I had the bypass vavle replaced a few months ago as it was leaking coolant. After reading all the forums on this subject i have tried to purge the cooling system of air by following the procedure of allowing the car to warm up with the resevoir cap off and squeezing all the hoses that i could get to to allow air to pass. The part of my problem that is unique is that when i accelerate quickly and spool the turbo the heat works very well and as soon as cruising speed is reached the heat fails and blows cold air. I know there is a vaccum aspect to the bypass valve but i am not sure what the entails. The turbo also doesnt seem to spool as well as it used to and i have to downshift more to get the turbo to spool where it would have done so without a downshift before.

Can these two things be related??? any ideas would be greatly appreciated.
 

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Could also be a faulty interior temp sensor, do a diagnostic by pressing AUTO and OFF simultaneously and let us know the fault code (if any).
 

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Kermit said:
Could also be a faulty interior temp sensor, do a diagnostic by pressing AUTO and OFF simultaneously and let us know the fault code (if any).
He said there were none. :confused:
 

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jlthunder said:
Is the engine temperature OK? If your thermostat is stuck open, you won't get much heat.
But why would it open at cruise only?
 

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Discussion Starter #6
the engine temp warms up as usual and stays dead center in the range. I have checked for codes many times with no results. thanks for the response guys. how would i check for a vacuum leak in the system that would affect the heat?
 

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Possibly the vaccum hoses were not reconnected correctly. Or possibly one of them is cracked.

Could be related if the turbo and bypass valve share a common vaccum line.

Just a guess, i have no experience with the bypass vavle or turbo hoses.

Best of luck.
Wayne
 

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I don't get why it would be warm before cruise... :cry:
 

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Maybe the change in vaccum pressure while under heavier acceleration is changed enough to allow the bypass valve to function and pass hot coolant to the heater unit. Or if the thermostat is not open completely, the increase in coolant pressure could push enough hot coolant to the heater unit.
As far as i know, only water pressure and vaccum pressure are affected under heavier acceleration.

Personally, i'd check all the hoses for leaks, then check to see that the bypass valve was installed correctly. Then i'd look at swapping out the thermostat.
 

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Discussion Starter #10
OK that sounds good does anyone have a place that i can start looking for leaks. I have looked briefely but dont really know what i am looking at. Thanks for your help.
 

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jmh8802 said:
OK that sounds good does anyone have a place that i can start looking for leaks. I have looked briefely but dont really know what i am looking at. Thanks for your help.
This is a general picture from the WIS which shows the placement of all the cooling hoses. Hope this helps!
 

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pab95 said:
This is a general picture from the WIS which shows the placement of all the cooling hoses. Hope this helps!
But... he has a heating problem, not a cooling one... :confused:
 

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Discussion Starter #13
Hey guys i fixed the problem this evening.

I went on my hunch that it was a vaccum problem and just shoved my hand around by the coolant bypass valve to see if anything was loose and there were two connections undone. I put them where i thought they went and did not get any results. I took another look on the forums for vaccum hose locations and found some pictures which showed me that they were not right. I played around with some configurations and apparently the person who replaced the bypass valve did not put the vaccum hoses back where they belonged.

Anyway i now have hot hot heat...thanks for all your help...i love this forum.
 
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jmh8802 said:
Hey guys i fixed the problem this evening.

I went on my hunch that it was a vaccum problem and just shoved my hand around by the coolant bypass valve to see if anything was loose and there were two connections undone. I put them where i thought they went and did not get any results. I took another look on the forums for vaccum hose locations and found some pictures which showed me that they were not right. I played around with some configurations and apparently the person who replaced the bypass valve did not put the vaccum hoses back where they belonged.

Anyway i now have hot hot heat...thanks for all your help...i love this forum.
Maybe My problem is the same with yours.
Could you tell me the link about the vaccum hose locations and pircutres?
Thank you very much~
 
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