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[estaszew]

I am confused by my 98 V6 car's heating issue and I have not been able to find a solution despite reading many posts.

In cold weather just over 0C my car takes awhile to blow warm air.  Generally after driving on the highway for several miles and then coming to a stop, it will blow hot air.  The temperature gauge is consistently low and usually near zero if the heater is on.  Once the car is fully warmed up from driving 20 or so minutes, there is no problem with the heating.

I thought it could be the thermostat, so I replaced that without improvement.  I have also pulled the vacuum line going to the HBV and plugged it-no change.  The overfill tank is at max. 

Any ideas?

[gibby]

Hello sir MeryChrismas, back to ur probs, have you tried to bleed the system? There might be air in the system, no sure though, hope some genius will come along soon.

[Andy B]

Still sounds like a thermostat stuck open-ish to me. From cold, hold your hand on the top hose to the radiator, it should get hot all of a sudden as the 'stat opens, if it's stuck open, the top hose will gradually get hot. Was your new 'stat a pattern part or a GM part?

[ffcgary1]

Sounds like the heater matrix needs a flush to clear any sludge build up. flush both ways with a hose and mains water pressure only.
If that does not help then start looking at poss faulty theromstat. or even less likley a water pump issue but that would usually mean over heating issues.
As to the air lock the cooling system on the omega/caddy is self bleeding. Air lock not possible.
PS      Merry Christmas to all over the pond.

[Andy B]

Sounds like the heater matrix needs a flush to clear any sludge build up. ....

but a blocked matrix wouldn't affect the temp gauge ...... which is consistently low and usually near zero if the heater is on 

[ffcgary1]

Ok agreed, but that could be a faulty temp sensor, replace the sender which is screwed into the coolant bridge and see if the gauge returns to normal operation, if it does then the fault is with either the matrix or the HBV. then finally water pump.(unlikley)
Just a thought is the vac connection from the servo to the heater controls ok, it is from the small t piece in the pipe to the plenium from the servo, it could be a broken t piece.
Hence when you plugged the vac line no change was noticed.

[Bob G]

would disagree on no air lock possible, had heating issues, so ran it up to normal temp, then very very carefully remove coolant cap, ran it at full temp and slowly but surly the air bubbles began to appear in the header tank, burp burp it went on for around 10 mins then no more bubbles, lots of heat though.

[estaszew]

Thanks for all the replies and sorry for my delay.  Yes it was genuine OEM thermostat.

I have not had a chance to flush the heater matrix, but I don't believe my symptoms are caused by that.

I have pinpointed that the cabin heats up as expected, however with RPM>2000, (highway speeds) it blows cold air.  As soon as the RPM decreases, it blows hot.  I did have the head gaskets changed about a year ago, but did not live in a cold climate last year and likely did not notice this.  Could this be due to the heater core hoses being flip-flopped?  I found this as a possibility while searching.

[05omegav6]

would disagree on no air lock possible, had heating issues, so ran it up to normal temp, then very very carefully remove coolant cap, ran it at full temp and slowly but surly the air bubbles began to appear in the header tank, burp burp it went on for around 10 mins then no more bubbles, lots of heat though.

System is self bleeding just run up to temp with cabin heater on max and the header cap off. After the fan has cut in, recheck the coolant level and refit the cap

[05omegav6]

Thanks for all the replies and sorry for my delay.  Yes it was genuine OEM thermostat.

I have not had a chance to flush the heater matrix, but I don't believe my symptoms are caused by that.

I have pinpointed that the cabin heats up as expected, however with RPM>2000, (highway speeds) it blows cold air.  As soon as the RPM decreases, it blows hot.  I did have the head gaskets changed about a year ago, but did not live in a cold climate last year and likely did not notice this.  Could this be due to the heater core hoses being flip-flopped?  I found this as a possibility while searching.

if the HBV has been changed that could be a possibility not sure how this would affect the cabin heater though

[RayONeill]

Hi, Before Christmas had the same issue luke warm air in cabin, temp guage barely moves above 70 - New thermostate fitted and flushed out the matrix, which took me less than 15 mins. Car now running 85, and lovely heat in car