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[Marc Taylor]

i have changed my thermostat and now the water temp stays where it should be and i get heat. Every now and again itll be blowing hot/warm but then go cool and then warms back up again, it seems to go cool when it goes just over 90 degrees.  If i put it on recurculate it gets as hot as i want it.  Any ideas on how to get constant heat and temp control without having to recurculate it and having steamy windows?  Could it be an airlock as iv tried releasing the coolant cap to release bubbles but not many have ever come out.  i would be gratefull for any more suggestions or ideas,    Thank you

[Pete Elite]

Marc see my thread(Heater Problem)and answers below, may be of help to you .

[Marc Taylor]

cheers pete it could be of help if i knoew what and where they were, im not very familiar with these cars at all but im sure ill get there

[RobG]

Two identical solenoids behind R/H side of glovebox. One controls vac to the recirc flap, other, vac to the HBV. As you get constant heat in recirc mode there`s a possibility that the solenoid controlling vac to the HBV is on it`s way out. Solenoid with black pipe is for HBV, one with blue/black pipe is for recirc

[Marc Taylor]

does it make any difference that it only appears to blow cool when the rad fan is on, when driving its fine its when you have stopped for long enough for the temp to rise enough for the fan to come on it happens. if it is a solenoid, is it an easy job and how much to fix???

Thanks

[Boatboy]

I'm wondering if your heater matrix is a bit cruded up, and the lower flow rates at idle are not forcing enough hot water through, and the rad fan issue is a red herring.

Have you tried siting stationary but holding the revs high?

Does a 2.0 have a hbv? If so pull the vacuum pipe off the top of that and test the end of the pipe with your tongue while somebody operates the controls. There should only be vacuum when both driver AND passenger are set to absolute minimum.

If there is a vacuum when you want heat suspect the solenoids next as previously posted. Part no is 9194863. Got mine from car parts connexion for c£12, though list is nearer £60. Could test it by swapping out with the recirc solenoid or just pulling the electrical connector off the end. They're identical and side by side attcached to the pass side of the heater box behind the glovebox. Fiddley but not difficult, though pass air bag may complicate things if you have such luxuries.

But back to the start, hot when driving cool when stationary sounds like a sluggish matrix. Does the output temp vary greatly with changing the fan setting ie hotter on one than five?

Steve

[size=8]ps I dont know much, but what I do is based on a v6 with rotary heater knobs and manual air con.[/size]

[Marc Taylor]

i might have to give that a try, the fan could possibly be a red herring.  on outside air it doesnt get very hot barely luke warm even after driving for quite a while. on recirc it is a little hotter but still not hot.  i think ill try heating it up and holding the revs and see if that works, can you empty the heating system and flush or would that be done with the engine coolant???

could this be in any way down to an air lock somewhere in the system after the thermostat change???

[Boatboy]

There are two seperate elements involved in getting heat from the engine into the car.

First the matrix needs to be full of hot water with a good flow to keep it constantly replenished with new hot water, so yes either crud or an airlock (or both) could affect it. On cars the age of ours, possibly with dubious coolant change history, a build up of crud in the narrow waterways is a distinct probability. As the paths through the matrix are paralell there is little pressure to keep the crud moving. There is a picture of a dissected one in maint guides...

Are the flow and return to the matrix getting hot? Feel the 2 bright stainless pipes up behind where your clutch pedal would be. With a hot running engine and blower off I would expect these 2 pipes to be about the same temperature. With the blower on full for a while I would expect a slight but not great difference between the pipes.

Did you test for vacuum at the hbv?

Heater is best flushed by removing the 2 pipes in the engine bay where they feed through the bulkhead (there's a how too somewhere, seems to be a bit of a knack to it). That way you get direct pressure where its needed, and if you do shift some muck it does not just get deposited elsewhere in the cooling system. You will lose some coolant and have to burp it again when you top up.


If these and previous tests suggest the water side is ok and the matrix is stinking hot, the second element to consider is the air mix flaps behind the dash. If they are not operating correctly and putting a sufficient proportion of the blown air through the matrix the result will be cooler output than you expect. Perhaps more on that from someone more knowledgeable once you've determined the water side is ok.