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[Pete Elite]

Hi, Can anyone answer me this? When the heater is on and the 2 pipes to the Matrix are hot, if you turn the heater completely off by pressing off on the climate control switches would or should one of the pipes go lukewarm(top one IIRC)and the other stay hot?
 The reason I'm asking this is although it seems that I've cured my overheating problem(now staying between 95 to 97.5) this is what is happening to the Matrix pipes :-/.

[MutantCav]

Might be worth flushing the matrix mate...

[Ghost]

I thought that they would cool down a bit with the heater off due to the hbv

[Pete Elite]

Might be worth flushing the matrix mate...

   I've just done a complete flush of the system and used 2 bottles of Wynn's coolant flush leaving it in the system for 24 hours and running the engine up to temp. a few times before flushing it out and refilling with VX antifreeze.

   The heater worked perfectly whilst the treatment was in the system and after it was flushed and refilled but when i turned the heater off about 3 miles before arriving home i checked the pipes and found that one was hot and the other lukewarm :-?.

[Andy H]

I am a little confused, how else do think it might behave?

My expectation is that when you want heat the heater bypass valve (HBV) lets hot coolant flow through the heater matrix and when you don't the HBV bypasses the heater matrix & avoids cooking the centre console.

[Pete Elite]

I am a little confused, how else do think it might behave?

My expectation is that when you want heat the heater bypass valve (HBV) lets hot coolant flow through the heater matrix and when you don't the HBV bypasses the heater matrix & avoids cooking the centre console.

  That's the problem Andy, with these climate controlled/HBV fitted type cars which I'm not used to, I'm not quite sure how it's supposed to behave which is why I'm asking the ? to be reassured it's doing what it's meant to do .

[Andy B]

I am a little confused, how else do think it might behave?

My expectation is that when you want heat the heater bypass valve (HBV) lets hot coolant flow through the heater matrix and when you don't the HBV bypasses the heater matrix & avoids cooking the centre console.

  That's the problem Andy, with these climate controlled/HBV fitted type cars which I'm not used to, I'm not quite sure how it's supposed to behave which is why I'm asking the ? to be reassured it's doing what it's meant to do .

The HBV works along the lines of the cable opperated heater valve you'd find on an MGB etc except it use a vacuum. I think your confusing what you got now, with perhaps a MK I Cavalier/etc where you have a constant flow of hot water through the matrix & the heater allows more or less air flow into the car via the heater box that the matrix is sat in.     

[Andy H]

I haven't got the digital climate controls, just the early manual controls linked to a mass of vacuum hoses. It is noticeable that when you turn either of the temperature control knobs a short way the hot coolant starts flowing and the heater matrix gets hot (& smells hot if I haven't used it all summer)

I think that in GM's quest to cram everything into the Omega they left out effective insulation on the heater box. The flow through the hoses at the rear of the engine has to be maintained otherwise it would mess up the cooling flow through oil cooler and cylinder heads so they couldn't fit an on/off valve & had to fit a 3 port bypass valve instead.

With 3 equal size pipes it might be possible for someone to fit the HBV incorrectly & mess up the flow through the rear of the engine which might cause overheating or misleading temperature readings. The important thing is that the flow through the engine is continuous.

When I had my engine out a few years ago I was careful not to disconnect the HBV completely because I wasn't sure I could remember how to put it back otherwise. I assume there should be some markings on the valve but being black plastic they probably don't show up in photos.

[Pete Elite]

Yes Andy H as Andy A was saying I wasn't sure how this particular setup worked in comparison to an older type setup and as you say a lot of this system seems to be an afterthought .

 At least it's put my mind a rest especially after all the time and money I've spent doing it .