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[Opelduude]

On my way home from work the temperature stared to rise.

Came home and ripped open the hood and there was little or no coolant left.
The engine and front subframe was completely dry.

Filled it up with coolant again and took it for a spin. Temperature lies steady and 80-85 degrees again.
Check all the fuses for the cooling fan. All okey. Both fans run when i turn on the AC.
The fan was not running when i came home from work and the car was overheated.
Strange.
The radiator, both temp sensors on it and the water pump was replaced 1,5 years ago.
Any suggestions?

[Doctor Gollum]

Hbv is the usual suspect for sudden unexpected water loss.

[Opelduude]

Hbv?

[johnnydog]

Hbv?

HBV is an abbreviation for the heater bypass valve situated on the rear right side of the top of the engine. It's a scuttle off to get to - bit of a fiddle to access but not difficult. Might be easier to access on a 2.2 - I'm only going off my experience with the V6.

[terry paget]

Heater bypass valve, plastic item with three pipes and a cable attached, see picture above. To test, run engine and set heat to maximum and watch for drips below rear of engine, if no drips set to minimum and watch again.
To replace, allow engine to cool, remove header tank cap, remove scuttle, locate HBV below rear of cylinder head, heave it up with its hoses, disconnect hoses and cable, and replace with new HBV.

[Opelduude]

Started up the car and set the heat to HI and yep there is was dripping quite a lot from around the gearbox.

I have a brand new one lying around because i ment to replace it as a preventive matter but it's so tight around it that it needs to be replaced from the bottom.  So i won't be doing this without a lift.

[terry paget]

Started up the car and set the heat to HI and yep there is was dripping quite a lot from around the gearbox.

I have a brand new one lying around because i ment to replace it as a preventive matter but it's so tight around it that it needs to be replaced from the bottom.  So i won't be doing this without a lift.

On a 2.2, you can see the HBV from below, but it's a long way up, and it's difficult to get both arms up to hold the valve while pulling off the hoses. Working above means removing the scuttle, but the hoses have enough slack to allow you to pull it up, as in my picture, hold the HBV in one hand while pulling off the hoses with the other.
The hoses can be hard to remove. It helps to label the hoses.

[terry paget]

Started up the car and set the heat to HI and yep there is was dripping quite a lot from around the gearbox.

I have a brand new one lying around because i ment to replace it as a preventive matter but it's so tight around it that it needs to be replaced from the bottom.  So i won't be doing this without a lift.

On a 2.2, you can see the HBV from below, but it's a long way up, and it's difficult to get both arms up to hold the valve while pulling off the hoses. Working above means removing the scuttle, but the hoses have enough slack to allow you to pull it up, as in my picture, hold the HBV in one hand while pulling off the hoses with the other.
The hoses can be hard to remove. It helps to label the hoses.

Correction; it is controlled by a vacuum hose, not a cable, it can be seen in the pic running under my left thumb, it goes into a connector above the diaphragm.

[Nick W]

Started up the car and set the heat to HI and yep there is was dripping quite a lot from around the gearbox.

I have a brand new one lying around because i ment to replace it as a preventive matter but it's so tight around it that it needs to be replaced from the bottom.  So i won't be doing this without a lift.

It's a real stretch from underneath, so is much easier if you remove the scuttle. Possible if you don't, but that does depend on the hoses coming loose without too much effort.

[Doctor Gollum]

Easier to access than a v6, but the hoses can be a pain to get at.

[Opelduude]

None of my friends had a lift available this weekend so i decided to do it on the ground.
It went okay despite being soaked in coolant. Now i got a new problem. I managed to pull the vacuum hose free from where it enters the cabin.
It's so short that the hoses needs to be aligned perfectly on the valve for the vacuum hose to be long enough. 

[terry paget]

Bad luck. Release the spring hose clips, move them along the hoses, take the hoses off the new HBV again, grease the pipes of the HBV, then replace the hoses on the HBV, and move them around until they are all relaxed and you can replace the vacuum hose. Then replace the hose clips to hold the hoses on the HBV.

[Opelduude]

I will take of the scuttle panel this weekend to get it right.
At least the car is driveable and i don't need the heating now in June.

Thank you for all the reply's to this thread.