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[mong00sehun]

Hi guys,
i have a clue, maybe my heater always hot when the car is running because of the heater bypass valve is always 'open' so there is no vacuum. And its blowing hot air to my feet. So where can i find the HBV?  I read some topic about it, they said its behind the glovebox, but i have an Opel Omega soooo i have the steering wheel in the normal position (on the left side  ), the HBV still behind the glovebox?
thx

[Doctor Gollum]

It's in the engine bay on a bracket behind the #5 cylinder. It's in the same place on every petrol Omega.

[RallyArde]

I think the easiest way to gain access to HBV, is to take cabin filter off and then there should be kind of hatch. After removing that hatch you are able to see the HBV and hoses that are coming to it. Also (in 4-cylinder models) you can get to it underneaht the car.



If you have V6 you might want to remove scuttle panel and plenum as well to get more room/visibility.

[mong00sehun]

yeah thx guys i found it. so how can i test it? or what happens if i just remove the plug from the additional water pump below the water tank? if there is no water flow i think to the heater matrix dont heat up sooo...

[Doctor Gollum]

That pump is to provide cabin heat whilst stationary/engine off whilst there's enough heat in the coolant.

The HBV can be tested by applying a vacuum. Normally they leak externally, but a failed diaphragm is also a reasonable possibility.

For the effort, you may as well just replace it 

[mong00sehun]

sorry i am noob to vacuum things  . so if i remove it how can i test with homemade stuff?

[Doctor Gollum]

A rubber hose, such as the one attached to the top of it, and suck.

You'll hear if it's working or not.

But, given their cost, likelihood to fail and faff involved removing it, it's a no brainer to fit a new one.

[mong00sehun]

thx i ordered the new one. it will arrive on monday. we going to croatia at tuesday morning, so ive got one shot 

[mong00sehun]

i changed the HBV its good i think, but there is no vacuum at all.

[Doctor Gollum]

Follow the vacuum line up under the scuttle and there should be a box there. From memory there's also a vacuum line to the same place from the brake servo/plenum pipe.

The box is switched electronically by the climate/heater panel and applies a variable vacuum to the hbv to control flow to the heater matrix.

[TheBoy]

In the Maintenance Guides section there is a vac diagram for both types of vac system used.

Not uncommon for the inbuilt one way valves in the vac tank(s) to fail.