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[Bumbazor]

Is there any way to bypass the hbv?

The reason is that I replaced it for new after suspecting the original as the cause of a coolant leak. It still leaks coolant which drips under the car near enough directly under the hbv. When I had the car on axle stands I noticed it dripped toward the lowest side whenever the car was tilted.

Apart from the coolant pooling somewhere and dripping over the side of whatever it's collecting on I don't know what else could explain it, and I want to try removing the hbv altogether before I investigate further. Also I'm getting strange characteristics from my heating system which makes me suspect the hbv initially.

[Kevin Wood]

Sounds like one of the hoses up there has perished.

Was the new HBV a genuine one? GM markings?

Whilst they are a relatively common failure item they aren't bad enough to warrant hacking the plumbing around (and putting up with heater either on or off) IMHO.

Kevin

[Andy H]

If you must swap out the HBV then a motor factors will sell you a T piece for connecting the heater hoses together. If you follow that route though you are pretty much guaranteed pain & frustration as you seek the elusive leak(s).

Either beg/borrow/make a pressure test kit and pump the system up to operating pressure. With a cold engine leaking coolant won't evaporate and will be easier to trace. You can dismantle the inlet manifold & see the top of the oil cooler and the coolant bridge.

A pressure test kit cost about £200. I made my own by using the pressure cap from a Carlton to which I fitted a tyre valve. I use a bicycle pump to pressurise the system.

Good luck.

[RossMk2]

I am also having some sort of a coolant leak, nothing majour but its enough to keep the bottom of the heads wet and the gearbox, the conversion into my astra mk2 has no HBV its as already stated got a T-piece to connect the hoses. Im trying to find the leak, you say i can remove the intake and there is a coolant bridge there that could be the cause?

[feeutfo]

I am also having some sort of a coolant leak, nothing majour but its enough to keep the bottom of the heads wet and the gearbox, the conversion into my astra mk2 has no HBV its as already stated got a T-piece to connect the hoses. Im trying to find the leak, you say i can remove the intake and there is a coolant bridge there that could be the cause?

Yes. Plenum off, injector manifold off, plastic inlet off, to reveals oil cooler cover plate etc. Oil cooler is cooled by a coolent run from cam belt end through stat housing to water pump to oil cooler chamber to coolent bridge to exit at the rear(side on yours) to where hbv would normally be. All can leak and usually coolent exits at coolent bridge end. Also check core plugs in cylinder head, which i guess would be easier to check on your Astra than on Omega perhaps?

[feeutfo]

re hbv, would def rather have a properly working heater and risk the odd leak imho.

[Bumbazor]

If you must swap out the HBV then a motor factors will sell you a T piece for connecting the heater hoses together. If you follow that route though you are pretty much guaranteed pain & frustration as you seek the elusive leak(s).

Either beg/borrow/make a pressure test kit and pump the system up to operating pressure. With a cold engine leaking coolant won't evaporate and will be easier to trace. You can dismantle the inlet manifold & see the top of the oil cooler and the coolant bridge.


I did the pressure test. With the engine off pressure was maintained with no leak. Only when the engine is running does the leak occur.

Looks like I'll be checking the hoses this weekend!

[Andy H]

So your thinking is that it has to be either something that leaks when it gets hot or when it moves (such as the vacuum operated HBV) ?

I won't insult your intelligence by asking if it is water that has come from the air con condense drains or from a flooded bulkhead because you have already said it is coolant.....

[Kevin Wood]

Worth bearing in mind that a failed HBV often only leaks in one position. With the engine off, there'll be no vacuum supply to actuate it, so we know what position it will be in.

With engine running, it could be in either position, so may start leaking.

Kevin

[Bumbazor]

So your thinking is that it has to be either something that leaks when it gets hot or when it moves (such as the vacuum operated HBV) ?

I won't insult your intelligence by asking if it is water that has come from the air con condense drains or from a flooded bulkhead because you have already said it is coolant.....

Deffo coolant as I have collected it and its pink. Also coolant level drops when this happens.

[Bumbazor]

Worth bearing in mind that a failed HBV often only leaks in one position. With the engine off, there'll be no vacuum supply to actuate it, so we know what position it will be in.

With engine running, it could be in either position, so may start leaking.

Kevin

That sounds reasonable. But as I replaced the hbv with genuine, and as said earlier I'm beginning to suspect one of the three pipes. In particular the one that isn't 'active' with the engine off like you say.
Any ideas which one this will be?

[Kevin Wood]

Hmm. :-/ Can't remember which way round the HBV works.

Both pipes will still be "open" to the pressurised coolant regardless of which one actually has flow through it so I'd have thought the position of the HBV would have little impact on a leak from a hose..

Kevin

[RossMk2]

I am also having some sort of a coolant leak, nothing majour but its enough to keep the bottom of the heads wet and the gearbox, the conversion into my astra mk2 has no HBV its as already stated got a T-piece to connect the hoses. Im trying to find the leak, you say i can remove the intake and there is a coolant bridge there that could be the cause?

Yes. Plenum off, injector manifold off, plastic inlet off, to reveals oil cooler cover plate etc. Oil cooler is cooled by a coolent run from cam belt end through stat housing to water pump to oil cooler chamber to coolent bridge to exit at the rear(side on yours) to where hbv would normally be. All can leak and usually coolent exits at coolent bridge end. Also check core plugs in cylinder head, which i guess would be easier to check on your Astra than on Omega perhaps?

Thanks mate, will have to rip it all off and take a look, what parts would possibly need changing? As i dont want to be stuck with the engine in pieces and have to wait 2-3 working days for parts! hehe

Also the conversion was done by another Astra Mk2 go'er and i have never quizzed him about the missing HBV as i have not long realised it! What does it acctually do and can you see any reason why it would have been dumped in mine?

[Andy H]

Difficult to predict what the cause of the leak will be. Worst case is the head gaskets (this happened to me, the head gaskets were wet with coolant but it wasn't leaking into the cylinders or oilways). If you want to reseat the coolant bridge you will need a couple of new sealing washers for the two hollow bolts (4 total). If you want to reseal the oil cooler you will need to disconnect the oil pipes (a pig of a job on an Omega but might be relatively easy if your oil filter is facing forwards). The aluminium plate is sealed using a tube of mysterious Vauxhall sealant and you will need new sealing washers on the oil cooler nuts. (I think there were 4 for the coolant & 2 for the oil).

In an Omega the heating/ventilation/climate control are controlled by vacuum solenoids. When the heater flap is shut the HBV bypasses and allows the heater matrix to run cold. If your Astra doesn't have vacuum controls it probably can't use the HBV.

[Stu_Bart]

A pressure test kit cost about £200. I made my own by using the pressure cap from a Carlton to which I fitted a tyre valve. I use a bicycle pump to pressurise the system.

I did the same thing after replacing the HBV and still had a leak used the above method and found the leak it was a pipe that went to the water bridge between the heads at the back under the scuttle.

All sorted now ....just an MOT to get through next month.

Stu.