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[andyjstew]

Hi Folks,

I have a Vauxhall Omega 3.0 V6 24V Elite.

She has 107000 miles on the clock.

The other day she overheated and i found that it was a water pipe that was bust so i had that replaced, but the engine is still overheating and there is an exteme amount of pressure building up in the water coolent tank and also when i turn the engine off and open the watertank loads of water is pushed up and out and tons of steam comes out.

When she is sittign idling i can hear a slight hissing noise coming from the engine bay, i am not sure what this is, it has been suggested that it is the Heater Bypass Valve, If so does anyone know where i can get one of these?

Please help as i love this car to bits and want t get her runnign smooth again!

Any help appeciated.

[omegaV6CD]

Sorry to hear that,
well it can be many things but first of all check if the HBV is leaking, to do that get a torch run the engine and look at the valve so that you can spot any leaks. It is very possible due to your burst hose that air is in the system which would explain the pressure build up. To vent the system let the engine cool down completely, fill it with coolant up to the cold mark and then with the filler cap off run the engine at 2k rpm while the heater is at maximum hot. You need to wait until the thermostat opens and then run the engine for about 10 minutes (do not let it go above 100degrees.) THen switch off let it cool down again without filler cap on, fill again with coolant if needed put the cap back on and you should not see any excessive pressure build up unless there is a leak.

[Eliteman Steve]

How hot did it get when it over heated?

[rhydV6]

Was always of the opinion these systems were self bleeding so no need to leave cap off etc?

[Auto Addict]

Was always of the opinion these systems were self bleeding so no need to leave cap off etc?

So was I.

Welcome to the Forum andystew.

[JasonH]

My experience is that you definitely need to coax all the air out by running with the filler cap off, squeezing hoses etc.

[andyjstew]

I have ran her and i have squeezed all the hoses etc and i am sure i have gotten all the air out of the system, the only thing that i am worried about now is the hissing sound i can hear from the car when sitting in her just idling, do you think the heater bypass valve may have split? if if split would it cause a hissing noise? Where can i get a replacement heater bypass valve from anyways?

Cheers

[Matchless]

The cooling system is supposed to be under pressure when hot !!

Increasing pressure in the system raises the boiling point of the coolant above 100C so the system is able to cope with a wider range of operating temperatures. The cap on the header tank has a pressure relief valve built into it, if this has not lifted then the system is not overpressure.

Are you losing any coolant? if the HBV was leaking then there would be signs of coolant or staining around the gearbox bell housing (look underneath).

The hissing noise is likely to be from the breather assembly on top of engine (bit with Ecotec on it), these make quite a noise at idle, but do check that all the vacuum hoses and breather pipes are connected.

[wormnroller]

Hi, I may be off the mark here but it costs nothing to try this out...

If you can get at the radiator whilst it's warm, (avoiding the fan which could kick in at any time) carefully check that there isn't a cold area that indicates a blockage. If there is, try some radiator flush . I had this probelm on a Carlton and it took me ages to find out what it was. Eventually I had to chang the radiator but the problem was sorted instantly.
I had hissing noises too but it was the higher pressure caused by overheated coolant operating within a reduced area.

All the best

Worm

[nixoro]

Hi Folks,

I have a Vauxhall Omega 3.0 V6 24V Elite.

She has 107000 miles on the clock.

The other day she overheated and i found that it was a water pipe that was bust so i had that replaced, but the engine is still overheating and there is an exteme amount of pressure building up in the water coolent tank and also when i turn the engine off and open the watertank loads of water is pushed up and out and tons of steam comes out.

When she is sittign idling i can hear a slight hissing noise coming from the engine bay, i am not sure what this is, it has been suggested that it is the Heater Bypass Valve, If so does anyone know where i can get one of these?

Please help as i love this car to bits and want t get her runnign smooth again!

Any help appeciated.

A mate of mine had a problem where the car was overheating and when the top pipe got to a certain temperature water was forced back into the header tank and out the lid, we found it to be the thermostat not opening at temperature changed it and all was sorted maybe a similar problem you have. The above sounds very much the same problem my mate had having re-read your post again.

HTH

[omegaV6CD]

The cooling system is supposed to be under pressure when hot !!

Increasing pressure in the system raises the boiling point of the coolant above 100C so the system is able to cope with a wider range of operating temperatures. The cap on the header tank has a pressure relief valve built into it, if this has not lifted then the system is not overpressure.

Are you losing any coolant? if the HBV was leaking then there would be signs of coolant or staining around the gearbox bell housing (look underneath).

The hissing noise is likely to be from the breather assembly on top of engine (bit with Ecotec on it), these make quite a noise at idle, but do check that all the vacuum hoses and breather pipes are connected.

The coolant system is indeed supposed to be under pressure when hot which should be about 2 bar with the stat closed and about 1bar with the stat open (ish values). BUT it is not supposed to overpressurise and hold any air in it.

[andyjstew]

Hey folks,

I am still having the same problem with the engine overheating, i have fitted a new heater bypass valve and i have also flushed the radiator with soem high pressure clean water and after flushing it the car now takes instead of 15 minutes to overheat it takes about an hour, i have bought a replacement thermostat but do you thik this will sort it?

Any other ideas on things to try at all apart from fitting the thermostat which i am going to do tomorrow?

Cheers

[Admin]

2 questions...

1. When was the cambelt kit last changed? It has no direct relevance, but I just thought I would ask.

2. When was the water pump last changed? This does have a lot more relevance...

Oh, and changing the thermostat on the V6 is a git of a job.

[andyjstew]

The cambelt kit was changed about 10,000 miles ago

The water pump has never been changed.

[Markie]

ideally waterpump when cambelt changed as its the same strip down process,

also HBV check it out at back of engine, just let one go or you could have had it to test as i am in Glasgow area.

And if thatHBV goes bad its gonna leak onto DIS pack worst case! And thats a fiddly job!