Omega 3.0 V6 - mystery coolant leak - Chad.R
My Neighbours \'94 Omega Elite 3.0 saloon (auto) has developed a curious coolant leak;

He tops up the coolant in the morning when cold and drives to work (15 miles suburban), no overheating or coolant level warning lights. He checks the coolant after 2-3 hours - the level\'s fine.
He drives home in the evening (same route, same traffic conditions), when invariably the coolant level warning light comes on, but no engine overheating. At this stage you can see the coolant dibbling down in a steady drip underneath the car from a point below the middle of the windscreen\'s front edge (back of the engine block?).
In the morning when you check the expansion tank there is hardly any coolant in it.

Any ideas ? - Head gasket failure ? hope not, he won\'t be too pleased.


PS. I\'m waiting to see which Neighbour gets hit by this mystery coolant \"bug\" next. My Xantia\'s getting a new radiator on Thursday.
Omega 3.0 V6 - mystery coolant leak - Dave N
Are you sure the heater matrix is OK?
Omega 3.0 V6 - mystery coolant leak - Dynamic Dave
Are you sure the heater matrix is OK?

Surely if it was the heater matrix, then the water would be inside the car, not outside!!
Omega 3.0 V6 - mystery coolant leak - Jase
Could it be a leaking water pump?

My old Astra lost coolant in this way and I had to top it up most days like this chappie seems to.

Cheers from Jase

p.s I like Elite Omega's, good bargain barges.

Omega 3.0 V6 - mystery coolant leak - Dave N
>> Are you sure the heater matrix is OK?
Surely if it was the heater matrix, then the water would
be inside the car, not outside!!


Not if it's running out the evaporator drain tube!!!!!!!
Omega 3.0 V6 - mystery coolant leak - Chad.R
After researching this on the Backroom, I found the number for DC Auto's in Thatcham that someone had recommended as a specialist for larger Vx cars - gave them a ring and after about 5 seconds into the conversation and as soon as I mentioned "Omega...coolant...leak" it was diagnosed as a faulty "three-way-valve" and the guy described the symptoms almost exactly before I hand a chance to take a deep breath.

Phoned a Vauxhall dealer and the part costs £30, phoned (their number had been kindly provided as agood source of Vx parts by David.W in a earlier thread about same Omega) and sourced the part for £20.

So all in all not bad considering that I haven't got a clue about these things! and you never know, I may get 2 bottles of single malt from my Neighbour this Xmas!

The Backroom rules OK!

Omega 3.0 V6 - mystery coolant leak - robert
Hi Chad,

I'd be very interested to hear how you get on changing the valve as its actually behind the engine and underneath the windscreen wiper valance panel - which can be removed but is still very restricted.

I also suggest that you remove the vacuum pipe from the brake servo as it is exactly where you want to put your arm! It plugs into the vacuum servo (its a tight fit but it will pull out as it has a rubber seal), and then screws into the inlet plenum @ the other end of the pipe. Coming off this pipe (about 7mm diameter) are two small vacuum pipes - these will just pull off as they have rubber sleeves.

You must be careful here, if you try and gain access you will break one of these pipes and as the large one feeds the brake servo !!!!

Good, luck, and can you let me know how you get on as I have to do mine shortly - I've just repaired the vacuum pipe this weekend and am waiting to do the proper repair this next weekend.

Regards ........ Robert
Omega 3.0 V6 - mystery coolant leak - Chad.R

My Neighbour's going to take it to a Vx specialist - have the new valve fitted and have a service done at the same time. He also want's to check what other bits may be on the way out when it's ready for the "next" service.

Omega 3.0 V6 - mystery coolant leak - robert
Might be worth getting the plug leads done - they also route from the rear of the engine and are a pig to change!
Omega 3.0 V6 - mystery coolant leak - Highland Idler
Chad - Could you kindly bung up DC Autos 'phone number as BT don't seem to know & I can't find a DC Autos in Thatcham on the Internet (but it's probably me being stupid)

They sound usefull people!
Omega 3.0 V6 - mystery coolant leak - robert
Thats easy. Its DK not DC:

(01635) 863080

They also have a web site:

hope this helps .........
Omega 3.0 V6 - mystery coolant leak - henry k
Thats easy. Its DK not DC:
(01635) 863080
They also have a web site:
hope this helps .........

Surely one of you Omega satisfied owners should get DK into the HJ good garages list.

I think you have found a star.
Omega 3.0 V6 - mystery coolant leak - IanR
Chad - Did this cure the problem?
I also have a coolant leak at the rear of the engine on my 1999 2.5 V6 Omega although it is only minor and doesn't necesitate frequently topping up the reservoir.

The leak runs down the back of the block on the offside, adjacent to the gearbox leaving a very small drip on the garage floor but is only apparent once the engine has cooled down.

My local Vauxhall dealer has had the car in three times now and charged me over £550 to replace the coolant bridge seals at the back of the engine, a thermostat housing and a heater valve. On each occasion the system as been pressure tested. Within a couple of weeks the leak reappears.

If any one else has any ideas, would be much appreciated.

Omega 3.0 V6 - mystery coolant leak - Chad.R

Sorry for the late reply...

In my case the 3 way heater valve turned out to be leaking and was replaced (cost £20 from Autovaux + 1/2 hr labour).

However a few weeks later another very similar leak appeared and after some investigation turned out to be the heater matrix - water was leaking out of the evaporator tube (see Dave.N's post earlier in the thread) this was fixed by putting a £3 bottle of "radweld" in and going for a lengthy run. The coolant system was flushed and refilled about 2K after the radweld treatment during a routine service. It's about 7K after that now and the leak hasn't re-appeared so I assume it has been "cured".

Again it was "Dave" from DK cars at Thatham that sorted it out for me - he's seen the heater matrix problem on many Omegas and said that the radweld treatment always worked in his experience - that was good enough for me. Otherwise your looking at around 10 hrs labour to dismantle/re-assemble the dash to replace the heater matrix.

P.S. The mention of the word "radweld" on this site is enough to spark some colourful debate, so I never did! :-)

Omega 3.0 V6 - mystery coolant leak - IanR
Thanks Chad - I was particularly interested in your comment of only 1/2 hour to change the valve as my dealer charged me £150 for labour - which was a reduced price. They told me it was a 4 to 5 hour job. Time to go back and see their service manager I think.
Omega 3.0 V6 - mystery coolant leak - Chad.R

The heater valve was replaced by DK cars and as the car was being serviced at the same time, to their credit only charged me for the actual time it took to replace the valve i.e 1/2 hr. The job involved removing the wiper arms to access the rear of the engine and Dave (DK) did say that he has this down to a fine art and can do it in around 30-40 mins. Though some can take considerably longer.

A main dealer may have a set price for this ...

Good Luck.

Omega 3.0 V6 - mystery coolant leak - rileyrm
I would recommend any Omega owner to be aware of this poorly engineered 3 way valve if they get a coolant low light up. It should never have been positioned in the rear of engine area where it is impossible to get easy access to.

Omega 3.0 V6 - mystery coolant leak - BodgeJob
For the record this failure manifests itslf in many ways. Having never had any previous problems with water leaks, I returned to my car an hour after parking it to find a fair stream of coolant running down the street. Having topped the coolant up with about a 2 litres of water I was not expecting to get the 30 miles home without having to repeat the operation if not get breakdown assistance. Especially as it was a hot day.

30 minutes later pulled up on the drive at home relieved at not having had to stop. Lifted the bonnet (with engine running) to find the level had not dropped at all! Switched off engine and coolant immediately starts pouring out.

Seems the valve is vacuum controlled and if hot water is not needed to the matrix the valve is closed. Switch off engine loose vacuum and leak restarts. Call to Vx dealer to enquire about valve and adjacent hoses (not sure at that time what had failed) to find hoses were not kept in stock. They did however have 5 three way valves. Says it all really. Took me about 2 hours in all to replace having removed the induction hardware (already removed it once before so knew what I was doing).

Omega 3.0 V6 - mystery coolant leak - smokie
I am losing coolant. I spoke to DK Cars who guessed poss 3 way vavle and it was booked in to be looked at next Wed. I am checking the coolant level before each journey and topping up if required. (and I've noticed that it doesn't seem to be losing it on every journey - each journey being about 100 miles or more).

So this morning I get ready to check the coolant and the bonnet won't open - cable stretched.

So, to the point. I was almost passing Thatcham today so I dropped into DK, hoping for a quick fix to the bonnet problem so I could struggle through to next Wed with some confidence. Anyway, Dave (for it was he) had a look immediately and said he didn't believe it was the 3 way valve. On releasing the coolant cover, the level shot up to overflowing - and I had only filled it to the line the other day (poss air lock???). He put a pressure device onto the coolant tank and pumped it up, but this didn't cause any leakage. He topped it up with Vauxhall anyifreeze.

The conclusion was that it is probably an intermittent leak somewhere (Radweld?), and on his recommendation I have changed the coolant cap.

So I am to monitor it and see what happens over the weekend. It is still booked in for Wed, but I will call him on Tuesday with observations. Oh, and while I wasn't looking, he sorted out the bonnet cable too.

And the cost for all this, on an unannounced visit? Zilch. I am glad I live in this area as he will definitely see me again (although not TOO regularly I hope!).

I will update the backroom once I have found out more...
Omega 3.0 V6 - mystery coolant leak - smokie
I am still losing coolant. Dave is away right now, so any ideas from here gratefully appreciated. So far it has had pressure test, new cap and Radweld.

After using Radweld it didn't lose any for about 4 or 5 days. Which I am thinking is coincidence. Since then, every so often it needs about 1 and a 1/2 pints to fill.

Today was the oddest experience so far. 80 mile round trip, so I checked it and topped up before leaving and within 10 miles the coolant warning light was on. Keeping an eye on engine temp I continued the journey. At the other end, immediately before setting out, I topped it up to the line. Within about 4 miles, even before the engine had reached proper operating temp, the coolant warning came on. Journey completed successfully.

So I'm starting to think it's a sudden "dump" of a fairly specific amount of coolant rather than a slow leak. Maybe a blockage, causing it to overflow?? Which then clears?? Is this possible? Or does anyone have a better idea?

The engine is running at normal temp all the time so I don't suspect the thermostat.
Omega 3.0 V6 - mystery coolant leak - Sooty Tailpipes
This sounds like the head gasket.
The engine will consume the water via the combustion chamber.
It will also pressurise the cooling system with combustion hases, so all the hoses ballon making the level go low, and rise when the cap is undone and the pressure relieved.
Also, the return to the reservoir tank via the thin pipe near the cap will pump coolant against the cap, so any venting via the cap will also expell coolant (bad design)

When you next need to top up, top the bottle up right to the top, leave the lid off, and rev the engine to about 3000rpm, and see if the water being returned to the reservoir via the thin pipe has bubbles in, as you have overfilled, and there is no pressure in the system, you may see a stram of bubble coming into the water via this pipe, if so, it is probably leaking from a cylinder or two.

Omega 3.0 V6 - mystery coolant leak - smokie
Thanks Sooty, will try the trick at next convenient opportunity and report back...

Head gasket sounds expensive :-(

But not as expensive as a cracked cylinder I guess.
Omega 3.0 V6 - mystery coolant leak - smokie
Further browsing here reveals the oil cooler problem which seems similar to mine, and will cost around £400 to fix. My car will go to DK @ Thatcham for a proper job!
Omega 3.0 V6 - mystery coolant leak - smokie
That's this one
Omega 3.0 V6 - mystery coolant leak - smokie
Well I tried the suggestion. Thedre certainly weren't lots of bubbles coming up the small tube - in fact, none for most of the time then just a few small ones in a line.

I then did a 80 mile journey and the coolant low light didn't light up. A colleague parked next to my car about 10 minutes after I had parked, and came into teh building to say that my car was leaking water. Later ibn the day when checking it, the level was normal (remember it was overfilled at the start of the journey).

Left work that evening and within about 20 miles it had lost enough coolant to trigger the coolant low warning.
Omega 3.0 V6 - mystery coolant leak - geoff C
I have it on good account that the most common cause of water loss on V6 Omegas, apart from the infamous heater shutoff valve, is the oil coooler cover seal.

This is a face joint with sealant. The oil cooler connections also pass through it. If this leaks most of the water runs down the sides of the bell-housing, leaving tell-tale deposits as it evaporates. It is otherwise difficult to see. See
Omega 3.0 V6 - mystery coolant leak - smokie
Took the car back into DK Cars Thatcham today to have the three way valve changed (as it was the cheapest of the options, and some static tests led Dave to believe it was at fault after all).

Despite coming off a 20 mile motorway drive to get there (i.e. hot engine) Dave completed the work for a very reasonable price in under two hours.

I can't recommend them highly enough as Omega specialists- D K Cars, 01635 863080. And thanks to the Back Room for help and advice too.

I now have a new problem...but will start a new post.
Omega 3.0 V6 - mystery coolant leak - ST3V3
Hi people,

This 3-Way valve, has anyone got a Vaux part number for it please?


Omega 3.0 V6 - mystery coolant leak - Chad.R
Sorry don't know the part No. but when I rang around Vx dealers asking for "Omega 3-way heater Valve" they all knew what I referring to.... about £20+VAT IIRC.

Omega 3.0 V6 - mystery coolant leak - smokie
...and if you live anywhere within a reasonable radius of Thatcham call D K Cars (I travelled about 30 miles, no regrets )and ask if Dave can do it for you. He has them down to a fine art. I can't imagine anyone could do it quicker. From what I've read it would take a DIYer a day to do what he does in a hour...
Omega 3.0 V6 - mystery coolant leak - Juststarted


I have the same issue, with my MV6 it no water on the motorway driving. But leaks from behind the engine onto the floor after driving 3 miles to a Supermarket. It seems the more runs with the fan keeping the car cool, the more often leaks appear on the floor.

I have bought the 3 way valve for £15 and I am hoping it is the problem, the next step would be the oil cooler which i am told is a much bigger deal to change.

It is annoying though, that so many vital parts of the car are located behind the engine of an Omega, where access is nearly zero.

Apart from these issues, I do think they are good cars, parts are cheap and the fuel consumption is good for such a big car from the 90's.

Any instructions on how best to access this valve would be helpful though, as my mechanical knowledge isn't fantastic.

Omega 3.0 V6 - mystery coolant leak - Collos25

Has the car got air con because it sounds like water coming from the evaporator which is quite normal.


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