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Discussion Starter #1
My first post, only found this site a week ago and I've been reading ever since. I have an omega 2.5 td cd (estate), all was well until 2 days ago, done about 3000k since buying it (kilometres, it's an opel), when I looked under the bonnet to check oil / water / fluids before returning from France to England.
Fluid levels were fine, then I noticed a constant leak (engine just switched off) from the heater bypass valve. I (foolishly it turned out) whipped it off, checked it visually, couldn't see where the problem was so thought I'd replace it until I could get a new 'un.
Valve back on, fill up the header tank, start the engine and pump away at the top hose to clear the air. I now have no heating, engine idles at about 97 degrees and if revved the coolant gushes out of the header tank. I thought I maight have a leak from the valve, so swapped it for a piece of straight pipe (bypassing the bypass) - no difference.:cry:
I now have:
  • serious overheating, previously it never got above 90, now it idles at 95-97, under load it quickly boils
  • heating works intermittently, usually blows cold air, got 5 minutes of hot this evening whilst testing (messing)
  • water in header tank never seems to get that hot
  • still starts fine, sounds and runs fine until it overheats, then won't go over 2000 revs in top (limp mode?)
  • if revved when cap off it will gush water out of the header tank
  • no mayonnaise on the dipstick or oil cap, but I have noticed oil seeping down from the filler cap (don't know if this is new or related)
  • :cry:
I went to a garage today, they looked over the car for 10 mins and diagnosed head gasket immediately. If so then fair enough, but could it be something else? - i don't want to pay out a fortune for that and find the same problems still there.
I had a chat with an english mechanic (mate of my dad) over the phone, he suggested first taking out the thermostat and then try changing the water pump to see if any change. Does this sound right, or is it bound to be the head?:mmmm
Now the big one:
I'm a mechanical numpty - can follow instructions in Hayne's as long as there are pics to guide but no real experience. I wouldn't recognise the thermostat and water pump if they jumped up and bit me on the bum!
Could anyone tell me where they are found on the 2.5td (1998) engine, what they look like, are they easy to get to (photo would be too perfect but you never know):D
If so I'll try changing them, if not it's get the French dictionary and the credit card out.
Apologies for the length of the post, I didn't want to miss anything (but probably have)
Thanks
 

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Omega Tank Commander
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Number one rule of fault fixing......correct the obvious first.......fit a new bypass valve.

I assume the engine has not been run without coolant.

The valve has three pipes on it so how did you bypass it, did you bung one of them up?

It also has a vaccum line to turn the coolant flow on and off....

Remember that what might appear to be boiling water might simply be lots of air getting out of the system.
 

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Discussion Starter #3
Marks DTM Calib said:
Number one rule of fault fixing......correct the obvious first.......fit a new bypass valve.

I assume the engine has not been run without coolant.
No, it's been filled up all the time, got nearly to the red a couple of times before shutting down. Not been too hot yet, touch wood.:rolleyes:
I'll fit a new one asap, trouble is in the middle of the french countryside it's not so straightforward - I was supposed to be in England yesterday, mum-in-law's 60th approaching fast and my name is becoming muddy.:shame:
The valve has three pipes on it so how did you bypass it, did you bung one of them up?
This one has only two pipes plus the vacuum, so used a piece of straight pipe and jubilee clips.

Remember that what might appear to be boiling water might simply be lots of air getting out of the system.
It seems to correspond with 100 on the guauge though.


Thanks for the quick reply.
 

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Welcome :)

Do as Mark says (he knows most things) - new hbv is about £26, most dealers stock them (common fault). May as well do a full coolant flush whilst you're at it as well....
 

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Discussion Starter #6
TheBoy said:
Eh? That aint the hbv then...
I don't know what else it could be. Two hoses both running from the direction of the heater matrix, going into the 'valve', round shape with pipe either end and an arrow on top which pointed backwards (towards the matrix),a vacuum tube on top. When vacuum is applied the valve closes. After the overheating started I first blocked both tubes, made no difference to the engine but heating inside the car was non-existent; I then (5 mins later) put the straight pipe through, you can now feel heat at the vents, when the fan is switched on most often it cools down fairly quickly but this evening it gave proper heat for 5 minutes.
I've seen pics of these valves with 3 pipes, this looks very similar but with 2 (plus vacuum). Could it be anything else?:think
 

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Maybe the diesel ones are different then, though can't really see how that would work. Certainly the one on my V6 is a 3 pipe affair, plus vacuum. Hopefully one of the diesel guys will be able to confirm...?
 

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Discussion Starter #8
TheBoy said:
Maybe the diesel ones are different then, though can't really see how that would work. Certainly the one on my V6 is a 3 pipe affair, plus vacuum. Hopefully one of the diesel guys will be able to confirm...?
Hopefully.

Anyone know where the thermostat / water pump are on the 2.5DT?
I imagine it's different to all the others being the BMW lump, but can't find anything on the site. I've got a TIS cd but it's in Hinckley!!!
 

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Discussion Starter #9
Many thanks to all those who've replied. Well I followed advice and fitted a new heater bypass valve this morning. Car is no different but:
I checked the expansion tank and water was stone cold when guage was reading 95, after 15 minute drive (engine between 95 and 98 mostly, never reached 100) the water in the expansion tank was still only lukewarm. So I'm now thinking thermostat is the next place to try???
Anyone know where it is?
 

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trogggy said:
Many thanks to all those who've replied. Well I followed advice and fitted a new heater bypass valve this morning. Car is no different but:
I checked the expansion tank and water was stone cold when guage was reading 95, after 15 minute drive (engine between 95 and 98 mostly, never reached 100) the water in the expansion tank was still only lukewarm. So I'm now thinking thermostat is the next place to try???
Anyone know where it is?
Front left of the engine from standing in front of it, just follow the large water hose from the radiator. Oh and another thing, check your water pump just in case it's busted as BMW in their wisdom used a plastic impeller!!:turd
 

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Discussion Starter #11
DC3 aero said:
Oh and another thing, check your water pump just in case it's busted as BMW in their wisdom used a plastic impeller!!:turd
Spot on that man.
The water pump was absolutely knackered (plastic blades, looked just like yours DC3).
Had to leave the omega in France, so only just running again, touch wood it's fine now as it never seriously overheated.
Thanks to all who replied.
Dave
 
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