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[Paulus]

I have been having a problem with coolant dissapearing somewhere. There are no external leaks, but I have to top of the tank every 100-200 miles or-so.

Yesterday, when topping it up, I got a strong smell of petrol from the expansion tank when I took the cap off. Is that something hinting at impending doom or could it be nice and simple (like me)?

[TheBoy]

I have been having a problem with coolant dissapearing somewhere. There are no external leaks, but I have to top of the tank every 100-200 miles or-so.

Yesterday, when topping it up, I got a strong smell of petrol from the expansion tank when I took the cap off. Is that something hinting at impending doom or could it be nice and simple (like me)?

Is performance down? If firerings let go, normally a lack of performance is noticible.

[Paulus]

There's no noticable reduction in performance...it still hauls ass. It's been losing water for a couple of months now. It's not got any worse, there's no noticable smoke on acceleration and on the whole, it runs really well (I'd like to think that this is down to the 5K oil changes). I averaged 38mpg when crusing home from Chester yesterday at 60mph.

It's really worrying me now as I am going on holiday in a couple of weeks...driving to Lands End.

[philhoward]

Start the car from cold with the expansion cap off..Look for a trickle of bubbles (like you get from a glass of coke/etc).  Bubbles = bad, alas...
Might not start bubbling straight from cold..so leave it for a couple of minutes.

Gush of bubbles = really bad...empties the header tank if you rev the engine (like i had on a BMW 318is i was trying to diagnose) = really, really bad!  ON that BMW, it only had compression on 2 cylinders, though...

A gasket to coolant leak doesn't always manifest itself in a loss of performance - water injection!

[Paulus]

Oh good. So it could be the head gasket then...

I will have to test the bubbles thing at lunch time. I'll look forward to it. I know that it doesn't gush out, but as you say, there may be small bubbles.  

[philhoward]

As you've probably read from on here, HG issues are very rare on V6's - water loss is usually HBV/coolant bridge.

Just out of interest - does it retain pressure in the header tank overnight/standing?  BTW, it should do...

[Paulus]

As you've probably read from on here, HG issues are very rare on V6's - water loss is usually HBV/coolant bridge.

Just out of interest - does it retain pressure in the header tank overnight/standing?  BTW, it should do...

Now that's a very good question. IIRC it does, but I will confirm tomorrow morning when it has had a rest.

I know that the HBV isn't leaking. I have only recently replaced it (in the hope that it was leaking). It made no difference. As for the coolant bridge, how and where do I check that?

[philhoward]

I'll have to throw in the towel here, as i don't have a V6......but i gather most of the "prime suspects" are much easier to get at/see with the plenum off...awaiting help from a V6 guru (like JamesV6CDX)..

[Paulus]

Well you've done a grand job so far.

COME ON JAMESV6CDX (or similar)!!!!  

[TheBoy]

Usual places for v6 coolant leaks:

HBV (behind 1/3/5 bank)
Water pump seal (front of engine)
Stat housing (in the valley)
Oil Cooler plate (in valley)
coolant bridge dowty washers (in the valley)
Radiator
Transfer pipe (rear of engine)
If the hoses have gone soft, any of them, particularly one from HBV to coolant bridge
back of 2/4/6 block on 1998 3.0l, HG.

[Paulus]

Thanks for the help guys. I'll have to wait till the weekend as I work away from home...currently in Swindon designing Pay-and-Display machines (don't hate me)...and I haven't got any tools here.

[Andy B]

It must be in the air. My car has decided to join in losing coolant. I noticed it was a little low last week after we got back from a weekend up in a field near Grassington - about 50 miles away - so I topped it up. I used the car today for the first time since then, and the 'low coolant' message came up. I'm about 1" below the mark but as in other cases, no obvious signs of loss.
If any one sees a black Omega, fastened to a caravan, with the bonnet up on the hard shoulder heading south on Saturday morning .... it'll be me!  
I just have a feeling it's my water pump as I think I saw the odd bit of water 'spitting' up towards the bagpipes at the front. Oh well! Ce la vie!  

[markey mark]

dont leave water pump mate if it fails you will be in the $hit  

[Andy B]

dont leave water pump mate if it fails you will be in the $hit  

I know!   I shall be under the bonnet in the morning - weather permitting - looking for where my water is escaping. A failed water pump is the last thing I want while we're so far away from home with a caravan and with no recovery  :-?

[Andy B]

Can't find anything obvious, but with the bonnet up & the engine running I was very aware of the 'fan belt' tensioner bearing being as dry as a witches .... . With the belt removed to remove the roller (seal popped off & a little grease added) I can feel some play in the pump.
I eventually managed to order another pump from the dealers - had to go down there in the end   - so I'll start stripping it down.