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[cwill144]

A few weeks ago I went to London and my 3.0L MV6 overheated.
I topped it up and it has ran fine. But ever since it has been using water.
Can’t find a leak anywhere but needs about 2l of water a week. There is no water in the oil, or oil in the water. Has anyone experienced anything similar on a V6? The only think I can think of is the head gasket and it is burning off the water.
Have already changed the engine twice so if I can’t sort the issue may have to scrap the car.
Thanks.

[Doctor Gollum]

If your go to reaction is headgasket, no wonder you keep replacing engines

More obvious places to look, in no particular order:

Coolant cap. They fail.
Coolant bottle. They crack around the neck, almost impossible to spot.
Radiator leak, usually the left hand end where the thermos witches live.
Heater core. These fail if poor coolant maintenance has been a theme
Heater Bypass Valve. These are a service item. If adjusting the cabin temperature to HI or LO reduces the leak, then it's the HBV. Every time.

[cwill144]

Thanks for the info, the 2 previous engines one had the big end go, and the other a massive oil leak so changed to the current one. I still have old one in my garage.
When it first over heated it was dry for a couple of weeks, and there were never any wet patches on the ground. The HBV was replaced a couple of years ago along with all the hoses when the engine was fitted and a new radiator.
I will check all the things listed above, but can’t find a leak. Any more ideas would be great.
Thanks

[Nick W]

You need to do some proper testing:


leak down test, and check that the pressure isn't leaking into the cooling system - that's caused by head gasket (or worse) failure.


cooling system pressure test. Allows you to investigate where the pressure is going(if it is!) without the engine running.


Sniffer test in the coolant for combustion gasses - a different way of achieving the first result.


Pull the spark plugs and see if any of them are getting steam cleaned -do this first as it's quick, easy and free


The only repairable massive oil leak that can't be fixed for less work and expense than changing the engine is the crank rear main seal - that requires removing the engine or gearbox.

[robson]

I have just replaced the water pump for a similar problem. Antifreeze seen on front centre engine shelf

[robson]

I see you are from Oxford talk to JamesV6CDX

[JamesV6CDX]

Just seen you’re in Oxford. A stones throw from me.

I will diagnose this free of charge. Methodical diagnosis - inlets off, car raised, and system artificially pressurised, to accurately find the leak.

The 3.0 DOES suffer HG problems on the 2-4-6 bank in the rear corner (especially 1998 models for some reason) - and this will happen more as time goes on, because the gaskets are composite items which deteriorate in time (depending on coolant maintenance)

But as has been rightly pointed out there are more, much likely candidates.

PM me your number / WhatsApp or similar and we will sort it. I’m on the Oxfordshire border

[JamesV6CDX]

Just seen it’s a 1998 3.0.

And has overheated.

I’m not saying that condemns the HG by any means but I’m sure TheBoy will add his experiences soon

Even if it’s the HG it’s really not a bad fix and definitely not worth scrapping a good omega for. I’ll do it

[cwill144]

Pm sent. Thanks for all the advice.

[JamesV6CDX]

Sent you a text message

[Doctor Gollum]

The car has had two engines, chances are the engine isn't the one prone to HG failure, and they tend to leak externally... for the reasons MarkDTM outlined a few years ago

[YZ250]

Just seen it’s a 1998 3.0.

And has overheated.

I’m not saying that condemns the HG by any means but I’m sure TheBoy will add his experiences soon

Even if it’s the HG it’s really not a bad fix and definitely not worth scrapping a good omega for. I’ll do it

Obviously check the places mentioned in previous posts but I had one of the same era (although I see you’ve swapped the engine previously) and my head gasket had rotted away on the rear outer corner of the 246 bank. Took me a while to find as, like you, I had no drips on the floor. Tell tale sign in the end was milky water marks on the rear side of the block, immediately below where the cylinder head and block meet. The engine heat was evaporating the leaking coolant before it could drip. When I took the cylinder head off, the gasket rear outer corner had rotted outwards, so engine performance and the cylinders were not affected.

[JamesV6CDX]

If your go to reaction is headgasket, no wonder you keep replacing engines

More obvious places to look, in no particular order:

Coolant cap. They fail.
Coolant bottle. They crack around the neck, almost impossible to spot.
Radiator leak, usually the left hand end where the thermos witches live.
Heater core. These fail if poor coolant maintenance has been a theme
Heater Bypass Valve. These are a service item. If adjusting the cabin temperature to HI or LO reduces the leak, then it's the HBV. Every time.

Pleasure to meet you today

Turns out to be two leaks in different places. Both of which were in Dr G’s list

That’s a very nice car you have there especially in manual form. So pleased it’s nothing terminal