V6 pressurising coolant massively

[SD1too]

Originally Posted by FrazzleTC

The car has had its coolant flushed several times, yet persistently uses a lot ... Today, it boiled ... It is now sitting around 100-105 degrees in traffic ... Time to scrap this engine, I think?

No. Your evidence suggests that the cooling system isn't sealed; in other words there's a leak. That's where the coolant is going, and that's why your running temperature is so high (because there's no pressurisation).

The other possibility is that the oil cooler is blocked with K-seal. You haven't mentioned that you've removed this and checked it. It's in a critical position, and if the coolant flow is impeded the tempertaure will rise and be ejected through the expansion tank cap.

After any work, the cooling system should be bled by raising the expansion tank as specified by MGR. If this isn't done, air locks can occur leading to overheating.

Simon

[Jules]

Oil cooler is favourite.
Flushing won't help.
Sounds like internal pin hole in cooler.

Fairly easy to replace.

[T-Cut]

So where's the residual cold coolant pressure coming from?

The car can be left sitting overnight and there is still a lot of pressure when the cap is removed.

TC

[murphyv310]

Hi Fraser.
Before you condemn the engine for HGF. I would bypass the oil cooler, mine has been like this for months and I have no intention of re connecting it, if you live in Spain or Aussie land yes but not in this cold place.
Make sure there are no external leaks and refill the cooling system with the correct bleeding procedure.
I really thought MFL was suffering the same fate as your dads but mine is 100%. Incidentally fit a thermostat with a jiggle pin, some don't and they wont bleed correctly, that's the reason for having one in the first place. You'll hear the jiggle pin if you shake the thermostat.
Pockets of air seem to keep the system pressurised overnight, perhaps due to spot boiling.

[kaiser]

If there is substantial pressure left in the system after having stood overnight, there is only one explanation, exhaust gases in the coolant.

so make sure your diagnosis is right!

[cooper.mg190]

This was one of the problems I had,

After completely bypassing the oil cooler, the coolant no longer flows out the cap, and never gets above 102c,

This is all i did.
and the parts I used,




I should add, thats only a temporary position, it will be mover soon,

and the parts

http://www.ebay.co.uk/itm/Aluminium-...lF198ByGZ-FVFA

http://www.ebay.co.uk/itm/Blue-Silic...Pgx8MKm5X1QdhA

Hope you get it sorted

[murphyv310]

I removed the metal coolant rail pipes and only used one short length of alloy tubing for the "Bypass"
I've monitored the oil temperature with a contact gauge, although not 100% accurate its close enough, the temperature stays well within spec even when I towed a heavy trailer a couple of months ago.

[Jules]

Pulling at straws here but check both inlet manifold coolant bleed pipes are not blocked also small
Make sure header tank bleed stub is clear also.

We've cured only a couple of pressurising KV6's over the years so it's not common but possible.

[Ross R75]

My first KV6 had this problem. I bypassed the oil cooler for both oil and coolant and the problem went away. It never ejected much coolant, and certainly never from the expansion tank, but it was losing it somewhere, and the amount of mayo under the oil cap wouldn't have done KFC proud.

Try bypassing the cooler, the later ones are a different design and easier to do. If that doesn't fix it, it sounds like a dropped liner or cracked head to me. There should be no mayo under the cap on a car that does 500 miles a week.

Sadly, I won't own another KV6 because of this issue. I'd rather just have a mapped 1.8T, they're quicker and a lot easier to fix if they suffer HGF.

[murphyv310]

Originally Posted by Ross R75

My first KV6 had this problem. I bypassed the oil cooler for both oil and coolant and the problem went away. It never ejected much coolant, and certainly never from the expansion tank, but it was losing it somewhere, and the amount of mayo under the oil cap wouldn't have done KFC proud.

Try bypassing the cooler, the later ones are a different design and easier to do. If that doesn't fix it, it sounds like a dropped liner or cracked head to me. There should be no mayo under the cap on a car that does 500 miles a week.

Sadly, I won't own another KV6 because of this issue. I'd rather just have a mapped 1.8T, they're quicker and a lot easier to fix if they suffer HGF.

Sadly I agree.
The V6 is a beautifully smooth unit and sounds wonderful under load but that is as far as it goes. The Turbo 1.8 is light, flexible and powerful. Not only that its got plenty of room round it to make repairs easy!