KV6 - Oil emulsification / coolant loss.

[Sebastienclement]

Hi all.

I have a 2.0Kv6 which a family member has been running for the past 2 years... It has needed a fair amount of TLC in the cooling department, and has now had the following completed:

• Waterpump
• Thermostat Assembly
• Header tank cap
• Radiator (old one found to be leaking)

A couple of months ago it developed a slight lumpiness on a cold start, and around the same time re-developed it's appetite for coolant. Previous to the above work being done, it did overheat on 3 occasions (OBD showing temps of 115'c / 118'c), the final time it threw most of it's coolant out through the header tank. The final time it was recovered where the garage found a leaky radiator, that was "pulling air into the cooling system and over-pressurising it".

I now have the car in my care to try and get to the bottom of the problems. At present the symptoms are:

• It's not running on all 6 cylinders from a cold start. This clears in a maximum of 4 seconds to smooth running.
• The car is losing coolant, however it seems to be losing coolant when the car is left to stand. It has covered 200 miles today, and the coolant was checked 3 times during the trip - no loss.
• There is emulsified oil present under the oil filler cap. Not a lot, but enough to be a worry.
• The car is not presently overheating, and the cooling fans are in working order.
• There does not seem to be excess pressure in the cooling system, however I will check properly in the morning.
• Plenty of toasty air from the cabin heater

The garage in question have supposedly had the oil cooler off to test it and is OK (not sure I trust them though!) and their 'diagnosis' is a "cracked engine block". They claim to have done a sniff test & emissions test which all were fine.

Any ideas?!

[kaiser]

Inlet manifold gaskets for starters.

[Lovel]

With the KV6, initially after changing the inlet manifold gaskets it is prudent to retorque the manifold nuts, as I have found that over the years of use they can slacken off which can allow coolant leaks. If I ever come across a KV6 engined car that’s the first thing I would check by tightening up the nuts.

Additionally if the water pump was replaced the set pins can leak coolant if whoever changed the pump doesn’t use new set pins(c/w sealer) or used ones with sealer applied by the installer.

Even though the thermostat and associated pipes have been changed depending upon the technical ability of the installer you could still get leaks in this area as there are only single o-ring grooves manufactured on the components. If the installer does not clean up the bore (assuming they used new o-rings of course) before fitting and use silicon grease then the leaks can still occur. Using old compression set o-rings is a no-no, but usually when you replace the thermostat and other pipes they come with new o-rings.
Begs the question does the V between the inlet manifolds still have coolant laying in it ?

[Sebastienclement]

Had a play with the car. With the coolant cap off, and modest revs (around 2k) there are bubbles evident and the level rises quickly...

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[kaiser]

Originally Posted by Sebastienclement

Had a play with the car. With the coolant cap off, and modest revs (around 2k) there are bubbles evident and the level rises quickly...

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This test is supposed to show what?
I have had cars that did that and still they were quite OK.
I don't think this shows anything necessarily.

[Sebastienclement]

Originally Posted by kaiser

This test is supposed to show what?
I have had cars that did that and still they were quite OK.
I don't think this shows anything necessarily.

Ah ok - I had read it on a thread here.

As a control the same test on my 2.5kv6 doesn't act the same. No bubbles in coolant and the level doesn't rise in the expansion tank until it's mid 90'c

The car in question here is doing that at temps under 60'c

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[T-Cut]

Originally Posted by Sebastienclement

With the coolant cap off, and modest revs (around 2k) there are bubbles evident and the level rises quickly...

The bubbles are either air trapped in the cooling system or exhaust gas. Trapped air is very likely because of the contorted design of the cooling system. However, that can be removed by doing a 'proper' bleeding exercise. Obviously, trapped air will eventually be eliminated, so the bubbles shouldn't continue 'forever'.
If they do, bad sign.


TC

[kaiser]

I think we have to be careful here.
If, anywhere in the engine, a spot exists where heat transfer is great enough, you will create bubbles because you can exceed the boiling point of water. Especially when there is no cap and increased pressure.

If you have ever tried to open a hot cooling system, you will first see pressure escape, as you open the cap a bit, next you will see the water level rise, and plenty of bubbles.

That is not exhaust gas.

So yes, I agree, if the engine is stone cold, and you get bubbles, you might have trapped air, or even exhaust gas!. But you can expect a rise in water level just because of the pump creating positive pressure in front and negative behind. Water loss will be substituted with air, that could be what you see. It could still be inlet manifold gaskets.

I would not put too much emphasis on this, unless there are clear signs of head gasket failure.

The easiest way to check for leaking gaskets is to inspect the spark plugs in each corner. They have water very close to the inlet tract, and a large pressure differential between coolant pressure and inlet vacuum, which tends to draw water into the corner cylinders.
I will almost bet a case of beer, that this will be the problem.
It might not be the whole story, but this is where I would start.

[Yorkshire GOC]

I would advise the OP to do the T-Cut test - take her out for a good thrash at motorway speeds for 10 miles or so. Leave the car till next day and open the expansion cap - if silent then good - however if there is the hiss of gas this is a clear indicator of exhaust gases in the coolant system - there should be no pressure in a cold system.

[kaiser]

Originally Posted by Yorkshire GOC

I would advise the OP to do the T-Cut test - take her out for a good thrash at motorway speeds for 10 miles or so. Leave the car till next day and open the expansion cap - if silent then good - however if there is the hiss of gas this is a clear indicator of exhaust gases in the coolant system - there should be no pressure in a cold system.

Again careful. You can have differences in ambient pressure (barometric) or even a lazy relief valve, which could cause a small differential in pressure between a cold system and ambient.
Not much, for sure, but a small "pfft" or a "sigh" when opening, is quite normal.

Bloated hoses and significant pressure in a cold system is a dead giveaway, however.