KV6 HG - what tests to run

[zefrench]

Hi all

I have a KV6 Freelander (same engine) that I am very convinced the head gasket on the head of cylinder 1,3,5 has gone.

I loose roughly 250 ml of coolant every 50ish km.

The thermostat has been changed to Kaiser's excellent aluminium one.

I pressure tested the expansion bottle cap, it does let pressure out at 16 PSI. The coolant system holds pressure as well when pressure tested.

When I run the engine at idle, the coolant system does not over-pressurize, but as soon as I go over 2000 RPM, the pressure rises. I stopped the test at 19 PSI, I did not want to break anything. I cannot think of anything else that would raise the pressure so high.


I also did a compression test, and after adjusting value (the Lisle compression tester I own is known for being +20 psi over) I get the following

2: 173 4: 174 6: 175
1: 175 3: 126 5: 182


I did a chemical test, but maybe I did not wait long enough, it turned green but not yellow. Other then a cylinder leak test, what other tests could I do?

There is no "mayo" in the oil.

I live in Canada so parts are always pricey to ship so I want to run as many tests as possible.

[DMGRS]

Have you monitored the temperature via the IPK?
This will show you if the thermostat sticking could be the cause of the problem - I had similar on a friend's 75 V6, the temperature would suddenly 'spike' under load, we assumed it could be HGF.

We replaced the thermostat as a last measure, and it completely resolved the issue. Monitor the temp via the instrument pack diagnostics, and if you see a sudden climbing in temperature, this is likely to be the issue.

[T-Cut]

Originally Posted by zefrench

I pressure tested the expansion bottle cap, it does let pressure out at 16 PSI.

That seems a bit low to me, assuming the same cap is used as in the 75/ZT. The standard cap (marked '140') should relieve at about 21-22 psi (140kiloPascals).

When I run the engine at idle, the coolant system does not over-pressurize, but as soon as I go over 2000 RPM, the pressure rises. I stopped the test at 19 PSI, I did not want to break anything. I cannot think of anything else that would raise the pressure so high.

Certainly the header tank pressure shouldn't be affected by the engine speed in normal circumstances (apart from the temperature effect). Maybe there is some evidence of exhaust getting into the cooling system.

I did a chemical test

Your carbon dioxide test suggest this as well, though a blue to green change isn't definitive.

I also did a compression test

One cylinder is clearly low.

what other tests could I do?

Check for residual cold system pressure. Drive it normally for at least ten miles. Park up without touching anything. Next day, open the header tank cap and listen for pressure release (like a pop bottle).There shouldn't be any.

TC

[zefrench]

Originally Posted by T-Cut

That seems a bit low to me, assuming the same cap is used as in the 75/ZT. The standard cap (marked '140') should relieve at about 21-22 psi (140kiloPascals).

Check for residual cold system pressure. Drive it normally for at least ten miles. Park up without touching anything. Next day, open the header tank cap and listen for pressure release (like a pop bottle).There shouldn't be any.

TC

The Freelander cap PCD500030 (latest part number) is rated for 16 PSI. Strange that there is such a difference.

I will do the rest of the tests and report back.

[T-Cut]

Originally Posted by zefrench

The Freelander cap PCD500030 (latest part number) is rated for 16 PSI.

Interestingly it's a completely different cap.



TC

[zefrench]

Well today I did a few tests with the expansion tank cap removed.

I drove two trips of 20 minutes, let the car cool a few minutes and then removed the expansion tank cap.


If I let the car idle, the coolant level keeps rising and rising until it over flows.

Furthermore, I was about to try another combustion gas test but as you can see in this video

https://youtu.be/jCwu8ZkSlUM

There are bubbles (seen in the tester even though I am not sucking in air) and pressure in the expansion tank.

I am wondering if I need to buy a cylinder leak down tester at this point as I am thinking it is pretty confirmed.

Opinions ?

Thanks again

Martin

[kaiser]

I think you have a leak. I have just had one on my two metal pipes and on the main cooling pipe from the thermostat. I also did a sniff test and it also changed colour, eventually.
If you let your car idle, the water level will rise, if you wait long enough, it proves nothing in itself.
The leak can be difficult to find.
Get the car on a lift and inspect. Don't forget the water pump, which often can show up as a trace of water near the pulley!
Get the proper cap from BMW, don't worry about the 200 printed.

A compression test is not a good test for the head gasket. Pour a bit of oil in the bore. Repeat the test. If improved - rings, if not - valve.

If you continue to look for signs of hgf, everything can be taken as such, but essentially you are looking for a leak.
Also make sure your fan works! and monitor the temperature, if you can on your instruments.

If you look, you will find it.

The copy below is what I recently experienced on my engine.

I know the V6 engine well, and yet, recently it fooled me.
My daughter used the car everyday for an extended period, and came home one day with the fan running.
I felt the pipe to the radiator being cold and assumed a stuck stat. Since I make them, I was not overly concerned by having to replace it, as this car still runs with the prototype I built nearly 9 years ago. So I ripped it out and tested it. It is made from steel pipes I machined and welded together, so it was rusty, but in spite of the bad looks, it worked! Which surprised me.
Anyway fitted all, and the engine would not run properly. Turned out I could not get the inlet manifold down far enough, because the rear plugs for the injectors faced towards the back, and were then high enough to prevent the manifold from coming over the green O-rings! Sounds easy enough, but it had me stumped on more than one occasion.!
Anyway, getting the engine to run properly, then showed that it would still overheat, and it lost water.
I thought the head gasket was gone, but after a searching I found two pinprick sized holes in the two metal pipes under the radiator, both on the corners, and one in the main rubber pipe from radiator to thermostat. Both were low and facing to the back, and in retrospect must have let out water while driving in a spray that was not easily noticeable, by the time you stop to check, no leak because the water had already gone!.
I am happy to say that the car is now fixed, but it required a repair of the bleed screw in the pipe as well, as that has had it, (another piece of plastic!) and the bypassing of the oil cooler, now done with a bend pipe to retain the original hoses for the cooling system.
So the moral of the story is find the water loss!

Also, in addition, when I ran the engine in the workshop, I had water coming out the exhaust, and condensing on the concrete floor. And quite a bit of it, I thought. That added to my suspicion of HGF. When you get into this mind set, you see everything in the light of HGF. It is of course possible that you do have a failed gasket, but be very careful of cementing your views, they can easily lead you astray.

[T-Cut]

Originally Posted by zefrench

I drove two trips of 20 minutes, let the car cool a few minutes and then removed the expansion tank cap.

You must leave the car at least six hours, preferably overnight for that sort of test to mean anything. You must check for residul pressure in the stone cold system. It's a good indicator.

TC

[zefrench]

Originally Posted by kaiser

I think you have a leak. I have just had one on my two metal pipes and on the main cooling pipe from the thermostat. I also did a sniff test and it also changed colour, eventually.
If you let your car idle, the water level will rise, if you wait long enough, it proves nothing in itself.
The leak can be difficult to find.

...
If you continue to look for signs of hgf, everything can be taken as such, but essentially you are looking for a leak.
..
If you look, you will find it.
...

Hi Kaiser

The issue I have is that my cooling system holds pressure, I have a cooling system pressure tester, and it holds 16 PSI for at least 30 minutes when cold (I have not tried longer). I also tested my cap, and it tests as a 16 PSI cap (my tester has a mark on its gauge to indicate at what PSI a cap should "let air out"


I am all for learning from other's experience without having to relive it to learn, but at the moment I fail to see how my cooling system can hold pressure and yet have a leak? Do you have some thoughts on this?

Thanks again

Martin

[kaiser]

Yes, strange world!
But I can immediately think of three non hgf reasons.
1, the pump might only leak when hot and running depending on type of failure.
2. Inlet manifold pressure differential, is twice as big as static pressure test, when vacuum is pulled on suction parts. Ie when throttle closed and running.
3. Hot pipes and plastic parts are softer and more prone to deformation when hot and vibrating. I have had a plastic T piece that would leak madly when car stopped and heat soaked, yet showed no leak when engine running and cooling.
4. Radiators can leak around the core, much more pronounced when running, check for marks.

All the checking is far cheaper than open heart surgery.

Just an addition, use higher pressure for the test, don't worry about breaking something. Something is already broken and yielding you want to find that. The system should take pressure to 200kPa, 2 bar or 32psi without ill effect. Sometimes you have to be cruel to be kind!!
But get it to a friendly mechanic with a lift. Choose an old hand that don't mind you asking for advice and helping/watching/asking. They usually work on their own, and have been in business for years, fixing old cars, washing machines, tractors and prams etc. They have seen many odd problems.! Ask around.