Thermostat KV6 2,5....leakage.

[Azur]

Hello,

yesterday I have changed my thermostat, keyhole method. Took a lot of images (and blood, sweat and tears). Outcoming thermostat had no visual damage (changed 7 years ago), but had flattened O-rings and had developed a leakage....
I have done everything via the book, double checked everything was in position again, including proper bleading at the end etc.

Very unhappy to just notice the V is still getting wet again.
I have bought everything new from Rimmers OEM. Lubricated the new original O-rings (vegetable grease), checked the hoses, made sure all the clamps are fully tightened and at the right position and connections are fine. I did check the inlet holes where the thermostat went out and in, they all seem fine, no damage.

Now, I am at the point of giving up and kicking the car away, which would be a shame because it is a beauty and I have spent 8 K on it...

What to do....?


Thanks,
Emiel

[Matt_75]

Did you manage to check the condition of the sealing bores in the engine block (that the o-rings interface with)? I'm told that if they're rough, this can cause a leak as the o-ring can't seal properly.

The only other things I can think of that could cause a leak are hoses not properly secured to the thermostat and curved pipe, faulty new parts or that something wasn't quite properly seated.

Could you possibly run the engine whilst using a borescope camera to look for leaks?

[Azur]

Thank you Matt for your reaction! I did, and the hoses where secured properly.

While investigating it looked like the curved pipe was not fully 2 cm in the bore. I have decided to take it off again, keyhole method again, get the O-rings off, cleaned them and put them on dry this time. Double checked the bores and they are fine. The 2 plastic clips on the straight pipe could not be pushed fully to the ends, just a millimeter off on both sides in order to fit. Did the hole job a lot quicker than yesterday.



Unfortunately I have just noticed it is getting wet again! So, I do not know what to do anymore. I will leave it for now, as 2 days spending on it has taken enough energy, but not feeling happy about it.

I will buy a proper borescope for my cellphone which can be used to investigate these kind of things.

Thanks again.

Cheers from Holland.

Emiel

[SD1too]

Originally Posted by Azur

The 2 plastic clips on the straight pipe could not be pushed fully to the ends, just a millimetre off on both sides in order to fit.

This is most likely your problem Emiel.

Originally Posted by Azur

I have bought everything new from Rimmers OEM.

Which part numbers exactly have you fitted? Is the replacement straight pipe PEP101970LP by any chance?

To cure leaks into the 'V' all you need are four new 'O' rings (CDU 3858) and two new serrated clips (PYC 101320) for the straight pipe. Fit those to your original thermostat housing, curved pipe and straight pipe and all should be well.

Simon

[xsport]

Two Centimeters seems a lot for the elbow seating ... i presume you have the main thermostat fully seated home first before the elbow is fitted ? Some members have made the mistake of trying to seat these two items ,by just tightening the mounting bolt .. I would check that first the stat is fully home , (is this the reason for the clips on the pipe not fitting correctly ? ) second make sure that the elbow is fully into the "swivel flat area " on the stat bolt area ,and pushed firmly home. The bolt should be firmly tightened but do not over tighten , but fully home. Forgive me if you are aware of all these things , but something is sadly not correct, unless of course the parts that you have purchased are not the same dimensions , you could check this against your old parts .. as it has been known before ...

[xsport]

Originally Posted by Matt_75

Did you manage to check the condition of the sealing bores in the engine block (that the o-rings interface with)? I'm told that if they're rough, this can cause a leak as the o-ring can't seal properly.

The only other things I can think of that could cause a leak are hoses not properly secured to the thermostat and curved pipe, faulty new parts or that something wasn't quite properly seated.

Could you possibly run the engine whilst using a borescope camera to look for leaks?

I have noticed mat , that on the ones i have changed that the "O" rings were not the correct size , too thin , and were stretched as they had been fitted to the stat over a period of time. Other thing to mention is that the bores often have broken plastic elbow pieces stuck still in them from a broken elbow removal. If the elbow was broken upon removal, the knee -jerk
tool to use is a screw diver !! This can leave a deep scratch inside the bore ,whilst trying to oust a stubborn piece of plastic elbow . This then will not seal if sufficiently deep,and requires a thicker ring .This is not really possible given the plastic is very brittle. Its only very soft alloy in the bores and can turn oval if tried to remove with emery cloth or similar. Oh the joys of KV6..

[SD1too]

Originally Posted by xsport

Some members have made the mistake of trying to seat these two items ,by just tightening the mounting bolt ... The bolt should be firmly tightened but do not over tighten ...

There is actually a torque setting for the thermostat housing/elbow bolt. It is 18 Nm; easy to achieve using the official repair method.

Originally Posted by xsport

... the bores often have broken plastic elbow pieces stuck still in them from a broken elbow removal. If the elbow was broken upon removal, the knee -jerk tool to use is a screwdriver !!

Again, following the MG Rover dismantling method allows the parts to be released carefully at their mounting in the block without breakage.

Originally Posted by xsport

... and requires a thicker ring .This is not really possible given the plastic is very brittle.

Two points here Stefan; during my research into the cause of the leakage I tried a thicker 'O' ring but there's insufficient clearance in the block for that with the result that the plastic component fractures. The plastic isn't intrinsically brittle but non-standard methods of removal such as putting a screwdriver into an open coolant port not designed for the purpose will obviously risk breakage.

Simon

[vitesse]

Originally Posted by xsport

unless of course the parts that you have purchased are not the same dimensions , you could check this against your old parts .. as it has been known before ...

Certainly has been known before: when I last replaced a thermostat I found that the supplied curved pipe just wouldn't fit as it should. I compared it to my old pipe and there was a measurable difference - I reported it to Mat at DMGRS.

Swopped the new O ring over to the old pipe and it went in just like it should.

Mind you, I always do thermostats in my mind properly and remove both inlet manifolds (I know the gaskets can leak), then you've got every chance of discovering broken plastic, unclean surfaces etc.

Good luck

[Typhoon190]

This is just my opinion, but I feel there is too much free space in the latest plastic components of the thermostat kit where the o rings sit. They are far too loose across the section diameter which allows movement of the o ring. I also provides too much space for the o ring to collapse into.

If I remember correctly the o ring section is 3.0mm, yet the mould grooves are 4.0mm+.

It was a little while back now, but I had a very similar situation when changing the kit on my Dad's 190.

To rectify the issue a purchased some smaller section, slightly smaller diameter o rings to 'pack' the gap inwards and below of the stock o ring.

Hard to explain but hopefully it makes sense?

I would also suggest whilst perhaps a bit more work and cost, removing the upper manifold and at least the front lower inlet manifold gives you much more access and visibility to ensure everything is clean, in suitable condition and aligned properly. Again only my opinion but having tried both methods, the keyhole method is more likely to lead to an issue.

[Arctic]

Originally Posted by Typhoon190

This is just my opinion, but I feel there is too much free space in the latest plastic components of the thermostat kit where the o rings sit. They are far too loose across the section diameter which allows movement of the o ring. I also provides too much space for the o ring to collapse into.

If I remember correctly the o ring section is 3.0mm, yet the mould grooves are 4.0mm+.

It was a little while back now, but I had a very similar situation when changing the kit on my Dad's 190.

Hard to explain but hopefully it makes sense?

I would also suggest whilst perhaps a bit more work and cost, removing the upper manifold and at least the front lower inlet manifold gives you much more access and visibility to ensure everything is clean, in suitable condition and aligned properly. Again only my opinion but having tried both methods, the keyhole method is more likely to lead to an issue.

Hi Ben.
Therefore it sounds like you doubled up the O-ring instead of one you used two ? correct.

Also has you pointed out the stat gives way to movement/rocking when engine is running this then helps flat the O-rings quicker.

Back in 2013/14 i did find some stats that had three stabilising pegs on the stat i used this stat and my car was leak free from stat area 6years right up until it went for spares, my idea due to cost of other items needing doing.

1

As opposed to the ones before and after the one i used which i think are no longer available.
2

3