Kv6 new thermostat leaks?

[biffa75]

If you search for the forum member called Kaiser I believe he developed these thermostats and would be the best person to advise.

Best of luck and welcome to the forum

[Aidan Collingwood]

Hello biffa75 and thank you for your quick reply and your welcome message.

Reading through the thread again, and some others regarding the KV6 engines - trying to get my head around the many mysteries of the KV6 engine! - I see that you bought a "Summit Garage" thermostat which should open at the correct specified temperatures. I could be wrong here but I believe Kaiser only produces the housing and pipes in metal but uses a thermostat that seems to open at too cool a temp for UK cars. I'm aware that I'm new to the forum and that this subject seems to have been going round in circles for a while, so I don't want to tread on anybody's toes, but I'll contact Kaiser as you suggest to ask his opinion. But in the interim, have you managed to test the opening temperature of the thermostat your bought, biffa75?

I'm just wondering if I could just pop a "Summit" thermostat into a "Kaiser" metal housing whilst doing the work, and have the best of both worlds? I don't fancy spending three or four hours replacing a thermostat and housing only to find the thermostat isn't suited to our climate.
I imagine a South African spec car would have a cooler opening spec to prevent overheating in sustained hot weather, but I'm just guessing here.

If I can't arrive at a workable solution, I just won't buy the car. It seems silly that something like a thermostat specification is a mystery in these days.

I hope that this can be fixed once and for all, not just for me, but for other owners who have replaced, or who will replace thermostats, and found they don't/wont perform correctly.

It seems to be a very confusing subject involving several different thermostat suppliers/manufacturers? Thanks again for the advice.

Regards,

[Aidan Collingwood]

Hello again,

I've been doing a bit more searching around the forum and I followed a link to the DMGRS website. They sell the "Kaiser" housing and hoses etc. (currently out of stock till August) which is supplied with a Lucas thermostat already installed. However, they also supply a "Vernet 6773 Equivalent" thermostat which says 87C which I suppose is suited to the UK climate? DMGRS' phone lines are already closed but I'll contact them tomorrow, have a chat with them and report back.

Regards

[SD1too]

Originally Posted by Aidan Collingwood

... I'm considering buying a 2.5l V6 75 Tourer which has a thermostat housing leak.

Hello Aiden and to the club.

If you buy this car the solution to the leak is simple and cheap. Keep the existing plastic thermostat housing so that your engine runs at the correct temperature. Next buy and fit four new *genuine 'O' rings (CDU 3858) and finish by pushing the serrated clips on the straight pipe fully outwards, then squeeze to tighten them. This last procedure is vital and the key to stopping the leakage.

* Buy parts only from an X-Part agent such as Rimmer Bros., Summit Garage and E Car Parts of Sandy.

Simon

[Aidan Collingwood]

Hello Simon and thank you for the welcome to the club, too.

Just to fill you in on the story, the garage that had the car when I saw it first isn't going to do any work on it for the seller as she doesn't want to spend anymore money on the car (she's clearing out her deceased husband's car collection). After I'd taken it for a test-drive up to operating temperature, there was water in the V despite the garage doing a "temporary fix" with K-seal or similar just so that it didn't overheat on her before she sold it. That's all she asked them to do for her.

I think, from what the garage said to me, the problem is not a failed O-ring but a cracked or split plastic housing itself. I'm not sure how replacing just the O-rings would solve the problem, unless I've misunderstood your advice. Would you mind elaborating a bit more on this for me please?

Regards,

[SD1too]

Originally Posted by Aidan Collingwood

I think, from what the garage said to me, the problem is not a failed O-ring but a cracked or split plastic housing itself. I'm not sure how replacing just the O-rings would solve the problem, unless I've misunderstood your advice. Would you mind elaborating a bit more on this for me please?

Yes of course Aidan.

The garage will have observed coolant residue all over the central seam of the thermostat housing rather like that on my own car:



They can't be blamed for assuming that the housing had cracked or split around the seam but that isn't what's happened. I tested the housing you see in the picture off my car for leaks and there was none so I refitted it with new 'O' rings. There was no more coolant in the 'V' but the cure was only temporary.

After much investigation and trial and error on my own car I worked out the real reason. The 'O' rings were flattening over time, particularly the ring at the base of the thermostat housing. The resulting imperfect seal probably produced a fine spray of coolant upwards which hit the widest point of the housing, the seam, and created the familiar antifreeze deposits. But why were the 'O' rings flattening? More to the point, why were only some engines affected and why did the time taken for the flattening to occur vary from weeks to years? There have been various theories about this but the answer turned out to be very simple.

No-one had considered the purpose of the strange serrated plastic clips on the straight pipe. I noticed that another club member had suggested that the flattening of the 'O' rings might be caused by movement. A mild tug on the hoses attached to the housing confirmed his theory; it rocked quite alarmingly. This was the breakthrough. If normal engine vibration and torque reaction produced even minor movement, over time could this change the profile of the 'O' ring and cause a coolant leak? It was then that I realised what the serrated clips are for.

To fit the straight pipe/thermostat housing into the engine requires the pipe to slide longitudinally. Once everything's in place however, this is undesirable since the 'O' rings then cease to be just a seal but become a friction joint or a basic bearing if you like. If the two serrated clips are pushed in their channels firmly against the water pump and thermostat housings, the assembly becomes rigid and movement is impossible. With this technique my engine has been free of leaks for over four years now (and it runs at the correct temperature in the low nineties).

Further evidence confirming my findings is that the Chinese have improved the thermostat housing by including four supporting legs at the base. They must also have realised that movement, or to be more specific "rocking", of the housing was the issue. I have one of these fitted to my car and if you can find one, they are the best choice.

I'm sending you a PM as well Aiden.

All the best,

Simon

[biffa75]

Simon, great write up and you are 100% correct on the serrated clips providing rigidity to the assembly
Many thanks for this tip that you gave me some months ago!

In regards to the thermostat housing with the four supporting legs... My latest thermostat from summit garage in Dudley that came from x-part that had the saic roewe and mg branding, didn't have these four legs. Being fitted to the car, it didn't appear any less stable than the previous faulty thermostat that had the four legs.

If anything the elbow pipe was less stable than the housing and straight pipe assembly once all fitted nice and snug.

I aren't sure who is actually making the thermostats with the four supporting legs, but my from my latest experience, they aren't made by saic. Do you know who manufactures them? Would be good to get a name.

Rob

[SD1too]

Originally Posted by biffa75

My latest thermostat from summit garage in Dudley that came from x-part that had the saic roewe and mg branding, didn't have these four legs. Being fitted to the car, it didn't appear any less stable than the previous faulty thermostat that had the four legs.

Thanks for this Rob. I agree with you that correct setting of the serrated clips is the most effective procedure. The four legged versions of the thermostat housing just add a bit of extra stability.

Originally Posted by biffa75

I aren't sure who is actually making the thermostats with the four supporting legs, but my from my latest experience, they aren't made by saic. Do you know who manufactures them?

I don't. Mine came from E Car Parts four years ago.

Simon

[trikey]

Hello and welcome Aiden, when you get the car, the first thing to do is flush the system a few times to remove as much of the Kseal as possible, this stuff causes blockages in your heater matrix (normally blows cooler on the passenger side when it’s blocked)

Secondly, remove all the thermostat components and inspect them for cracking, age and OAT coolant does no favours to the material that the thermostat housing and particularly the elbow pipe are made from.

Good luck with the car, a days work should see you sort the issue.

[Arctic]

I went through this when i had my MGZT 190, Simon kindly sent me some O-rings which i fitted to the housing with the stabilising lugs.

I think at the time i was the first to fit this type of housing or one of the first few ? it was still on the car when i let it go in 2018

https://www.the75andztclub.co.uk/for...d.php?t=177152