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Old 15th March 2018, 09:07   #31
SD1too
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Originally Posted by Randyjim View Post
Do we know what the OE ring material is?
According to MarinaBrian, who kindly sent me an Austin Rover drawing quoting a coded specification, it is "ethylene oxide/epichlorohydrin/allyl glycidyl ether terpolymer"!
As you can see, delving into highly specialised technical fields from a point of relative ignorance doesn't really help at all.
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Simon, what spec are you currently using ..
The EPDM 'O' rings I obtained from Polymax (33.0 mm ID x 3 mm cross section).
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... and what do you think caused the failure on your epdm rings?
The same factor which caused the failure of the OEM MGR rings. I have concluded that it cannot be their material (because two different types suffered the same fate) or OAT antifreeze of any concentration and age (because there are many KV6s using this which do not fail).

Minimutly first had the idea that the flattened 'O' rings might be caused by slight but continuous movement of the components in service. I decided to investigate this. Sure enough, as I applied moderate deflection to the attached coolant hoses I could observe movement of the thermostat housing. My attention was then drawn to the mysterious clips on the straight pipe and I realised what their possible function could be. After renewing the 'O' rings, refitting the plastic components* and tightening the securing bolt to the specified torque, I pushed these clips outwards so that each bears upon the water pump housing and 'stat housing. I then repeated the deflection test on the hoses and noted that the whole assembly was now absolutely rigid.

I have only covered 2,000 miles since completing this work so it's too early to make any definite judgement, but the signs are encouraging. We will see.

Simon

* Including a new thermostat housing with the three supporting legs modification.
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Last edited by SD1too; 15th March 2018 at 09:09..
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Old 20th March 2018, 13:22   #32
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Well the AFLAS pricing is in. AS they're made to order its not cheap.

10 off @ £4.00 each (£40.00) of 20 off @ £3.20 each (£64.00) with a 12-14wk lead time.

Although If I could guarantee that they'd cure my problems then £40 isn't a huge amount to save me from annual o-ring servicing.

Perhaps I'll give the OE rings one more chance though.

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Originally Posted by SD1too View Post
The EPDM 'O' rings I obtained from Polymax (33.0 mm ID x 3 mm cross section).
Simon, is this the correct size? I was under the belief that 32.5mm was the original ID, but can't remember where I read that.
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Old 20th March 2018, 16:44   #33
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Originally Posted by Randyjim View Post
Well the AFLAS pricing is in. AS they're made to order its not cheap.

10 off @ £4.00 each (£40.00) of 20 off @ £3.20 each (£64.00) with a 12-14wk lead time.

Although If I could guarantee that they'd cure my problems then £40 isn't a huge amount to save me from annual o-ring servicing.

Perhaps I'll give the OE rings one more chance though.



Simon, is this the correct size? I was under the belief that 32.5mm was the original ID, but can't remember where I read that.
This is money out the window.
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Old 20th March 2018, 22:38   #34
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Simon, is this the correct size? I was under the belief that 32.5mm was the original ID ...
That is absolutely correct Jim. I wanted to try a different material and 33.0 was the closest I could get to the OEM spec. I judged that the marginally larger size might actually assist sealing but it didn’t make any difference.

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Old 21st March 2018, 13:54   #35
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It seems like a half-way step, but wonder if this might improve things?
Click: https://www.ebay.co.uk/itm/Stainless....c100752.m1982
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Old 21st March 2018, 19:31   #36
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It seems like a half-way step, but wonder if this might improve things?
Click: https://www.ebay.co.uk/itm/Stainless....c100752.m1982
That’s interesting. He’s also offering the 1.8 Turbo ‘T’ piece in stainless. I wonder if he’s getting them from SAIC?

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Old 21st March 2018, 21:00   #37
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Looking at his items, I reckon he was previously selling under the ID 'Tazo'. Or this seller is connected to Tazo. The 1.8T T-piece listed now is the cast aluminium one, but 'Tazo was definitely offering a stainless one, with machined ends (like the KV6 pipe above).

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Old 23rd March 2018, 01:05   #38
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From my experience, I’m currently running 3 kv6 cars and have done up and owned another 5 kv6 Rover 75s, that’s all we got over here engine wise.
I note Simmons comments re a lot of the leaks coming from the O rings and I’m sure that happens and have seen how the O rings do get flattened ,however all the replacement thermostats I’ve done , the leaks have always been from the ultrasonic welded plastic joint on the thermo housing.
Again, I’m sure the odd plastic thermo has lasted high miles but all my plastic thermos seemed to fail around the 70,000 km Mark.
This is born out by the fact that Mgr eventually started treating the thermo housing as a service item rather than just a spare part thus knew of the issue.
I sorted the issue out by replacing all my kv6 thermo housing with kaisers metal ones and have never lost a drop of coolant since.
I’m not sure what effect the metal piping has on the O rings but all have remained water tight ever since fitting.
My thought is the aluminun is more ridged and my even have a slightly tighter fit and maybe even being aluminium is slightly cooler on the O ring? Who knows but they work!!
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Old 23rd March 2018, 09:38   #39
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... all the replacement thermostats I’ve done , the leaks have always been from the ultrasonic welded plastic joint on the thermo housing.
What makes you so certain of that Peter? Did you test the joint with the housing on the bench? I tested this one, which was obviously leaking from the welded seam:



Except it wasn't. That housing went back on my car, just with a new 'O' ring, and worked perfectly with no leaks.
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This is born out by the fact that Mgr eventually started treating the thermo housing as a service item rather than just a spare part ..
Did they? I must admit that's news to me. Can you post the official evidence showing this please?
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My thought is the aluminun is more ridged ...
That would fit in with my theory that it's slight movement of the plastic items, due to incorrect setting or movement of the straight pipe's clips, which causes the flattening of the 'O' rings. But I may be proved wrong. We'll see.

Simon
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Old 23rd March 2018, 21:48   #40
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Interestingly, nobody's reported on the use of the KIA 2.5 litre v6 thermostat assembly, which apparently fits the KV6 and actually has two support lugs.

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