Kv6 new thermostat leaks?

[SD1too]

Originally Posted by Phil-T4

i asked X-Part about it and here is the reply....

"... According to the actual engineering drawing it has a range of S.T.O. ( start to open ) figures.
It was set at S.T.O. 88c until 1995 then it changed.

1995? That doesn't make sense.

My engine has always run in the low nineties with the original factory-fitted (in 1999) thermostat, a Circoli replacement (in 2012) and the final part with the four supporting legs bought from an X-Part agent (in 2017).

Under test, my factory-fitted (in 1999) thermostat, stamped 82˚ on the housing (as Phil's quote states) actually opens according to the spec. in RAVE which is 88˚ ± 2˚.

It may well be that the opening temperature has been lowered, but this could not have been in 1995! I would like to see the engineering drawing from then to which X-Part refers.
Edit: Also, I've never seen a Technical Bulletin from MG Rover during the production of the 75/ZT concerning a change of thermostat specification.

To avoid low running temperatures (in the eighties) don't change your thermostat! Fit new genuine CDU 3858 'O' rings to the original (safely extracted with the LH inlet manifold removed) and set the straight pipe serrated clips fully outwards.

Simon

[MGtom91]

Originally Posted by SD1too

1995? That doesn't make sense.

My engine has always run in the low nineties with the original factory-fitted (in 1999) thermostat, a Circoli replacement (in 2012) and the final part with the four supporting legs bought from an X-Part agent (in 2017).

Under test, my factory-fitted (in 1999) thermostat, stamped 82˚ on the housing (as Phil's quote states) actually opens according to the spec. in RAVE which is 88˚ ± 2˚.

It may well be that the opening temperature has been lowered, but this could not have been in 1995! I would like to see the engineering drawing from then to which X-Part refers.

To avoid low running temperatures (in the eighties) don't change your thermostat! Fit new genuine CDU 3858 'O' rings to the original (safely extracted with the LH inlet manifold removed) and set the straight pipe serrated clips fully outwards.

Simon

Didn't have a choice, the housing around the join was leaking. Did a 3 hour drive in the ZT to Goodwood today and on the motorway, the temperature settled at 78° sometimes reading 77° for a short blip now and again but always back to 78°. Didn't go any higher until the slower roads then crept up to 80° max.

[Arctic]

i fitted one f the thermostats with the three pegs for stability that stat and the one before it all ran from 91 would reach 100 and the fan would kick in to bring it back down to 91.

I don't know what's going on with these stats but surely there must be some around with the 88c start opening ?

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It seems these stats have been talked about forever

https://www.the75andztclub.co.uk/for...thermostat+88c

[SD1too]

Originally Posted by MGtom91

Didn't have a choice, the housing around the join was leaking.

Hello Tom,

Although it looks certain that this is the case, in fact it isn't! What happens is that the 'O' ring at the base of the housing flattens and a fine spray of coolant is then emitted upwards to coat the widest part of the housing; the seam. The solution is as I described in my previous post.

Simon

[Phil-T4]

Originally Posted by SD1too

1995? That doesn't make sense.

My engine has always run in the low nineties with the original factory-fitted (in 1999) thermostat, a Circoli replacement (in 2012) and the final part with the four supporting legs bought from an X-Part agent (in 2017).

Under test, my factory-fitted (in 1999) thermostat, stamped 82˚ on the housing (as Phil's quote states) actually opens according to the spec. in RAVE which is 88˚ ± 2˚.

It may well be that the opening temperature has been lowered, but this could not have been in 1995! I would like to see the engineering drawing from then to which X-Part refers.

To avoid low running temperatures (in the eighties) don't change your thermostat! Fit new genuine CDU 3858 'O' rings to the original (safely extracted with the LH inlet manifold removed) and set the straight pipe serrated clips fully outwards.

Simon

Don't forget the STO temp is when the wax stat STARTS to move it doesn't mean there is a lot of flow through it, they (x-part) say it is FULLY open at 96 but we know that around 89-90 there is sufficient flow to heat the hoses and radiator.

The other option to consider is the single temp sensor may not be reading correctly, i have seen one that got so cooked by over temp the ecu reading never went above 80C based on the sensors resistance reading although using external measurement showed the cooling system was much higher.

After the last thermostat change I did I have to agree with you, if the running temp is ok, nothing fractured then reuse what you have and fit new seals, we twice got faulty components from Rimmers, each time the curved pipe had a manufacturing flaw/damage which caused a leak (SIAC parts) the car was with us for over a week before it was sorted and leak free.


Try contacting x-part for a copy of the drawing.

[SD1too]

Originally Posted by Phil-T4

Don't forget the STO temp is when the wax stat STARTS to move it doesn't mean there is a lot of flow through it, they (x-part) say it is FULLY open at 96 ...

Hi Phil,

How could I forget this after staring into many saucepans full of water with thermostats suspended!

The temperature when fully open didn't apparently change which also makes me doubt the accuracy of X-Part's reply to you.

Originally Posted by Phil-T4

After the last thermostat change I did I have to agree with you, if the running temp is ok, nothing fractured then reuse what you have and fit new seals ...

Thank you very much for this Phil. I'm currently helping another member with his KV6 and the plastic curved pipe from an independent supplier well known on this forum, advertised as a genuine part, was too big to fit into the block, even with the 'O' ring removed! The supplier sent another one which was exactly the same.

Originally Posted by Phil-T4

Try contacting x-part for a copy of the drawing.

Ha ha! Did I hear someone say "corporate confidentiality"?

Thanks for your input Phil, much appreciated.

Simon

[MGtom91]

Originally Posted by SD1too

Hello Tom,

Although it looks certain that this is the case, in fact it isn't! What happens is that the 'O' ring at the base of the housing flattens and a fine spray of coolant is then emitted upwards to coat the widest part of the housing; the seam. The solution is as I described in my previous post.

Simon

Have to disagree as when I removed it, you could see where the join had split.

My head is telling me to buy another stat to achieve a higher temp, my heart isn't really telling me to do the job again for the sake of an 8 to 10° gain!

[SD1too]

Originally Posted by MGtom91

... you could see where the join had split.

Hi Tom,

Unfortunately a visual diagnosis alone is misleading. Had you filled it with water you'd have been surprised to find no evidence of a split. Nobody does this though, except for me!

I fully understand your reluctance to do the job again, particularly when others are finding it difficult to obtain a proper 88˚ thermostat.

Simon

[Dorchester2]

I'm following the thread since the beginning but I have a very silly question for you because I can't understand where lies the problem:
What's wrong with slightly low-ish temperatures say around 80°?
I thought the more dreadful problem was when temperatures were increasing too high...
Thank you to enlighten my knowledge.

[MGtom91]

Originally Posted by Dorchester2

I'm following the thread since the beginning but I have a very silly question for you because I can't understand where lies the problem:
What's wrong with slightly low-ish temperatures say around 80°?
I thought the more dreadful problem was when temperatures were increasing too high...
Thank you to enlighten my knowledge.

Good question. I have been told different things by different people. Some have suggested around 80° the temp is not high enough for the oil to burn off the nasties and prevent sludging but oil temp are considerably higher than this anyway? Also some have said fuel consumption could be affected whilst others have said 80° hot enough for the car to not increase fuelling for cold running conditions.

The way I see it is although 80 is slightly lower than 'ideal' , it is within calibrated range of 75 to 115° , hot enough for the fuelling to be normal and the car seems to run perfectly fine. MPG wise, I am averaging mid 20s around town and 29 ish on a motorway run determined by brim to brim calculations, which appears to be normal for the KV6?