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Old 4th March 2016, 20:08   #1
scoubix
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Default Rant on KV6 coolant design / introducing the little-known 82° official MGR stat

I just love the KV6 in my launch car. Nice sound, revs quite nicely...and I hate it at the same time, probably as much. Some of its design is just so poor...especially on the coolant side. Having the stat sitting in the V is just one example. But the whole cooling system is, as we all know, something to give worries to all KV6 owners. Air locks, blocked heater matrix, an expansion tank where the min/max levels can only be seen with a flashlight...and running temps that can not accurately be determined from the gauge.

Here's another one for you : did you know that MGR did design an 82° stat, with a different part number, that was provided as warranty kits to dealerships, together with an improved resistor for the two-speed fan?
It was designed to have the car run a bit cooler than on the standard stat (which opens at 88°), and was to be fitted to cars that had already had temp issues, including broken fans. Initially it would not be fitted separately of the new fan resistor.

This different stat is part nr. PEM100860 (the original stat is PEM101050). Try looking for PEM100860, you won't find it anywhere, its part nr. is not even referenced with XPart.





Turns out my launch car was fitted with this 82° stat when the belts were done in 2009. Even though the bill mentions the standard one (PEM101050). Of course it would : PEM100860 doesn't officially exist.

Ever since I've owned the car it's been running at 96° on idle roads, and while stationery with the slow-speed fan being on, has always struggled to go below 96° where the slow-speed fan would cut out. So while I had the belts done again a month ago, I asked my mechanic to change the stat, not knowing it was an 82° one, because I thought it was a bit sticky and I wanted the running temp to be what it's supposed to be ideally : 2 or 3 degrees less. He advised against it, saying the stat was perfectly fine from the outside, but upon my insisting, did it anyway.

He fitted me with another 82° stat, which he had in stock. Worse results : car was now running around 98-99 all the time. While stationary, would not go below 100°. I talked about this here : http://www.the75andztclub.co.uk/foru...d.php?t=236944
So this 82° stat is definitely opening up later than what my original one did.

So today I collected my car after he refitted the older 82° stat, the one originally fitted in 2009, which was still fine.
I'm now back to the original temps...the ones I've been having since I own the car.

But it makes me wonder what the results would be if my car were to be fitted with a standard 88° stat.

I did a test-drive of another KV6 automatic last week, a Tourer with only 18.000 kms. It had a brand new stat fitted last month (the regular one). Reading the real temp on the IPK while driving, it was between 95 and 98° at all times. Go wonder...

And we all know now why the needle won't bulge between 75° and 115° : MGR was not capable of having a coolant system reliable enough. They designed an 82° stat which they did not even think worthy enough to reference as an aftermarket part. They only waited for cars to overheat to fit those 82° stats to cars that had already been "weakened" so they would tentatively not run as hot as they used to. And this is all because they knew, down in their guts, that their coolant design could have been way better from the start...
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Last edited by scoubix; 4th March 2016 at 20:18..
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Old 4th March 2016, 20:58   #2
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Interesting read Nicolas. It is a shame the are so many issues with the coolant on both these and the 1.8's.

Mine has had coolant issues for a long while now, but with the 88 stat in, and coolant level where it should be, on a run she sits almost perfectly at 90 degrees, and won't deviate below 87 or 93 unless she comes to a halt. Odd that with either stat yours is running hotter.
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Old 4th March 2016, 21:04   #3
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And copied for the benefit of folks over here:

Nicolas, it is known that all MGR stats fitted to the 75 have 82 degrees on the housing, but actually open at 88 - my original stat is proof of this, as I tested it in a pan of water with a jam thermometer. It used to open at 88 degrees dead on on the car, and did so in the pan too.

The thoughts on this I have read in the past are that the moulding for the housing was already completed before the late change from 82 to 88 - and the housing moulding was never updated.

The parts numbers you can see in your photo show two different numbers for the two halves of the housing - it was typical MGR practice to use part numbers for sub-assemblies that were never mentioned in the official parts list as you could only buy the complete assembly. An example of this is the part number on the label stuck on the standard rear saloon factory-fitted dampers, and the part number in the parts list, which includes a plastic cap etc. I would expect PEN100510 to relate to the top half of the housing and PEM100860 to relate to the bottom half, with PEM101050 being the number for the complete assembly which was available to dealers and the public.

The numbers match my own original stat housing, which too has PEN100510 on the top and PEM100860 on the bottom, states 82 degrees and yet opens at 88 degrees as tested.

Where did you get the information about the warranty kits?

I think your problems are simply dodgy replacement stats - perhaps there have been a few bad batches. But yes, some parts of the KV6 cooling system are not ideal!
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Old 4th March 2016, 21:32   #4
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I had a replacement thermostat from DMGRS, and it was fitted by phil-t4 and I believe the replacments provided by matt are the 82c one? Correct me if I am wrong but my car runs about the 82c mark, often dropping to about 80 whilst driving, and takes forever to reach the 100c mark if stationary. I had a replacement one from him under warranty as it was opening even earlier than that!

It's either the thermostat is opening at the 82c mark or my car is almost as efficient as the diesel and doesn't produce much heat when running
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Old 4th March 2016, 21:56   #5
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Googling for Part Number PEN100510 has lots of interesting references overseas, Poland, Russia, China.

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Old 4th March 2016, 23:18   #6
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Quote:
Originally Posted by T-Cut View Post
Googling for Part Number PEN100510 has lots of interesting references overseas, Poland, Russia, China.

TC
Looks like those results are just taking the physical number off the top of the housing and using that, rather than the correct number for the two halves & 'stat insert assembly

Perhaps the 75/ZT used a modified upper moulding version of the Freelander 'stat (different ends) rather than a brand new moulding and so the 82 degrees refers to the opening of the Freelander version.
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Old 5th March 2016, 07:35   #7
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Just buy one of Kaisers metal thermostat housings, you can remove the top part if required and change the thermostats to what you want.
I believe he also modified the internal coolant flow as well.
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Old 6th March 2016, 18:37   #8
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There's also an 82 degree PRT for the K4 available from DMGRS. I fitted one about 2 years ago
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Old 7th March 2016, 20:25   #9
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Quote:
Originally Posted by Bolin View Post
Looks like those results are just taking the physical number off the top of the housing and using that, rather than the correct number for the two halves & 'stat insert assembly

Perhaps the 75/ZT used a modified upper moulding version of the Freelander 'stat (different ends) rather than a brand new moulding and so the 82 degrees refers to the opening of the Freelander version.
Actually the Rave manual for the Freelander states that the stat starts opening at 88° and is fully opened at 104°.
The Rave manual for the 75 says nothing at all about operating temps...
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