KV6 stat opening temperatures : is it a lottery?

[scoubix]

So this week I proceeded to do what each and every KV6 owner should do every 6 years or 90.000 miles : replace the belts, water pump and (oh lord why did I do it), the stat.
My last belt change, complete with pump and stat, was done by the previous owner in october 2009. Since then the car only did 45.000 kms (not miles) but 6 years it was.
My mechanic, while doing the job, called me and asked if I was really willing to do the stat. It was perfectly fine, no cracks of any kind. I told him yes because this one stat was opening up a bit too late : 93 degrees instead of the 88 it's supposed to do. Granted it can be + or - 2 deg from the 88 mark, since it's a mechanical one, but this resulted in my car driving 2 to 3 degrees too hot (usually at 96 on even roads), and staying at 96 on a full stop with slow-speed fan running, hardly going down to 95 where the fan switches off.

So I though...heck, let's do it anyway, it can only improve things...

Or not !

With the new stat, it's even worse. It's obviously opening up at 96 only, as a result, the car is constantly running at 98-99° on even roads, and staying at 100° with slow-speed fan running while on a full stop. So definitely too hot now...

I will take it back to the mechanic to fit a new stat...but now I'm seriously concerned that a new one might have the same faulty operation.

Does anyone sell "tested" stats to make sure they open when they should? Is the test with a pan of hot water really suited for these stats, considering the plastic body?

Advice needed, please, on how to make sure to source a good one...

btw, I can tell when the stat opens because of the real temp display I have in my car. With the older stat, the raising temp would come to a halt at 93, even going back down to 92, for a few minutes, when stat is opening and water mixing, before rising to 96. With the new stat, it's now happening at 96, going back down to 95, and raising again to 99.

[clf]

Originally Posted by scoubix

So this week I proceeded to do what each and every KV6 owner should do every 6 years or 90.000 miles : replace the belts, water pump and (oh lord why did I do it), the stat.
My last belt change, complete with pump and stat, was done by the previous owner in october 2009. Since then the car only did 45.000 kms (not miles) but 6 years it was.
My mechanic, while doing the job, called me and asked if I was really willing to do the stat. It was perfectly fine, no cracks of any kind. I told him yes because this one stat was opening up a bit too late : 93 degrees instead of the 88 it's supposed to do. Granted it can be + or - 2 deg from the 88 mark, since it's a mechanical one, but this resulted in my car driving 2 to 3 degrees too hot (usually at 96 on even roads), and staying at 96 on a full stop with slow-speed fan running, hardly going down to 95 where the fan switches off.

So I though...heck, let's do it anyway, it can only improve things...

Or not !

With the new stat, it's even worse. It's obviously opening up at 96 only, as a result, the car is constantly running at 98-99° on even roads, and staying at 100° with slow-speed fan running while on a full stop. So definitely too hot now...

I will take it back to the mechanic to fit a new stat...but now I'm seriously concerned that a new one might have the same faulty operation.

Does anyone sell "tested" stats to make sure they open when they should? Is the test with a pan of hot water really suited for these stats, considering the plastic body?

Advice needed, please, on how to make sure to source a good one...

btw, I can tell when the stat opens because of the real temp display I have in my car. With the older stat, the raising temp would come to a halt at 93, even going back down to 92, for a few minutes, when stat is opening and water mixing, before rising to 96. With the new stat, it's now happening at 96, going back down to 95, and raising again to 99.

I cant answer anything related to the stat itself, however, when I tested my inline stat, I didnt want the stat to come close to the heat. So I placed it into a colander inside a large pan of water. The handle on the colander came in handy to support the thermometer too.

I cant see how you would have a problem as long as the housing does not rest close to the direct heat.

[kaiser]

Cook it with a thermometer in a pot of water.

[Phil-T4]

I have seen this many times on KV6 engines when they arrive for cambelt replacements and have put it down to the cam timing being slightly out which you can see on the rear belts when its aligned and flywheel locked, however when they leave the running temp is 90 to 92

Might be worth checking ?

[kaiser]

While 100 degrees or close is too hot for a straight road (in my book!), one should not be blind to the possibility that the temperature gauge can be off as well.
2 or three degrees hotter than before I would not worry about, but I would check the temperature reading.

I think the outdoor temp reading should be the same as the engine temp reading, if the car has been parked in the shade and allowed to cool off.

Comparing those temperatures would then give an idea.

[Stag>75]

Originally Posted by scoubix

.I told him yes because this one stat was opening up a bit too late : 93 degrees instead of the 88 it's supposed to do.

Perhaps take the stat out of the old housing and independently check the opening temperature. I believe a pot of water and cooking thermometer is what people have used.

At least that way you have a starting point to work out what is going on. Perhaps you have a blockage in the cooling system or has been mentioned a timing problem.

Also has the system been bled properly to get all the air out?

[Mike Noc]

A good tip from Harry; heat the stat up in water until it opens, and then place a length of cotton thread between the valve faces. Let it cool down then suspend it in a pan of water by the cotton thread and slowly heat the pan up.

As soon as the stat starts to open it will fall down - more accurate than trying to see the first signs of valve movement.

[scoubix]

Thanks for all the advice gents.

I have seen this many times on KV6 engines when they arrive for cambelt replacements and have put it down to the cam timing being slightly out which you can see on the rear belts when its aligned and flywheel locked, however when they leave the running temp is 90 to 92

Might be worth checking ?

Well Phil, considering my mechanic is the foremost expert on all things MGR around Paris, I do consider that the timing is accurate, in fact he reported to me that on the previous belts it was slightly out on the inlet cams, about 1 tooth...
On a side-note, he showed me the previous main belt...was almost ready to snap in a couple of places, which has you wondering (not!) if you really should follow the 6-years change interval...only 45.000 kms and I probably wouldn't have done 10.000 more on these.

Will check when cold that both temp sensors report the same value. Last I checked (before the belt job), they did.

[Bolin]

My old OEM one always open dead on 88.

I also tested it in a pan of water (pan should be OK as the water inside the plastic will be just as hot, can't see the plastic being affected by the hot water being on the outside of it instead of the inside?), I positioned it so that a bubble of air would be released as the stat opened, and it was dead on 88.

I take it your real-time display is not the OBD and has the second sensor you mention? Does the OBD read anything different? Any maybe if the second sensor is in a different location, the water could be at a slightly different temperature whilst warming up, as the heat spreads through the system? Just some things to consider.

[scoubix]

Originally Posted by Bolin

My old OEM one always open dead on 88.

I also tested it in a pan of water (pan should be OK as the water inside the plastic will be just as hot, can't see the plastic being affected by the hot water being on the outside of it instead of the inside?), I positioned it so that a bubble of air would be released as the stat opened, and it was dead on 88.

I take it your real-time display is not the OBD and has the second sensor you mention? Does the OBD read anything different? Any maybe if the second sensor is in a different location, the water could be at a slightly different temperature whilst warming up, as the heat spreads through the system? Just some things to consider.

I don't have a second sensor, my display with the Intravee reads the value directly from the Kbus, identical to that of the OBD display.
What I meant by both sensors is the one used for the outside temp, and the one used for coolant temp. As Kaiser mentioned, with engine stone cold, both sensors should show the same temp, more or less.
In my case those values are identical. So my engine sensor is not faulty. I am indeed driving with the engine close to 100°...