Om642 Thermostat

[OneForTheRoad]

Postage whacks the price up with Autodoc

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already reemed out for that stupidly long bolt to slide into the slot, no need to remove it. Good tip for anyone diying .

 

[MrGreedy]

View attachment 136919already reemed out for that stupidly long bolt to slide into the slot, no need to remove it. Good tip for anyone diying .

The long bolt goes on the other side. I don't know why, but they all have that extra slot

Possibly to clip a thin fuel/air/vacuum line flexible rubber pipe?

 

[Gnasher141]

The long bolt goes on the other side. I don't know why, but they all have that extra slot

Possibly to clip a thin fuel/air/vacuum line flexible rubber pipe?

You wish!!!

Long bolt is the other side

 

[OneForTheRoad]

You wish!!!

Long bolt is the other side

Bugger .

 

[E55BOF]

Once you have it out, you could easily cut a slot in the lug the long bolt goes through to make it easily removable, but unless you could use something like a Dremel to cut the old one away, you have to do the dismantling to remove it before you can think about replacing it anyway.

 

[Gnasher141]

To be honest once you’ve done the job and overcome the hurdles it’s quite easy if you have to do it again.

 

[votnus24]

Are aftermarket thermostats good enough to install or should i stick to the oem one? I've found some with different prices that autodoc says will fit but i just can't choose. Difference in price of just a few tens of euros is not that important, i just want it to be good

 

[PolishGeorge85]

Are aftermarket thermostats good enough to install or should i stick to the oem one? I've found some with different prices that autodoc says will fit but i just can't choose. Difference in price of just a few tens of euros is not that important, i just want it to be good

Think this way... One which has failed I believe is the OEM one. It still failed and you have to replace it.
I don't think MB has own factory of spare parts,for example , just like your thermostats. I also don't think that there is a "thermostat" factory which is happily running only based on orders from MB. This factory has to make them to other customers as well, otherwise they would collapse.

This is a question, which nobody on here should really give you answer to. It your car, your money... of your new thermostat fails and is supplied by MB... I don't think you gonna gain anything, only because is supplied by MB.

HOPE this is something people should think while getting new/replacement parts.

 

[OneForTheRoad]

Think this way... One which has failed I believe is the OEM one. It still failed and you have to replace it.
I don't think MB has own factory of spare parts,for example , just like your thermostats. I also don't think that there is a "thermostat" factory which is happily running only based on orders from MB. This factory has to make them to other customers as well, otherwise they would collapse.

This is a question, which nobody on here should really give you answer to. It your car, your money... of your new thermostat fails and is supplied by MB... I don't think you gonna gain anything, only because is supplied by MB.

HOPE this is something people should think while getting new/replacement parts.

Pretty sure autodoc sell the thermostat itself for around £7 . You swap them over in the housing . The metal type anyhow .

 

[E55BOF]

If you have an electrical connection on top of your thermostat, it won't be £7. They were about £125 and up for an aftermarket version, or £175 for an OE one in the Mercedes box, a couple of years ago. EWither way, an aftermarket one will be fine if it's from a reputable manufacturer, but I wouldn't use a Circoli one.

 

[PolishGeorge85]

If you have an electrical connection on top of your thermostat, it won't be £7. They were about £125 and up for an aftermarket version, or £175 for an OE one in the Mercedes box, a couple of years ago. EWither way, an aftermarket one will be fine if it's from a reputable manufacturer, but I wouldn't use a Circoli one.

I maybe very wrong but, thermostat housing is the same no matter if you have temperature sensor or not. I'm saying this only because I've spent hours after doing my cooler seals and at the end I had one cable that I didn't remember where it was plugged in. What I thought was that I've lost sensor of the top of thermostat housing.

Looking at the pictures of thermostats ,they looking very alike with or without sensor. I'll have a look on MB service software to see if there are different part numbers.

 

[PolishGeorge85]

Pretty sure autodoc sell the thermostat itself for around £7 . You swap them over in the housing . The metal type anyhow .

Exactly what I thought, thermostat is a part inside the housing. Unless is designed the way you have to replace it all together

 

[E55BOF]

The electrical connector is not for a sensor; it is for a teeny tiny immersion heater element that is within the hollow centre shaft of the 'stat. It's something to do with emissions during warm-up, and it can cause premature 'stat failure because coolant crystallises between the shaft and the element. I very much doubt you would see a measurable difference in fuel consumption with a plain unheated 'stat, and the car would not fail MoT because the engine would be up to temperature for the test.

I strongly suspect you could physically replace your heated 'stat in the housing with a plain old basic non-heated version if you cut away the gubbins within the housing, or even fit a plain housing and 'stat from a version of the OM 642 that did not have a heated one, but you might have to fit a resistor to the loom connector to fool the ECU into thinking you still had a heated 'stat, or you might well get an EML and fault code. I just wanted the car sorted, so I fitted an OE heated version.

 

[PolishGeorge85]

The electrical connector is not for a sensor; it is for a teeny tiny immersion heater element that is within the hollow centre shaft of the 'stat. It's something to do with emissions during warm-up, and it can cause premature 'stat failure because coolant crystallises between the shaft and the element. I very much doubt you would see a measurable difference in fuel consumption with a plain unheated 'stat, and the car would not fail MoT because the engine would be up to temperature for the test.

I strongly suspect you could physically replace your heated 'stat in the housing with a plain old basic non-heated version if you cut away the gubbins within the housing, or even fit a plain housing and 'stat from a version of the OM 642 that did not have a heated one, but you might have to fit a resistor to the loom connector to fool the ECU into thinking you still had a heated 'stat, or you might well get an EML and fault code. I just wanted the car sorted, so I fitted an OE heated version.

And this is why we here for. Your reply makes sense, I understand principle of this. And obviously now, (I'm changing my opinion) if your thermostat housing has a connector, buy one with connector.

E55BOF.... I'll read other replies of yours... have a good weekend

 

[MrGreedy]

You might still get lucky and be able to replace the inner....


I'll report back in a bit...

 

[OneForTheRoad]

If you have an electrical connection on top of your thermostat, it won't be £7. They were about £125 and up for an aftermarket version, or £175 for an OE one in the Mercedes box, a couple of years ago. EWither way, an aftermarket one will be fine if it's from a reputable manufacturer, but I wouldn't use a Circoli one.

I'm talking about the thermostat itself , I know how much they cost with the housing , I paid well over £100 for one myself, it was for the L6 not the V6 , I did research this topic myself at the time , because I was wondering if it's possible to swap out the stat from the housing . It is possible in certain applications. I went with the mb one because water works is a very important factor within the engine ,so pointless skimping .

 

[E55BOF]

Those are all unheated versions. Now if you could identify an unheated housing that is otherwise identical to the heated one, game on apart from maybe the resistor...

Or eviscerate the heated housing, and (unless the eviscerated housing then leaks, and I can see no reason why it would, or there's not quite room for the plain thermostat below what remains of the heater element), game on again apart from the resistor...

Worst case, you've bought a 'stat that you can't make fit, and you then have to buy an OE heated version. The only way to find out is to try it and see. I hadn't the time, or I would have done so...

 

[MrGreedy]

Thermostat for OM642 with heating element. I swapped it for another because it was sticking open and engine wouldn't get warm unless weather was warm/booting it up a big long hill.
Part No. A6422002215 as hard to see in image.





Then, you can see on the underside, a little blue crystalization/deposit on the mechanical/expanding stat insert (this bit with the magic heat memory spring).


And also a view of the same crystalization from the other end of the stat



You can remove the traditional stat/sprung insert by pushing down and rotating the retaining bracket/plate as follows (pic below shows me only slightly starting to push down and turn):



And then fully turned and released. I found it easier to put some normal-sized long nosed pliers in between the retaining plate and the round disc at the end, and very easily levered the plate down to release it from the side arms and twist to free it.



The old stat insert into the housing needed a bit of a small tug to pull it out. Here it shows it sliding off the heating element probe/immersion heater that goes down the centre of the stat. It now comes over very easily with zero resistance.



Any now fully removed. I think we can see why it was sticking and I was having issues: the rubber seal is deteriorating and splitting in a bit way, so no wonder it was sticking. I'm glad I changed it when I did, and didn't get a bit of that rubber seal breaking off and travelling round the cooling system and getting lodged somewhere expensive!




And finally, as we can see, the heating element probe and inside of the 'bowl' of the thermostat housing is as clean as a whistle and shows no sign of deposits. It appears to be all inside/stuck to the mechanical part of the stat.

 

[MrGreedy]

The above shows that the mechanical part is easiler removed from the themostat housing.
IF the heating element still works you could replace the mechanical bit.
IF you can find the correct stat insert with a hole of the correct size down the centre to houe the element.

If so, it's likely to be a tenner, so if anyone finds an inser that fits, post it up here for our benefit.

Also might be useful info. On my 2011 (2012 year model) the thermostat steady stat (fully open) temperature is 88°C. I've seen various stead state/opening temperatures on stats for sale.
The ones shown in the picture by @OneForTheRoad above are all 92°C, so would be the correct one for my car. Check carefully when buying to make sure it is correct for your engine/ECU (so that it operates 100% correctly). They also show what looks like a long brass nipple (almost like the end of a rivet) sticking out of where the hole should be for the heating element to slide down. I don't know if they are throw-away inserts keeping debris out of the hole before install, or if they are permanently installed in which case they wouldn't fit in the newer thermostat housings with the immesion heater probe.
See here:



Edit: If I search Autodoc with my exact car (from my Autodoc garage), all the stat options it gives are also 92°C, which I am very sure is not correct. Or at least, it doesn't correspond to the temperature on the dash nor when fully warm via iCarsoft readout. Which is 88°C.

 

[E55BOF]

Thermostat for OM642 with heating element. I swapped it for another because it was sticking open and engine wouldn't get warm unless weather was warm/booting it up a big long hill.
Part No. A6422002215 as hard to see in image.

View attachment 148948



Then, you can see on the underside, a little blue crystalization/deposit on the mechanical/expanding stat insert (this bit with the magic heat memory spring).
View attachment 148949

And also a view of the same crystalization from the other end of the stat
View attachment 148950


You can remove the traditional stat/sprung insert by pushing down and rotating the retaining bracket/plate as follows (pic below shows me only slightly starting to push down and turn):
View attachment 148951


And then fully turned and released. I found it easier to put some normal-sized long nosed pliers in between the retaining plate and the round disc at the end, and very easily levered the plate down to release it from the side arms and twist to free it.
View attachment 148952


The old stat insert into the housing needed a bit of a small tug to pull it out. Here it shows it sliding off the heating element probe/immersion heater that goes down the centre of the stat. It now comes over very easily with zero resistance.
View attachment 148953


Any now fully removed. I think we can see why it was sticking and I was having issues: the rubber seal is deteriorating and splitting in a bit way, so no wonder it was sticking. I'm glad I changed it when I did, and didn't get a bit of that rubber seal breaking off and travelling round the cooling system and getting lodged somewhere expensive!
View attachment 148954



And finally, as we can see, the heating element probe and inside of the 'bowl' of the thermostat housing is as clean as a whistle and shows no sign of deposits. It appears to be all inside/stuck to the mechanical part of the stat.
View attachment 148955

That one looks to be in the closed position, though, and from your symptoms it had failed in the (fail-safe) open position. The seal only seals it in the closed position.

I've never had a 'stat fail closed - until I bought the MINI. That one had, and it was a pig to change...

92 degree 'stats are now the norm; either fuel consumption is apparently very slightly better, or emissions slightly lower, at the higher temperature, and it does no harm to the engine.