P38 2.5 diesel T'stat

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phantom21

New Member
Posts
58
Location
West Susex
Hi
How easy is it to remove the Thermostat on a 98 diesel, according to rave you have to remove viscouse fan and cowl. I don't have EGR pump in the way
Karl
 
Thanks
I didn't get a reply before I went out and did it as you say. Only had to remove top hose and the little cable tray holding ECU cable, and as you say it's fiddly. you need 1/4 inch deep 10mm or a very short extension

I was expecting to find the Thermostat stuck half open and was a little disapointed to find it looking in perfect condition. But on fitting the new one it's cured the problem of the temp gauge never reaching the centre zone, now it sits just below 12 Oclock all the time.

KArl
 
A new thermostat should come with a replacement o-ring.

I had the same result when i replaced mine, the gauge would always be in the blue zone, after taking out the old one and testing it side by side with a new one they both opened perfectly, so in went the new one expecting to see no difference, but lo and behold, the engine now rises to the correct temp at just below 12 o'clock on the gauge. Go figure!
 
bbjunkie said:
Just about to tackle this job myself, I have the thermostat, but do I need a gasket?
Click to expand...

I had a bit of confusion in this area, ended up doing the the job more than once.
With the Thermostat i got a round section O ring, but when i took the old stat out i did not see an o ring. I could have missed it dropping, it's very dark down there.
So I put it back together with the supplied O ring, but i wasn't happy while doing it as the O ring seemed too thick in section. Just didn't look good. Anyhow i put it all back and after warm up i noticed it was slightly leaking, so tore it down again and noticed the o ring was damaged where it had been squeezed out on tightening the housing down.

So this time i put it back together without the O ring, trake note there is a second square section o ring sitting in the cylinder head. But again it leaked.
Third time lucky, I put it back together with an O ring that i supplied, this was quite a bit thinner in section and it seems to be OK

I may have got away with the first O ring if i hadn't tightened the housing down all the way so that it mated with the cylinder head.

Its a crap design, the O ring has no recess to sit in, it's almost like an after thought. If i'd had the time i would have cut a paper gasket and done it the old way.
 
From experience.. where RAVE says 7lbs torque on thermo housing bolts they mean it, anymore and you damage the O-ring as you found out. The O-ring should go on the outside of the stat, and there should not be another ring in the block, this is why the O-ring looked too thick! I had to go out and get a new t-wrench as my old one only went down to 20lbs!
 
kernowdragon said:
From experience.. where RAVE says 7lbs torque on thermo housing bolts they mean it, anymore and you damage the O-ring as you found out. The O-ring should go on the outside of the stat, and there should not be another ring in the block, this is why the O-ring looked too thick! I had to go out and get a new t-wrench as my old one only went down to 20lbs!
Click to expand...

Mine definately has a rubber ring engine side, it is approx 4mm square section and sits inside a machined rebate, so that it is flush with head.
I think the incorrect outer O ring was supplied with my thermostat as when i used a thinner one everything went together better. with the supplied ring i couldn't get the housing anywhere near to mating with the head
 
phantom21 said:
Mine definately has a rubber ring engine side, it is approx 4mm square section and sits inside a machined rebate, so that it is flush with head.
I think the incorrect outer O ring was supplied with my thermostat as when i used a thinner one everything went together better. with the supplied ring i couldn't get the housing anywhere near to mating with the head
Click to expand...

That second ring definately shouldn't be there! There is no seal shown in the official RAVE manual. My guess would be that someone before you did the stat, couldn't get it to seal properly and added it. The stat should sit in that rebate with the o-ring around the raised section on the outside, the rebate helps keep the o-ring in place when torquing it up, hence your comment about the poor design of the housing not providing anyway of locating the ring.
 
kernowdragon said:
That second ring definately shouldn't be there! There is no seal shown in the official RAVE manual. My guess would be that someone before you did the stat, couldn't get it to seal properly and added it. The stat should sit in that rebate with the o-ring around the raised section on the outside, the rebate helps keep the o-ring in place when torquing it up, hence your comment about the poor design of the housing not providing anyway of locating the ring.
Click to expand...

Strange, This seal in the rebate is a perfect fit, not only the diameter but the depth also. If it wasn't such a pig to access i'd take it off and photograph it.

I can see your point, and now you can appreciate how awkward it would be with another O ring on the outside with nothing to locate it fully.

I have a suspision that the square section O ring i have should be on the outside of the thermostat. Possibly BMW used a bespoke designed seal before opting for a cheaper standard round section O ring. and at some point later it's been assembled incorrectly.

As I said earlier when I first dissmantled it, there was no ring on the outside, the thermostate was actually stuck to the seal in the rebate and i had to use a screwdriver to prise it off. So there is no mistaking the order of assembly

Out of interest have you seen more than one engine and were they all round section O rings?

Karl
 
I've seen a couple now, and just to be sure I checked with my local LR specialist, who's view was that someone must have found a leak and just packed it out to solve the problem, because that inner seal defo shouldn't be there. LR specify the round section o-ring as the correct seal, to be fitted to the outside of the stat. That's the way mine's assembled and I have had no problems with it. It's definately pain to reach though, why it couldn't be in a housing reachable from the top of the engine like so many others beats me.
 
Last edited:
kernowdragon said:
I've seen a couple now, and just to be sure I checked with my local LR specialist, who's view was that someone must have found a leak and just packed it out to solve the problem, because that inner seal defo shouldn't be there.
Click to expand...

OK, thanks for your input. what makes these forums so valuable is the experience others beforehnd. And i'll put it rght when i've fixed all the other isues I have.
 
You're right, the info and advice here is invaluable, it helped no end with my overheating problems, of which the stat was not part of the problem, the water pump rotors disintergrated! Good luck with your Rangey.
 
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