I am experimenting with a new diesel thermostat with a view to raising the running temperature. If anybody has examined a failed stat was it the centre shaft which had seized or just the large return spring which had failed? Could the stuck open valve be pushed to the closed position and, if so, did the large spring then rattle around because it had lost its temper? Thanks.
wuzerk
When they fail shut it is usually because the wax has escaped past the seal and not that the thermostat has seized.
Covert.
Fully agree with your comments Colvert but we've been getting quite a few where the thermostat has stuck in the open position. Also, the current one is set low and one would like to see a thermostat which opened at say 92 degrees. I've had a looksee but as yet, have not been successful in tracing one.
If it malfunctions by the wax leaking and not doing the job it is required to do - OK a new one would then be required but the Diesel currently runs, in my opinion, on the low tempature side.
TC and Flyer had a lot to say on this subject.(well discussed )
John
If it malfunctions by the wax leaking and not doing the job it is required to do - OK a new one would then be required but the Diesel currently runs, in my opinion, on the low tempature side.
TC and Flyer had a lot to say on this subject.(well discussed )
John
If the wax was lost through the shaft seal, the spring would close the valve and it wouldn't fully open or may never open at all. That would produce a stuck shut and therefore overheating thermostat. I suspect there's more to it in the case of the diesel stat. I very much doubt it's anything to do with the spring. More likely a mechanical glitch preventing it's closure, maybe in the piston design? So, they invariably stick open and it takes ages to warm up and the running temperature is too low. If the stat could be replaced with a more reliable one, maybe things would be OK. There's been no reported failure (yet) of the replacement stats going in country-wide, so maybe they are of better quality. That's one part of the cool running issue. The one I spout about more is about raising the stat temperature to get the engine hotter than the 90C or so that new stats seem to provide. IMO, the diesel will give more mpg if it ran like the petrols at 95-105C. That is a proposition which has to be checked out and is I believe the subject of this thread.
It would certainly be useful if the old stat were examined by anyone replacing it.
TC
It would certainly be useful if the old stat were examined by anyone replacing it.
TC
Stats !!!!!!
Hi I replaced my thermostat but before doing so I thought I would have a go at trying to obtain a hotter running stat, no chance I shopped all over the planet, I tried suppliers in the US, Canada and any other cold country I could think of, so how the hell they go on in -30° !!!! all the stats I come across are standard 82° even for the BMW’s, so good luck in trying to find one!! Let me know if you have any luck? Steve
Hi I replaced my thermostat but before doing so I thought I would have a go at trying to obtain a hotter running stat, no chance I shopped all over the planet, I tried suppliers in the US, Canada and any other cold country I could think of, so how the hell they go on in -30° !!!! all the stats I come across are standard 82° even for the BMW’s, so good luck in trying to find one!! Let me know if you have any luck? Steve
Results- diesel thermostat
To save anybody wasting their time I give the results of my experiments with a new diesel thermostat. Opening temperature unmodified (3 times)
=91 degrees C. Opening temp with a 57thou" shim under the return spring = 91 degrees C ! Since I think that it is the return spring which loses its power and allows the stat to remain open then shimming it would only hasten its failure. The other possibility of course is that the piston seizes up (always, it seems, in the open position). That would need an additive for the radiator which lubricates it! I do seem to remember' Bars Leaks' or similar which stated that it lubricated the water pump? I have not heard yet from any owner who examined their stat when it failed.
To save anybody wasting their time I give the results of my experiments with a new diesel thermostat. Opening temperature unmodified (3 times)
=91 degrees C. Opening temp with a 57thou" shim under the return spring = 91 degrees C ! Since I think that it is the return spring which loses its power and allows the stat to remain open then shimming it would only hasten its failure. The other possibility of course is that the piston seizes up (always, it seems, in the open position). That would need an additive for the radiator which lubricates it! I do seem to remember' Bars Leaks' or similar which stated that it lubricated the water pump? I have not heard yet from any owner who examined their stat when it failed.
No thickness of shim under the spring will stop a thermostat opening at the set temperature. If you welded it shut, it would explode around the set temperature. This is because liquids are incompressible. When the wax melts it creates a liquid with a greater volume than it started with. The forces within that expansion are irresistable. There's something wrong in this particular stat's design.
TC
TC
Yes! I've seen a layour of the Freelander's remote thermostat and its related pipework.
One would have to do an exercise to apply it to the 75 which would do away with the existing trermostat. If I remember correctly, it's like a bypass....
This was discussed before! well, at least comments thereon.
John
One would have to do an exercise to apply it to the 75 which would do away with the existing trermostat. If I remember correctly, it's like a bypass....
This was discussed before! well, at least comments thereon.
John
Wuzerk,
I changed my stat recently because it was taking a long time for the engine to warm up, I also noticed that the temperature would drop when I slowed up, I removed the old stat and found it in the open position, after cleaning, it closed and worked as normal, however as I had already purchased a new one I did not refit the old one.
BMW designed the engine to run at a certain temperature, I would not want to change any of the manufacturers design parameters for fear of causing damage to other engine components.
Tony
I changed my stat recently because it was taking a long time for the engine to warm up, I also noticed that the temperature would drop when I slowed up, I removed the old stat and found it in the open position, after cleaning, it closed and worked as normal, however as I had already purchased a new one I did not refit the old one.
BMW designed the engine to run at a certain temperature, I would not want to change any of the manufacturers design parameters for fear of causing damage to other engine components.
Tony
Thermostat
TONY: I have moved on quite a bit since my original post, I have been using a 91.6C thermostat in a top hose housing for over a year now with no problems. I have recently discovered a 'stat rated at 96.1C which I have been using for the past week. Regarding the temperature designed by
BMW, if you read the first post in the 'difinitive thermostat ' topic you will see that it seems that BMW themselves said that the diesel does not produce enough heat and that it would be fruitless to try a hotter thermostat! This is plainly rubbish as I am now running between 92-97C. It remains to be seen if the diesel can reach those temperatures in the really cold weather.
TONY: I have moved on quite a bit since my original post, I have been using a 91.6C thermostat in a top hose housing for over a year now with no problems. I have recently discovered a 'stat rated at 96.1C which I have been using for the past week. Regarding the temperature designed by
BMW, if you read the first post in the 'difinitive thermostat ' topic you will see that it seems that BMW themselves said that the diesel does not produce enough heat and that it would be fruitless to try a hotter thermostat! This is plainly rubbish as I am now running between 92-97C. It remains to be seen if the diesel can reach those temperatures in the really cold weather.
96.1c
NICPY: It is too early to say but I will report my findings after a decent test period. When I fitted the 'stat housing in the top hose over a year ago my temperature rose from a max of 74C to between 84-93C, depending on load, and the consumption improved by 2-3 mpg.
MINTEE: the 96.1C (205F) thermostat is the STANT 13352. It is American but was supplied to me by sales@americanautoparts.co.uk
NICPY: It is too early to say but I will report my findings after a decent test period. When I fitted the 'stat housing in the top hose over a year ago my temperature rose from a max of 74C to between 84-93C, depending on load, and the consumption improved by 2-3 mpg.
MINTEE: the 96.1C (205F) thermostat is the STANT 13352. It is American but was supplied to me by sales@americanautoparts.co.uk
Ask the trucking companies what temperature a diesel should run for best economy. After all, they make their living from it. To answer that, have a read of this post from somebody in the business.
Diesel temperature (Post 19): http://www.the75andztclub.co.uk/forum/showthread.php?t=90517&highlight=%22hurray%22&page=2
TC
Diesel temperature (Post 19): http://www.the75andztclub.co.uk/forum/showthread.php?t=90517&highlight=%22hurray%22&page=2
TC
Stat
MINTEE: There seems to be an immediate difference between the STANT and the CHEVY stat. In the short time that it has been fitted I am regularly seeing 95C which rises to 97C on any uphill ride when the 'stat then opens.
I will be doing my usual 'long' run this week so will find out more.
Price? Three cost me £40.63 including Vat and PandP. This was from a British supplier. The postage from America is very expensive.
MINTEE: There seems to be an immediate difference between the STANT and the CHEVY stat. In the short time that it has been fitted I am regularly seeing 95C which rises to 97C on any uphill ride when the 'stat then opens.
I will be doing my usual 'long' run this week so will find out more.
Price? Three cost me £40.63 including Vat and PandP. This was from a British supplier. The postage from America is very expensive.
I'm running an 82 degree stat in my top hose, and got the following temps:
- Takes about 4-5 miles of brisk A roads to heat up
- When 'giving it beans' max temp was about 83 degrees
- Stuck in traffic it peaked at 97, then the fan came on and straight back to 92
- It took over half a mile of engine braking down hill to drop below 75 degrees, and thus register on the temp gauge.
This is with a Renault 5 thermostat, £4 on eBay.
- Takes about 4-5 miles of brisk A roads to heat up
- When 'giving it beans' max temp was about 83 degrees
- Stuck in traffic it peaked at 97, then the fan came on and straight back to 92
- It took over half a mile of engine braking down hill to drop below 75 degrees, and thus register on the temp gauge.
This is with a Renault 5 thermostat, £4 on eBay.
Presumably the bypass circulation through the heater matrix provides enough cooling to prevent the stat opening for quite a while, particularly if the engine's not pushed. Fitting a ball valve in the heater feed hose would be an interesting experiment. Reducing coolant flow rate through the engine would certainly raise its temperature to any figure you like. There is radiant heat loss from the block obviously and convection to the airflow, but I doubt under normal driving this alone would prevent an overheat. You'd have to throttle the valve to some setting determined by experience. It would obviously reduce early cabin heating even more, but you can't have everything.
As to why old thermostats run too cool, there has been a limited number of observations reported on this. Contrary to many people's expectation, they do not stick in the open position. All cool running stats were found to be shut on removal, indicating that they remain functional. If they were stuck shut, then overheating would be common, but it isn't. What seems to happen is the original 88C opening point progressively reduces. This isn't a mechanical failure, nor does the return spring weaken or fatigue. It's far more likely IMO that there is a change in the chemistry of the wax used in the capsule. Where no wax is lost or there is no mechanical weakness to explain the problem, the answer seems to be that they simply begine to open at a lower and lower temperature as they age. It will be interesting to see if new OEM stats exhibit the same characteristic. Engines fitted with new OEM stats are reported to run in the 88-90C area, as they are designed to. I guess time will tell on these.
TC
As to why old thermostats run too cool, there has been a limited number of observations reported on this. Contrary to many people's expectation, they do not stick in the open position. All cool running stats were found to be shut on removal, indicating that they remain functional. If they were stuck shut, then overheating would be common, but it isn't. What seems to happen is the original 88C opening point progressively reduces. This isn't a mechanical failure, nor does the return spring weaken or fatigue. It's far more likely IMO that there is a change in the chemistry of the wax used in the capsule. Where no wax is lost or there is no mechanical weakness to explain the problem, the answer seems to be that they simply begine to open at a lower and lower temperature as they age. It will be interesting to see if new OEM stats exhibit the same characteristic. Engines fitted with new OEM stats are reported to run in the 88-90C area, as they are designed to. I guess time will tell on these.
TC
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
