symptoms of stuck thermostat

[macafee2]

How long does a diesel 75 take to warm up, if the thermostat is stuck open? Google maps shows I did over 20 miles and the gauge still did not get to 9 o'clock, this seems and awfully long time

macafee2

[Lee T]

Sounds like the usual o.e.m stat issue mate. Bung 1 in the top cooling hose it works just fine.

[clf]

Originally Posted by macafee2

How long does a diesel 75 take to warm up, if the thermostat is stuck open? Google maps shows I did over 20 miles and the gauge still did not get to 9 o'clock, this seems and awfully long time

macafee2

whilst it does sound like an early opening thermostat, forget the gauge and use the OBD to rule out a (very unlikely) faulty gauge.

As far as time goes, a lot depends on how the car is driven, and ambient temps will have an effect to a certain degree. I would suggest, 3 miles of 40mph driving with minimal acceleration, you should be up to around 70-75 degrees (the 9 o clock position starts around 75 degrees , and up to 105 I believe), then a further 2-3 miles of the same should see you at 84-86. This is how my commute works, after this I would be onto the motorway, and accelerate firmly to 70, 88 degrees, after about 1/2 a mile.

It would be important to note, I have an 89 degree Wahler inline stat, other stats I have used, opened lower. The lower opening to the stated rating of the (inline) stat, I believe is due to its location. (fit an 86 degree stat, and I would expect it to show opening at around 84 degrees on the OBD)

[macafee2]

Originally Posted by clf

whilst it does sound like an early opening thermostat, forget the gauge and use the OBD to rule out a (very unlikely) faulty gauge.

As far as time goes, a lot depends on how the car is driven, and ambient temps will have an effect to a certain degree. I would suggest, 3 miles of 40mph driving with minimal acceleration, you should be up to around 70-75 degrees (the 9 o clock position starts around 75 degrees , and up to 105 I believe), then a further 2-3 miles of the same should see you at 84-86. This is how my commute works, after this I would be onto the motorway, and accelerate firmly to 70, 88 degrees, after about 1/2 a mile.

It would be important to note, I have an 89 degree Wahler inline stat, other stats I have used, opened lower. The lower opening to the stated rating of the (inline) stat, I believe is due to its location. (fit an 86 degree stat, and I would expect it to show opening at around 84 degrees on the OBD)

obd? is that the on board readout via the ipk screen?
I have seen threads about how to access it but have never been able to take it onboard.

The car was driven at 2500 plus revs for the majority as I had used injector cleaner and it was at worst chilly, no frost on the windscreen when started

macafee2

[T-Cut]

Originally Posted by clf

It would be important to note, I have an 89 degree Wahler inline stat, other stats I have used, opened lower. The lower opening to the stated rating of the (inline) stat, I believe is due to its location. (fit an 86 degree stat, and I would expect it to show opening at around 84 degrees on the OBD)

The vital factor is the stat must be water-tight when closed. Many in-line stats have either a jiggle pin or small drilling the allow air bleed-by. Any bleed-by will prevent you getting the results you expect. Even a 1mm bleed will stop the engine reaching the temperature rating of the thermostat. So far, those branded FirstLine, Wahler and Gates are proven good.


TC

[Number 6]

Originally Posted by T-Cut

The vital factor is the stat must be water-tight when closed. Many in-line stats have either a jiggle pin or small drilling the allow air bleed-by. Any bleed-by will prevent you getting the results you expect. Even a 1mm bleed will stop the engine reaching the temperature rating of the thermostat. So far, those branded FirstLine, Wahler and Gates are proven good.


TC

That is interesting,,When I fitted an Inline stat some years ago I was told to drill a 1mm hole in the stat to aid the bleeding.It would now appear that this was the wrong thing to do..

Any one care to comment ??

[T-Cut]

The presence and size of bleed holes was investigated in the early days of the in-line thermostat project. Different size holes were drilled through the valve or the vave annulus to see what difference it makes. Also, the water-tightness of the closed stat has been checked out by comparing stats from different makers. All the results support the hypothesis that no bleed-by is the only way to ensure the diesel runs anywhere near the temperature rating of the stat. By following every detail of the in-line stat story, I'm pretty convinced that the varying results (running temperature) that people report from theirs are related to bleed-by. If anyone else is willing to do the experiments, it would add valuable data to the theory.


TC

[Number 6]

Originally Posted by T-Cut

The presence and size of bleed holes was investigated in the early days of the in-line thermostat project. Different size holes were drilled through the valve or the vave annulus to see what difference it makes. Also, the water-tightness of the closed stat has been checked out by comparing stats from different makers. All the results support the hypothesis that no bleed-by is the only way to ensure the diesel runs anywhere near the temperature rating of the stat. By following every detail of the in-line stat story, I'm pretty convinced that the varying results (running temperature) that people report from theirs are related to bleed-by. If anyone else is willing to do the experiments, it would add valuable data to the theory.


TC

OK thanks for that,So which stat is the now recommended one to fit ? as I will change it over

[clf]

Originally Posted by clf

It would be important to note, I have an 89 degree Wahler inline stat, other stats I have used, opened lower. The lower opening to the stated rating of the (inline) stat, I believe is due to its location. (fit an 86 degree stat, and I would expect it to show opening at around 84 degrees on the OBD)

Originally Posted by T-Cut

The vital factor is the stat must be water-tight when closed. Many in-line stats have either a jiggle pin or small drilling the allow air bleed-by. Any bleed-by will prevent you getting the results you expect. Even a 1mm bleed will stop the engine reaching the temperature rating of the thermostat. So far, those branded FirstLine, Wahler and Gates are proven good.


TC

I am not convinced re. the temp difference between the rating and the displayed temp. Each one I have had has always shown 2 degrees less than its rated opening temp. The first one was an 84 rated, but the OBD never showed more than 82 (I never thought it would be an issue, as I was happier than the 75 of before). Over time with that one it began to take longer and longer to heat up and eventually struggled to even reach 80. I think that was the leak by from the disc (I crushed it on removal so I couldnt check) - poor quality.

The next couple were both 86 degree rated ones, and they were bang on 84 degrees via OBD. The first of these I imagined still took too long to warm up. Replaced it again, but this one worked quicker but still only 84. But I was initially convinced there was another issue elsewhere, (remember the epic thread with my hypothesis of sludge on one corner of the rad? lol). I was convinced by you and others to remain focused on the 'stat', and I think you were correct. That was where the 'bowl' videos/tests came into play and the Wahler 89 degree version.

It though, opens at 88 via the OBD, drops, to around 86ish then builds up quickly again and settles at 88. Even though it is rated at 89. This is why I am convinced the location of a working (ie lets call it 'sealed') inline one has a bearing on the lower than rated OBD temps. A poor 'sealing' one will just take longer to reach temp with the bleed by. I only had an analogue cooking thermometer to test prior to fitting, but it was around 88-90 in a pan of hot water, when it was tested. A that time I just wanted it to open well above 75 lol.

I dont think it will be an issue, providing the inline stat allows the car to reach temp relatively quickly. I only mention it to pre-empt the question of 'why do I only get 84 degrees with an 86 degree stat fitted?' That was the reason I replaced with the Wahler. If it was fitted immediately before the OEM one somehow, I think it would go the other way and open slightly later than rated.

[T-Cut]

I think we have to factor in the accuracy and precision of thermostat settings and such. A thermostat's rated temperature is (as far as I can determine) the temperature at which it begins to open, which is not necesarily the running temperature. Because they're mass produced, the precision of this setting is unlikely to be high. From what I've read, it's unlikely to be better than 3 degrees. In other words an '88C' stat will typically start opening at 88+/-1.5 C. The same thing holds true for any thermometer you may use to measure the opening temperature - or indeed the engine running temperature (temperature gauge, sensor precision, etc.)


TC