Do we need another Diesel Thermostat Thread

[ceedy]

Back on the "to work" run this morning, and the temps are pretty much like those shown before, getting up to 65-70 ish after only a couple miles

except the max is 79-80..

Did see that the max was reached after less than 6 miles then it dropped to 72ish for about 2 miles then back up to 79-80 with no change then even after a blast along the A303.

Think ive still got a slightly working OEM Stat, so bit of 2 stage action , OEM opens after 5 miles or so then it all drops with the bit of cooler water moving, then back up to 80 ish on the inline stat.

All with heater off.

And despite what everyoe else has suggested ,putting the heater back on quite hot over the last few miles made no difference in the overall temp






C.

[clf]

Originally Posted by ceedy

Back on the "to work" run this morning, and the temps are pretty much like those shown before, getting up to 65-70 ish after only a couple miles

except the max is 79-80..

Did see that the max was reached after less than 6 miles then it dropped to 72ish for about 2 miles then back up to 79-80 with no change then even after a blast along the A303.

Think ive still got a slightly working OEM Stat, so bit of 2 stage action , OEM opens after 5 miles or so then it all drops with the bit of cooler water moving, then back up to 80 ish on the inline stat.

All with heater off.

And despite what everyoe else has suggested ,putting the heater back on quite hot over the last few miles made no difference in the overall temp






C.

I would change your inline stat. if it was mine. It reads like there is a fair bit of coolant leaking by the inline stat. If it was dropping to 80, and maintaining 80, I would probably leave it as it was, as changing it introduces the risk of physical damage to other components for not a great deal of benefit. But because it is dropping below 80, and as low as 72, I would replace. These are simply arbitrary figures in my head, and not official. The commonly fitted inline stats, seem to run (if working correctly) at 84 degrees, which is how I come up with my arbitrary figure. (Benefit versus risk).

The heater will maintain its heat, and not affect the temp drop much, providing the engine has already reached its max operating temperature, because the thermostat is cycling at this point. The heater is only an issue, if it is used before it has reached the max operating temp, by slowing down the warm up time, sometimes considerably.

All cars, with a faulty stat or not (inline, OEM or both) will reach 65-70 in roughly the same amount of time. Unless the OEM is really bad, the problem only really surfaces from roughly 70 degrees. It seems when the OEM stat has become faulty, 70 is approximately when it begins to open early, and once this happens it will struggle to reach 75, and therefore not show the 9 o'clock position.

[T-Cut]

The OEM stats can deteriorate to start opening in the mid-50s according to my investigations. This photo shows an OEM stat and housing that started off (cold) with the hose connector flooded to the brim. On being warmed up, the valve opens early causing the level to fall.





Remember that before coolant can pass through the OEM stat via the engine, the in-line stat has to open first. They're at opposite ends of the cooling loop with the in-line at the head outlet. If the engine runs at a lower temperature than the rating for the in-line stat, there must be sufficient coolant passing through to keep it there. The best figures I've seen are where the engine's running near the in-line setting, in the upper 80s.



TC

[hst125]

Well I’m stumped. Just swapped out the stat as it was running at 42mins on the gauge. It was an 88c stat that wasn’t dual clamped in. Replaced with a brand new QH 86c with clips either side, and after preheating, turning the heater to hot/off, idling for ages it wouldn’t budge past 43.5minutes. Neither did it open suddenly, I felt some thermal heat spread but when it got into the top hose it was slow rather than full on. Couldn’t get a Wahler in time for my day off, should have waited!


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[clf]

Originally Posted by hst125

Well I’m stumped. Just swapped out the stat as it was running at 42mins on the gauge. It was an 88c stat that wasn’t dual clamped in. Replaced with a brand new QH 86c with clips either side, and after preheating, turning the heater to hot/off, idling for ages it wouldn’t budge past 43.5minutes. Neither did it open suddenly, I felt some thermal heat spread but when it got into the top hose it was slow rather than full on. Couldn’t get a Wahler in time for my day off, should have waited!


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your first stat could have been fine, or doing what it was meant to be doing.

Before doing anything else, you need to check the temperature using the OBD, and do not rely on the gauge. I fitted two 86 inline stats which both gave 82 degrees on the OBD display, when cruising after reaching its maximum temp, when it opened at 84. The needle remained at, roughly, a needle's width below the 9 oclock position (which it did when reaching 75 degrees).

Even with the Wahler stat, the needle only reaches this, below the 9 oclock, position and this was normal (for my car) - it initially opens at 88-90 and maintains 86 whilst cruising. (I attribute this discrepancy deficit to the position of the inline stat - but I cannot prove this).

Take the car for a 10 mile drive, with the heater off, to test. Idling will take a very long time to encourage the stat to open. These engines are very thermally efficient and I have seen situations (on my commute) where the temp dropped whilst idling at traffic lights (this was prior to the initial opening of the stat and the heater off).

[hst125]

Thanks, I’m back at work tomorrow and it’s a 23 mile each way drive, I’ll pack my OBD. I don’t have IPK on this car. The main reason of fiddling is to try and sort the mpg out, I should be getting 5-10 more than I am, comparing like for like with my old 75. I’m struggling to break 35, and I’ve been through other things like removing the Synergy box, new genuine Bosch MAF, same remap as I had on the 75, clean air filter and quality fuel. Waiting for Amazon to deliver my new tyre gauge too. I haven’t even got roof bars!


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[hst125]

Just plugged in the OBD



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[clf]

Originally Posted by hst125

Thanks, I’m back at work tomorrow and it’s a 23 mile each way drive, I’ll pack my OBD. I don’t have IPK on this car. The main reason of fiddling is to try and sort the mpg out, I should be getting 5-10 more than I am, comparing like for like with my old 75. I’m struggling to break 35, and I’ve been through other things like removing the Synergy box, new genuine Bosch MAF, same remap as I had on the 75, clean air filter and quality fuel. Waiting for Amazon to deliver my new tyre gauge too. I haven’t even got roof bars!


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You cannot pack an OBD (On Board diagnostics ) - you already have it, all of our cars have it. OPTION 7

My auto diesel does roughly 34-36 consistently on a fill to fill measurement (only way to tell). On my commute, and driving style, this is adequate/normal. Driving it incredibly boringly, I can get this up to 38, so I drive now without hypermiling. On a run, I can get this up to 45 or so.

There are too many variables to determine mpg, even down to an interpretation of what is gentle acceleration can be the cause!

As an example, your Autolink tool displaying 81 degrees, means nothing without further data, I am afraid. What engine load was there, distance traveled, speeds reached and maintained for what distance etc. Forget about using that tool, and report what the temp is from the OBD after your 23 mile journey - even with all of the variables, the temp after a run of that distance will give you max temp. It will not tell if the stat is opening early etc. That takes a little more concentration, and comparison - eg if I drive 5 miles at 30 mph, it will be a lower temp for 5 miles of the same road at 50mph, also the stat may have opened on the 50 mph journey but not the 30 mph journey.

[hst125]

Well I never....
Anyhow I had this from my Jag experience so I used it! A little later on it said this..



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