Couple of theories on the diesel cool running problem?

[James.uk]

My car warms up fairly quickly, but never gets more than comfortably warm unless I drive for more than an hour or two, then I usually knock the temp in the cabin down a couple of degrees.. (ish)

Locally I have tried holding it in 3rd whilst climbing a very steep hill, the highest temp ever recorded was 105 but the temp dropped like a stone once on level ground again...

The car seems to like mid 70's to low 80's innit...

Using the fbh with no engine running flattens my battery fairly quickly..

I did it in Wimborne for an hour and needed the RAC to give me a jump start....

Life can get tedious innit...
...

[T-Cut]

Originally Posted by clf

Where would the bypass hose be?

The heater is the bypass loop. Either one of the hoses going to that will do as a test.

TC

[HarryM1BYT]

Originally Posted by clf

Where would the bypass hose be? I can't visualise it in my head and by the time i get home it is too dark, cold or wet to work at it

MY guess - T-Cut means the heater matrix hose, which passes through the bulkhead somewhere behind the engine, low down and on the drivers side. The two pipes appear behind the cover panel, to the left of the clutch pedal, as alloy pipes connecting to the heater matrix.

[klarzy]

Would having the AC off but previously set to a warm temp (tends to remember the last setting when off) and the fresh air control on the centre of the dash open, cause cold air to pass over the matrix and thus cool the engine unintentionally...?

[kaiser]

Originally Posted by SD1too

Alan,

Your variable running temperature related to road speed suggests that your cooling system isn't pressurising correctly.

????!

The only way to keep the Diesel warm in cold weather is to minimize the cold air in the engine compartment. Block part of the grill with a piece of cardboard.

That has been known for about 100 years

[Sector-9]

Has your EGR been blanked off? I've found on my diesel 45 that it warms up much slower once disabled by pulling off the vac pipe!

The reason that the cooling system seems to be over-specced for the engine is down to the turbocharger which will very quickly raise temps once blowing at more than a few PSI; normal maximum pressure is around 17-18psi for the diesel and it won't be contributing much heat below around 4psi. Also don't underestimate the cooling effect from the engine swallowing massive amounts of air such as when engine braking down a hill - not sure if the auto box freewheels at all (maybe only in D and above a certain road speed) but if it isn't then I can imagine that will shed heat whenever you let go of the throttle...

[clf]

Thanks for that T-Cut and Harry, that is what I had thought to myself. I was more concerned of its location. Not being able to check out things due to the dark wet and cold nights, means I have to visualise them in my head, and that can be frustrating at times lol.

Originally Posted by klarzy-dials.com

Would having the AC off but previously set to a warm temp (tends to remember the last setting when off) and the fresh air control on the centre of the dash open, cause cold air to pass over the matrix and thus cool the engine unintentionally...?

I was actually thinking along those lines too, which is why I mentioned it, even mentioning some of the mundane things, that perhaps I over look but give an indicator.

The thing is, why would MGR use a thermostat rated to open fully, at 88, and partially at less of course - lets say 80 degrees, yet under normal running conditions, it doesnt even reach 80? This is why I am thinking of other components.

I do have a video, using my phone, pointed towards the obd and rev counter for my journey home. I will try to get it uploaded later tonight.

The car on the way home tonight reached 75 at its highest, until I turned off the main road into my street. I drove to the shops, (about 300 yards from the main road) and when I reach there, driving at 20 mph, the temp began to climb. I reached the shops and the obd was showing 79. I switched on the heater whilst idling for the purpose of the video, and after about 2 minutes the temp dropped to 75. Idle again, and for 2 minutes with the heater off. it reached 79 again. I think airflow has a big part in it. (well I know that from what everyone has said previously ad from previous experimenting with covering the grill).

As I said, I cannot believe MGR would have used the stat for this engine rated with 88 degrees, yet I am getting these numbers. It is the numbers that are making me question the sender unit.

Thanks Mike for the resistance figures, if I can get to the sender with my multi meter at the weekend without dismantling the air intake I will be testing the resistance. That will be very useful!

Once again to all, thank you for participating. My thanks button runneth dry. This problem is something I have pondered on an almost weekly basis since I got the car. It isnt exactly rocket science and is all very logical, but there has to be a weak link somewhere in my cooling system.

[clf]

Originally Posted by Sector-9

Has your EGR been blanked off? I've found on my diesel 45 that it warms up much slower once disabled by pulling off the vac pipe!

The reason that the cooling system seems to be over-specced for the engine is down to the turbocharger which will very quickly raise temps once blowing at more than a few PSI; normal maximum pressure is around 17-18psi for the diesel and it won't be contributing much heat below around 4psi. Also don't underestimate the cooling effect from the engine swallowing massive amounts of air such as when engine braking down a hill - not sure if the auto box freewheels at all (maybe only in D and above a certain road speed) but if it isn't then I can imagine that will shed heat whenever you let go of the throttle...

Not exatly Sector 9, the EGR has had a by pass fitted, so theoretically there would be slightly more colder air entering the intake. But surely not that much more that it causes an over 10% drop in the coolant temp.

It does shed heat massively when the throttle is released and freewheeling begins. That is visible in the video.

[T-Cut]

Originally Posted by clf

I cannot believe MGR would have used the stat for this engine rated with 88 degrees

It wouldn't make much difference what rating they'd used under the circumstances.

TC

[ceedy]

This is basically the same as my Dizzle auto ...

My OEM repalement Stat lasted about 4 years then went off a bit( 78-80) , so fitted the inline one , temps went up to 82-83 with a 89 stat, replaced that just before this last christmas with another just in case it was a slightly out of spec stat, and now it runs at 80-82 max .so the stats seem to vary .

But the car has never ever got anywhere 88-89 even with the OEM stat in ?

C.