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-   -   Diesel thermostat definative answer (https://www.the75andztclub.co.uk/forum/showthread.php?t=68468)

James.uk 10th September 2010 16:16

Altering the cooling by replacing a non working thermo will undoubtedly make a difference as clearly the engine was designed to work with the existing thermostat working properly..

However, modifying the rad could be both time consuming and expensive, and may ultimately produce no better results than blocking part of the existing rad off with a piece of flat plastic.. :shrug:

Testing our theories is the hurdle, unless that's done we can waffle on about this forever. And personally, I don't think it's worth the risks involved.. :shrug:
...

BarryH 10th September 2010 16:20

Quote:

Originally Posted by T-Cut (Post 586130)
Agreed, but using the same radiator matrix for the diesel, V6 and K16 seems more like cost saving than engineering. IMO, the diesel is markedly over-cooled under 'normal' running conditions.

TC

I agree that the diesel is overcooled.Last winter mine got up to running temperature after about 6 miles,which was only around 80 degrees.This winter I intend blanking off the lower half of the rad to see if there is any improvement
Barry

gefary 10th September 2010 19:05

I have enjoyed you lot "waffling on" about radiators and anti freeze.
I have learned a lot.
But I'm not sure what to do with all this knowledge I have acquired.

kaiser 10th September 2010 20:03

I have read some of these posts with interest, and it is dawning on me that many people have got no clue about what is going on.

If the thermostat is closed, then there is no water going to the radiator, and it doesen't matter how good or bad the radiator is. The only cooling you will have comes from the heater matrix, if it is open, and from cooling around the engine as well as from heat lost in the exhaust. That is it!

If the car in this case does not reach operating temperature, you can only block the heater and/or increase the load on the engine, as the engineer says to increase the water temperature. That is it!! it does not matter what you do to the cooling system, you can block the radiator completely, take it out or sell it! it will make no difference!
This can typically be the case on a cold day where you are cruising at a constant speed.

Obviously, a stuck thermostat in an open position will make matters worse. As you then have an amount of water being cooled because of the radiator.

So chaps, face it. If your thermostat is not faulty, (that is sticking either open or closed), it does not help to replace it with a hotter unit, if the engine is over-cooled on a cold day. The temperature of the water will not even get to the triggering temperature of a hotter thermostat, if it does not trigger the original thermostat. The only thing you will achieve is to increase the temperature of the system on hotter days, when you don't need it.

The best advice is to reduce the use of the heater, and yes, blocking the radiator might help, but not for the blocking of the radiator itself, (which will not be in operation), but for reducing the flow of cold air around the engine and in that way limiting the cooling of the block itself.

Hope this makes a bit of sense to you!

Matt1960 10th September 2010 20:20

Kaiser
But what you are suggesting would make sense to me, except that even on a cold day, after about 10 miles or heavy load, the engine DOES get up to thermostat opening point of 88c.
This means that at this point the coolant starts circulating around the radiator, does it not?
All the stat does is limit the flow of coolant around the radiator at a set temp.
It might be that even with a 92c stat the engine might still not get hot enough to open this stat, but my gut feeling is that it would.
Matt

kaiser 10th September 2010 20:33

Quote:

Originally Posted by Matt1960 (Post 586281)
Kaiser
But what you are suggesting would make sense to me, except that even on a cold day, after about 10 miles or heavy load, the engine DOES get up to thermostat opening point of 88c.
This means that at this point the coolant starts circulating around the radiator, does it not?
All the stat does is limit the flow of coolant around the radiator at a set temp.
It might be that even with a 92c stat the engine might still not get hot enough to open this stat, but my gut feeling is that it would.
Matt

Yes, Matt, it does.
But, you have then laboured the engine to get it up to 88 degrees. Having a hotter stat in it will not have changed your experience for the first 10 miles at all!
What you would like is a car that got to that temperature after, say 2 miles, I guess?
If you want that, switch the heater off (then there is no flow of water out of the engine at all) and reduce the outside cooling of the block, by blocking some of the cold air around the block.
A piece of cardboard in front!?

You see the problem/solution?
The stat itself does not figure at all for the fisrt ten miles in your case.

Matt1960 10th September 2010 20:43

Kaiser,
I agree with that.
But I dont think the whole thread was about how quickly it gets to temp. More about efficiency once up to temp.
And the BMW engineers had the answer to the slow heating problem, and fitted a FBH for this very reason.
Without the FBH, limiting the loss of heat through the matrix is a very good way to speed up the engine heating.
Matt

T-Cut 10th September 2010 22:35

The experimental evidence is that diesels running at temperatures below the nominal stat setting get hotter when a new stat is fitted. There are dozens of reports on this. The statistical evidence therefore is that older stats tend to allow coolant flow to the radiator below the notional set temperature.

TC

Frank Incensed 10th September 2010 22:38

Quote:

Originally Posted by crashmarks (Post 585927)
Having now pondered the reply i have just sent them another note asking what cars they put the M57D in. Having regard to the last paragraph of their reply, if the thermostat manufacturer used the same design and there was a 92 degree for the M57 engine it may fit ! Perhaps somebody who has a spare / old thermostat (which I dont) could pop into the BMW dealer and compare them. mmmmmm food for thought.

I can answer that, Crashmarks. Using the part number on the thermostat I've found that the same one was used in the X5 3.0 D (M57 engine). I've seen one web site that shows it was used in 77 different models by various manufacturers, including Opel and Range Rover diesels! You'll note that all the other engines in which it's used seem to be bigger than ours. The original in the X5 was apparently notorious for failing. It appears that the revised thermostat still opens at 88C, though.
I believe that the thermostat alone is or was available in Europe as a separate item but my local BMW place was unable to trace the part, even with the part number. In the UK you can only get the thermostat for the M57 as a complete unit with housing and I doubt whether that would bolt straight on. This may mean that you'd have to buy the complete unit and transplant the thermostat.
I've now given up with BMW and I've turned my attention to the manufacturers, Behr and Wahler (I'm not sure if Motorrad actually make anything or whether they're just the spares arm of BMW. I'll write to them though, just in case). Behr's web site is very welcoming. They say, "What can we do for you? Give us a challenge! We will be glad to provide more information on our products". We'll see if they live up to that.
If anyone is interested in doing any dabbling, the relevant BMW part numbers are:
11 51 7 787 052
11 51 7 787 113
11 51 7 789 014
11 51 7 805 811
Someone might be able to trace the thermostat alone as a Range Rover, Opel or some other manufacturers' spare, rather than BMW's.

I REPEAT, I BELIEVE IT MAY ONLY BE THE THERMOSTAT IN THESE UNITS THAT IS THE SAME AS OURS.

Jules, I'm sending you a PM with some info which might or might not be useful

-Joe 14th September 2010 23:34

warm up tips
 
Well I have an FBH, which is nice! Everyone can significantly decrease engine warm up time just by ensuring the heater contols are set to full cold during warm up. You can feel the engine power diminish as you twist the heater control towards hot when the engine is very cold and warming up.

After reading these posts I think that most diesel owners complaining of slow warm up have a broken themostat. The thermostat is not closing properly, I have changed a thermostat before that looked ok to me but the replacement completely fixed a warm up problem that that car had.

If you have a water cooled EGR then it enables a quick warm up by using super hot exhaust temperatures to warm up the cooling water. If you remove the EGR then you get a cooler running engine.

What about fooling the EGR into opening after start up to enable super quick warm up times? Probably a bad idea, anyone tried it?


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