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20th January 2012, 13:50 | #1 |
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The Function and Malfunction of the Diesel Thermostat
In spite of lengthy discussions and interjections, the true functionality of the diesel thermostat remains to be established. It seems almost certain that it is different from what we know about 'ordinary' wax stats. It has two valves for a start. Well, it has a standard flow sealing valve/disc and a second, co-operating disc, moving on the same axis. The function of this second valve has yet to be identified. Since the stat is placed in the coolant flow to the pump, the usual understanding isn't valid.
The ultimate reason for this thread is to identify why so many diesel stats appear to malfunction. They seem to open early or begin opening at too low a temperature. This causes the already cool-running engine to run too cool, even tepid in many instances. That there is a change in the stat's workings seems to be undoubted, since replacing it with a new one restores the running temperature it originally had. Please note, this thread is not to discuss the in-line modifications. This thread does need your thinking head on. TC |
20th January 2012, 16:04 | #2 |
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The "thinking head" of Wikapedia seems worth reading.
Under the heading Radiator engine cooling sub section Waterflow control. |
20th January 2012, 16:08 | #3 |
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All I can say is that my 2005 tourer (german spec) has done over 100.000 miles on the same stat. The engine warms up very quickly and I have really good heat into the car also quickly. Have the inline mod ready if needed but the car doest need anything doing to it....
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21st January 2012, 08:23 | #4 | |
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Quote:
Mine is the same, 2005, over 100,000 miles and starts heating the interior after a couple of miles/minutes, even in freezing weather |
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20th January 2012, 19:36 | #5 | |
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Quote:
TC |
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20th January 2012, 20:35 | #6 | |
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Quote:
I still do not see what flow it might need to restrict though.
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20th January 2012, 20:56 | #7 |
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Probably due to the difference in the pipe diameters of the two circuits.
The second valve will bleed off excess pressure when the coolant is only flowing through the smaller heater matrix pipes, and allow full pump flow when coolant is flowing through the larger radiator pipes. Mike Last edited by Mike Noc; 20th January 2012 at 20:59.. |
20th January 2012, 22:19 | #8 | |
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Quote:
TC Last edited by T-Cut; 20th January 2012 at 22:22.. |
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13th January 2013, 19:42 | #9 |
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Hi Excuse me for butting in on this but I see a few people have mentioned the in-line stat which can be fitted I would like to know where I can purchase one and where does it fit as I have just purchased another Diesel 75 and I have got the same problem with the original stat that I had with my old one and I don't fancy another £300 bill for having the stat done again I have gone from an Auto to Manual as I was getting lazy lol.....Any help would be great full Thanks
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13th January 2013, 20:00 | #10 |
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Hi Dave. I've sent you a PM with all the details you should need. It's a very straightforward job and well worth doing!
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