Big_John Posted January 31, 2011 Share Posted January 31, 2011 Afternoon all, I finally changed the thermostat yesterday after suspecting for a while that the old one was stuck open. I bought the replacement from my local motor factors about a year ago! When I took the old one out it was indeed stuck open, but it was also different to the replacement one. The original one is a double-ended part with sprung stopper on the back and having looked online, most (but not all) of them have this second sprung part. Keen to get some temperature in the engine/cab, I've replaced it anyway, but now I'm wondering if I really need to get a proper one - what does the back stopper bit do? If I do need to change it again, should I get a genuine one or are the pattern parts ok? Drove it in to work ok this morning and it definately warmed up much quicker - still not much heat in the cab though, guess a matrix flush is next on the list... Thanks, John Quote Link to comment Share on other sites More sharing options...
markyboy Posted January 31, 2011 Share Posted January 31, 2011 Afternoon all, I finally changed the thermostat yesterday after suspecting for a while that the old one was stuck open. I bought the replacement from my local motor factors about a year ago! When I took the old one out it was indeed stuck open, but it was also different to the replacement one. The original one is a double-ended part with sprung stopper on the back and having looked online, most (but not all) of them have this second sprung part. Keen to get some temperature in the engine/cab, I've replaced it anyway, but now I'm wondering if I really need to get a proper one - what does the back stopper bit do? If I do need to change it again, should I get a genuine one or are the pattern parts ok? Drove it in to work ok this morning and it definately warmed up much quicker - still not much heat in the cab though, guess a matrix flush is next on the list... Thanks, John Hi John, The spring is what closes the thermostat and holds it closed when it is below operating temperature. As you say, most thermostats use this system, it's perfectly normal. I'm not surprised it warmed up quicker, a thermostat which is stuck open will mean that the engine will never reach its normal operating temperature and you will have very little warmth from the heater. If the heater is still not working too well, it may be worth checking Ralph's (Western) thread on setting up the heater flaps and cables, from what I have heard this can make a big difference to heater efficiency. HTH Mark. Quote Link to comment Share on other sites More sharing options...
Big_John Posted January 31, 2011 Author Share Posted January 31, 2011 Hi John, The spring is what closes the thermostat and holds it closed when it is below operating temperature. As you say, most thermostats use this system, it's perfectly normal. I'm not surprised it warmed up quicker, a thermostat which is stuck open will mean that the engine will never reach its normal operating temperature and you will have very little warmth from the heater. If the heater is still not working too well, it may be worth checking Ralph's (Western) thread on setting up the heater flaps and cables, from what I have heard this can make a big difference to heater efficiency. HTH Mark. Thanks Mark, but this thermostat has two sprung parts on it, a large one for the main valve as you'd expect, then a second small spring on which is attached to a second kinda trumpet-shaped part/valve sticking out the back! It looks like when the main valve opens the 'trumpet' is pushed back and closes the opening on the thermostat housing opposite the main pipe. Could be I'm completely mis-interpreting it, but it looks like there are two valves in one here. I'll look out Ralph's thread on the heater flaps - the cable is detached from the floor flaps but I couldn't see how to get to it to fix it without taking the whole dash apart and that looked like more of a job than I had time for! John Quote Link to comment Share on other sites More sharing options...
Diff Posted February 1, 2011 Share Posted February 1, 2011 Afternoon all, I finally changed the thermostat yesterday after suspecting for a while that the old one was stuck open. I bought the replacement from my local motor factors about a year ago! When I took the old one out it was indeed stuck open, but it was also different to the replacement one. The original one is a double-ended part with sprung stopper on the back and having looked online, most (but not all) of them have this second sprung part. Keen to get some temperature in the engine/cab, I've replaced it anyway, but now I'm wondering if I really need to get a proper one - what does the back stopper bit do? If I do need to change it again, should I get a genuine one or are the pattern parts ok? Drove it in to work ok this morning and it definately warmed up much quicker - still not much heat in the cab though, guess a matrix flush is next on the list... Thanks, John The correct 200 and 300tdi thermostats have a secondary valve as you have noted. I believe that when the engine is hot and the thermostat is fully open the secondary valve closes the bypass hose connection, which ensures that all the hot water from the head goes through the radiator to be cooled, rather than some of it take the short route back to the block via the bypass to the bottom hose. Regards, Diff. Quote Link to comment Share on other sites More sharing options...
Big_John Posted February 1, 2011 Author Share Posted February 1, 2011 The correct 200 and 300tdi thermostats have a secondary valve as you have noted. I believe that when the engine is hot and the thermostat is fully open the secondary valve closes the bypass hose connection, which ensures that all the hot water from the head goes through the radiator to be cooled, rather than some of it take the short route back to the block via the bypass to the bottom hose. Regards, Diff. Thanks Diff, sounds like I need to get the proper one then. John Quote Link to comment Share on other sites More sharing options...
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