nath 128 Report post Posted July 7, 2013 (edited) My audi runs an 87 degree thermostat which is visually in good condition, with hot/ cold water both opens well and shuts tightly, respectively. But I wonder, can an old 'stat come out of calibration? It is not a cheap item in this car to replace. When running, the engine is hot hot (turbo). --The ECU takes fuel trim temp off a sensor on the block, and the engine runs well no rich exhaust smell. --The temp gauge needle, which reads from a 'multi function sensor on coolant line under manifold, in traffic runs at 87 degrees, but will lower when cruising at 100kmh. --Climate control heater water temp sensor which reads from coolant near heater core (hidden function) reads similar if a little lower than needle, but rises and lowers proportionately to gauge needle. I have already had the 'stat out, thus am not immediately keen to remove it again and check function with a thermometer. Yet. Does anyone have educated/ experienced suggestions or advice for me? Cheers guys Nathan Edited July 7, 2013 by nath Quote Share this post Link to post Share on other sites
yng_750 247 Report post Posted July 8, 2013 generally speaking thermostats as you say open in temperatures approaching the set 87' but as temps keep increasing it opens further and further if you take it out and retest check that it opens smoothly all the way as temp increases past 100'c you often get a tight spot when they age from heat cycles expanding them slightly and if it sticks halfway open then it can handle normal driving but can fail with high heat production when it gets driven hard. other than that all i can say is that factory temp gauges aren't to be overly trusted, could be worth installing a small digital one (much better with digital readout as you can see every single degree) even temporarily to sort any issues. otherwise to be vehicle specific it would be worth talking to an audi specialist as you dont want to ignore a problem with cooling systems and you dont want to spend dollars chasing a problem that doesnt exist. Quote Share this post Link to post Share on other sites
nath 128 Report post Posted July 9, 2013 Cheers for that, managed to get hold of a 'stat from Qualitat for 38 plus 4 for o-ring (1/3 or prices elsewhere) so will pop that in tomorrow. Nothing else will hypercool a motor so far as I can see! Quote Share this post Link to post Share on other sites
yng_750 247 Report post Posted July 9, 2013 just in general all i can say to look out for is the type with the double spring and a second plunger on the back. the second plunger is often pressure based rather than heat and just changes the way water flows around an engine at various rpms. As i understand it it is a pressure bypass to slow the water flow, water flowing to fast at high rpms goes down the straight side paths and leaves water channels between cylinders untouched, and hence overheated. very hard to diagnose issue caused by age and fatigue but can cause huge issue in hard driven engines. Usually a jap thing but thought i would share. Quote Share this post Link to post Share on other sites
nath 128 Report post Posted July 9, 2013 Interesting to know as yes it has the double spring. Stamped wahler w. Germany yet the car isn't old enough to know the Berlin wall! Quote Share this post Link to post Share on other sites
nath 128 Report post Posted July 10, 2013 New one in thank you Qualitat, and car is running with needle at perfect temp, and heater sensor reading 87- 88 degrees Happy camper. Quote Share this post Link to post Share on other sites
nath 128 Report post Posted April 1, 2014 Temperature has started to run on the cold side when coasting down hills or similar non- power situations. Really, can my car kill a thermostat THIS fast? It hasnt been a year yet! Quote Share this post Link to post Share on other sites
lord_jagganath 421 Report post Posted April 2, 2014 you are driving a "hot" car ... it could well be a quality thing? warranty? Quote Share this post Link to post Share on other sites
