Hey all -

I am tring to keep my mother's Jag running down the road, and I have stumbled into an issue. The thermostat in her 3.0 V6 S-Type has catastrophically failed twice in the five years she has owned the car leaving her stranded and in need of a tow. I had my mechanic put in another thermostat about three months ago and this one will NOT reach operating temperature in even mildly cold weather leaving the heat inoperable. Does anyone know anything about these thermostats? I can't find out anything about them, not even who makes them. Stant makes no replacement for it, and I am at a loss as to what to do to make the car run reliably enough for a seventy year old woman. Any help that anyone can offer will be appeciated. Thanks - H

 

I went down to the Dealer and they said that they had never heard of a thermostat failing in an S Type 3.0 V6, and that I probably had a bad water pump. Did you have a bad thermostat in your car? Also do you think that a bad water pump could cause this sort of thing? I have never heard of a bad water pump causing a condition like this in a car, but I don't know much about Jags. Any other help that you might be able to offer and thanks for the previous advice? - H

 

3.0L THERMOSTATS AND WATER PUMPS RARLEY EVER GO.IN THE LAST 5 YEARS I CAN COUNT 2 THAT HAVE BEEN REPLASED AT MY SHOP.I THINK YOU HAVE AN UNDERLYING PROBLEM.THEY WERE REALY BAD FOR BLOWING UP THE EXPANSION TANK AND LEAKING COOLANT DOWN THE DRIVERS WHEEL ARCH.CHECK THIS.IF NOT YOU COULD HAVE KILLED THE WATERPUMP THE LAST TIME THE 'STAT FAILED WITCH WOULD CAUSE BAD CIRCULATION LEADING TO A LACK OF HEAT.ALSO WHEN THESE CARS OVER HEAT THE WATER VALVE BY THE RAD THAT OPENS TO SEND HOT COOLANT TO THE HEATER MATRIX TENDS TO MELT DOWN IN THE CLOSED POSITION CAUSING NO COOLANT FLOW TO THE MATRIX.HOPE THIS HELPS.

 

Hey -

Thanks for the reply. We already had the expansion tank go and replaced that a few years ago. I also checked the new one just tp be sure that it isn't bad, which it isn't.

I have been reading some TSB's one of which is for a bad water pump impellar materials in early 3.0 litres. Do you think that a bad water pump could cause either the consistent death of thermostats or the cold running condition that I currently have? What is currently happening is that the temperature gauge is having alot of trouble reaching operating temperature, say like about forty minutes of driving. Then when it does reach operating temperature, if I drive on the highway, it will fall to a quarter of the way up the gauge, and the temperature from the interior heater always runs colder than it should. Normally, these symptoms mean to me that I have a thermostat stuck open, but I agree that there must be something more going on here. It just isn't possible that all of these thermostats went bad independently of each other. The problem is that I can't figure out what that something more going on here is.

My thoughts have been this so far, that the water pump is pumping slow forcing the thermostats to all work harder to maintain system temperature and causing them to go bad, but I don't really like the idea because it is too speculative and doesn't make alot of common sense. The other thought is that there is something in this cooling system that is atypical and that I don't know about. Is it possible that the heater valve being bad could cause the car to both not heat up and kill the heater as well?

What do you think about my thoughts? Do you think that I am onto anything here? This has been going on for years, and it is getting to the point where the car is becoming unreliable because of the potential for overheat. Thanks again, and the posts have been really helpful. I am starting to get an idea of what components are in the system to potentially go bad.