thermostat keeps failing
 

Community of Sages,
I have an e36 '95 319ti. I have replaced the thermostat 3x in that past year. Yesterday, my car overheated again. It had been running fine since I replace the thermostat back in August. The outside temp was in the low 60's yesterday. I was driving in DC at the time during rush hour. I replaced the water pump last year with a metal one.

I don't really understand why a non-electronic part should fail so often. Please help.

:thanks
bryon

Questions:

Where are you getting these thermostats? Are they Wahler or Behr?

What kind of antifreeze are you using? Is it BMW (ethylene glycol with no phosphates or silicates) antifreeze or some kind of long-life (organic acid) antifreeze?

Are you sure the thermostats are failing? Do you boil them in a pan of water to check?

I will check to see which model of thermostat I bought last time. I saved the box.

I know I'm not using BMW antifreeze. I about the high milage Prestone stuff last time. Perhaps I will switch?

I am sure that they were failing because I did test the last 2 I yanked out of the car. But my car is experiencing another likely related problem now. My heat is not working. This car demands so much of my time. And because I don't have much money right now, all I can spend is time. I was planning to goto a DIY next month and do a coolant flush and perhaps a transmission one too. Maybe that'll fix the problems.

I highly recommend the coolant flush because I had a BAD experience using long life Prestone in a '97 BMW 328. Since then, I use BMW antifreeze that I buy on line, as it is prohibitively expensive from the dealer.

Fresh oil in your automatic tranny every 50k miles will make it work better and last longer, but a common cause of quirky transmission problems is a failing battery. The computer that controls your transmission likes a strong battery and nice clean battery terminals. If it does not have them, it can do some weird stuff.

If your radiator external reservoir is original, it is likely crumbling inside by now. I could never get all the air out of the cooling systems on my two '97s until I replaced those reservoirs. I cut one open to see what was going on and the tube that runs down inside the tank had a big hole in the back.