ericline1

Purchased a new thermostat to go in to my 08 e60 550i and installed it myself sunday afternoon. Today my car over heats cracking the expansion tank. DAMN!!!! I know i installed that damn thing correctly!!! It wasn't a hard install. Has anyone else installed a faulty thermostat before? is that common? Not sure what to do!! NEED ADVICE!!!

BimmerFan52

Did you get the yellow or red overheating warning message or just lose coolant?

What brand thermostat?

I tried to save a little money and bought the Beck & Arnley unit when I did preventive maintenance on the cooling system, and got burned ( really no pun intended). My thermostat didn't freeze closed and overheat, but the heater coil burned out after a day or two and generated a P0128 error upon every start up. Replaced it with the OE Wahler unit and haven't heard a peep in almost two years.

But are you sure it is the thermostat? If the expansion tank failed due to age and split, the pressure the system is designed to build in the sealed system to increase the boiling point of the coolant/ water mix is lost and the coolant will boil at a lower temperature and of course gush out of the split tank.

e6t.lab.rat

It may be an unfortunate coincidence. A failed thermo will throw a P0128 code as stated in the previous post due to it being stuck in the open position. Did you get this code?

I too made the mistake of purchasing non-OEM. The connection inside the thermo disintegrated within 6 months creating an open circuit, so I replaced with an OEM Wahler and been fine ever since.

ericline1

Yes, i purchased an OEM Wahler thermostat. I didn't know the expansion tanks on BMW's have this problem? It very well could be the expansion tank that caused the problem. I was unable to clear the code after I changed the thermostat and was going to take it to the stealership to have it cleared, so I don't know if it coded with the new thermostat or not. So at this point I don't know if it was the thermostat or not?

ericline1

Do you guys know if I should have bleed the coolant system?

twh

Yes, you need to bleed it.

Bentley says:

Before filling radiator:
- Switch ignition on (do not start engine).
- Set temperature controls to full warm.
- Set blower control to low.
- Set seat heat control to maximum.

Using a coolant mixture of 50% antifreeze and 50% distilled water, fill expansion tank slowly to MAX.

Start engine and run at idle speed for one minute (cap open). Adjust coolant level to MAX. Close cap.
- Run engine until it reaches operating temperature.
- After engine has cooled, recheck coolant level.
- Top up so that coolant level indicator is at MAX.
- If trapped air cannot be bled manually, pressure-bleed system using cooling system pressure tester.

RIHI

You will need to check other issues that might cause it to overheat.

Also you can take out the new thermostat and test it in boiling water. It should open around 180 degrees, or depending on what temp is stamped on the thermostat. While you have the boiling water, check the old thermostat too. If it opens, then it isn't the thermostat isn't your problem.

justoracle

I think your problem is not the new thermostat but the fact the system wasn't bled. This happened to me when I replaced some hoses and didn't bleed the system correctly, it cracked my expansion tank. Tough lesson to learned, so any time I deal with the cooling system I make sure it's bled out of any air.

ericline1

Thanks for all the info! I had the expansion tank replaced and I bled the air out of the system. Car is still overheating though? Radiator fan is only working intermittently. IT didn't work at all yesterday and this morning low and behold it's working...FOR NOW? The car only overheats in stop and go traffic with the AC on? I had it in the shop all day thursday NO CODES, it never overheated UNTIL late afternoon after I picked it up, turned AC off and it cooled off. Could this be a relay or sensor or does this sound like another bad thermostat? I think I have gremlins in my car!

pcy

There is a fuse for engine fan. Since you are saying the fan is working now, the fuse must be ok.
Based on the description of the issue "Radiator fan is only working intermittently" , I am thinking the fan is the culprit. See if you can connect 12V directly to the fan and see if it's working at full speed.