Bossie

I recently had to change my upper radiator hose do to the overflow hose hanging and getting cut by fan. I put the new hose on and topped off with fluid that I purchased from MB and was fine for a day. Yesterday I get an engine light and the code from my reader says the thermostat is stuck open. I ordered a new thermostat but my question is. Do I need to bleed the system, could not bleeding it after the change of the hose cause this code? Also, anyone know of how to bleed the system in a 2010 E350 4dr base?

Plutoe

If done correctly----YES.....wait for Konigstar to post the WIS docs

belarus27

I ordered my thermostat on Friday
as i have this problem too.
You dont have to bleed the coolant , some of it you will lose when disconnecting the hose from thermostat , but at the end of replacement you can just top off whatever amount you need. At least that what im gonna do once i receive mine.

Bossie

Thanks for the info. Will it be ok to drive while I wait for the new one?

KEY08

Yes. The default failure condition is full open as you are experiencing.

belarus27

I been driving like this for almost a week now.
waiting for my new part to come..but these holidays dont make it any faster.
it stays around 80... 75-80 sometimes it does go to 85ish.

cetialpha5

Wahler is the OEM maker of the thermostat and it's pretty common that they fail open. I think I got mine on Amazon. Didn't need to bleed the system, you lose a little coolant when you swap it out, but I just topped it off and it was fine. While you're doing the thermostat, check the two pulleys and tensioner for play, those are also well known to go too and you have to take off one of the pulleys to replace the thermostat.

belarus27

Update.
got thermostat today and replaced it.
Right now just need to reset the CEL light.

Bossie

update: I replaced the thermostat and all is well. The temp is back up and running good.