O,ring on thermostat,1990 190E 2.6
 

Hi gang I replaced my thermostat on my wifes 190, now the thing is leaking, I put a new oring under the thermostat did I do it wrong?

Make sure the O ring is an OEM part. Many of the O rings that come with off market thermostats are no good.

The thermostat goes in first, spring down. The O-ring lays on top of the thermostat. Tighten to spec. which is probably around 6 ft/lbs (check on that though). That's not real tight so Don't overtighten them. Once the metal surfaces of the housing and pump snug together the O-ring can't get squashed any more anyway, and further tightening just risks ruining the easily stripped aluminum threads.

I don't know about the O-ring but I would really recommend using an OEM thermostat. The last one I took out was an aftermarket and the metal bridge was actually broken off the plate.

thermostat
 

ok thank you for the heads up on the oring placement, I do not know how I missed how I took it apart but I did, I placed the oring in first rather then last thanks again JNT:P