SANDEEP:

Thanks for the kind words. Apparently I'm not as knowledgeable as I had hoped.

You can buy a t-stat housing with a bleed bolt on top. I purchased one of those from this site and the housing and bleed bolt washer were apparently substandard. The thing leaked badly, so I went back to the sealed t-stat housing that was on the car from the day I bought it.

The M103 motor has 2 plugs on top along side the drivers side - 14mm removes them. I used to refill thru the front plug as outlined in the 103 manual, but no longer do so. The last time I reinstalled these plugs(or small bolts), things didn't feel quite right. It almost felt like the thing was starting to strip out. I believe that psfred commented about this once, so he too ran across this issue. Didn't mean to get side-tracked from your original question just trying to be thorough.

OK - how do I refill and bleed? I use a technique that's been discussed at this site.

1. After draining coolant and doing whatever sort of flushing one cares to do, close up 19mm drain plug on passenger side of block.
2. Reconnect drain hose on bottom of radiator - passenger side. I do not drain the radiator thru the front radiator drain plug as it's all but impossible to get to.
3. Remove t-stat housing cover - 3/10mm bolts. Remove t-stat and gasket. Slowly pour in a 50/50 mix of MB coolant and distilled water(please! - no arguments about coolant brand/water type) until coolant comes to the top of the housing. Refit new t-stat with jiggler valve in highest position. Refit new gasket - install t-stat housing and 3/10mm bolts - torque sufficiently.
4. Slowly add 50/50 mix to overflow tank to complete coolant refill.
5. With cap off overflow tank, start engine and ensure heat is set to max position. This was actually done before the draining process began.
5. Monitior temp. gauge. Temp gradually climbs to just above 80 degrees centigrade. Blip the throttle a number of times to about 3000 rpm or so. Allow to idle for a bit more. All in all - idle time is about 30 mins. Temp gauge never goes over 82C-83C.
6. Shut off engine. Reinstall cap. Go for test drive - approx 30 miles. Temp gauge never goes over 82C-83C. Does not overheat at idle.
7. Return home. Allow to cool a bit. Coolant level down a bit in overflow tank - not unusual as I've seen just about every car I owned do this after a refill. Top off coolant. Drive car again a few miles. Return home. Allow to sit overnight.

Upper hose collapsed the following morning after cooling down overnight.

That pretty much covers the flow of events.

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"