I have a 1983 240d and I flushed the coolant and took the lermastat out and ran it like that. Tryed to get all the air out by putting it up on ramps and pop the rad cap and saw a bunch of bubbles out and brought it up to running temp. As I drive the temp gage climes to 100c and keeps going. Any help would be good but I think that I still have air in the system

Running warm on highway

First couple of posts.

I've never had a problem with air in the system, so I can't comment on that. I just refill my coolant and go. Maybe it's a bigger problem on the 616 than the 617?

Check the easy stuff first.

-Rog

If lermastat is thermostat, the FSM has specific warning to not take it out since engine will overheat without it.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Without it? That's interesting. I had one get stuck open because of a rock (explain that one??) and the temp gauge just never moved off of cold. This was in the winter. I'm guessing the thermostat itself provides some physical function then?

-Rog

Trying to avoid getting TOO technical (heat transfer and all that) but the velocity of the coolant thru the system has a significant effect on how much heat the coolant can transfer into the radiator. In the winter I can see where the radiator could be so cool that it would over-cool the coolant if it wasn't held in the engine (another function of the tstat) but in warm weather it acts as a restriction, slowing down the velocity of the coolant thru the rad and giving it time to dump its heat into the cooling fins and (of course) subsequently into the air.

Sometimes a race car will use a flat disc with an orifice in the center to act like a tstat but w/o the possibility of having the tstat stick open or closed, either of which would be a big deal during a race. I always run a tstat and so far have had zero issues with it. You CAN buy those flat plates I referred to and it can take a while to figure out just how big a hole works in your particular engine.

Dan

Do you know how to access the Startek online FSM? Look at the cooling section, there's a diagram showing the bypass and flow path and text explaining why the thermostat must not be removed.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

The thermostat is located between the bypass passage and the cool water supply from the radiator. As it opens the radiator passage, it closes the bypass passage, so you always have a proportional flow of hot and cold coolant, which is why it's called a constant flow design. If you remove the thermostat, both passages are wide open, and the water pump will be pulling from either source or both, depending on the hydrodynamics of the particular system. For some engines, this results in instant overheating. Others run cold. Most will run hotter without a thermostat.