I'm about to do a coolant flush on my 1981 300SD and would like to also flush the heater core, since when I checked my mono valve last week. I noticed it was incredibly cruddy.

I read in another thread (Is 100 c too hot, 300SD) about doing this but I'm unsure how exactly to do it and the original poster wasn't sure on my model ether.

Can anyone help me out with a guide or some direction on what I need to disconnect for this flush? I read there might be some risks of blowing the heater core apart? Not sure if those are valid concerns.

Thanks

I think they are valid concerns, having had the heater core out of one of these, it's not a very robust thing. I flushed mine when I had it out, I suppose you could undo all the monovalve and feed hose, and low pressure flush with the feed hose?

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1983 W123 300TD US spec Turbo engine, with Euro bumpers and manual climate control, and manual transmission.

Guess I'm not sure which hose I should be running the water through.

That's what he's wanting to do, like I did. I just wasn't sure where the hoses run through the firewall at on an SD to show him how to do it..

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Hum, I'm not too sure either, but I don't image it's much different that the W123 with automatic system...

There are two hoses coming from the firewall next to each other, undo them at the firewall thereby bypassing the monovalve. Then undo the feed hose, which should be on the opposite side of the firewall (the engine being the center) hook up a hose to that pipe and gently flush it out...

I think I have that right.

Here's a picture of the heater core.

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1983 W123 300TD US spec Turbo engine, with Euro bumpers and manual climate control, and manual transmission.