Thermostat Housing W126 vs W123
 

I have a bolt siezed in my thermostat housing that will not come out despite my best efforts. I need to get one from a junk yard (I can't find one new and I cringe to think of the cost for a new one anyway.) Would the housing in a 300D be the same as that in the 300SD?

Thanks,

It should be engine specific, not chassis specific.

That's good to know. The only thing I guess I can think of that might be different is that mine has a temperature sensor that controls the climate control. I don't recall the D that I looked at last year having that. But then again, I wasn't looking to compare housings either.

If the car has ACC, it should have the temp switch. (My '82 300D has one.) In any case, the only thing the switch does is prevents the blower from trying to blow heat when the engine is cold. If you just ground the wire, the blower will work regardless of coolant temp. It's hardly worth having, in my opinion.

These are actually very standard bolts - available off the rack at Autozone and the like - any store that sells standard metric hardware.

Had the same thing happen on my 240D and thought it would be an expensive trip to the dealer. Was advised otherwise and had no problem finding a replacement in the auto store.

Standard size bolt.

Ken300D

It's not getting the bolt that is the problem, it is seized inside my housing that is the problem and I can't get it out.

EDIT, I think I see the confusion, I need a new housing, not bolt, since the bolt is stuck inside my housing. My original post did not make that clear.

When that happened to me, I was able to drill out the old bolt and re-tap for a new one.

Yes, that's what happened to me too. The head of the bolt is what turned off and there was enough bolt left to grind flats so I could get a wrench on it. The grinding vibration along with PB Blaster broke it loose enough to get it out.

Definitely a place for anti-seize!

Ken300D

This one is not coming out. I tried a few methods, the last of which was to use an easy-out, which then broke off inside the bolt. I'm guesing maybe it was cross threaded into the housing? I don't know, but that sucker does not want to turn, at all.

yikes, those easy outs give me the willies.

although the stat houseings should bolt up to either engine, it seems possible that the angle of the hose connection might be different.

tom w

After doing some checking, it appears that the 116 models with the 617.95 engine had the temp switch in the thermostat cover, instead of in the housing itself.
What year is the 300D?

Another option might be to drill the existing bolt completely out. Then use a longer bolt with a nut on the back of it, instead of the bolt threading into the housing. (ie, the bolt will go all the way through the housing.) Looks to me that there would be adequate room for the nut.

I think the angle of the hose connection was different on 'older models' vs. 'newer models.' I believe that's what my Haines manual says, anyway (it's not here with me to look at).

I don't know when the design changed.

Edit: I would assume this would be the same for the w126...

I don't know the year of the 300D. I'll have to ask.

That is a viable option, drilling it out and through bolting it. I think I'd like a drill press to do that though, which I don't have. Maybe it's time to buy one. Either way, holding the housing steady while I drill is going to be difficult, and keeping it center difficult as well, now that there are two different types on metal in the bolt.

i think it will be hard to seal a thru bolt.

i am pretty sure someone will have a good used one for you. i prob have several off 123 240 motors and at least one off the 115 240 motor if you can determine if they will fit yours.

tom w

Buying antiques new?
 

I don't even think you could buy a new thermostat housing, could you?