Vacuum valve and glow harness

I'll look and see if I have any part numbers for those, but they seem to be pretty generic items. You didn't mention what year and model you have. So I assume its for a '79 300TD.

The vacuum valve is just a check valve with two exit ports. The trick for that one is getting the right size fittings at the auto parts store. As long as you are replacing the valve, you can replace the vacuum hose that its connected to as well. Getting all that shouldn't cost more than $10 or $15 at the local auto parts store. Assuming, of course, that they have those hose and valve sizes in stock.

I would think that the harness for the glow plug is also generic. If, by harness, you mean the large diameter wires that run from the glow plug relay to the plugs. Assuming you have enough length to work with (which may be a bad assumption), you can cut the old connection off and strip back the wire and attach a new connection. Otherwise, its just getting a few feet of large wire to replace it.

I should mention that I haven't done either of these things, but I have been looking at my check valve on my 84 300D recently to inspect it.

Ah crap, yeah it's the '85 D that I've mentioned more recently, wrt the glow plug problems it's been having.

I got new plugs, the pencil-type are the ones Performance sent me. Pulled the #1 cylinder plug, but the wire connection is totally corroded onto the nut. I wondered how I'd ever get it out of there and then discovered that that portion of the glow plug was actually separated from the body of the plug. Anyway, got that all out but even with vice grips I can't break the corrosion. I'll try more tomorrow (nicer to work in the daytime) and if nothing else I'll put the five new plugs in. #1 is the only one I've pulled so far, 2, 3, and 4 look like they shouldn't be too bad but #5 also looks like a total bitch with the oil filter right there (not to mention that's where the tap for my fuel heater goes into the cooling system, which means joy as well).

I found this part on BuyMBParts.com. $26 plus shipping, and it comes with the hose and presumably the proper fittings for the vacpump and brake booster.

It's one of those MB plugs on the relay side. I haven't opened one of those up to see if it's easy to swap out connections, but I ended up calling BuyMBParts today and they found one for me. I don't want to screw around with cutting the wires, hoping they reach, and replacing the connectors, so I just ordered it. Turns out they just ordered it from MB, so I would have been just as well to go to the dealer myself, but whatever; it's on its way and I can't drive the car 'til the vacuum line gets here anyway (the two smaller fittings off of the valve are broken off clean; didn't even think about disconnecting the vacuum lines before pulling the fuel rails).

I'm relatively certain the one in my '79 isn't holding vacuum either, and now that I think about it I can't believe I forgot to order the one for that car as well. Ah, so it goes. Now I know how it comes maybe I should just get that at the dealer... I'm not sure how to diagnose it though, as I'm not sure which direction it's supposed to block flow. Does it provide and hold vacuum to the booster regardless of other system leaks, or does it use the booster to generate additional vacuum for the system?

thanks for the response.

-tom!