I pulled the pump out today, hoping that a disassembly, cleaning and lubing might get it going again. No dice-it looked like it must have stopped working years ago. The screws sheared off due to be being seized and corroded and the inside was a mass of rust and crud. Luckily, I had some heater hose, clamps and an elbow so I got everything back together (less the bad pump). Maybe the flow will be better now!

Also, I figured out how to prop the floor vents open. It was cool figuring out which vacuum pods operate what. Now I know which one is bad!

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1979 300D 275K

If you are getting heat then your acc amp is working. If your battery has not been drainiing then your Klima servo is not stuck in the ON position. So you can bypass it and keep the amp in place hoping your A/C will eventually come back to life. Otherwise just pull the amp out also.

Don't bother repairing the temp selector wheel if in fact it is defective. If your ac is broken, you don't need it.
If your Klima servo is broken then you might as well bypass it and after that you still don't need the temp selector because that system has been bypassed.
The only thing that serves function on that module are your fan selector buttons and A/C power switch.

If you end up bypassing your Klima servo, I would not bother buying a new aux water pump.
Waste of money.
True it does increase the flow of hot air (water) intensity at idle but definitely not worth the bucks.

Wait until you go to a pick n pull and get it for $4 if you really MUST have it.

If that pump was so dirty, you need to back flush your coolant system and the heater core.
Get the mud out.

Don't waste your money.

__________________
1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD

p.s. there is a lad up your way north selling parts off a 79 300D...go to parts threads

__________________
1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD

I can't locate this thread.....

__________________
1979 300D 275K

I think that what I am going to attempt is to bypass the servo and not even put in a valve. If I get more hot than I want then I will go ahead and rig up the valve and cable. Do I need to cap off the inlet/outlet to the servo if I don't bypass the other side? Or will I be spewing coolant?

I like the sound of skipping the water pump replacement. I can always do it later.

And good point about doing a coolant flush. Is this something to be trusted to your average franchise repair shop? I will search threads for recommended techniques.

Thanks...

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1979 300D 275K

Theoretically, if your servo is not cracked, you can bypass only the inlet side and leave the outlet side connected thru the servo. I think that is how ************** sells their kit. Test it.
However, if your servo is not rusted in a stuck position inside (interior leaks happen also, not visible as external leaks), you might later consider bypassing the outlet side in order to save the possibley working servo mechanics/electronics from future leaks and rust.. That way you can keep the amp installed and maybe revive your A/C.

Just back flush yourself instead of hiring.

buy a garden hose attachement to stick into the open heater hose (use a hose clamp if needed, then detach the outlet side hose and divert it into a bucket.
Attach garden hose and flush away.
you gain by knowing the actual 'before and after' condition. flush until clean.
use store bought water and a good antifreeze like MBZ coolant for refill.
Flush or drain your radiator while u r at it. easy.
top off via the top radiator hose to prevent air bubbles.
not hard. just get organized and take your time.

__________________
1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD

also parts

2 mercedes 300d parts cars

also hogweed is selling w123 parts, nice guy....

__________________
1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD