I have a 1982 300sd that I am slowly refreshing. The next system that I will tackle is the heating.

Questions are:

#1 Do/should I replace the entire Mono Valve or is rebuilding it just fine? If rebuilding it will do the trick is Einstatz a quality product? I found a kit for $14.95. Have read and will look at putting an inline fuse in the circuit as well to protect the HVAC Pushbutton controller which will be replaced with a rebuilt unit from Programa.

#2 As a safeguard I plan to replace the auxillary water pump. I see the prices are all over the place for OEM and aftermarket. Recommendations?

FCP Euro OEM $421.95
Eckler's OEM $90.00

MTC Brand $75.13
Vollig Brand $52.00 (quality aftermarket part?)

In addition to this all the hoses will be renewed, new MB thermostat, the heater control flap vacuum pods either replaced or rebuilt, and the AC system upgraded.

Thanks

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1982 300SD
1992 190e 2.3 8v
2002 P38 Range Rover

The monovalve case is just a case and isn't prone to leaking. The solenoid can be replaced as a cartridge but there's no need to do so unless you have heat at standstill that fades with speed. Come to think of it, I don't know if replacement cartridges are still available.

I don't know what safety is gained by replacing a functional OE aux pump. Put a fuse on it like you're doing with the monovalve and don't think about it until the fuse blows. Try this - show a friend the aux pump electrical connector. Have the friend choose to unplug it or leave it connected without telling you the choice. Repeat for a few days. At the end of the experiment compare notes as to which days the aux pump was offline and which days you sensed it was offline. It's not conclusive. I suppose if you couldn't tell the difference it could mean the aux pump isn't healthy

If you need to invest time and money in the heating system, invest it in replacing the vacuum pods throughout the ACC ducting and a can or two of evaporator core cleaner.

Sixto
MB-less