Diesel RVs: Re: [diesel_mercedes] Re: Monovalve repair 84 300D

Jim,

I've never seen that. But it's such an easy thing to check. Just take out the four screws, lift the valve body and LOOK.

Since failure involves disintegration of the rubber parts (and maybe the little screen) it is entirely possible, even likely, that bits of rubber are down in the housing. Flowing water should wash them away to the radiator or heater core where then can cause blockage, but not to worry. just fish out what you can.

OR, go to P-a-P and find a good, recent one, in good, clean condition, and buy it for $5 and install it in 15 minutes.

Tom

In a message dated 10/6/2011 7:50:51 A.M. Pacific Daylight Time, jim@tazwade.com writes:

Thanks for the info. But do the guts of these valves ever get corroded so much that a new valve won't seat properly and thus allow coolant to leak through continuously?

Jim

--- In diesel_mercedes@yahoogroups.com, audiolaw@... wrote:
>
> Jim,
>
> Monovalves are among the easiest service tasks that you can do. The
> valve is easy to find and work on on the 123 (much easier than on the 126).
>
> You can either replace just the active part, by removing the four
> screws on the top of the valve body and lifting it out (remember to unplug it
> first. Then drop a 'new' one in, reinstall the screws, connect the plug and
> you're good to go.
>
> Or you can pull the whole thing by unplugging, then disconnecting the
> water hoses, then dismounting. Install the 'new' one.
>
> I say 'new' instead of new, because these are easily pulled from cars
> in P-a-P yards. You can open the valve up (remove the four screws) and see
> if the rubber is OK, and see if the channels look clean or clogged.
> CHEAP, CHEAP, CHEAP. And good exercise walking the yard.
>
>
>
>
> In a message dated 10/6/2011 7:01:58 A.M. Pacific Daylight Time,
> jim@... writes:
>
>
>
>
> Howdy, the monovalve on my 84 300D lets coolant through all the time, never
> completely shuts it off, raises the air temp 10 - 15 degrees at its
> coldest setting when it should be shut off. The valve was replaced a couple years
> ago by a Mercedes shop. Seems too soon for it to have gone bad, but who
> knows.... I see that those valves have rubber washers or o-rings or whatever
> rubber parts on them to create the seal to stop the flow of coolant, and
> was wondering if there is a seat inside the monovalve housing that could be
> pitted or corroded that could be causing the rubber parts of the valve to
> not seal properly. I have never taken one of these apart. Any advice is
> appreciated. I'd like to fix this once and be done with it for a while.
>
> Thanks,
>
> Jim
>