Can early WRD be swapped with later WRD

[Jordan]

I see there are various threads on the WRD and I have a few questions I am hoping someone can answer.

The first is can an early WRD (I am including both the long thermostat and lower valve assembly) be swapped with a later WRD (both the short thermostat and valve assembly).  I understand that the connection between the two different thermostats to the lower valve assembly are different so was wondering if the entire system could be swapped.

Second question.  The rod that sticks out of the thermostats should extend out when it gets hot.  In the case of the short thermostat, if the rod comes out can it be put back in and will it still function properly or is it toast.

Third question.  The Tech Manual has a cross section of the WRD with the short thermostat and a number of parts are numbered.  Does anyone have the names of these parts.  I am assuming it came from some publication (BBB?).

Many thanks to anyone that can help with this.  I am also interested in anyone that has spare parts, particularly the entire valve assembly for the earlier WRD.

Cheers
Marcus

[amg65ri]

hey jordan,

I am in the process of fixing my WRD right now... Not sure this issue yet, but I seems the car is running a bit rich so i am guessing the rod is staying out after the car cools down. I would imagine that you could use another wrd device as long as the travel of the rod is the same. i dont know the difference between these devices or if they are matched to a IP system.

keep us posted as to what you find.

[Benz Dr.]

No. They're different.

I probably have some spare parts.

[Jordan]

To follow up on my earlier questions does anyone know how long the rod sticks out the bottom of the valve housing when cold and how far it should stick out when hot?  I am not sure why there is a spring in the housing if the thermostat pushes down on the valve as it gets hot which then causes the lower rod to push down on the rack in the IP.  If they are suppose to move together why is there a spring?  I am also unclear why the later short thermostat and lower valve housing cannot be installed in place of the ealier long thermo and housing (they both need to be swapped in order for it to work)?  Has anyone else tried this?
Thanks
Marcus

[glenn]

Jordan, The (captive)spring on the guide pin in the valve housing is there to return the valve piston upward to the open position when the thermo  cools off and the thermo pin recedes.    The next time the engine coolant heats up, the thermo pins pushes down on the valve piston, which pushes down on the spring/guide pin, which pushes down on the lever inside the FIP.   Cool down starts the cycle again.   If the valve freezes open, you can NEVER get proper idle adjustment because there is too much air going thru the valve and there is too much fuel from the FIP remaining in the rich mode of the lever. 
That's why the early 220SE 2 plunger pumps and 230SL WRDs had the On/Off knob on the side of the WRD.  The knob just locked the valve piston in the down position and pushed the FIP lever to the hot coolant/no fuel enrichment position.   Probably better solution in a warmer/South area than in Canada or the Schwartzwald.

[twistedtree]

The other reason for the captive spring is to take up additional plunger movement after the FIP lever is against its stop.

I don't believe the tall and short assemblies are swappable.  The tall unit only has a 2mm or so throw where the short unit is more like 8mm.  This implies very different FIP mixture response to lever movement.

Also, I have two tall WRDs and they are not physically interchangeable.   The protrusion that goes into the FIP body is fatter on one so it cannot be fit up to the wrong body.  I haven't checked later models, but would not be surprised to find this keying method used to ensure compatible WRD and FIP pairing.

[George Des]

That thermostat on the early cars is a sealed, wax filled cartridge that is very expensive if you can find one new. They were used on MB FI models other than the 230SL so if you happen upon one of the early FI injected sedans with the FI system intact you may be able to find yourself a usable spare.

George