Hot fire wall

[zak]

I am happy to say that I put about 100 top down miles on my 250 SL this past weekend.
I had a blast charging up the mountain roads in 3rd gear and 4000+ rpms, plus some high speed highway driving. Great fun.
I had forgotten how hot the under dash area can get even with the heater levers turned to the cold side. Hot/warm air seems to be entering the cabin somewhere behind the clutch and brake pedals.
Could the temp levers not be closing off the heat 100% and still be admitting hot air?
Or is hot air coming thru the penetrations in the fire wall where the rubber gromets have deteriorated? I have a full set of new gromets but am waiting to put them on when I install a new fire wall pad.
thanks,

jz
 

[BaronYoungman]

My guess is the heater value.  You can search archives on how to check from the engine compartment (PS the string is essential if working on it trust me). Do you hear and rattling coming from the dash?  If so could be head deflector weld is broken on the drivers side and the hot air going that way , but if your valve working properly should not be a issue. 
Bob

[zak]

Thanks for the reply Baron.
No, no rattle noise, just warm air.
I will research how to check the heater valve.
My temperature dash dial is a bit stiff when adjusting too. Maybe it is not closing off the hot water flow totally? Just a thought.
jz   

[neelyrc]

jz,
The control valve may be binding partially and thus causing stiff operation and possibly not closing the valve fully.

Take a look here in the technical manual for removal procedure:

https://www.sl113.org/wiki/Electrical/HeaterControlValve

[zak]

Ralph, I read up on the control valve and you may be right.
I don't trust my self to successfully complete that procedure but I will put on the list for the next service.

Questions: if I open the rubber cap could I test to see if the valve is fully closed? Could I manually fully close it or open it from there?

I also have to say that if I wait till October the problem solves itself- haha!
Thanks,
jz   

[Benz Dr.]

The heater valve is indexed into four quadrants so even if your lever says it's closed it might not be. When adjusted properly, you will either get no heat or lots of heat when you want it. It took me a while to figure out how to do all of these small adjustments but for most people who only drive in warm weather, getting it to shut off completely is all they ever ask for.

[mbzse]

Take a look here in the technical manual for removal procedure:

Note: Statement retracted 
I note that the heater valve is under heading "electrical systems" in our Tech Manual...
Not much electric in those levers and that valve

Anyway, the parts in the heater valve assembly can be put together in 32 different ways... Only one is right

[Peter van Es]

Which section doe you believe it should be? Dashboard ?

[mbzse]

Which section doe you believe it should be? Dashboard ?

Maybe a reference note there in the Dash section would be good.
But, Re: my comment, I instantly retract my steps   
Namely, because I found this note in the Tech Manual:
"For historic reasons (don't ask) the heating system is described in the Electrical Systems section of the Technical Manual, and it is too much hassle to move it elsewhere"

[Peter van Es]

References added. See also: https://www.sl113.org/wiki/Cooling/Start which is the Cooling, Heating and Airconditioning section. I've added links and cross references such that the heating system can be found in many different ways...