Do I have a 50C switch? - PeachParts Mercedes-Benz Forum

Maroon 300D · #1 06-22-2006, 12:37 PM

I have read about a 50C switch that some MB's have. Evidently this switch does something with the vacuum when the engine temp. is below 50C, and shifts are harder.

I've been trying to track down the source of harder-than-normal shifts in the morning, particularly on cool mornings. A standard sort of vac leak is still a possibility, but I'm wondering about this 50C switch and maybe if I have a leak related to it. Given my symptoms I think this would make some sense.

I understand the '85 w126 had a 50C switch. Anyone know if my car would have one (the car in my sig)? And if so, how does it work? And of course, where is this thing?

Palangi · #2 06-22-2006, 04:52 PM

I know nothing about an 85 California, except that it is a strange beast. On earlier 49 state versions, the thermal vacuum valve is the last thing the vacuum line passes through before it reaches the EGR. Located on the front of the engine about 6 inches from the EGR. Unlikely to leak unless the plastic nipples have broken off. On 49 state cars, I would say check the vacuum switches on the valve cover box, but I don't think an 85 California car has those.

Maroon 300D · #3 06-22-2006, 05:30 PM

Hmm..on my car the line to the EGR comes out of a piece mounted near the driver's side fender. There are several lines connected to that thing but I will have to look at the sticker on the car again as I can't remember what the piece is called. I discovered my EGR wasn't working yesterday (I saw nothing in that little 'window' when I gave it vacuum) so I disconnected it and plugged the line.

Thermal vacuum valve - is that another name for this mysterious 50C switch? I guess I'll do a search.

Palangi · #4 06-22-2006, 05:42 PM

Sorry I can't help more than that, If it has a temperature actuated vacuum switch, it would have to be located in the coolant flow at the front side of the engine. If it switches vacuum directly, it would have a pair of vacuum lines going to it.

Maroon 300D · #5 06-22-2006, 06:09 PM

Yeah, after I posted that I realized I would have to have something connected to the vacuum line that hooked into the coolant somewhere. I'm not sure I do but I'll look.

Thanks a lot for your help!

Brian Carlton · #6 06-22-2006, 06:16 PM

Quote:

Originally Posted by Maroon 300D

Yeah, after I posted that I realized I would have to have something connected to the vacuum line that hooked into the coolant somewhere. I'm not sure I do but I'll look.

Thanks a lot for your help!

The 50°C. switch on the 603 is electrical. It closes a vacuum solenoid over near the vacuum amplifier (blue flying saucer). No vacuum lines run to it.

Maroon 300D · #7 06-22-2006, 06:24 PM

Thanks. I'll look for a similar thing while I test the vac system again this afternoon. It's becomng a daily ritual: the hood up, me with oily hands, my vac gauge, and a pensive look on my face.