OM603 coolant temp sensor / switch on water pump - PeachParts Mercedes-Benz Forum

compu_85 · #1 08-01-2016, 09:55 PM

I'm going to convert my SDL to electric radiator fans. BMW has a temp switch with the same thread as the MB ones.

My 91 does not have a temp sensor / switch at the water pump like some 60x models. Looking in EPC some cars had a 50*C switch there... which I presume was for the climate control low temp cutout.

Is the coolant at this location at the temp of the radiator return or the block? I'm thinking the switch that turns the fan on low at 91*c and high at 99*c would be appropriate. But if it's sensing the cold water return I'd want the fan to come on at a lower temp.

-J

Mxfrank · #2 08-01-2016, 10:47 PM

I think this one is for the glow plug system The switch is at the junction of the bypass passage and the water inlet (from the radiator). It should be reading the blended temp of the feed water.

May I make a suggestion. Along the left side of the head, there are a series of 22mm bungs in the water jacket. One of them is used as the source for the heater core. Another has a 16mm adapter and is used fo the gauge sensor. There are at least three other bungs, plugged and not being used for anything. Since they are in the water jacket just after the exhaust ports, they are exposed to the highest temps in the system. The thread size is 22x1.5, which is the size used by many Euro cars, including VW and Porsche. Switches are available in any range you like, and there are dual switches available if you want to do a low/high speed thing. I use the switch from a Porsche 944 which has two throws, one on at 85 and the other at 100.

tjts1 · #3 08-01-2016, 11:11 PM

Quote:

Originally Posted by compu_85

I'm going to convert my SDL to electric radiator fans. BMW has a temp switch with the same thread as the MB ones.

My 91 does not have a temp sensor / switch at the water pump like some 60x models. Looking in EPC some cars had a 50*C switch there... which I presume was for the climate control low temp cutout.

Is the coolant at this location at the temp of the radiator return or the block? I'm thinking the switch that turns the fan on low at 91*c and high at 99*c would be appropriate. But if it's sensing the cold water return I'd want the fan to come on at a lower temp.

-J

I use an 82c BMW temp switch in that location to turn on my electric cooling fan conversion. Initially I tried the top coolant outlet location but the fans were running before the gauge hit 82c. In the lower location its spot on with the temp gauge.

compu_85 · #4 08-12-2016, 12:19 PM

tjts1, what fan did you use? I got a Volvo fan, but looking at things now I think it'll be too thick.

-J

compu_85 · #5 09-11-2016, 09:24 PM

So the BMW switch I got was too long to fit at the location on the water pump housing. I mounted it on the upper water neck (I had to remove the EDS temp sensor). I'll relocate the EDS sensor to the water pump housing eventually.

sixto · #6 09-11-2016, 09:57 PM

SPAL makes a 16" puller that's 2-1/16" deep and moves 1300cfm. A pair of 12s moves 1800cfm combined.

Sixto
83 300SD

martureo · #7 09-12-2016, 10:50 AM

I'm in the midst of this right now. I tried using two 12" Mishimoto fans (1100 CFM each) but couldn't fit them both on the radiator. I've now switched to a 17" Derale two speed fan (2400/1800 CFM). The difference in thickness isn't much. The Derale is 2-5/8".

compu_85 · #8 09-13-2016, 05:53 PM

Here's the fan I ended up going with, an "Imperial" 1400 cfm 16". I think it's probably about the size of the stock single fan:

I still have the clutch fan installed. I might remove it later and install the smaller fan I had up front behind the radiator since it will clear.

-J