190E 2.6 Water Temperature is 60*?
 

I seem to have a 190E that runs extremely cool. The ambient temp is only 59*F and the car only seems to warm up to 60 (second notch from the bottom) maybe a little bit above it when I'm stuck in bumper to bumper traffic with the A/C on.

I'm gonna check the water temperature sender - if my research is correct it is a single prong sensor right?

Where is this on the M103? Is it behind the valve cover?

Thanks in advance,
Holson

It should be a single pin sensor towards the rear on the drivers side of valve cover, between the 2 pin aux. fan switch and the CIS temp. sensor.

Check the sender values before replacing
It is a Negative thermistor.

OHM 110 = 60C
67 = 80C
38 = 100C

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Can anyone explain what he means by negative and how do I do the test...

Maybe it's right, it could be the thermostat. I always thought changing them should be part of regular maintance. If you've never changed it now would be a good time.

And the replacement thermostat cover is now metal.

Look at the chart....negative means as the temperature goes UP , the resistance value [ Ohms] of the sensor goes DOWN [ negative].

So , you measure the ohms and compare it to the gauge ..
I have a 38 ohm resistor in my tool box for checking these real easy..if you sub that resistor for the sensor, the gauge has to read 100C... just like the chart I posted says............simple.

Thanks Jim, I just got the car actually. I'm not sure if the previous owner changed it but the thermostat cover is metal. I was wondering about that because in the Haynes manual that also came with the car it shows a picture of a plastic cover.

I'll try shorting the connector to the temp gauge and see if it'll spike to overheat

I will buy some resistors to test the gauge this evening. But I took some readings and it came back as 800ohms and the gauge read 40*, maybe a hair above it.

It did fluctuate wildly between 400-800 though.

I sprayed some electric parts cleaner on the sensor and its surrounding area (including the harness connector) and now the gauge jumps around more but does read above 60*

will try to clean the contact points of the sensor and see how that goes.

UPDATE: I cleaned and sanded down the connecting surfaces of the harness and sensor. The gauge is now consistent and not dancing around.

I grounded the harness to the ground and the temp gauge shot to 120+

So the gauge works, the temp sender is fine.

The temperature was still at 65-70 on the highway and between 75-80 when I'm idling in a warmer place (a garage).

I guess it's the Thermostat - I wonder if it even has one :)

Thx for all the help guys

you have a stuck open thermostat.

That's what I'm thinking too, is there a way to check it? Say when the car is just starting to warm up, basically the line from the t-stat to the radiator should be cold right?

Btw, is it enough to just siphon out some coolant from the expansion tank (just so the water level is below the t-stat) to change it?

Thx

just replace it, its cheap and easy.

There's a drain cock on the bottom side of the radiator, and I think you can get awayt with only draining partially.

Right. Mine was like you describe. It never warmed up all the way. When I took it out I expected it to be stuck open but it wasn't. However the new one fixed the problem and now it works right. There was a certain brand I was advised to get. But I don't remember which one it was!

Behr is excellent.