I think my tempreture gouge is wrong. How can I check/calibrate the tempreture reading system ? I don't have the laser termometer, is there any other conventional ways to read the tempreture ? The only thing I can think of is taking out the temp. sensor ( I think it goes into the termostat housing ) and sticking it into the pot of hot water, than reading the gouge and comparing it to the termometer in the pot.

Try cold first!
 

If it's like mine, it 'clips' to the front grill below the bumper. Remove the clips and then use ice cubes in a cup (with water). That should test the low temperature portion of the thermometer ok.

If it's close there, then you probably will need to get another data point, so hot water would be appropriate. Not sure that MB go to 212 deg F (boiling water). So maybe just hot water measured with a cooking thermometer would suffice for the second data point.

Ooops ! I ment the engine/coolant tempreture. Sorry

temp
 

I was just thinking that you might want several data points to compare witht the thermometer because maybe its right on one temperature but way off on another

I need the method guys !
My tech did this really quick with a laser termometer.
He got the reading from the termostat cover where the tempreture sensor goes in. 175 F (80 C) was on his scale. Gouge showed 98 C. Since I dont have the laser termometer, I need an alternative method to duble check this.

If your tech already tested it, then why do you want to test it again?

Also, before you think something might be wrong with it, tell us why you think that. It might be normal. Also, has your thermostat been changed recently?

Everething had been changed ! Termostat, waterpump, radiator, fan clutch. The only two posible reasons are the head gusket or scrued up tempreture gouge. (guess wich one I hope it is). I did mess with the gouges when installing white faces, but they worked fine afterwords (temp. was around 87-90). Recently replaced the fan clutch (car overheated in the summer). The next day, when got stuck in trafic t went to 100+. I want to recalibrate the gouge, thats why I am asking. The tech took a mesurment very quickly, I want to take my time and figure out by how much my gouge is off.

100+C. stuck in traffic on a hot summer day is
normal. Aux fan doesn't come on until something like
105-107.

Running at 100+ temperature in traffic is quite normal for your Mercedes. If it goes above 110, then I'd worry a little, otherwise, your car is NORMAL and just fine. :)

I think I confused a lot of people :(.
I went through this overheating story before and knew how car acts in the summer heat.
But this 100+ hapened with 36 F outside ! All winter long the gouge was steady on 90 mark in trafic and on the highway. As soon as I changed the fan clutch, off it went. It now goes up and down like crazy depending on the cars movement. Ranges from 90 (high speed) to 100-110 (slow trafic-gridlock) and te temp outside is below 40 F. What will happen in the summer ?!
If the gouge is wrong than car is runing 70-85 and everything is ok. Thats why I need to check the reading to actual T.

You could pull the sensor, and put it in boiling water (100 degree C) and see if your gauge is correct....but I bet it is ok.

If when running down the highway you're at 88 or 90 degrees C, but heats up at slow speed, are you sure that the new fan clutch is ok?? You should be able to tell if the fan is locked up at the higher temp by feeling the air flow FROM THE FRONT OF THE RADIATOR. BE CAREFUL, as we need you to have all your fingers to post on this forum. At the higher temp on the gauge, the fan should be pulling air through the radiator.

I had a toyota that would heat up at idle but was fine at speed...turned out to be a bad vacuum advance unit. Your car is gasoline...correct? If the vacuum advance is too far retarded at idle, the engine will run hot at slow speeds. It only took me about a year to figure out the toyota, after, of course, I changed everything in the whole cooling system. If your car is gasoline, check the ignition timing at idle to make sure the vacuum advance is working at speed and idle.

Hope this helps....be careful..

Joe

If you have a volt meter (digital) you can measure the resistence of the temp sensor and compare it to MB spec. HTH

Thats 100 c boiling temp at sea level ,it goes down with elevation , heard some place that coffee tasted best if brewed at the elevation where water boils at 203 f ....
William Rogers.......

I did suspect the the new fan clutch. The tech changed it again but it didn't make any diference. It didn't feel like the clutch was ingaging, but than again may be its becouse the car wasn't hot.
Does MB has that vacuum advance ? I never hert of that one before.

ECT Temp vs Resistance
 

Here's what the manual says for the ECT's temp (deg C) vs resistance. Pull of the top and use an ohmmeter to measure the resistance between adjacent terminals. Readings should be no more than +/-5% from those below. If so replace the sensor.

Temp(C)-Temp(F)---- Ohms
20 -------- 68 ----------- 2500
30 -------- 86 ----------- 1700
40 ---------104 ---------- 1170
50 ---------122 ----------- 830
60 ---------140 ----------- 600
70 ---------158 ----------- 435
80 ---------176 ----------- 325
90 ---------194 ----------- 245
100---------212 ----------- 185

Fixed TYPO error, tnx to Arthur Dalton


[Edited by JimF on 04-04-2001 at 03:03 PM]