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]

Thanks Jim
One more question, wich one is the temp. sensor? I got two sensors going in verticaly into the termostat casing. They look almost identicle.

ECT position
 

It's the "FAT" one and has a black cap (probably). Pull off the top and it has four terminals.

By the way, each section should track one another.

Jim F.,
Do you have the resistance for aux. fan cut-in ?
[above 100c]
Thanks
Arthur

Water Wetter
 

This is a corollary to what's going on here but not directly related.

Saw a post re the use of a wetting agent to lower the operating engine temperature. Product is called "Water Wetter" by Red Line Oil. This is the first that I've heard of it so I gave it a try. Check out this direct link: http://www.redlineoil.com/redlineoil/wwti.htm

My engine temp runs around 90 - 92 deg C when warm (ambient temp around 65 deg F) in driving in stop/go traffic. Also "estimate" that the mix was more like 60% antifreeze/40% water.

Replaced some of the antifreeze by siphoning off about a 1 gallon so mix was about 30%/60%. Then added 1-1/2 cans of Water Wetter introduced into the small overflow tube after removing the fluid from the overflow reservoir.

Lowered temp to around 83-85 deg C using same conditions as above.

Some words from Water Wetter site:
COOLANT EFFECTS ON PERFORMANCE
Under moderate load conditions, each percent glycol raises cylinder head temperatures by 1°F. 50% glycol raises head temperatures by 45°F. This increase in temperature will raise the octane required for trace knock levels by typically 3.5 octane numbers. A car equipped with a knock sensor will retard the timing to compensate for the increase in octane requirement by approximately 5°, which will reduce the maximum brake torque by about 2.1%.

I'm impressed with the stuff!


[Edited by JimF on 04-04-2001 at 02:16 PM]

Fan Cut in
 

Arthur,

That's my next project. Want to lower the temp at which the fans (two on my car) cut in. Have seen that the fans are set to cut in around 100 deg C. I personally think that that's too high; sb more like 90 deg C but 95 deg C tops in my book.

When I find out how-to-do-it, it'll be posted!

Jom,
That would be great.
I have wired just about every aux fan on my previous
Benz's, but ran them with manual switching.
Nice to have that option.
Let me know what you find.
Many Thanks
Arthur

Tested the T sensor this weekend by stikcing it in hot water (right after boiling). Looked like the gauge was ok.
Than on Tuesday I went to the tech. We did it together. Reading the gauge and lazer termometer. His reading was 75 C
when he pointed on the Temp sensor casing and on the part of the waterpump where the sensor goes in. The gauge read 95 C. What the hell..... Can a Benz run below 80 C ?!?!
In any case, summer is coming, any news on lowering that cut in tempreture for aux fans.
This is what I know on cut in T for fans (on W124):
Viscous fan clutch 96-104 C
Electrick aux fan on 107 C of 100C

Procedure for calibrating engine temperature gauge
 

Dmitry, sounds like your coolant sensor and gauge are certainly out of whack! Actually, it's a good idea for everyone to occasionally check gauge accuracy since these meter movement mechanisms can easily go 'off' with time. Below is my procedure for calibrating the coolant temperature gauge and sensor. The specific locations and values apply to a W124 with a 103 engine. Since you probably have the first year of the 104 engine on your 300CE you may need to adapt them to your particular engine.

1) locate the coolant temperature gauge sensor. There are several engine temperature sensors so be sure to get the correct one. On the 103 engine it is located on the cylinder head, second sensor from the rear and has a single-pole connector. You can verify the correct sensor by pulling the connector when the engine has warmed up - the gauge display will drop out of range on the low side.

2) measure resistance at the sensor when the engine reaches operating temperature. For example, on a 124/103 the resistance will be 63 ohms (+/- 2) at an operating temperature of 80C IF the gauge is accurate and the sensor is good. If you want to measure resistance at a different temperature or if the sensor is different on the 124/104 then let me know and I'll calculate the appropriate values for you. (Btw, I suspect that the resistance value posted by JimF are for one of the other sensors?)

3) if your gauge shows a large discrepancy between sensor resistance and the ideal value you will need to either reset the meter pointer or at least make a mental adjustment. (It's possible that you inadvertently stretched the pointer when you were working on your instrument gauges.)

Hope this helps,
Barrie
-----------------
'86 300E

A little different problem
 

My display comes on and displays a temp for about 10-15 seconds and then goes off. The display is on about as long as the set belt warning, just a little longer. It seems like it is working correctly however it is using c and it takes a greater temp to change. If I can not get it to work can I just turn off the light on the display?

Different on
 

Barrie,

Just to confirm that temp chart was for my S500's ECT sensor. You are correct in that temperature measurement for your car (W124 with a 103 engine) is different.

The S class cars have two coolant sensors; an ECT (B11/2) and CT sensor (B10/8). The latter sensor controls the A/C and the auxillary fans. The ECT sensor's output is what is read on the temperature gauge in the instrument cluster for S cars.

The chart values was for the ECT sensor which is completely different for the CT sensor. A bit confusing!

Since Dmitry's problem is with a '90 300CE he should use the relevant procedure and values as provided for the W124.

Where can I get the values for my car?

Engine temp gauge sensor for E-Class (124)
 

Dmitry,
Except for the difference in sensor location on the 104 engine vs the 103, I believe the temp gauge system is the same on your car as any other 124. You should be able to use the procedure and values that I provided above to locate, test, and calibrate engine temperature with your instrument gauge.
Be sure to locate the correct sensor for your purpose - you do NOT want the sensors that control the fuel system or fans (B10/11/12). There is a *separate* sensor for the gauge (B13). Btw, I suspect S-Class and others of the same vintage use the same system (and probably the same values), but I have not checked that.

Barrie