Well I have good news and bad news. The good news is that I removed the radiator today since my new one (Behr) will be here tomorow. The bad news is that when I looked into the radiator today and fully expected to see corroded passages, they were not corroded from what I could see and appeared to look perfect.
Questions:
1) If the internal passages that I can see look clear does that mean the rest of the core is clear from corrosion as well?
2) Where is the coolant temp sensor located that provides the signal to the coolant temp gage? Alldata does not tell me where it is.
3) Has anyone ever found a bad coolant temp sensor? Anything special to replace, i.e. teflon tape or special gasket?
Thank you again.
Hynek
__________________
1995 S500
1990 300E (Sold)
"Pay attention to the engineering of the past, many problems have already been solved" - Unknown
I have been told that if someone used regular tap water in the car even with coolant and that there is hard water you can get a buildup of lime and other crap in there that can stop it working as well as it should, if your got the tools open it up when you finish the job and see whats inside.
Here is my latest status and I still do not know if I found the root cause. After replacing the fan drive (clutch), radiator cap, t-connector at firewall, and radiator it still seems that my temp gage is reading higher than it should (used to).
I finished installing the radiator today and filled it with MB coolant (45%) and distilled water (55%). I took a test drive today with a pad of paper and wrote down the temp readings taken from the REST button at position 6 on the AC temp display and compared these with the temp gage observations.
Here is what I recorded in position 6 during my driving today:
Outside Air Speed Sensor #6 AC
78F 65mph 92C Off
78F 35mph(city) 97C Off
78F 35mph(city) 99C On
70F Idle (15 min) 93C Off
70F Idle (15min) 101C On
75F 45mph* 93C moving, 97C stopped, AC Off
I guess my question is do I have a problem or is this normal?
Next I compared the position 6 readings with the approx. position on the temperature gage.
Here is what I saw:
Gage (approx) Position 6 Display
100C 95C
102C 96C
101C 95C
101C 94C
It appeared to be off by quite a lot.
Is this normal or does this indicate that my sensor for the gage reading is off?
I just don't know what to replace next.
If I do need to replace the sensor for the temp gage which one is it. There appear to be three sensors on the thermostat housing.
Still not knowing if I fixed the running hot problem or is my problem a gage that reads high?
Please advise - Thank you.
"Running hot or not??" Mercedes owner
Last edited by 1995S500W140 : 10-14-2007 at 08:43 PM.
Looks more or less normal. At 101C your aux fans should come on the low speed and cool engine down to about 95C and shut off. Same, with the AC on and high pressure 14 bars - aux fans are coming on until pressure drops to 12 bars. Read freon pressure in position 7. If your AC is a little low on freon it may not reach 14 bars in low ambient temperature condition. In this case AC condenser produce enough heat to keep coolant at close to 98 - 100C without aux fans coming on. I would not worry about it too much, just have your AC charge checked next spring.
Mike
Looks more or less normal. At 101C your aux fans should come on the low speed and cool engine down to about 95C and shut off. Same, with the AC on and high pressure 14 bars - aux fans are coming on until pressure drops to 12 bars. Read freon pressure in position 7. If your AC is a little low on freon it may not reach 14 bars in low ambient temperature condition. In this case AC condenser produce enough heat to keep coolant at close to 98 - 100C without aux fans coming on. I would not worry about it too much, just have your AC charge checked next spring.
Mike
My aux fans seem to work fine. Thank you for the info on position #7.
Any idea which of the three sensors on the thermostat housing control the temp gage?
Is the temp sensor for position #6 located in this area as well?
I'm wondering if the gage sensor and the position #6 sensor read in the same location.
The sensor you read in pos 6 is not the same as for the gauge. It is for the aux fan control and for HVAC and it's connector has two wires. The sensor for the gauge has single wire connector. There is yet another temperature sensor for the engine control, it has big round plug with 4 pins. This one can only be accessed by a scanner. All these sensors are in the same general area and should read same temperatures.
I replaced the temp guage sending unit today. Just got back from a test drive - no change.
I did notice that while moving 35mph or higher coolant temp stays at 88 - 90C (position 6) which is good. But when stopped for only 2 minutes at a light the temperature guage rises rapidly to 100C (outside temp is 70F). Then cools down when I start moving.
Can the rapid rise in temp while standing still be caused by an old waterpump?
This is a common look of my S600 during summer. New water pump and fan clutch.
The temp have never been higher than this and at this temp both my cooling fans are running pretty fast.
While driving the temp always stays around 90 dregrees celsius.
Even at this temp there is a long way to the red markings so I'm not worried.
I dont think the cooling harness is necessary. I guess MB knew what they were doing when they made the car.
With a MB enthusiast, something like the temp gauge can get to be a little manic...
1) Aircon, I would suggest you take note from the post that mentioned the aircon., anything out of what adds upside temp to your engine compartment..have the aircon checked and properly refilled, which mens vacuum out the old refridgerant and replaced topped off.
2) GEt a Cool Harness from Forgione, great product and a sense of accomplishemt by bringing down the temp 10 degrees for less than $30
Linear Mode
