Is it just me or do Mercedes naturally run hot?
Senior Member
Joined: Aug 2007
Posts: 344
Likes: 5
From: Los Angeles, CA
w202
I used my "cool harness" for many years now and works excellent. Every time i sold any of my vehicles, w124 or w202, this piece of harness was the only thing i always kept from car to car.
Even in heavy traffic here in SoCal, the temp rarely reaches the 100deg mark on the cluster. With this harness, the aux fans will work overtime, but so far i never had any issues.
You can make your own one, but at the time i was just lazy and got it from here:
http://k6jrf.com/MB_S500.html#MYCH
I see the price went up, i remember paying around $70 for mine a while back.
Even in heavy traffic here in SoCal, the temp rarely reaches the 100deg mark on the cluster. With this harness, the aux fans will work overtime, but so far i never had any issues.
You can make your own one, but at the time i was just lazy and got it from here:
http://k6jrf.com/MB_S500.html#MYCH
I see the price went up, i remember paying around $70 for mine a while back.
Newbie
Joined: Apr 2020
Posts: 3
Likes: 0
CLK430
Runs Too Hot In Tucson
I've been dealing with this "running hot, but not overheating" controversy for year. On the gauge, one would expect the needle to stabilize in center of the sweep which is 80C or 176F. For years my CLK430 ran centered, maybe slightly above 80C. A couple of years ago I noticed the needle edging up slightly. No big deal...except over time the needle continue to edge up. Month after month the needle would settle a little higher. I also noticed the coolant temp became very sensitive to airflow and ambient temperature. Ultimately, when the running temp went to 100C or 212F I noticed another problem. I got codes the Transmission was overtemp...in fact at that temp the computer would proactively shut the Transmission down by commanding limp mode. Letting the engine cool removed the limp mode. Taking action I have replaced the water pump, flushed, back-flushed, replaced thermostat all with very marginal improvement. I live in Tucson and it's hot here. While I don't have any solid evidence, I cannot believe this is "normal operation." I believe the engine is constantly running over-temp...which of course can shorten the its life. At this point I can only assume I have a poorly functioning radiator; I plan to change it out within a week or two. The engine has never had an acute episode or "overheated," it does have a chronic cooling problem. The consensus of this thread is: an engine running around 100C is OK...not to worry. I disagree. The CLK430 engine is an elegant beast; I am convinced it should run between 80 to 90C. I am hoping the new radiator drops the running temp...I'll post the result....
Junior Member
Joined: Jun 2015
Posts: 68
Likes: 0
Mercedes 200E W124
I have noticed that my W124 gets warm a lot faster than the newer cars I have/had, especially the newer the longer they take to warm up. I guess it depends also on efficiency, at the end.
On my W124 the air starts to come out warm in winter at the first roundabout, a couple of minutes from home, while with my Jaguar it takes a few more minutes. Normal running temperature is reached in a few minutes with the W124 while it takes a lot longer with my other car.
But once it reaches the 80 degrees it stays there. In heavy traffic of course it goes up and down, but never overheating.
I had a problem on the thermostat some time ago and it was keeping the radiator on even with the cold car, and in winter I could drive to work without reaching the 80 degrees. I think it's just made to reach the working temperature, then it's quite properly sized (on the 200E at least). I have been living for years in south of Spain and never had any problem of overheating -and it can get HOT there, when you start the car and the temperature needle is already raised
On my W124 the air starts to come out warm in winter at the first roundabout, a couple of minutes from home, while with my Jaguar it takes a few more minutes. Normal running temperature is reached in a few minutes with the W124 while it takes a lot longer with my other car.
But once it reaches the 80 degrees it stays there. In heavy traffic of course it goes up and down, but never overheating.
I had a problem on the thermostat some time ago and it was keeping the radiator on even with the cold car, and in winter I could drive to work without reaching the 80 degrees. I think it's just made to reach the working temperature, then it's quite properly sized (on the 200E at least). I have been living for years in south of Spain and never had any problem of overheating -and it can get HOT there, when you start the car and the temperature needle is already raised
