Is my SL500 running too hot?
 

1996 SL500. Had some overheating issues and had my thermostat replaced at the dealers yesterday. Seems like it is running hotter than it did before this problem, but then again yesterday was 90+ degrees and I was in stop and go traffic.

So in stop and go traffic the car was running at about 100 degrees celsius, or the hash mark in between 80 and 120. If I put the AC on it would get above this, maybe 105. Once I hit the highway it would go down to a bit below 100, maybe 95. Is this high?

What is the normal operating temperature range of a SL500?

Thanks guys.

Not high
 

The auxiliary fans in the M119 engine come on at 107C and 115C (I believe). There is also a pressure switch that activates the fans based on A/C refrigerant pressure.

So - in hot weather your car running around 100C with the A/C on is not abnormal.

I, however, think this is too hot. So do many others. Jim F., a regular poster on this website, has his own site that shows instructions for setting the fans to come on at a cooler temperature. It costs about $1.00 for a resistor, if you buy it at radio shack, or you can buy his ready made harness that plugs into the coolant temp. sensor for $30.

I did the mod with radio shack resistors, and now my car never gets above 95C. It makes me feel a whole lot better. There's too many expensive parts to cook in the M119 at 105C.

Here's the link to Jim's website (great for much more than cooling problems too).

http://pages.prodigy.net/jforgione/MB_CTS.html

Troy
1995 E420 82k

Your car is running exactly at the temperatures at which it was designed to run.

Mine runs with those temps during the dog days of Texas summers...even flat out on the highways in the evenings.

But right now, temps are cooler and I'm not seeing the high side of 90 in the SL just yet.

I believe you are running okay for your ambient temps.

BTW, when's the last time you did a coolant flush?

Mine runs around the same tempereature.....i have had many people check it out and everything works fine.....and they replaced everything that "might" be on its way out. The tempereature still remained the same.
I find it a little high, but I guess this is normal for the car.

Great thanks guys, you have put me at ease. I am curious about that plug to lower the temp the aux fans come on. Anyone else recommend this? I am wondering if one guy with a website could know more than all of MB's engineers?

I'm that guy . . . .
 

and sometimes I do know more than the MB guys! What makes you think that they are 'gods'??? Far from it!

105C or so on a hot day w/ A/C on is ok. What this does is to retard the car's timing, so, and I'm sure you will agree, the car has less power.

Running it at, say 85F or so, allows much better performance as compared to 105F. Mercedes specs your engine to meet all performance specs at 80C. So, personally, I like to see the car's engine run at close to 85C as I can get.

Unfortunately for your car, startng after model year '95, the CTS sensor was removed and combined with another sensor, so my Cool Harness won't fit.

Check you coolant/water ratio. Read Menu #17 on my page and it explains how you can check. You'd be surprised how many people run 60 - 70% af/water mixture. That will contribute to higher engine temp.

Thanks Jim, we exchanged emails and I'm pretty bummed there is no solution for my 96 SL, but I am looking forward to my codes CD. I would really rather it ran cooler. I am not sure what the coolant ratio is since it was done at the factory, do they have a specification they follow?

Thanks much.

Sure it was but that was . . . .
 

four years ago! You need to flush at least every two (2) years.

Take the time to READ Menu #17 and SEE how to check it!