1986 560SL slight over heating

[RR3]

We have a 1986 560SL with about 130,000km.
In hot weather and in stop and go traffic the temp guage goes up past 90 and sometimes towards 100.

Is there something wrong with the clutch fan?
Or perhaps a leak in the cooling system?

Any thoughts?

R

[Strife]

I just replaced my thermostat, water pump, fan clutch, both front hoses, and my car is at these temperatures in hot weather. The thermostat begins to open at 80 and is full open at 95.

[ctaylor738]

My "new" 1987 560SL sits happily at 80 or a tiny bit above, no matter what the driving conditions or outside temp. Not bragging, just a factoid.

[RR3]

Strife, I agree with ctaylor, it SHOULD only sit slightly above 80. Our 560SL would never go above 90 in any temperature - but for some reason now it does.

[Strife]

Well, I certainly must agree that I'd RATHER see 80 all the time. But when I played around with my old thermostat in some hot water I noticed that it never really fully closed. The phenomenon of "changed everything, now runs hotter" has been reported by a lot of people with MB's other than 107's.

The original and intended way it was supposed to work (somewhat hotter) was probably pollution-control related, etc (it's supposed to be easier to pass emissions with a hot engine).

It's also possible that there is a significant difference from thermostat to thermostat in the "analog" area between 80-95C - maybe the movement between "fully closed" and "fully open" is not linear.

[ctaylor738]

I would suspect the fan clutch. a. it is a common replacement item; b. it makes sense because in stop and go driving, that's the only way that air gets moved through the radiator.

I would expect a thermostat or radiator issue to cause higher temps under other conditions as well.

[1984 280SL]

My thought would be to have the radiator "rodded out". this involves removing it from the car and having a radiator shop do a complete cleaning of the cooling tubes. This is quite similar to have you blood veins rotorouted in the hospital when you get old. Same crap happens to an older car - plaque builds up over the years and is the main contributor to temp rising when stopped. It will be your best money spent. The radiator shops do this service all the time.

[cbdo]

I'm not sure that it's not fairly normal behavior to do this. Mine hit the mid 90's last week in stop-and-go with ambient in low 90's. The fan clutch works fine and the radiator was new in 2003; the only questionable part to me would be the thermostat. Most of my other European cars have behaved the same way, going all the way back to Dad's then-new Benz in 1969; in all cases, temp comes down pretty promptly once I'm moving steadily. Cooling fan flow when at rest never quite equals airflow when in motion.

[Strife]

Originally Posted by ctaylor738

I would suspect the fan clutch. a. it is a common replacement item;

I considered this also so I replaced mine; it did not change my temps. I'm not ordinarily one to throw parts and money at a problem, but I figured it was 19 years old, and I got an incredible deal on a new one (about $150 shipped), so I did it. At least I have a spare for my wife's (future) 560SL!!

[Robert Mowbray]

Put in a bottle of Water Wetter. It dropped my temps about 10-15 degrees.

[Litton]

Interesting thread. I just picked up my 560 after having the AC compressor replaced and noticed that on the way home I was right at 100 with the AC on full blast cruisin' at 75. Of course the ambient temp outside is 112 today so I'm really not surprised.

The aux fan comes on at 100 and holds the temp right there. I'm not sure, but I think this is just fine. My 420SEL did the same thing in the summer except it had dual aux fans.

[balsa]

Any experience in using the lower temp. Engine Temperature sensor part number 006 545 3624?

This part is in red collor and is used in Euro models. I beleive it turns the fan at lower temeperature than the green engine temeperature sender used on US models.

Balsa

[tubbee]

I recently purchased a 1981 280 SLC and had some over heating problems as well. Replaced the fan clutch, thermostat and retroffited a larger, faster aux fan from the W113( I think). My mechanic was the one who advised me to put in a larger fan unit.

It worked, car is running pretty constant now in traffic and its cooler on the freeway. I live in atropical climate so its always hot and humid.

Cheers

[Walrus]

Originally Posted by Strife

Well, I certainly must agree that I'd RATHER see 80 all the time. But when I played around with my old thermostat in some hot water I noticed that it never really fully closed. The phenomenon of "changed everything, now runs hotter" has been reported by a lot of people with MB's other than 107's...

Yep, this has played out many times. When I got my '88, I marveled at how I could chew up hills and never see above 80+ on the temp. speed was not a worry, neither stop or go traffic.

The water neck broke on my rad, so I procured a new one. While at it, why not flush system, change thermo, etc? All back together and WHAMMO! Now in stop/go it hits 100 routinely. Rapid driving (plus 90mph), or rapid hill climbing with AC on produces same results. Normal cruising yeilds a steady 90 or slightly less. All systems are functioning normally... Water Wetter? BS in my case. First a half-bottle, then the rest a couple of days later yeilded no discernible change. Further research has indicated these temps are normal and not to be worried with. I motor happily on... I DO WISH a 70-85C thermo were available. I just feel more comfortable with the coolant temp about 10-15 lower.

[Pili380SL]

I had symptoms very similar to yours, RR3,at about the same mileage, and replacing the radiator fixed my problem. I would try a thermostat first, which I did, since it's a fairly easy job. Make sure the fan doesn't just freewheel; it should have some damping when you turn it.