SL/R129: 95 500SL Operating Temp High???
06-12-2010, 06:32 PM
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1995 500SL & 2001 CLK 430
95 500SL Operating Temp High???
Normal driving cond., A/C on, all fans working, temp runs up to and stays at 110, it has not overheated yet, I'v had the car for 8 yrs and no previous probs till just recently, Any suggestions greatly appreciated.
06-13-2010, 10:19 AM
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1991 500SL
Hi,
Is the 2 electric fan operating at full speed when temp is high? I would check that first. You can check once the the temp is high, stopped the car and walk around to the front of the car and if both the electric fan is operating, you cannot missed it. The sound of the fan is quite loud.
Cheers- Heung
Is the 2 electric fan operating at full speed when temp is high? I would check that first. You can check once the the temp is high, stopped the car and walk around to the front of the car and if both the electric fan is operating, you cannot missed it. The sound of the fan is quite loud.
Cheers- Heung
06-13-2010, 07:46 PM
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1998 SL500
Sunchaser, can you give us some more information? What is the ambient temperature when you car is running 110c? Are you driving in the city or on the highway? When your car is running at 110c and you drive it on the highway what happens to the temp?
Those electric fans are part of the air conditioning system and not really for cooling the engine. They are designed to ensure air flows across the condenser when the car is driving slowly or stopped.
If your temps are pegged at 110c all the time, I would think you either have a stuck thermostat or your radiator is clogged on the inside or outside or both. If your temps go down when running at highway speeds, but back up when driving slowly, check the fan clutch by rolling up a newspaper and gradually trying to stop the fan with the engine up to operating temps. If it stops, with slight pressure then you need to replace it.
Those electric fans are part of the air conditioning system and not really for cooling the engine. They are designed to ensure air flows across the condenser when the car is driving slowly or stopped.
If your temps are pegged at 110c all the time, I would think you either have a stuck thermostat or your radiator is clogged on the inside or outside or both. If your temps go down when running at highway speeds, but back up when driving slowly, check the fan clutch by rolling up a newspaper and gradually trying to stop the fan with the engine up to operating temps. If it stops, with slight pressure then you need to replace it.
06-13-2010, 08:43 PM
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1995 500SL & 2001 CLK 430
Thanks for your detailed response. The car runs fine for approx 20-30 minutes hgwy & city, but then creeps up to 110 and stays there, never overheats but i know this temp is not normal, i have tried turning full heat just to see if i could bring the temp way down but it only helps a little and the heat coming out of vents is super HOT, it doesnt act like the Thermo is stuck. Outside temp is approx. 95 degrees, i know thats a little warm, but this car never usually got over 90-95. i will try the newspaper trick. Is it common for Radiatiors to lose there effectiveness????
06-14-2010, 01:43 AM
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1998 SL500
If you are setting at 110c no matter what type of driving you are doing the first thing I would change would be the thermostat. It is possible for the bimetal strip inside to migrate over time. It is the cheapest place to start.
Radiators become clogged with corrosion over time if they are not serviced properly and at the specified intervals. Mercedes specs a particular type of antifreeze that is only available at the dealer or Zerex G-05 which was getting hard to find last time I checked. Regardless if the thermostat helps or not, I would take it to the dealer for a coolant change. You can often find specials on it if you ask. They will get most of the coolant out. I have done this job and it is hard to get over half of the coolant. The block drains have to be opened and they are hard to get to.
If your car is running 110c during extended highway driving, your fan clutch will not be the issue but you can check it anyway. Air moving into the front of the car at 70mph provides way more air than the fan could ever move.
If you change the thermostat, change the coolant, and are still having temps at 110c, you likely have a clogged up radiator which usually requires replacement.
Lots of guys complain about the temps that the M119 runs at but Mercedes says its ok. Mine runs at 80c during the winter but will creep up to 95 or 100 on hot days and city driving. I would say that yours is running a little warmer than most.
Radiators become clogged with corrosion over time if they are not serviced properly and at the specified intervals. Mercedes specs a particular type of antifreeze that is only available at the dealer or Zerex G-05 which was getting hard to find last time I checked. Regardless if the thermostat helps or not, I would take it to the dealer for a coolant change. You can often find specials on it if you ask. They will get most of the coolant out. I have done this job and it is hard to get over half of the coolant. The block drains have to be opened and they are hard to get to.
If your car is running 110c during extended highway driving, your fan clutch will not be the issue but you can check it anyway. Air moving into the front of the car at 70mph provides way more air than the fan could ever move.
If you change the thermostat, change the coolant, and are still having temps at 110c, you likely have a clogged up radiator which usually requires replacement.
Lots of guys complain about the temps that the M119 runs at but Mercedes says its ok. Mine runs at 80c during the winter but will creep up to 95 or 100 on hot days and city driving. I would say that yours is running a little warmer than most.
Last edited by msmith66; 06-14-2010 at 01:48 AM.
06-14-2010, 06:24 PM
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1995 500SL & 2001 CLK 430
MSMITH, Thank you for your reply. I think I will try the thermostat route and a coolant flush. The car has been serviced regularly, so maybe the radiator is O.K.. I hate to spend the money on a radiator if thats not the problem. Is there any way to check the radiator without replacing?
Your info has been very helpful. Thanks.
Your info has been very helpful. Thanks.
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10-02-2010, 03:57 PM
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1993 SL 500 R129
To check the radiator for clogs, I pulled the fan shroud - it just snaps in - and with the engine running at idle, slide hand down to feel for hot and cool areas on the radiator. Yes, there's plenty of room, but take off your watch and no shirt sleeves - bare arm only.
cool arear are clogged as no hot water is running through that area.
Good luck
cool arear are clogged as no hot water is running through that area.
Good luck
10-02-2010, 05:15 PM
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'87 560SL Sold, '99 SL500 For Keeps
sunchaser,
Everything that's been posted is the track I'd be on too in chasing down the heat problem. A couple small points...I'm taking it for granted that you're using either MB branded or MB approved coolant in the radiator and have changed it every several years.
The other small thing is that I would also change the pressure cap on the reservoir tank. The cap seal can go bad and begin to leak, pressure drops, temp goes up. The caps are cheap enough and if you've not changed it in 5 years or so, I would.
Bob
Everything that's been posted is the track I'd be on too in chasing down the heat problem. A couple small points...I'm taking it for granted that you're using either MB branded or MB approved coolant in the radiator and have changed it every several years.
The other small thing is that I would also change the pressure cap on the reservoir tank. The cap seal can go bad and begin to leak, pressure drops, temp goes up. The caps are cheap enough and if you've not changed it in 5 years or so, I would.
Bob
