SL/R230: Overheating Help!
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Newbie
Joined: Jan 2022
Posts: 8
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2004 SL55
Overheating Help!
I have a 2004 SL55 with about 110k miles, and my engine will run at 80* C for the beginning of any of my drives, but pretty soon it starts ticking up and once it goes to about 95* C I'll flip on the heater for fear of the engine overheating. Doing that will keep it around 90-95ish. Sometimes if I'm cruising it will start to go back down to near 80*C but anytime I stop in traffic it climbs back up. It almost seems like the fan never wants to kick on, or there's possibly air in the system?
I did recently replace the water pump, thermostat, and radiator, but not radiator fan or coolant temp sensor. I also added a larger heat exchanger, and swapped the secondary IC pump to the Bosch, but I didn't split the system. There's no coolant leaks that I've seen so far, but I would still think the car should always be running at about 80* C? I don't know how to check for air other than running it with the heater at full blast for a while. It doesn't have the bleed nipple that the E55 has. Is there a better way to bleed the system? Is there anything else I can check or do to get this running right? Currently I don't want to drive it over a few mules for fear of it overheating. Thanks.
I did recently replace the water pump, thermostat, and radiator, but not radiator fan or coolant temp sensor. I also added a larger heat exchanger, and swapped the secondary IC pump to the Bosch, but I didn't split the system. There's no coolant leaks that I've seen so far, but I would still think the car should always be running at about 80* C? I don't know how to check for air other than running it with the heater at full blast for a while. It doesn't have the bleed nipple that the E55 has. Is there a better way to bleed the system? Is there anything else I can check or do to get this running right? Currently I don't want to drive it over a few mules for fear of it overheating. Thanks.
MBWorld Fanatic!
Joined: Sep 2007
Posts: 1,481
Likes: 310
95 SL600
The fan may be bad. I bleed the system by taking the top intercooler line off where it goes I under the supercharger. and bleeding the air out. I would check the fan operation with a good diagnostic tool. You can turn it on. Next step is checking the thermostat temperature and function. Maybe you got a 95 stat or it’s not functioning as it should.
Last edited by cdk4219; May 7, 2023 at 05:59 PM.
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Joined: Apr 2021
Posts: 846
Likes: 560
From: San Jose, CA
11 E550, 16 AMG GTS, 13 S550
You can have an air bubble trapped in a hose, thermostat neck, or at the top of the heat exchanger, you just gotta drive and jostle the car sometimes and use the cap very carefully, with a towel to vent it. I do it barehanded at the shop but I care much more about you than me. I doubt there are anything wrong with the parts though. If it's only overheating 10C it's usually air. If it was the fan the temp spike would be a bit worse than that I reckon.
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Purchase Amsoil at 25% off from me
Chris Tran, Retired Alpha European Autotech Owner
Amsoil Independent Dealer #7236674
