SL/R230: 2005 SL 500 No heat under 1300 RPM
#1
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2005 Mercedes SL 500 Roadster
2005 SL 500 No heat under 1300 RPM
My car will not push any heat unless the car is revving over 1300 RPM. Then it puts out a ton of heat. But as soon as you let off the throttle it blows cold. I just changed out the thermostat and still the same. Could a air lock cause this and if so what is the best way to evac the air from the system.? I have run it for a long time with cap off. still same results.
#2
MBworld Guru
The coolant system is self-bleeding, so there's no possibility of an air block. Is the coolant temp changing with engine speed? If not, then I don't think it's a coolant problem. Maybe it's electrical.
#4
Senior Member
The R230 has 2 Water Pumps. Check that your (2nd) Auxiliary Water Pump is operational. This is the small pump that "Helps" the mechanical water pump that's attached to the engine block circulate coolant through the heater core. When that 2nd pump fails, then you're just relying on the normal pressure created by the primary pump. The result would be exactly what you're experiencing - no heat until the engine has reached a sufficient speeed for the mechanical pump to work the coolant through.
https://mbworld.org/forums/attachmen...ation-pump.pdf
https://mbworld.org/forums/attachmen...ation-pump.pdf
Last edited by Aussiesuede; 01-31-2018 at 10:43 PM.