When she stops she's hot? - PeachParts Mercedes-Benz Forum

droederer · #1 07-12-2004, 10:56 AM

My 1986 560SL is on the verge of overheating (almost in the red) when I am at idle (500rpm) for more than a couple of minutes. If I raise the ideal to 1500 rpm the temp starts to go to midrange almost immediately. The system shows coolant at the proper line in the reservoir. What should I check?

G-Benz · #2 07-12-2004, 12:18 PM

Thermostat first...cheapest fix.

Next. Aux fans. Normally running when the A/C is on and/or ambient temps are high. There should be a temp sensor of some sort that signals the fans to start up when temps get high...

droederer · #3 07-12-2004, 06:55 PM

Thanks for the help. This happen with the AC off. Should the Aux Fans come on if the outside temp is high even if you have the AC off?

Holson Adi · #4 07-12-2004, 07:39 PM

Quote:

Originally posted by droederer
Thanks for the help. This happen with the AC off. Should the Aux Fans come on if the outside temp is high even if you have the AC off?

yes they should.

Check the fuse first.

The fuse is in the aux. fan relay just behind the fusebox (you have to take whole fuse box cover off by unscrewing some 6 or so screws)

btw, the fuse/relay panel is located in the left rear of the engine compartment.

The aux. fan relay module is in Position B in the Relay Panel.

It's a 30A fuse...

if that's fine, check the aux. fan switches (one is A/C pressure activated and the other is water temperature activated)

the aux. fans come on at low speed when the AC is on and the AC pressure is high

and they come on at high speed when the water temperature exceeds 110* I believe..

there is also a resistor mod that you can do to activate the aux. fans at a lower temperature..

robertge · #5 07-13-2004, 09:22 AM

haveing same problem on my 88 560sl have you found your problem??

droederer · #6 07-13-2004, 09:52 AM

No, I will not have an opportunity to address the problem until the weekend. I will post my results.
Dave

droederer · #7 07-19-2004, 10:41 AM

This is what I found out this weekend. The aux fans were eazy to check. All I did was ground the Brown/Gray wire on the temp switch. This confirmed everything in the Aux Fan circuit, including the fan (except the temp switch) was OK. Everything in the circuit was working, My problem was that the radiator was low on coolent. For some reason the radiator will not fully fill from the reservior. I took the top radiator hose off and filled it. This solved my problem.