86 300SDL Overheating Randomly - Page 2 - PeachParts Mercedes-Benz Forum

Base1375 · #16 11-22-2015, 03:43 PM

Will start working on all the small help you guys gave me. but i did find a bottle of green coolant in the trunk. :/ Any idea how bad it is since he most likely filled it with that after it overheated the first time....?

Base1375 · #17 11-22-2015, 04:06 PM

Also the fan is working. Car was overheating while it was being driven and while it was just irked too. Thought I mentioned that.

Mxfrank · #18 11-22-2015, 04:14 PM

Quote:

Originally Posted by CarpeDiem51392

Thanks for the reply gents. I've heard it said that the 603 aux fan is inadequate but I thought it worked pretty well. Well enough that I was fine without the mechanical fan; but the weather here is moderate in terms of heat. Plus I rarely hit stop and go traffic. Anyway hope I can get it fixed, seems like there is just one electrical component to wear out. Looks like a big resistor but it's probably a capacitor or something else. I've seen similar fans at the yard, maybe interchangeable. Well that's enough of a sidetrack. Cheers!

None will be interchangeable, unless they are other 124 fans.The fans draw about 25 amps, and they have an aggressive blade design. Not to mention that they are configured as pushers.

If the fans are jammed, you may be able to revive them. The trick to disassembly is that the nut that holds the blade to the motor is left hand thread. Open the fan, clean and lube the bearings, hope for the best.

The electric fans operate at two speeds. High speed is triggered by the switch that's on the water outlet, at the engine side of the upper hose. Unless it's a later car, in which case it's triggered by the climate control head unit.

Low speed is triggered by A/C system pressure, by one of the pressure switches located on your receiver dryer. There is a resistor on the firewall that causes the fans to run at low speed. If you find the resistor has failed, it's possible that a fan is binding, which causes a powerful voltage surge. The point is, if you have to replace the fan resistor, you want to clean up your fan bearings as well.

The high speed fan circuit is driven directly from the battery. The only protection is the relay, which has a built-in fuse. The early relays are black, and the fuse is internal and not replaceable. They are awful. The fuse can blow and you would never know it. If you buy a new replacement, it will be orange, and will have a replaceable fuse in the top.

The low speed circuit is protected by two regular fuses in the fusebox. One for the relay coil and one for the contacts. Can they have made it any more complicated?

TRoubleshooting electric fans

mannys9130 · #19 11-22-2015, 04:26 PM

If green coolant was added to the stock MB G-05, drain the cooling system and flush with distilled water. It's not good, but it's not going to blow anything up right away. Sort out the overheating, and once it's running at op temp flush the coolant. MB no longer carries the yellow G-05. Instead, call up your local NAPA or Orielly's Auto Parts and ask them if they have Zerex G-05 in stock.