93SL600 cooling.

[phelan]

Running a bit hot this year. Wish to get the cooling system flushed. Dealer states citric acid only needed when oil in system. What else is used beside water?. Incidently where is the coolant overfow tank located, I see a hose going from the radiator cap area but cannot see its terminus. Is the tank in the fender and how does one get to it?

[suginami]

In the W124's, the coolant overflow tank is hidden behind the passenger side front fender well.

The overflow tank could be there, as well, but I'm not sure.

[Kebowers]

The W129's SL600 has the overflow tank under the front fender well. Got to remove fender liner to get to it. They run hot by design. Try cleaning the exterior of the radiator to make sure no road gunk is on it. Also be sure the antifreeze mixture is not too stout. A 40% AF/water works best all around. Less AF in the mix gives better cooling.

[Gilly]

They could also check between the radiator and AC condensor for debris as has been previously discussed. Another possiblity is an inop electric cooling fan or a problem with the engine fan itself. if it seems to run hot at intown speeds or stop and go traffic, I would suspect the aux fan, but it's recommended to have the coolant flushed every 3 years, so if it's been longer than that I'd recommend doing it anyways. A flush and refill is fine IMHO, unless as your source stated, you had oil in the cooling system caused by an engine malfunction like a blown head gasket. Other possiblities would be a internally plugged radiator, low coolant level (caused by leaks), or simply a bad thermostat. It's even possible the temp sender or gauge is bad and the engine temp is actually fine.

Gilly

[phelan]

Problem appeared after cam box oil leak fixed. Cannot see connection except thermostat replaced. This was then changed again to make sure it was not in itself defective. The fans come on appropiately, ie viscous at approx 96-7, front electrical @ 105. Again what should be used for flushing eg citric acid or some Prestone product?.

[Gilly]

Many recommend the citric acid, what MB advised us to use is liquid concentrate bilge cleaner, which is available at marina's for use in boats. Seems to work well for us when we have a car with oil in the cooling system caused by a blown headgasket.

Gilly

[phelan]

Viscous fan sounds very loud when it comes on , especialy with top down street driving. The engine needs it for cooling but any way to make it run quieter and with similar efficency. Ideas.