V12...runs hot...need cooling experts assistance - PeachParts Mercedes-Benz Forum

pcmaher · #1 08-28-2004, 09:12 AM

I've read through all the posts I can find about engines running hot. I see very little with respect to the V12 120.980 engine. My S600 usually runs around 95 C in 75 - 80 F weather while driving. Yesterday, 86 F weather, in stop and go traffic with A/C on, temp was approaching 120 C. I know MB states this is normal and acceptable, but I'm uncomfortable with engines running this hot.

Radiator exterior is clean, recently flushed and using MB coolant, using Water Wetter, has JimF's resistor mod to B10/8 sensor, both auxilliary fans working, fan clutch APPEARS to be working. I must examine it more closely. I am still a little unsure about proper fan clutch operation (ie what temps affect operation, and how it should behave at those temps). I am interested in modifying the fan clutch per Stu Ritter's method. Has anyone tried this with a V12?

h_shek · #2 08-28-2004, 09:24 AM

120C is way too hot. The A/C runs into emergency shut off at around a little over 120C so thats definitely not normal.

The Fan clutch may be loose. Try hand swinging the fan clutch operated fan and see if you feel any resistance. If it swings freely, i.e. the fan turns very easily, the fan clutch needs to go.

If you Aux. fans are working as you indicated, have your thermo stat been looked at? Thats a start. Next I will look at the water pump which I have replaced with the same problem.

I don't have the V12, only the M104 stright six engine.

my 2 cents.

cheers

Ali Al-Chalabi · #3 08-28-2004, 12:58 PM

Check the fan clutch more closely. It should be at full lock by the time the engine starts to go over 100C. At this point, there should be a mass amount of airflow and audible noise of airflow when the engine is revved. I second replacing the thermostat. If both the thermostat and fan clutch are good, I would look at the possibility of a flow porblem as in water pump and/or radiator.

pcmaher · #4 08-28-2004, 01:28 PM

I watched the fan with the engine idling at 110-120 C. It does not seem to spin at engine RPM. Shutting the engine off, the fan rotated maybe 1 revolution max. Also, the fan can still be turned by hand with some resistance. It is by no means very stiff, and absolutley not "locked up". First glance at prices for this fan clutch...ouch.

Thanks all!

psfred · #5 08-28-2004, 01:57 PM

At that temp, the fan should run at engine speed and roar.

Quick test is to start it up cold -- fan should roar for about a second or two as the fluid spins out, then slow down. If not, it's toast.

Usually oily if failed, too.

Check the temp sender, it's possible it or the gauge is bad, too, and you don't actually have a problem!

V12s are a pain -- too big for the body, lousy air flow.

It's pretty new to have a clogged rad, but anything is possible! Best way to check that is an infared thermometer, look for cold spots. Usually show up first behind or in front of a fan.

Peter

Hatterasguy · #6 08-28-2004, 07:20 PM

The fan clutch on my friends S600 is very stiff, it will not spin at all if you try to push it with your hand. It is a lot stiffer than the older one on my SDL.