The engine will not run at 87C 100% of the time no matter how much you rant about it. I don't wish to ram that down your throat. Quit being a simpleton.

 

Quit telling people who are asking for tech help that it is normal when their engine is running 25 degrees F hotter than it should.

 

I'm sorry. I don't recall saying that. Will you either point out where I said that or shut up and get back to work?

I've never heard anyone be so silly as to claim that an automobile thermostat is a precision instrument.

Since you are reading-impaired I'll intrepret for you what I wrote. Read slowly. MB engines operate within a range of temperatures that is considered normal. MB engines operate at a normal (or ideal) temperature of 87C which the cooling system endeavors to maintain. If the cooling system can't maintain the normal operating temperature, then there is a problem. That's what I wrote.

You claim there is no range, normal or otherwise, I think. That's not true. As I said, you contradict yourself so it's hard to tell.

Finally, I'm not saying he doesn't need a new fan clutch or other repair. I'm simply stating that the temperature will fluctuate and that it's normal, excluding extremes. Are you able to add up all this info and comprehend it, or do we have to go another round? Sheesh!

 

A thermostat stamped 87 does not mean the car should remain at this temp. All this means is the thermostat opens at 87 and allows water to flow and cool the engine only once the engine has reached the 87 mark. This prevents you from cooling a cold engine .After the engine reached the 87 mark the thermostat has done its job, anything after is not the thermostats problem unless its stuck closed and not allowing for proper cooling. "duxthe1" says " When everything is right Mercedes do not run hotter than their thermostat" what are you talking about man, your an 8 year mechanic? all the 87 means is the engine will not be cooled off when its 87 or below. meaning the thermostat will stay shut. Athermostat will not regulate the temperature, if the engine overheats the thermostat can not do anything to say hey lets cool it. It only regulates the temperature when the engine is cold.

"Duxthe1" says "Why would one of the most precisely engineered cars take such a lacksidasical approach to the cooling system"
Well i hate to break this to you dux " During severe operating conditions and stop and go city traffic, the cooling level may rise" this is straight from an s420 owners manual, page 84.

 

You're not entirely correct. The thermostat does indeed play a part in regulating the coolant temperature on either side of its specified opening temperature. You have the warm up cycle correct. But the thermostat will also begin to close when the coolant temperature drops below the opening spec to help re-warm the coolant. Just ask any Eskimo.

 

yes lugnut the thermo does regulate the engine temp when its 87 or below, the therrmo will not do anything when its 87 or above. The bottom line is even my MB manual states that there will be an increase in temp during heavy traffic.

 

Which is what I've been saying all along. Sheesh! What's wrong with you people?

 

From the symptoms that you describe, the most likely and probable cause of your engine running somewhat hotter than normal is a failed Viscous Fan Clutch.

Its very easy to check. Next time your engine's temperature is over 100C, open the hood and have someone shut-off the engine while you look at the Fan Clutch. If it continues to spin for more than 1-2 seconds after the engine shuts-off, your clutch is defective and should be replaced. If it stops spinning almost instantly its OK, and your problem lies elsewhere.

I'll bet you'll find that it will keep on spinning.

Phil

 

that was a nice tip!

 

Only one problem...not all have the viscous type fan clutch. Mine is a spring clutch....according to the shop manual. Does that apply to spring clutches too?