I agree with Forced on that.I built a 351c once in a mustang.We tried running with out a stat.It ran hot,because coolant never had time to cool.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt

Thanks Forced. Those images set the record straight for me about the role of the thermostat in these fine diesel vehicles... One thing that is appreciated about these cars in colder climates is the warmth they offer the driver (in comparison to modern vehicles) and I can now see one of the reasons how that comes about (as the radiator is only used in cold weather when "need be").

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1983 300SD, 1999 200 cdi and 1998 1,6 (gasser)

The stat in a benz is not an on off valve like a garden hose. Off on is how a traditional american made car stat works. With an on off valve you can cool fine without it but the car will run too cool under light loading.

A benz stat is a diverter valve. Its more like a switch in a rail line. When the engine is cool the stat diverts all water back to the head without ever going into the rad. When its hot it diverts all water to the rad and none to the head directly. It goes to the head after passing through the rad in that case.

If you remove the benz stat you will allow the water to seek its own course and it will send about half directly to the head and half to the rad. Thus when its really needing cooling its only cooling half the water and the car will run hot.

If its cold outside and the car needs to warm up half the water will continue to go to the rad and it will not warm up.

Drilling holes in the stat will only reduce its effeciency. A good stat working the way the system is designed to be operated cannot be beaten.

If you don't understand look in your repair manual for a diagram of how it works.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Your operating temperature also depends how much rust etc is in your system. A cooling system with rust will make the car run hotter than normal

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1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)

How did you come to this rate? It is dependent on the restrictions in the head/block vs. radiator. You are saying they are perfectly equal.


this is what I am trying to say.

the natural course of flow w/o the t-stat allows only one rate of cooling. Therefore, until that rate of cooling is matched by an equal rate of heating from combustion, the engine is overcooling itself.

Once the equilibrium of heat production and cooling (w/o t-stat) is breached, you begin overheating and it cannot be controlled.

I have driven well over 200 miles in the summer w/o t-stat and continuously overcooled the entire time. ie..highway 65 mph

only until I climbed a mountain for 15 miles at a very slow speed on a dirt trail did I breach operating temp, and I never hit over 100*c in 85*f weather.

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How did you come to this rate? It is dependent on the restrictions in the head/block vs. radiator. You are saying they are perfectly equal.

Not only that...Heat expansion of the coolant (thereby affecting density) would probably play a role in what portion would flow thru the rad at different stages... But...why would you want to run your Benz without the Tstat? The extra cost in fuel (while reaching operating temp) ought to be prohibitive... no?

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1983 300SD, 1999 200 cdi and 1998 1,6 (gasser)