Just wondering what the normal operating temps are for other people's OM603 cars. I think that my '87 SDL is running a little hot, (but not overheating), it seems to be about 90-95deg. on the gauge most of the time in normal city driving. I live in Los Angeles so it's usually about 80deg. outside, more or less...

My engine is in good general condition and the thermostat is a new 80deg. OEM piece. (Wahler). I'm thinking maybe my radiator is partially blocked with deposits and not 100% efficient, might get it flushed and pressure tested at a radiator shop. I don't have any leaks. My fan clutch is also working.

TIA for the input!

mines at 60C then again i have 60 thermostat in mine but 90-95 is a bit hot

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

How on earth could a thermostat keep it @ 60deg.?? You must live on the North Pole.

A 60deg. therm would open @ 60 deg. and then stay open for the rest of the day. It is not at all desirable for an engine to run that cold, especially a diesel. Diesels run at maximum efficiency on the hot side.

The water temperature is dependent on ambient temperature and load.

For engines with cooling systems in good condition, the temperature will run 85-90C. when lightly loaded under most ambients. When the ambient gets quite warm...........close to 100F...........expect the lightly loaded temperature to climb to slightly above 90.

Under load (uphill or high speeds or with a/c), the temperature can climb up to 100C. or in high ambients, possibly touch 105C. None of this is of concern, however, unless you desire to cruise at 95 mph in 100 degree ambients. The temperature might then exceed 105C.

The system takes some time to stabilize at any temperature and, generally, the high load is reduced before the temperature gets close to dangerous levels (anything that nearing 110C.)

Feel free to chase all the potential contributors to additional coolant flow in a valiant effort to reduce the temperature by 5C. or so. The engine won't be thanking your for it.

Thanks Brian Carlton. That seems logical and about where my car runs. It's around 90deg. most of the time. I'm still going to have my radiator flushed and tested because I'm taking some long drives and I'm a stickler when it comes to cooling systems.

I'm a little baffled with the poster above who claims that his car runs @ 60 deg., didn't think that was possible. Or desirable. I had a Ford Powerstroke 7.3 and the first mod I did was put the 203 deg. therm in it. The factory put a 195 in them, (~90C), but the earlier 7.3s came w/ 203 therms. The engines run a lot nicer w/ the hotter therm but the NOX is slightly higher so Ford (or International) had to put the colder one in for emissions. The hotter thermostat is one of the most popular/no-brainer mods on most PS BBSs. Diesels run better hot, as long as they don't overheat. Most diesels are so efficient that they will NEVER warm-up idling in cold weather, they need to be under load.

I'm not...............

Even my gasser rarely ever goes over 82C.....even when *enjoying* it. Highest I've seen so far is 84C. With a healthy water pump, clean/good condition radiator and proper coolant mix, its very difficult to get them to rise much past operating temp.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

This is a factually incorrect statement for the OM603.............

So what is the reason the 603 gets so hot? None of the other engines seem to have this issue...the M103 gets a bit warm (maybe 90C) during extended idling on a very hot day..........

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

80-85°C almost always.

Hot summer with A/C? 85-90°C.

Roads are quite flat here so rarely any heavy load driving unless merging or driving with 'spirit' 80-85mph with A/C I have seen high mid/high 90s.

My radiator is from '07? So very new, made significant difference in cooling capacity. Also have red fan switch.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

The gauge on my 87 300D shows about 90C pretty much all the time once warmed up. I don't think that is necessarily too high. But, I also don't necessarily think the gauge is dead-on accurate, either. You might look at alternate methods of measurement.

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-Louis

'87 300D Anthracite

Mercedes sell a 60 or 70 degree thermostat for these engines, I believe its for cars running in the arid sahara desert.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

yes thats what i have in the car, just took it for an extended road test and it stayed at 60-70C the whole trip. The car runs wonderfully

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

Well, it is of course your car and the thermostat is your prerogative but I do not think that is the optimum operating temp for the efficiency of that engine. (Power/economy).

I think I need this. Has anyone driven a SDL thru desert at 115+ deg F outside? The temp gauge was reaching 120 deg C, the red zone. It did not kill the head but very close to it. I needed to rig up the aux fan to be turned on all the time to get me home.

So if the engine is running at 90-95C during normal traffic then it may not survive a trip to Death Valley. I believe it should be < 85C under normal traffic. Anything more than that indicates the cooling system is not as efficient as it should be.

My $0.02.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

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1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.