Im was pretty sick n tired of the 85 stat that comes from the factory in my car and the temps at 90 and I beleive stuck at 95 in traffic with the fan clutch locked, I replaced it with an 80 degree Wahler, the temps settled down a hair - but I live in TX - which is a desert - sometimes a humid desert.

I thinks a condenser clean should help, and some sort of rad flush. btw there are holes on the thermostat bypass block off plate of a 60X MB thermostat - wouldnt it help if it were just a plate like the older 61X had.

I've sat in traffic this past summer in my 300E when it was almost 100F outside and when it got to about 92C the massive electric fans powered up and brought it back down to about 85C before they shut down, it continued this cycle the whole time I was sitting. As soon as I was moving again the engine fan was in full force until it was back down to about 82C then it was quiet again. :D Makes no sense why the 300 diesel inline 6 would run so warm, it generates a lot less waste heat than its gasser cousin.....

My 420 engages the engine fan full lock once the temp is at 85C....it keeps it engaged until its back down to about 81-82C.....it has never needed the electric fan so far...

My 300SD powers up the aux fan idling around 84C....and will stay on until I've been moving again for a while. With my old original radiator it'd get up to 105-110C working it on a hot day or idling in hot weather. With new radiator, t-stat, pump, and coolant, I've never seen it over 85 even on the hottest days.

It's because the 603 fan is off to one side. The blade tips go beyond the end tank, for crying out loud ;)

Sixto
87 300D

Cooling
 

Seems to me I read somewhere that engines are more efficient if the temperature difference between the engine and the ambient air is greater rather than less. Obviously you can't overdo that, especially with our alloy-headed diesels, but the principle is sound. I remember seeing a change between pre-smog and post-smog cars when I was driving GM iron. The older cars ran around 180F (82C) while the newer cars ran much closer to 200F (93C). With an 80C thermostat, an OM603 engine should sit at about 90C depending on ambient temps and load.

Keeping the cooling system clean is probably the best way to make sure the temperature stays below the danger area. In addition to Hit Man X, as previously posted, both Sixto and I have the red top aux fan switch (S25/5) that turns on the fan at 100C instead of the factory 105C and additionally turns off the a/c when the coolant hits 110C (instead of 128C :eek: in the original blue top factory switch used in the 1987 300D Turbo). There are at least four different temperature combinations to choose from.

Jeremy

........further confirming your lack of knowledge and understanding of the cooling system on the 603.

Anyone have part numbers for these alternate fan switches? That sounds like a smart mod considering the fan/radiator design of the 300SDL. Thx. :cool:

There's a few different ones you can use.

Red: 006-545-42-24 (100/110)
Green: 006-545-45-24 (105/115)
Grey: 006-545-61-24 (105/120)
Blue: 006-545-64-24 (105/128)

The first number in parenthesis is the temperature that the aux fan engages at high speed, and the second number is when the AC compresor will cut out.

Thank a lot. I've already gotten the red one and will be installing it soon. :)

Hey, since I've got the attention of some people w/ knowledge of these motors here, can someone tell me what these two things are? TIA. :)

Well, that's your VCV and your ELR (respectively).

My 603 sits at 80C, except nowadays, I'm blocking the rad with cardboard already to try and warm it sooner and keep temps up near 80 when it's -5C outside.

In plain english, what are these things?

VCV vacuum control valve, a variable signal to the transmission related it accelerator pedal position

ELR idle speed adjustment knob, sets RPM at idle

Thanks! That's valuable information and really explains a problem I'm having. The small rubber vacuum *elbow connection* on my VCV is damaged and the vac line keeps coming off. Does anyone know if that small rubber piece is available as a replacement part?

It's not available separately from MB. Here is my experience with parts store replacements -

http://www.peachparts.com/shopforum/diesel-discussion/247286-60x-vcv-vent-hose-fitting-alternative.html

http://www.peachparts.com/shopforum/diesel-discussion/259141-603-96-vcv-replacement-bowden-cable-adjustment.html

Sixto
87 300D

Really good write-ups! Question: How did you know that your VCV needed replacing? What were the symptoms of the old (bad) one? Thanks! :cool: