On my beater 300SD, it's always run a little hot, not sure the fan clutch is engaging, and the aux. fan was disconnected, was getting to those, but after doing the valves and turning up the alda, it's running much cooler, didn't edge above 90 even after sustained 75-85 mph driving that used to send it to 100-105 on the temp gauge. I do have the aux. fan hooked up now, but seems to not be a problem anymore. Who knew a properly tuned engine would run so much better? (rhetorical question)

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'84 300SD veg-oil bliss
'83 300SD veg-oil beater

I adjusted my ALDA this last weekend, and I was amazed how it woke that motor up!

I also noticed while driving on the freeway, that my engine temp also dropped. It now runs just below 80. So anyone who is worried about EGT, no worrie.

I also don't notice any black smoke, this car never smoked at all, now just a little light smoke on heavy accelaration. What I like is I am not scared to pull into traffic anymore.

That's not good! The engine should never run below 80C when warmed up. You either have:

1) A faulty thermostat, or
2) A bad gauge sender

If the thermostat is old or of unknown age, it should be replaced on principle anyway - use OE/OEM, Wahler or Behr. (I assume you know to only use MB antifreeze, or Zerex G-05). If the t-stat is recent (and OE/OEM), the other common problem is for the gauge to read too low. The sensors tend to be inaccurate, and read below actual temp, when they get old. The good news is they are cheap ($15?) and pretty easy to change, located between the #2 and #3 glow plugs (I think).

My 1984 had BOTH problems when I bought it - gauge read 50C and put out weak heat in winter. A new t-stat fixed the heater but the gauge still read 60-70C. A new sender was the cure, now reads 85-90C most of the time, which is PERFECT. The car has never gone over 100C in any conditions. Optimum temp for best power, economy, etc is (IMO) 85-95C.

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Dave
Boise, ID
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