Quote:
Originally Posted by Jason SVO
Well, after a citric acid flush and new expansion tank, I am still getting high temps. The gauge does sit right above 80 C on downhills, where it hasn't before. But the car still cannot maintain it's temp under load.
What's next? New radiator?
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I had exactly the same problem with my '87 300SDL. Fixed all the things you have fixed and the vehicle kept overheating. Going up a long steep hill with constant boost, it would get to ~ 90 C and hang there and just when I thought things were good, the temperature would shoot straight to 100 C & beyond (if I let it, which I tried to not to allow).
I was reading about what exhaust backpressure is normal (2 Bar or less) when I saw a reference to an "oxidation catalytic converter" in my service manual. At first I thought that this was the dreaded "trap oxidizer" which I knew my vehicle did not have. Then I saw the attached figure. The first of the 3 cans is the oxidation catalytic converter and I did have one of those.
Now I have a nice empty metal shell in that location, having removed it's innards. My car no longer overheats and hangs near 85 C, when under a light to moderate load, instead of hard against 90 C most of the time. I don't know why this is not very frequently mentioned as a source of overheating issues. It should be gutted before even doing a citric acid flush. 2 Bar exhaust backpressure is not a good thing for any engine.
The ceramic honeycomb in the OCC had about 75% blockage. It takes a fair amount of hammering to get it out, but it is satisfying work, with great benefits. The turbo sounds much happier.
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1986 300SDL
1987 300SDL
1997 F-350 Powerstroke Turbo Diesel
1969 32' Luhrs Perkins HT3.54M Turbo Diesel
WVO & biodiesel when I can get it
(there is a de-facto ban on biodiesel in CA
- ask the Water Quality Resources Board why
underground storage isn't allowed for biodiesel -
heck, you can drink the stuff
)