My former 82 300SD ran hot when I first got it, but only at speeds above about
30-40 mph. If you got out on the highway it would run up in the 90s (C) and
just sit there. Drop down to a lower speed and the temp dropped down to the
expected 87C.
1.) Cleaned the radiator. That is, removed it and pressure washed the core.
It was nasty. No joy.
2.) Replaced the thermostat. Rumors abound of Behr thermostats being grossly
inconsistent. Not this time.
3.) Made sure the little bypass line was working. Yup, clean as a whistle.
4.) Replace water pump - the pump that came off was a NAPA pump. Oh, boy, this
has GOT to be it. Nope.
5.) Take radiator out and have the guy that did all of our industrial engine
radiators take a look at it. Bingo.
At some point in time, the PO ran the evil green stuff in it, and long enough
that it got exhausted and a great deal of the chemicals dropped out of
solution. So much so to the point that it clogged the center tubes of the
core. Interestingly enough, when he rodded the core out, only a circular
portion of the radiator tubes were clogged, that is, the very center of the
core where air flow (fan hub) was at the lowest.
So, the reason it would work fine at lower speeds was because I had plenty of
surface area to dump the heat. At high speeds when I needed all of the
radiator surface to dump engine heat to ambient air, I didn't have it.
Therefore, the excess heat remained in the cooling system and the temperature
of the system increased.
I got into the habit of taking every radiator out of my MBs after that point
and having them professionally cleaned. It's an easy job and relatively cheap
(used to be well under $100.)
Dan
--- On Sat, 4/25/09, Luther <benz-n-h...@gulseth.net> wrote:
> From: Luther <benz-n-h...@gulseth.net>
> Subject: Re: [MBZ] 87 MBZ 420 SEL High temp
> To: "Mercedes Discussion List" <mercedes@okiebenz.com>
> Date: Saturday, April 25, 2009, 2:25 PM
> My SDL is in that same shape....
>
> Luther
>
> OK Don wrote:
> > Every time I've had an engine runnig hot, a new
> radiator cured it. Cleaning
> > the old one has only made minor differences. Seems
> that every car I've
> > gotten that has had green coolant has needed a new
> radiator.
> >
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