My '85 300D turbo 617-952 engine- CA version water temp is too hot with the AC on, when idling and when driving up the hill at about 100 deg. C and sometimes a little higher almost close and getting closer to redline 120 deg. C. It is also hotter when driving st speeds above 85 MPH, when engine is in high rev.(above 3000 RPM). But it is always in normal temp. 90 deg. C (about in the middle of 80-100 deg. C points) when in normal driving speeds and engine rev. range at about 40-70 MPH (2000-3000 RPM) on flat road and not in a slow stop and go traffic rush.

assuming that I:

a) have installed brand new thermostat;
b) flushed the whole system and switched to ZEREX-G05 antifreeze;
c) new set of belts and proper tension;

but still no noticable improvements.

QUESTION:
a) bad thermostat??? still???
b) bad water pump???
c) bad fan clutch??? blade???
d) bad radiator???
e) for some reason, this particular car doesn't have the small C-shaped line
(metal pipe or tube) that goes between the top of the waterpump housing
and front-right hand side of the cylinder head, actually, (it is on your left
when you are facing to the firewall).both ends of this line should look like
he ends on the ALDA banjo bolt except that this is not made of vinyl or
plastic hose it is all cad-plated metal. do i have to install one of those to
lower water temp???
f) bad valve clearance???
g) bad IP timing??? engine running lean???
h) if engine is running lean, main and in-line fuel filters are brand new, is it
bad in-tank fuel screen???

Hows your fan clutch?

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