[W126 Coupe] Temperature gauge at about 10 PM on my 1989 560 SEC
Dick Spellman
spell.yy at verizon.net
Tue Dec 20 08:26:43 EST 2005
Hi Jack:
You've got (3) items that would impact the higher than normal temperatures while in stop n go traffic.
a.. Thermostat (I'd renew this if you have more than 120k on the one in there now)
b.. Viscous fan clutch (I'd renew if it's got over 100k on it) Easy to test if it's bad -see the archives.
c.. Auxiliary electric fan (I'd apply 12VDC directly to the fan connector to see if it's good and tap the fan hub if it does not kick in with volts applied to see if it's bearings or brushes that have failed) There is a DIY fix to lubricate the hub bearing if that proves to be the problem. Don't have much experience with this but, have the notes.
If the aux fan is good, then I'd be testing the temp sensors on the AC receiver/dryer and the cylinder head to make sure it cycles that fan on at whatever the 89 560 spec calls for. In any event the tstat and visco fan clutch (either one or both) are at the top of the list for the problem you describe.
A few notes from MB mechanics worth considering once you renew whatever has failed.
There is a simple set-up to kick the aux fan on at all times when AC compressor is selected for travel at high elevations or in hot climates.
There is an adjustment you can make to the front bi-metal spring to engage the fan clutch continuously for hot weather and then revert to normal use when the temperature starts to moderate or really colder temps will be with you for a season. This presumes the fan clutch has not lost the visco fluid which seems to be a function of age/mileage on these cars.
Regards,
Dick
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