Hello everyone,

I just completed a 300 mile highway trip in my 1987 760 2.3 turbo wagon and have a weird, disturbing noise...that I fear may be leading to some sort of failure.

So...half way through the trip I notice that a grinding, whining sound (like a bearing in alternator?)--- that ONLY makes noise from 67 mph up!
It does not care about engine speed at all, or what gear it is in... if I drop below 58 mph the noise completely goes away! I mean SILENT not a peep.

Also the noise (very annoying) stays there at least up to 95 mph (well,I had to check...open highway).
Not likely a wheel bearing because high g load turns on ramps have no effect.

The noise is the loudest thing you hear with radio off and windows up (cannot hear it from the engine compartment with windows down)...and is completely silent when the hood is up and the engine is throttled up.

It seems to come from engine compartment on drivers side...so at first I was thinking alternator bearing, water pump, or the fan clutch?

Recently...pulled the top part of timing belt cover and checked whole belt...pleasently surprised that it looked brand new...other belts are good...no leaks at water pump... alternator seems fine-- the guage is in the middle-- never dims lights even with AC and lights on at idle...AC works great.

Now I even wonder if the speedo cable could be making the noise.

HELP...what do you think and why do you think it would make this happen?
This just started today !

I hope that the Brickboard brainbank can help... thanks in advance !!!

Dave

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Car Info: 1987 760 2.3 turbo wagon good condition

I rescued this wagon with 112k on the clock and have driven it another 4k more or less... in the last 4-6 months.

Sorted out the usual stuff-
Complete brakes, redone calipers, new pads, new rotors, complete brake system flush.

Fuel pressure regulator, fuel filter--- prem. fuel ONLY and always!

New cap + rotor, NGK plugs,new Bosch prem. wires, new battery.

Excellent compression, new knock sensor, patched some of the "green/enviromental" wiring harness issues (have a new one, when I have the time and need).

Resoldered Bosch ACC controller relay, vaccumed and recharged with R12...system is good for now.
Replaced coolant hoses,coolant flush, thermostat, radiator temp. sensor

Complete IPD flush of automatic with Mobil One ATF---highly reccomend!!!
Oil changes with Mobile One and filters at 3,000 miles (2x so far),changed rear end oil to Mobile One Rear end Lube. Flushed power steering.

New heater core...a real pain to clean all that coolant that is "distributed" by your luxury ventilation tubing...just take it ALL out, clean,clean and clean.

New set of Nitto HR Radials 205/60r15 nice surprise after they broke in...New exhaust from Cat back (due to someone hitting it) and new Boge shocks on rear.