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help! disturbing new noise at higway speeds...a little detailed 700

posted by  dgltrader on  Thu Apr 29 19:59 CST 2004
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last visit: Wed Aug 15 07:25 CST 2007
[RELATED]

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

______

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.








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    help! disturbing new noise at higway speeds...a little detailed 700

    posted by  david hunter on  Fri Apr 30 12:18 CST 2004
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    last visit: Mon Jun 30 22:10 CST 2014
    [RELATED]

    Also check for a bad output shaft bushing at rear of tranny. Easily done by shaking the drive shaft flange checking for any slop. If worn you will get a load noise/vibration/hum at higher speeds, very hard to detect hear where it is coming from. It may come and go or be consistant at certain speeds. It's an easy fix but requires a puller. Any good shop that knows Volvos can do it in less than an hour, a new seal goes in as well at the same time.
    --
    David Hunter








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    help! disturbing new noise at higway speeds...a little detailed 700

    posted by  ronald on  Fri Apr 30 03:26 CST 2004
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    last visit: Wed Oct 10 11:04 CST 2012
    [RELATED]

    Check the FAQ for information on the driveshaft centre support bearing. It can make quite a racket when it is failing, usually high pitched and relative to car speed not engine speed. These do not tend to fail catastrophically I'm told. You will be amazed how quiet your car is after you get it fixed.

    Ron
    87 745, 265000 km
    near Brantford, ON, Can








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      help! disturbing new noise at higway speeds...a little detailed 700

      posted by  someone claiming to be Chrissij on  Sun May 2 07:10 CST 2004 [RELATED]

      I agree; it sounds like driveshaft center support to me. Just to be on the safe side, also check your differential fluid (don't want to be low on that), though a leaking axle bearing definitely does not "throw" it's voice, it stays constant in the rear. A center support bearing can sound like it is coming from anywhere and everywhere at the same time. It makes you slow down, turn sharp, etc...to rule out wheel bearing, turn off your overdrive, slow to second, etc...to rule out transmission. Given your description...center support.

      Also look at the rear of your transmission for looseness at the tailshaft, a floppy center support will take out the extension housing bushing, in fact too much play in the driveshaft can also take out your transmission mount. All that vibration transfers along the drivetrain. In addition, look at your rear shocks, if they are original, and bottoming out, scraping the undercoating on the way back up, they contributed to the demise of the center support bearing. It goes with that old adage, "keeping things in line."








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        help! disturbing new noise at higway speeds...a little detailed 700

        posted by  someone claiming to be Chrissij on  Sun May 2 07:14 CST 2004 [RELATED]

        Ooops...just noticed the new rear shocks and rear end boo boo...definitely look at the trans mount as well! Should "read" instead of "skim", huh?!








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      help! disturbing new noise at higway speeds...a little detailed 700

      posted by  dgltrader on  Fri Apr 30 09:12 CST 2004
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      last visit: Wed Aug 15 07:25 CST 2007
      [RELATED]

      Thanks,

      I read the section...looks loike a bit of PITA but not too bad.
      I will try to get parts today and see if I can get under the car this weekend. Probably something that needs to be done regardless.

      The only thing is the noise really did sound like it was coming from the front of the car...sort of thru the dash, from the driver's side engine compartment...and I cannot hear ANY of the noise from the "outside" with windows and or sunroof open.

      Also, no noise from the trasmission console area.

      I also open to other noise source ideas... I haven't bought parts yet!

      I have been making real efforts to track down and eliminate "old car" noises...so I am really sensative to what and where they come from.
      ____________________________________

      By the way, Here is a noise TIP for everyone (this may be something for FAQ tips)--

      ALL wagon owners should go out and buy a large sheet of DYNAMAT from BestBuy or autosound shop...then cut it in strips- about 4" by 8"- put at least 2 strip on the bottom of the spare wheel well and 2 more on the rounded sides...then place at least 1 strip on the flat sheet metal to each side of the well...and a couple of smaller strips in the storage wells on each side. These areas are essentially large low frequencey "drums" that are adding quite a bit of background sound...especially in a wagon.

      The sheet metal even seems to amplifiy the rear mufler resonaces to some degree. The Dynamat is an audio damping material foil cover / and an asphalt? adhesive and the stuff really works great!

      Use it anywhere you feel that the metal is transmitting excess sound or creating sound through vibration.

      good luck
      Dave






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