Motor Problem - a new "squeal"

[jcd]

Car is a 1977 300D, 170,000 Miles. Great condition, well maintained, runs great.

I have started to hear a high pitched squeal coming from the engine compartment. It is very high pitched and has the nauseating sound of metal on metal.

It only appears at certain RPM ranges, (no tach). Generally I will hear it at 65 MPH with the engine under a full or at least a little load, i.e. if I lift of the accelerator it stops. Step on the accelerator it starts again.

Last nite, I checked it in the garage. Again, it only appears during certain RPM ranges. It is most audible at or below the firewall when I stick my head behind the air cleaner and as close to the exhaust manifold as I can get.

Help is greatly appreciated.

JCD

[william rogers]

Is your car a non turbo charged model ?

William Rogers.....

[SW]

Assuming its got the original engine, a '77 it should be normally aspirated.

[jcd]

Non-Turbocharged.

The best way to describe the sound, is a high pitched metal to metal sounding squeak or squeal, only at certain RPM ranges. When the range is hit, ex at 55-60 MPH the squeak/squeal is constant unless I feather the accelerator or increase the speed.

Again, no loss in performance, leaks, or any other issues.

My friend said to turn the radio up.

Thanks for your help

[MarkM]

As I understand, this squeal happens when you are driving the car, and when still in the garage, and is most noticable in exhaust manifold area. Also no turbo. Most likely is alternator bearing...the alternator is in the very location you describe, and its rpm is directly linked to engine speed.

Alternators fail in various ways...electrical, mechanical, gradual, quickly, etc. Mine went a year ago and it sounded like a tin can was stuck inside the engine, was due to immediate failure of rear bearing.

Get a piece of hard wood (broom handle, dowel, cut to 2-3 feet long) and use it as a stethoscope.... place it firmly against bone in your temple...use other end to touch various locations in engine compartment. You should be able to isolate the exact noise source.

good luck.

[jcd]

Thanks for the reply Mark,

Don't thinks it's the alternator. It is less than a year old, plus the sound is more to the back of the engine rather than the front. It is just below the exhaust manifold, at or just past the plane of the firewall.

I'll try the broom handle, if my wife promises not to come into the garage with the video/digital camera.

JCD

[MarkM]

Your'e not supposed to hide in the garage when you do the broom handle thing.....you should be out in your driveway for all of your neighbors to see!! They all figure that you must have a screw loose anyway.....wanting to own a dirty old noisy smelly diesel foreign car!!!!

Noise can bounce around in funny ways inside the engine compartment...the broom handle should tell you what it is.

Good luck.


mark

85 300D

jcd
any luck with the diagnosis? I have very similar symptoms with my 83 300d, my tech thinks the turbo is on the way out, but you don't have one! I have already replaced the fan clutch, it was a little wobbly. I think I'll try driving without the alternator belt and see if the noise is still there. I cannot reproduce my noise in the driveway.
btw, my ride is still for sale in the classifieds section of this board albeit at a lower price if I cannot determine the source of this noise.
Doug

[jcd]

Wolfed,

No I have not figured it out yet. It is not because of the potential shame associated with the broomhandle listening device. It is due to time.

I'll have my head under the hood this weekend and let you know.

Worn/Loose belts chirping under load??

Not sure about jcd, but all of my belts were replaced recently with the water pump and fan clutch. Squeal there both before and after. I just bought an automotive stethescope, I can reproduce the sound in the driveway, so hopefully I can isolate it now. Will advise.....

Doug

[jcd]

I did not forget the thread that "I" started. I've spent the weekend trying to fix the heater.

I have not tried the broom yet, but I do not think it is the alternator or the belts as all of the belts and the alternator are less than a year old.

Doug, how much is the stethescope??? I REALLY don;t want to use the broom. Plus, my head it too hard to pick up subtleties.

JCD

I got a cheapie for $10 at autozone. Hope to check it out here in a bit.

Doug

[jcd]

Discovered my problem.

Transmission fluid was just a little low. I think I'll take the broomstick and beat myself in the head, especially if it resulted in an issue with the transmission, that thankfully has not surfaced as of yet.

Interesting note, The fluid level was checked and OK a couple of weeks before the squeal surfaced. I religiously check for "puddles" and leaks and park in the same spot every day. No sign of any leaks. Any idea how fluid level drops in a relatively short period of time, with no visible sign of leaking.

Sheepishly,

JCD

[william rogers]

I dought very much if the noise is comeing from the transmission,put your car on a rack and check for a leak.I think the low level of fluid is unrelated......
William Rogers......