I recently purchased a 1984 300D Turbo and it's been a blast getting to know it. I've been reading through a lot of posts here and really been learning a lot.

So... on to the question. I have noticed that when i get up to around-town cruising speed (25-35mph), and ease off the accelerator pedal, I hear a high-pitched squealing sound. When I step on the accelerator again, it goes away, but if I ease up on the accelerator, i.e. going from accelerating to steady speed, the sound comes back. It also seems to go away when the car is decelerating.

What would be causing this?

__________________
1984 300D Turbo 163k.

Could be a number of things....

..... like a loose belt slipping...or if the ac is on it could be the ac compressor clutch....

__________________
the sooner you start... the sooner you'll get done If it ain't broke, don't fix it.. Its always simpler to tell the truth...
2007 Honda Accord EX
2007 Honda Accord SE V6
96 C220
97 Explorer - Found Another Home
2000 Honda Accord V6 - Found Another Home
85 300D - Found Another Home
84 300D - Found Another Home
80 300TD - Found Another Home
Previous cars:
96 Caravan
87 Camry
84 Cressida
82 Vanagon
80 Fiesta
78 Nova
Ford Cortina
Opel Kadet
68 Kombi
Contessa

After listening more carefully, it seems to be related to the automatic transmission..? When I ease off the accelerator, does that mean that it is shifting into Neutral? Is there a flywheel that spins up and could be squealey?

__________________
1984 300D Turbo 163k.

I've got the ACC set to "econ" mode, so I don't think it's the A/C compressor. I've noticed that I hear it the most when going uphill. Especially around 3rd gear. As I'm heading up a hill and I can feel that the car is about to shift up into 3rd at about 33mph, it will start to squeal until it shifts.

On level road or downhill, I don't notice it.

__________________
1984 300D Turbo 163k.

I'll go with a loose belt somewhere.

__________________
83 SD

84 CD

Check alternator and P/S belts as well.

There is no flywheel that spins up. There is a flywheel on the engine that is bolted to the crankshaft and the T/C on the tranny. The flywheel spins when the engine is running.

How are the engine mounts? I wonder if something is rubbing when the engine is under load.

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Turn off the ac and see if you still have the noise, If its still present. get some "No squeal, anti-slip" belt treatment and spray it on one belt at a time and take it for a drive. if the sound doesnt change at all then its not a belt.

__________________
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac?

As long as they would add one additional commandment for you to keep thy religion to thyself.
George Carlin (Wonder where he is now..)

1981 240d (engine donor 1983 240d) recently rebuilt engine hurray! - No more.. fought a tree and the tree won.

pearl black 1983 240d 4speed (Converted!@$$%) atleast the tranny was rebuilt.

I listened closely again today while on a road trip. Perhaps "rings" is a better description of the sound than "squeals". bah, it's somewhere in between. I always hear it when going uphill and easing off the accelerator. A brief "ring/squeal" that lasts for about 2-3 seconds and then goes away. I also hear it just before the transmission shifts into 3rd and again into 4th.

__________________
1984 300D Turbo 163k.

My mechanic diagnosed the noise as coming from the Air Recirculation Valve, which is a component of the Turbo system. He said not to worry about it.

__________________
1984 300D Turbo 163k.

I had the same noise coming from me ARV. Drop a BB into the vacuum line going to the ARV, like I did. The noise will be gone. That's what I did.

__________________
'85 300D 190K miles
running on B100 Biodiesel since 156K, SCRATCH THAT! I can only find Biodiesel at 1 location in Houston! (not very convenient)

I have this same problem, it sounds like the turbo is still spinning while letting off the throttle at slow speeds.
My mechanic friend that helps me said do not worry about it.
Sorry but while I am driving my fine 1980 300SD I do not wont people looking at me because my car is making noise.
Any body have an idea wait might be my problem or my cars problem.

should I try this from the last post Drop a BB into the vacuum line going to the ARV, like I did. The noise will be gone.

__________________
1976 240D
1976 240D parts car
1970 220D daily driver