Turbo whistle '81 300TD - PeachParts Mercedes-Benz Forum

MaineCedes · #1 01-06-2012, 04:46 PM

Okay, so this is the official start of my asking a lot of questions. Some will be very dumb

I am very green to this MB diesel thing.

My commute to work is 4 miles of easy driving, 15miles of highway, and 4 more miles of easy (~30mph). I look at this as the perfect commute. Warm her up, stretch her out, and warm her down. Anyway,

On the highway, when I (gently) accelerate, I get the turbo whistle. But It is still noticeable at cruising (65+-) speed. In fact I would say it is almost constant. Not always there, but usually (I almost feel like I can make it go away if I ever so slightly ease up on gas, but keep the same speed, if that makes any sense). If a take my foot off the accel. it immediately stops, and it is less intense than the accelerating version. But still there. Is this normal? Harbinger of anything bad?

Zacharias · #2 01-06-2012, 05:02 PM

Quote:

Originally Posted by MaineCedes

Harbinger of anything bad?

Generalized answer: most likely not. Most turbos make some noise on a car of this age. Some more than others. It may be a sign of wear but turbo failures on these cars are much more infrequent than on gas engined cars.

There are two places where you might be getting some turbo whine from, the turbo inlet and the top part of the exhaust.

At the inlet is a C-shaped (or U-shaped, if you prefer) fat air intake hose that runs from the air cleaner assembly downward into the turbo inlet. It has a clamp on each end and should have a sealing ring inside, where it meets the turbo.

First check that this is securely in place. They have been known to pop off at the turbo inlet, which lets noise out. This will be doubly true if there is oil present around the inlet and/or the sealing ring has deteriorated or is missing.

You might also have a small exhaust leak. There is a flexible section (flex-pipe) where the exhaust downpipe bolts up that allows the engine to move about a bit. This can deteriorate and open a small hole. The downpipe 'hard' section itself doesn't last forever either.

If the connections are good and there isn't a hole in the exhaust, I would not worry about it.

If you have not inspected the air filter, now would be a good time to do it as well. If it looks dirty at all, replace it.

MaineCedes · #3 01-06-2012, 06:01 PM

Thanks, I look forward to my first official tinkering session tomorrow.

Diesel911 · #4 01-06-2012, 06:39 PM

A leak at the Intake Manfold can cause a wine also.

With the Engine Cold spray down the manifolds with a mix of Dawn Dish Soap and water (mixed so it forms bubbles that you can blow).

Start the Engine and speed the Engine above 2,500 rpms (so the Turbo starts to give boost pressure. and if there is a leak bubbles will form from the Intake Manifold or Exhaust pressure.

Give some Kids the extra bubble mix and who ever does you Dishes the rest of the Dawn.

rhodes2010 · #5 01-06-2012, 11:54 PM

MaineCedes - these folks are right on. A little looking around will go a long way.

Your air cleaner on the passenger side has a 10mm nut on top.
After you lift the cover three more 10mm nuts hold the lower air cleaner
housing to the intake manifold. Do not worry if any of the three rubber
mounts are broken. Not a problem.

Now - at the front are are the U tube spoken of above that goes from the air outlet to the turbo inlet. Below that is a wastegate hose to protect from over boosting. What you are looking for is a nice snug fit and no broken leaking
anything.

Next lesson - at the back of the manifold is a single nut facing backwards. 10mm or 12mm. This holds in what we call a banjo bolt and that bolt has a tube that runs across the engine bay the back of engine on drivers side.
On the drivers side this tube from your intake manifold goes to a small device
on the firewall next to the brake booster , this is a turbo overboost electronic
switch (that I have removed completely). The tube continues to the top of the injection pump and to something round we call the ALDA.

I added the part above to help you become familiar with your new diesel engine. This small line needs to flow boost and also could be squealing out air.

Later we will talk about ALDA's, overboost and other fun stuff.

For now - marvel at the absence of any throttle body and no mechanism that controls how much air goes in to a diesel engine.
Air goes in , through air filter, and straight to intake.
No control over how much air is going in. Significantly different than
a gasoline engine as all RPM in a gas engine is controlled by how much air
we let in.

MaineCedes · #6 01-07-2012, 11:59 AM

Thanks all. After a morning of staring at her, I am getting more acquainted with some of the pieces parts of the diesel. Still not sure really how it all comes together, but I will learn (like how is there combustion without a spark-assuming I have that right).

Anyway, about the turbo whistle. Everything that you guys asked me to look at looks and 'feels' very secure and tight. I haven't yet done the manifold test - mostly because I use Ivory dish soap and not Dawn (and I do the dishes

).

I also wasn't able to reproduce any noise in the driveway. I brought the engine up to 'speed' but never heard the turbo even kick in (did I read somewhere that the car needs to actually be accelerating?) Perhaps I did not get enough RPM's, but there is no tach, and honestly I was afraid to take it too high thinking I might be making a mistake...

I will keep at it. Maybe see if my wife would take me out on the open highway clinging on to the engine with hood removed. Come to think of it, I'm sure she would agree to that.

Diesel911 · #7 01-07-2012, 12:20 PM

Quote:

Originally Posted by MaineCedes

Thanks all. After a morning of staring at her, I am getting more acquainted with some of the pieces parts of the diesel. Still not sure really how it all comes together, but I will learn (like how is there combustion without a spark-assuming I have that right).

Anyway, about the turbo whistle. Everything that you guys asked me to look at looks and 'feels' very secure and tight. I haven't yet done the manifold test - mostly because I use Ivory dish soap and not Dawn (and I do the dishes

).

I also wasn't able to reproduce any noise in the driveway. I brought the engine up to 'speed' but never heard the turbo even kick in (did I read somewhere that the car needs to actually be accelerating?) Perhaps I did not get enough RPM's, but there is no tach, and honestly I was afraid to take it too high thinking I might be making a mistake...

I will keep at it. Maybe see if my wife would take me out on the open highway clinging on to the engine with hood removed. Come to think of it, I'm sure she would agree to that.

Ivory may work. I always mention Dawn because my Wife is a Pre-school Teacher and that is what they use when the want to make bubble mix for the Kids to Blow bubbles.

Just get a Paper clip and bend it into a loop and see if you can mix the Ivory with water to blow some Bubbles.

MaineCedes · #8 02-11-2012, 04:36 PM

So I can't seem to track down any leaks that might be whistling. And this noise is starting to bug me. Trying not to turn on the radio to drown this sound out...

One more question. Is it possible that this sound is actually the bearing (I'm assuming there is one) in the turbo fan going south? This 'screech' is not there all the time, only when I am either accelerating, or at higher highway speeds (65+). Does the turbo fan run constantly at speed? If I cruise along at around 55-60, I can get it to stop, but if I just tap the accel a hair it is there.
Also, If I remove my foot from the accel, it stops immediately... Any thoughts?

I was wondering if there was some way to test turbo fan bearing? Thanks

JHZR2 · #9 02-11-2012, 10:04 PM

Quote:

Originally Posted by Diesel911

A leak at the Intake Manfold can cause a wine also.

With the Engine Cold spray down the manifolds with a mix of Dawn Dish Soap and water (mixed so it forms bubbles that you can blow).

Start the Engine and speed the Engine above 2,500 rpms (so the Turbo starts to give boost pressure. and if there is a leak bubbles will form from the Intake Manifold or Exhaust pressure.

Give some Kids the extra bubble mix and who ever does you Dishes the rest of the Dawn.

2500 or not, without load, doubt the turbo would give any boost.

May need to power brake the thing.

A whistle is common on w123 cars.

What id check for is boost pressure. Pull a sample off the over post protection going to the alda, on the manifold side. Should optimally see 10.7 psi under hard acceleration, full load.

toomany MBZ · #10 02-11-2012, 04:42 PM

A whistle and a screech are two different sounds, the latter may be an indication of an issue.

Remove the air cleaner assembly, how much play is in the turbo blades? Up, down and side to side.

MaineCedes · #11 02-11-2012, 04:48 PM

There is a very small bit of play up and down/side to side. There is zero play in and out. I probably said screech, because it is starting to get to me a bit. Perhaps I should try and get an audio clipping and post it here. Would that be helpful??

shadetreemechan · #12 02-11-2012, 06:59 PM

Quote:

Originally Posted by MaineCedes

There is a very small bit of play up and down/side to side. There is zero play in and out. I probably said screech, because it is starting to get to me a bit. Perhaps I should try and get an audio clipping and post it here. Would that be helpful??

yes, very.