1985 300D strange screeching when under load
 

1985 300D 300K miles runs great no problems, reasonable pickup for a W123 diesel, nice and smooth...EXCEPT...

There's a strange screeching sound when engine is under load (heavy acceleration, going up a hill on the highway, etc.). It usually goes away on its own, if I change my speed a bit, or if I ask for more or less performance:
https://photos.app.goo.gl/xw6Rc5Do7QEZGs4V6 (4 sec vid)

I removed all the belts and drove it around the block and still got the noise so that eliminates the fan, fan clutch, water pump, and all the accessories.

I am able to get the noise when in park but that's difficult to do, it lasts for only a second, and it seems to happen only when the engine is warmed up:
https://photos.app.goo.gl/qyWoLKzksL2dQeEM8 (3 sec vid)

so that eliminates the driveshaft and friends.

So what's left? Could it be the turbo? Something internal? Is it serious? Can any issue with the timing chain cause this? I'm baffled.

John

Not low on oil are you?

Or transmission fluid?

I'm not low on oil. I'll check transmission fluid today. The car would still make the noise in park if transmission fluid was the issue? The transmission feels good.

Yes.

trans fluid looks good and clean and is just barely at the top of the line with engine running, warmed up and in park after I went through drive and reverse each for 30 sec so I think the fluid isn't the issue.

I'm suspecting the turbo. It's so hard to tell but I sense the sound may be coming from that area. There was a fair amount of oil at the turbo intake but I don't feel play in the impeller and it spins freely. I tried a 8x slow motion video of the turbo when I revved up the engine. I could hear the screech but somehow that sound didn't clearly come through in the video and to my untrained eye everything looks fine?
https://photos.app.goo.gl/sXzcyfCvo7np1MW5A


Here's a photo of the turbo blades. I see a small nick but otherwise look OK?
https://photos.app.goo.gl/uyLe1mn99hUv2ACe7

Hey, I actually took the time to watch your first vids. Sorry. Should have done that. From your description I thought it was something like a trans pump issue but it doesn’t sound like that at all. If I had to guess it sounds like a boost pressure leak.

It seems well correlated with boost pressure (judging from your tach and speedo). The fact you see less in park may suggest less boost = less noise.

Just a wild guess. It definitely sounds like turbo noise. I’d search for a pressure leak (manifold, Alda, manifold o-ring, intake runner seal, switchover valve etc).

You can verify by hooking up a boost gauge by Teeing off your manifold pressure line at the back of the engine. Drive around and check to see if you are losing boost.

Are you making good power?

Also check your wastegate plumbing and actuator. If possible pull the little access cover off the wastegate valve and take a look in there. I think you are on the right track with the turbo.

If everything checks out with the turbo, you might take a look at the manifolds to make sure they are properly attached. I had a similar screeching sound on my '85 300D about 10 years ago. I just checked the repair order and it states:

"Customer concern: screeching sound at around 2500 RPM under load. Found intake/exhaust manifolds loose on cylinder head and missing hardware. Replaced missing nuts and washers and tightened all fasteners. Sound is gone."

I remember speaking with my mechanic and he told me it wasn't the first time he had seen the issue. The car had 274,332 miles on it at the time (2013).

I've had loose exhaust manifold fasteners similar sound on the E300. Sounded like belt squeel

Hi John,


It sounds like the group honed in on what's driving your noise. I listened to the videos too. I support their conclusions, but share your frustration. I had similar experiences drive me nuts too.


One was a '77 Cadillac, squeak/squawk only at highway speeds, would come and go, after much investigation in the dash, it turned out to be a loose wiper stop squeaking against the glass. Another was today - I was out shaking down my '84 Wanderlodge FC (front diesel CAT 3208), and had a very similar sound to yours periodically, got me thinking a cat (animal) had climbed in there and would periodically vocalize. I'm driving and wondering what is causing this. It dawned on me that I had side-loaded the accelerator pedal and the rod to the linkage was rubbing the floor pan. Best of luck solving yours!

I also agree that it sounds like a boost leak. Since you can replicate the noise while underhood, I would suggest spraying soapy water on all of the charge pipes/fittings and look for bubbles when the noise appears, may help you narrow it down a bit.

One thing that I did find a little odd, and possibly could be a contributor is the oil spray on your EGR valve. You may want to pull that off and inspect it for clogging, operation and the sealing on the exhaust side, it might be a slight high pressure exhaust leak there where it's mounted, so close to the turbo. Didn't see smoke, but the wet oil seems odd given how dry the surrounding area seems to be in the vid

Thanks for all these comments.

@87tdwagon: I was wondering about all that oil spray too. I changed the valve cover gasket recently when I adjusted the valves and I cleaned the valve cover then. It was also covered with oil spray, especially around the oil cap, so the current photo might be misleading as to where that oil spray is coming from. But if that spray is coming from some area near the EGR valve...why would we see oil there at all unless a seal in the turbo was bad?

Regarding the soapy water, I'm nervous some of that might find its way into the intake and that would be catastrophic? Am I worrying about nothing?

@ykobayashi I haven't noticed a change in the car's performance, and from my limited knowledge it seems OK for a W123 diesel. The alda and friends were long ago disabled so the intake manifold pressure line is plugged up. I attached a gauge to it and saw some boost while revving in park but I haven't driven around the block yet to see what kind of boost I'm really getting under load. The last time I did this it was around 9psi.

The 8x slow video I shared doesn't show the impeller hitting the housing so I assume even in the worst case the turbo is rebuildable? With possibly more than 300K on the turbo do I just need to rebuild it regardless? I've read you can have a runaway engine if the oil seals on the turbo get too bad. I'm worried about getting that turbo out if I need to do that --- seems that can be a bit of a bear.

This weekend I had to give my work with "The Red Baron" a bit of a rest. My wife was wondering where I disappeared and besides the car and I were getting frustrated with each other. I hope to take a 2nd (or rather 99th) look during the next few days after work before I leave town for the rest of the week. This used to be my daily driver and my goal is to return it to be that again.

Thank you everybody. I appreciate the help and encouragement. I'll get to the bottom of this.

The oil spray could be from blowby, maybe at the valve cover PCV line (rubber elbow). Since you cleaned up the surrounding area, why not clean it all up and that way you can monitor afterwards.

Regarding the soapy spray, use that on everything after the turbo inlet, while under boost the system is pressurized, so nothing to suck in. Would also be helpful for exhaust leaks as well as intake manifold leaks under pressure.

If it still concerns you, the old mechanics stethoscope works well or use a long screwdriver, metal rod cupped to your ear, and probe various components when your hear the squeal, this will help pinpoint the source of the noise quite readily, just stay away from moving parts ;)

It was a turbo boost leak. You guys are my heroes! :)

I found the egr valve very loose. The intake manifold gasket bolts were also borderline so I snugged them up. The wastegate hose was cracked so I replaced it with fuel hose (is that the appropriate hose to use? That looks like what was on there.) Now the sound is gone!

I drove around with a gauge in the car showing the manifold pressure. My gauge only goes up to 10psi and when I floor the car the gauge just barely gets pinned. That sounds reasonably acceptable to me?

I have a little housekeeping to do now. I like the idea of cleaning the area as general good practice, but basically I'm home free now.

Thank you all for helping me out.

John

:)

I think my boost would go to 12 psi on a long climb. It takes awhile to get up there.

Glad to hear you got things sorted. This forum still delivers the goods. Love this place.