Hello,

On a recent trip, near the end of the first day of driving, the turbo on my '85 300TD started squealing/whistling at about 2,500 rpm, at about 6 pounds boost, and suffering power loss under heavy load up hills. Luckily, when grabbing tools and parts for the long trip, I grabbed a tool box that happened to have a boost gauge with a threaded fitting that attached directly to the intake manifold. The hose was long enough to bring into the car through the passenger window. When the engine had cooled after stopping for the night, I determined there was no play I could detect in the impeller shaft, and it turned smoothly and easily.

Driving the next day with the boost gauge it was apparent I have plenty of boost (and noise) and the wastegate is not dumping any of it. When the gauge hits the peg at 15 psi, the overboost protection cuts fuel, I guess, and boost drops to about 6 pounds. I can back off the accelerator and rebuild boost. Other than the noise, the car runs fine if I don't push it beyond 12 psi or so, especially up hills.

I am suspecting either a stuck valve or that the diaphragm has torn or some how lost its seal. I will investigate this weekend, but before I get in there, I was hoping for some suggestions of a sealant to use if it is a torn diaphragm and there is a way to repair it until I can obtain a functional one. It would be nice to have what I need before I open the wastegate actuator.

If the valve is stuck, has anyone had success freeing one?

Thanks in advance.

300TD, 370,000 miles, daily driver, hoping to install the jamesdean refreshed cruise control amp before my next 2,000 mile trip!

Do you have the Garret or the KKK turbo? If you have the Garret, there is a rubber hose that runs up to the wastegate diaphragm. It commonly cracks, splits, or fails. Try replacing it first with a piece of vacuum hose and see if that takes care of the problem.

If you have a failed diaphragm, you need a new one.

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]

I had a stuck waste gate on a Garret once. I disconnected the actuator, sprayed the wastegate shaft with Kroil, and worked it with pliers until it was free. If the problem is with the actuator, just replace it. There's no practical way to open the crimps and replace the diaphragm.

Yeah, I forgot to mention it's a Garret. I inspected the hose and it's clear and I did not see any cracking, but I think I will put a piece of new fuel hose on there to see if it clears up the problem.

I did just watch a video showing how to take the cover off the assembly, not hard or crimped, and then the diaphragm just unscrews from the threaded valve shaft. I will try to find a good used assembly, but it may take a while. That's why I was wondering about a temporary fix for the rubber diaphragm if it is ripped.

If my valve is stuck, I'll give the kroil a try, and maybe polish up the valve shaft some

Thanks for your replies.

______________________
1985 300TD

Got into it today. I first replaced the hose from below the ARV to the wastegate actuator. The squeal/whine was still present starting at 6 lbs boost.

The rubber diaphragm is in fine shape, but the valve was pretty much stuck closed. I hit it with Areokroil and worked it in and out starting at about 1/8 inch at a time until I could move it about an inch in and out and I could turn it a little. Then tapped it all the way through and out with a brass drift. It was coated with carbon from blow by oil. I cleaned it off with a scotch bright pad, and ran a strip of scotch bright through the hole the valve shaft goes through. When all was cleaned up, the valve moved freely.
I put the diaphragm back on with the same number of exposed threads it had before I took it off.

The wastegate is now operating as it should. Boost goes up to 9 pounds, and stays there steady with the pedal to the floor even while shifting until I back off the accelerator. I'll adjust it up to around 12.

However, the noise is still there, starting at 6 lbs boost. I am thinking that some seal or valve let loose downstream from the compressor when the wastegate valve stuck and the overboost protection cut in. ( The noise and overboost protection - loss of boost and power under a load - started at the same time.) My ARV has been disconnected from vacuum for about a year, but I've read that the ARV valve can make a lot of noise. I'll open that up to look at it tomorrow and maybe shim the valve closed.

I am wondering though, if anyone has experienced whistling under boost if the o-rings on the connector tube between the turbo and intake manifold are bad. I don't think I replaced the o-rings with new when I had the turbo off remove the trap oxidizer. Not so smart.

I am having trouble thinking of anything else that would have started making noise at the same time. The banjo bolt and line to the alda though the overboost valve are clean and clear. the overboost protection is certainly working.

Any suggestions are appreciated.

Thanks

____________________________
1985 300TD

The sealing rings on the U-tube between the air box and the turbo inlet may need replacing, or the clamps on the U-tube may be loose.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

My nephew just called me up about his 85 300D which has the same whistling problem at 2400 rpm or so.


Your comments are valuable but I need to know how to tell a Garrett from a KKK?


Is the waste gate actuator diaphragm (if the problem) a dealer-only item?


Anyone know?

__________________
Strelnik
Invest in America: Buy a Congressman!

1950 170SD
1951 Citroen 11BN
1953 Citroen 11BNF limo
1953 220a project
1959 180D
1960 190D
1960 Borgward Isabella TS 2dr
1983 240D daily driver
1983 380SL
1990 350SDL daily driver alt
3 x Citroen DS21M, down from 5
3 x Citroen 2CV, down from 6

The Garrett turbo has a horizontal external wastegate and has Garrett or AiResearch cast into the aluminum compressor housing .

The KKK turbo has a vertical external wastegate with heat sink type fins, and has 3 K's in an equilateral triangle cast into the iron turbine housing.

Turbo Information Thread (Needs your contributions!)

I imagine the wastegate diaphragm would only be availabe as NOS from the original turbo maufacturer or its successor.
(Honeywell Garrett for the Garrett turbo and BorgWarner for the KKK turbo)

The whistling is most probably due to hardened, loose, or dislodged seals in the U-tube from the air filter housing to the turbo intake.
They lose their flexibility after a few years of being baked by the heat in the engine bay.
When the turbo spools up, if the seals have failed, outside sir gets sucked in past the seals and the air leak becomes audible as a whistling sound.

__________________
78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

I've read that often the u-tube seals are the culprit, but my 85TD had the trap oxidizer so I do not have the u-tube and its seals. I cleaned and tightened the clamps on the air intake hose, and even put small hose clamps on the connections from the valve cover to the turbo and air cleaner. That plus new O-rings on the short tube between the turbo compressor and intake manifold and making sure the arv valve stays closed did not cure the problem. Boost adjusted up to 11 lbs, and it is running great.

The noise seems to have quieted down some, not due to anything I did I don't think, and doesn't start up as soon, and not unless I've got my foot pretty well into it at about 3,000 rpm or up.

Double checked for play in turbine/compressor shaft again and did not find any.

I'm thinking now, it might be a thrust bearing in the turbo itself. It will probably be a while before I get to it, as I'm in the middle of a bathroom redo and reflooring in my home. I can easily drive the car, even at 70 on the freeway, keeping the turbo under the point where it starts making noise. I also want to have a second turbo on hand with it successfully unbolted before I risk snapping bolts on mine.

I'll report if that stops the noise.

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85 300TD 371,000 mi daily driver

Oops..it failed to register that you have an 85 with the fender mounted airbox and the ARV on the turbo.
No engine mounted air box and no U-tube in this setup.
So sorry about the mis-information originally posted.

You've eliminated the ARV and turbo connector seals as culprits for the whistling that has now lessened.
The whistling started when you had overboost conditions.

The sound that now remains at higher rpms (3k) is likely from an slight imbalance in the turbine.
The crankcase vapors if excessive may(???) cause a slight imbalance.
A damage impeller vane may also be present.

Try disconnecting the crankcase vapor return line from the rubber air intake tube from the air box to the turbo inlet.
Let it vent to astmosphere for the test run.
Plug the port on the rubber air intake tube with a rubber plug (or wine bottle cork).
See if the whistle disappears.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022