I am getting a real gut-wrenching whining sound coming from under the hood of my '86 300SDL. It seems to be when to turbo gets to full boost. What's the possibility that that sound is the overboost releasing pressure?

I am going to try and rig up the boost gauge from my '85 tomorrow and see what it says.

I rebuilt the turbo about 6 weeks ago (the sound started yesterday), but never messed with the wastegate, because it couldn't really be opened. The car has been breaking piece by piece since I bought it, so I wouldn't be surprised if it was exactly that.

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My Primary Driver - '85 300CD - 4-speed conversion, 2.47 rear, lowered, euro headlights, rebuilding (not restoring so much)

Wife's - '08 Saab Sportcombi Aero

Riding a '03 Yamaha Warrior

Loose manifold or a bad gasket perchance? I got a pretty bad squeal from my 300sd when the nuts that hold the manifolds on got loose.

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"spreading a trail of obnoxious where ever we go"
1981 300sd w/ 341,500 miles

http://www.wecrash.com/pics/ddda_banner.gif

I second something less than an airtight seal between the turbo and the intake manifold.

"I rebuilt the turbo" makes me nervous. The rotating assembly has to be precisely balanced because it spins something like 30-50K rpm at full tilt. If you moved the turbine wheel relative to the compressor wheel, it's possible the imbalance is causing one of the wheels, likely the compressor wheel, to scrape the compressor housing. Pull the crossover pipe and make sure there aren't aluminum shards getting to the engine. Pull the turbo air inlet hose and check that the turbine blades aren't shinier or sharper than you left them.

Sixto
87 300D

Two problems.

1, You are about 100,000rpm off.
2, The compressor wheel and turbine/shaft are balanced independently, you can put them on at any position without causing imbalance. If they needed to be put on at a specific orientation there would be a key on the shaft to align them.

The nature of balancing any component and then assembling that component to another component results in unbalance. While these components may be balanced independently, it's a far better result to balance them as a unit.

I'm quite sure that any rebuilder would do exactly that.

BTW, there is no such term as "Imbalance".

imbalance |imˈbaləns|
noun
lack of proportion or relation between corresponding things : tension is generated by the imbalance of power | the condition is caused by a hormonal imbalance.

http://www.thefreedictionary.com/imbalance

Most turbine and compressor wheels are not match balanced, they are balanced independently.

The "free dictionary" is hardly the source to quote for an engineering term. The proper term is unbalance.

Turbine and compressor wheels are properly balanced as an assembly. The result is significantly better than the alternative.

You can do what you wish with your own vehicle.

Incorrect on both counts.

1- Imbalance is a proper term and a common word. It's not just the "free" dictionary, open up ANY dictionary and look at it. The quoted definition is from Apple's own included dictionary application.
2- The T3 and K2x used on the OM6xx engines are NOT balanced together. This is evidenced by the fact the nut securing the compressor wheel on the shaft is unmodified.

You can tell how the balancing was done by the shape/appearance of the COMPRESSOR nut. If the nut appears to be ground down then the turbine wheel and shaft and the compressor wheel (and nut) were balanced together. If the nut is not ground down then the wheels were done individually. If the wheels were done individually then it is not absolutely necessary to mark them and get them in the same location as they were prior to removal. In the case of the "ground down nut" turbo, it is a good idea to keep the wheels lined up in their original positions.

http://www.gnttype.org/techarea/turbo/turborebuild.html

I'm not going to argue with you about it. "Imbalance" is a technically incorrect term and it's not proper in the industry. It's used by people who don't have an understanding of balancing. Use it at your own risk.

Whether they are balanced independently is not relevant. The result that one will achieve with independently balanced components is not all that good. The use of a balancing arbor introduces certain errors that are unavoidable and the process is fundamentally harmed due to the use of that arbor.

The assembly will run with significantly reduced vibration if the two are balanced as an assembly.

Look all around and you will see "Imbalance" (lack of proportion or relation between corresponding things) in many places. Unbalance (upset or disturb the equilibrium of) is a less common word. Fact is, they mean the EXACT same thing. The same way "flammable" and "inflammable" are both adjectives meaning "easily set on fire."
Thats all well and good when they are balanced as an assembly. The fact still remains that the T25, T3, K26 and K24 turbos used on the OM6xx engines are not balanced as an assembly, they are all balanced independently so making a big effort to keep everything lined up is a waste of time.

Left is an example of one that IS balanced as an assembly, a 2003 Ford Powerjoke GT37V. Notice the notch cut into the nut.

Right is a T25 from a member's 602, notice the whole nut.

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Do you know what I do for a living..........for the past 28 years? If so, you might defer to my knowledge of the industry rather than cite what you find on various google sites and take as fact.

You make the conclusion that the nut is the only place that one can correct the unbalance of the assembly. This is not true. The wheels also have limited correction capabilities via certain balancing lands which they possess.

While some turbo components may be balanced individually at the factory, the assembly balancing technique is the generally accepted practice if one desires a unit with low vibration.

I would not make the conclusion that the wheels are balanced independently simply because the nut remains unground.

OK, well I did a little searching for anything out of the ordinary today. I took the crossover tube off, It didn't have any metal in it, but did have a pretty good bit of oil. I took off all of the air filter system up to the turbo...nothing blocking, and the air filter is immaculate. The teeth of the turbo are in good shape, the turbine spins well, but does move up and down a little. There was oil in every section of the intake after the air sensor. I did rebuild the turbo about 2 months ago...a friend at work was saying the center of the housing was probably too far gone before I ever rebuilt it.

Anyways, I made a new gasket for the crossover tube, tightened it, as well as the intake manifold. Like damn near everything else on this car, the bolts weren't tightened enough, each needed about 1/8 of a turn. I didn't see oil anywhere around the gasket of the intake (however I know there was some in it). I did see some oil around the first o-ring above the turbo compressor, but I am worried about a larger problem with the turbo now. Any thoughts?

PS. I don't really know the how it should be said, but if our current President has taught us anything, it's that we can make up words as we see fit. That given, it all works fine for me, as long as we all know what we are talking about.

When I talked to the guy at 'The Turbo Shop' locally where I got my parts, he did say that the parts of the compressor were balanced separately, so it didn't matter how I put them together. Again, I don't know these things...so that's why I am asking, that's just what the guys said.

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My Primary Driver - '85 300CD - 4-speed conversion, 2.47 rear, lowered, euro headlights, rebuilding (not restoring so much)

Wife's - '08 Saab Sportcombi Aero

Riding a '03 Yamaha Warrior

Oh yeah, I also rigged up the boost gauge today. I am running right at 14 PSI max, and the whining sound comes at about 8-10 PSI, and just gets louder as the boost goes up.

__________________
My Primary Driver - '85 300CD - 4-speed conversion, 2.47 rear, lowered, euro headlights, rebuilding (not restoring so much)

Wife's - '08 Saab Sportcombi Aero

Riding a '03 Yamaha Warrior

anything?

__________________
My Primary Driver - '85 300CD - 4-speed conversion, 2.47 rear, lowered, euro headlights, rebuilding (not restoring so much)

Wife's - '08 Saab Sportcombi Aero

Riding a '03 Yamaha Warrior

Check the exhaust manifold for cracks, the manifold gasket and turbo gasket for black streaks that would show exhaust leaking.