Hi all,

So - to clarify, my car is running normally, decent fuel economy (about 21-22 mpg in 90% city driving). I have noticed (over a period of months) that I can hear a bit of a 'whistle' noise under certain driving conditions. I'm almost entirely convinced I'm hearing the turbo (this is the first turbocharged car I have ever owned) so my apologies if this is a silly question.

Mostly I hear this noise (coming from the engine bay) if I am loading the engine (like going up a hill) and the rpm's are climbing up to about 2300 or 2400. I only notice it under acceleration, as well. Would the turbo be a good guess? Should I be able to hear the turbo? It's faint - if I have the climate control on, it's harder to hear it, and if I have the stereo going too, it's faint enough that I doubt I'd hear the noise period.

Is it abnormal to be able to hear the turbo, if this is infact what I am hearing? Maybe I have some loose ductwork leading into the turbo? Last time I looked around (maybe a few weeks ago) nothing seemed out of place.

Thanks for any advice, and for setting me straight if I am wondering about nothing at all

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1984 300D Turbo, 326000 Km, Thistle Green Metallic

No, its not normal to hear it. You are on the right track, check the seals in the u-tube and the air filter to make sure everything is seating and nothing is torn.

Good to know. I'll have a look at the intake system leading up to the turbo, and will see what I find. I'll see what the FSM says too, once I am home from work.

Hopefully I haven't been doing too much damage by driving around in this state! It seems like this shouldn't be too tough to deal with though (crosses fingers)

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1984 300D Turbo, 326000 Km, Thistle Green Metallic

Hypothetically speaking, I wonder if this noise could be caused by a cracked connection hose from the turbo's boost pressure control valve back into the turbo. Looking at this hose, the fitting where the hose connects back into the turbo, the hose looks old and cracked around the hose clamp. I can't say if it is or is not cracked enough to leak under bypass conditions, but maybe... ?

For reference my car has a KKK turbo. I'll go take some pictures later on after dinner!

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1984 300D Turbo, 326000 Km, Thistle Green Metallic

More info:

I just pulled apart the intake and visually inspected it. What I found was this: the u-boot was poorly seated at both the aircleaner and the turbo intake. At the turbo I could plainly see about 5-6mm of the turbo flange (right name? the part onto with the u-boot mates) showing nice and shiny bright metal, and the part where the aircleaner mounts was off by a similar amount.

The seals themselves inside the uboot, well, the turbo one is intact but obviously old and brittle due to heat - it has no flex in it at all.

While I was in there I made a discovery - the boot compensator hose seems to follow an interesting path from the boot compensator - i would assume it would take the gentlest curve possible. That is, under the u-boot and up to the mounting point on the front of the turbo.

My hose goes /over/ the u-boot (like, it passes right between the two arms of the "u") and then into the turbo. This means instead of one long graceful curve in the hose, it makes two tighter curves. This seems to be putting a lot of strain on the hose where it mounts up to the turbo and there is in fact a decent sized crack there.

I'll post some pics in just a few minutes of all this.

Naturally I put it all back together and while I do not yet have new u-boot seals, it seems to be mounted a lot more securely than previously. I'll be listening for noise tomorrow and am going to renew the seals.

Also - the air cleaner guts are squeaky clean - no oil on the filter element at all. Obviously some is coming out of the oil separator as I can see it in the u-boot, but it doesn't appear to be a lot. I think the total volume in there is 1 tbsp or less.

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1984 300D Turbo, 326000 Km, Thistle Green Metallic

Here are some helpful photos I took showing the bypass hose on the turbo and how it is cracked and also the area where the u-boot mounts to the turbo's intake.

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1984 300D Turbo, 326000 Km, Thistle Green Metallic

Yes, definitely time for a new wastegate hose ASAP. Should be 3/8".

I bought my car in 2006. I've been able to hear the turbo since I bought it. New U-tube seals, new air filters, always hear the whistle. I was told it was normal, but it's not extremely loud. Garrett turbo, just whistles while it works.

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RRGrassi


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

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

99 W210 E300 Turbo Diesel, chipped, DPF/Converter Delete. Still needs EGR Delete, 232K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Gone and still missed...1982 w123 300D, 1991 w124 300D

Yep - for all I know, that's the original hose on there! Is the mounting I describe for it correct? Upon further inspection that seems like the only real way to route the hose, but it seems like it puts some strain on it at the terminus (as we can see in my photo).

It was surprising just how far off the u-boot was for being snugly mounted. I'm sure it'll be much better with new seals in it.

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1984 300D Turbo, 326000 Km, Thistle Green Metallic

Huh! and actually after checking the FSM and looking at my own photos, I too seem to have a Garrett turbocharger, not the KKK like I thought I had.

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1984 300D Turbo, 326000 Km, Thistle Green Metallic

Ok, so a further update on things now that I've reseated the intake boot. The whistling noise still exists, although it is fainter than before. I have to strain to hear it even under ideal circumstances.

I'm going to call up the stealership today and order new seals (and wastegate hose) and we'll see how things change (if at all) after I install those.

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1984 300D Turbo, 326000 Km, Thistle Green Metallic

DO NOT drive it hard until you get that wastegate hose replaced. You can damage the engine and turbo with that hose being broken.

don't use any ole hose.. you need the proper style. IIRC you can get them from fastlane

Whew! Good to know. I haven't been driving it hard at all lately, just gently putting through traffic. Rare is the day I take it past 2500 rpm.

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1984 300D Turbo, 326000 Km, Thistle Green Metallic

Do a search for "air recirculation valve" or ARV...

I had a whistle at a very specific rpm range... turned out to be the ARV; yet another gadget that was added to meet EPA requirements. IIRC, no German version of the car had an ARV.

Search for it and you'll find out how to disable it.