For some reason the turbo on my 350SDL is putting out 14 psi. I did verify that the wastegate is not stuck (compressed air in the line going to the actuator). Watching with a boost gauge the control seems really good, only when grossly exceeding the speed limit at WOT in 4th could I get it to 14.5. The book says 13.7 is the max allowable boost... and I wouldn't want to run this much without an intercooler.

That much boost is just enough to trip the protection circuit. I looked at the actuator and it doesn't look like there is an adjustment on it, it looks like only the length of the rod is adjustable. If I make the rod longer that won't help will it? Would that make the wastegate leak all the time? I can snap a picture of the actuator if it would be helpful.

-Jason

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

That seems really close to me...I don't think I would call it a problem.

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Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles

Well I have to drive with the protection circuit disabled otherwise it cuts in and out at WOT...

I believe these have the EDS controlled vacuum wastegate like the 90-93 300D's. Full vacuum = fully closed wastegate, more boost. Lack of vacuum = wastegate open, low boost. A pressure sensor connected to the manifold is what tells the computer when to open the wastegate.

If something was bad, the computer would freak out and cut all boost. The wastegate could be getting stuck, but then I would imagine your boost would be getting higher than 14PSI on WOT runs.

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Dale

http://i52.photobucket.com/albums/g1...MG_2277sig.jpg

1990 300D 2.5 Turbo -155k
2000 E430 - 103k
2014 Jeep Grand Cherokee Ecodiesel 4x4 - 11k
2014 VW Passat TDI SE - 7k Bro's Diesel
2006 E320 CDI - 128k Pop's Benz

Pre-glow - A moment of silence in honor of Rudolph Diesel

I don't think mine is run by the computer. There is a short rubber hose connecting the wastegate to the clean air side of the turbo.

Maybe you have a boost/vacuum leak somewhere? I would check all the vacuum lines that see positive pressure...make sure they aren't cracked or leaking. I'm using knowledge I have from gasoline turbo cars...so I don't know how much of it applies to this diesel...

I'm thinking that you could have a leak in the vac line that goes from the wastegate actuator, to the intake manifold, which would not allow the wategate to open fully, resulting in higher boost pressures...maybe the vac line is clogged?

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Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles

If all else is in order, you can adjust the wastegate actuator rod length.

__________________

Gone to the dark side

- Jeff

Yeah, take a turn out of the rod (make it longer). It will slightly reduce the tension on the spring and cause the W-G to open slightly earlier.

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-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

That's what I was thinking too. The line doesn't go to the intake, it goes to the compressor outlet on the turbo. It's about 4" long. I replaced it and it didn't make any difference. This illustration is from the VW repair manual, but it shows how the line is routed:



I'll give the rod adjustment a try.

-Jason

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

maybe your actuator is leaking. I would try pressure testing it to see if it holds pressure before adjusting the rod. The rod did not shorten its self, so I don't think it is the problem, but it should fix the symptom.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

Yes, any leaks in the wastegate system will increase boost pressure. If you haven't replaced the hose yet, do so now.

Have you tested the wastegate's internal diaphragm?

__________________
Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles

If you need an actuator there is one on ebay.

http://cgi.ebay.com/ebaymotors/Garrett-Adjustable-Wastegate-Actuator-15psi-Large-body_W0QQcmdZViewItemQQcategoryZ33742QQihZ002QQitemZ120271008403QQrdZ1QQsspagenameZWDVW

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

Ah that one looks exactly like the one fitted to my 350. If I have time I'll get the car and do the rod adjustment later today (It's at a buddy's house... where my TDI had been for quite a while due to a broken part on the trans. Time to drive the ECOdiesel over that way and replace the rear suspension bushings!)

-Jason