Turbo not working? - PeachParts Mercedes-Benz Forum

mangrum · #1 03-24-2009, 09:50 AM

How do I tell if my Turbo is working on my '82 300D? Acceleration is now very slow and it's acting like the turbo is not working. How do I test it?

Thanks,
Mike

GRIESL · #2 03-24-2009, 10:38 AM

The best way is to get a vac/boost guage. They're cheap ($30 or so) and good to have anyway. But if you don't want to do that, do a search on the most common culprits: banjo bolt on the intake, and overboost protection switch. That banjo bolt on the intake tends to get muckety mucked, and the overboost switch located on the firewall sometiems gets stuck. Good luck.

rrgrassi · #3 03-24-2009, 10:42 AM

If the ALDA is not getting boost signal, the car will feel like the turbo is notworking due to the lack of extra fueling by the IP.

Have you cleaned the banjo bolt? Also check the turbo switch overvalve and the hard lines running from the banjo bolt to the switch over valve, then to the ALDA.

DieselBone · #4 03-24-2009, 02:54 PM

If you want to do a VERY basic test, remove the air intake elbow and check to see if you can spin the compressor wheel in the turbo, !CAUTION! make sure the engine is OFF! The compressor wheel should spin very easily, if it is hard to spin, or stuck, you may have other problems, like worn out bearings, or even a mice nest in the turbo (its happened to me)
Good luck!

mangrum · #5 03-26-2009, 09:55 AM

Thanks for the replies. I'll try the simple test and go from there. I'll need to figure out what/where the ALDA and banjo bolt are

I'll report progress.

Thanks again.
Mike

blackestate · #6 03-26-2009, 09:59 AM

the banjo bolt is on the back of the manifold, it is a hollow bolt, this allows pressire to pass to the overboots protection valve, then on to the alda, which adjusts the fuel based on the pressure.
Check that bolt, and hose. They are known to clog frequently. Make sue the connection is also tight.

LUVMBDiesels · #7 03-26-2009, 10:37 AM

Make sure that you do not break metal rings off of the plastic hoses attached to the banjo bolts.

Take the bolts out carefully and pull the hoses out of the switchover valve on the firewall. Spray carb cleaner into the hoses and into the switchover valve. Spray the cleaner into the bolts as well paying attention to the small holes that the rings cover to get the air pressure.

You will be surprised at the black crud that will come out.

The next thing you can do is 'tee' in a pressure gauge into the line going from the switchover valve to the ALDA and run it into the cabin so you can check the pressure as you drive. The turbo will not produce boost in the driveway.

mangrum · #8 03-28-2009, 03:04 PM

Are one of these the banjo bolt?
http://i493.photobucket.com/albums/rr291/mike_mangrum/82MB300D/Picture003.jpg

Is this the switchover valve?
http://i493.photobucket.com/albums/rr291/mike_mangrum/82MB300D/Picture004.jpg

Thanks,
Mike

Quote:

Originally Posted by LUVMBDiesels

Make sure that you do not break metal rings off of the plastic hoses attached to the banjo bolts.

Take the bolts out carefully and pull the hoses out of the switchover valve on the firewall. Spray carb cleaner into the hoses and into the switchover valve. Spray the cleaner into the bolts as well paying attention to the small holes that the rings cover to get the air pressure.

You will be surprised at the black crud that will come out.

The next thing you can do is 'tee' in a pressure gauge into the line going from the switchover valve to the ALDA and run it into the cabin so you can check the pressure as you drive. The turbo will not produce boost in the driveway.