350SDL (OM603) Turbo Operation Test - PeachParts Mercedes-Benz Forum

vitop · #1 12-29-2009, 10:19 PM

Is there a good way to test the turbo unit on these cars? I have read the posts about trying to move the shaft, but I am looking for a more comprehensive test. Is there a way to check the turbo pressure and the wastegate operation to see if everything is working well?

Hit Man X · #2 12-30-2009, 03:18 AM

Well, what symptoms are you experiencing that would lead you to suspect you have a failed turbocharger?

vitop · #3 12-30-2009, 07:36 AM

Well, I'm not sure it has a problem, but my other car seems to have more pep and if I listen, I can hear the sound of the turbo. This car is not as sharp on the acceleration (but not bad enough to indicate no turbo), and I can not hear any turbo sound at all. Also, there was quite a bit of buildup of soot in the intake (could definitely be normal from the EGR though).

I'm just trying to determine if the operation is proper, if I have too much oil moving through it, etc. I just can't find a real test procedure. Seems like there must be some way of checking pressures, blow by, etc.

Eric · #4 12-30-2009, 09:49 AM

get a boost gauge and find out!

LUVMBDiesels · #5 12-30-2009, 01:49 PM

Tee in a boost gauge where the line from the ALDA connects to the intake manifold...

Hit Man X · #6 12-30-2009, 04:46 PM

Quote:

Originally Posted by vitop

Well, I'm not sure it has a problem, but my other car seems to have more pep and if I listen, I can hear the sound of the turbo. This car is not as sharp on the acceleration (but not bad enough to indicate no turbo), and I can not hear any turbo sound at all. Also, there was quite a bit of buildup of soot in the intake (could definitely be normal from the EGR though).

I'm just trying to determine if the operation is proper, if I have too much oil moving through it, etc. I just can't find a real test procedure. Seems like there must be some way of checking pressures, blow by, etc.

603 cars in the W126 have an emission air meter under the air intake that silences the intake track quite a bit... combine that with a KKK turbocharger some cars have and they are nearly silent.

What is your other vehicle that is turbocharged? I own many so comparing one to another is difficult unless they are the same make/model

If the vehicle feels sluggish, the the boost lines to the IP get plugged up often on these vehicles.

vitop · #7 12-30-2009, 06:57 PM

It's exactly the same car (one is a 1991 SD and the other a 1991 SDL). I didn't think there were any lines that ran between the IP and the turbo unit. Is is a vacuum line of some sort?

As far as the suggestions on the meter -- what type meter and what is the process? Is there a process to test the wastegate also?

Quote:

Originally Posted by Hit Man X

603 cars in the W126 have an emission air meter under the air intake that silences the intake track quite a bit... combine that with a KKK turbocharger some cars have and they are nearly silent.

What is your other vehicle that is turbocharged? I own many so comparing one to another is difficult unless they are the same make/model

If the vehicle feels sluggish, the the boost lines to the IP get plugged up often on these vehicles.

Hit Man X · #8 12-30-2009, 08:44 PM

Quote:

Originally Posted by vitop

It's exactly the same car (one is a 1991 SD and the other a 1991 SDL). I didn't think there were any lines that ran between the IP and the turbo unit. Is is a vacuum line of some sort?

As far as the suggestions on the meter -- what type meter and what is the process? Is there a process to test the wastegate also?

Same turbocharger? MB used KKK and Garrett in this time frame. KKKs are just not loud at all where I can hear the T3 Garrett easily.

Just some goofy flapper door AFM like BMW used on the M30 based inline six motors and other similar motors from BMW, Porsche, etc. You can remove it and bypass with a 617 air intake tube, I did many moons ago. It does not add power by removing it, but it is one less failure point to deal with down the road.

Turbocharger failure is simply not common, if the shaft has little to no play, the turbocharger is going to be fine which is why everyone suggests it as a quick, simple test... it would take maybe 5-10 minutes with a long phillips head screw driver. Wastegates do become tired with age as the spring wears (just like the coil springs under the car) so you need to scoop up a boost gauge and see what is going on. Figure $20-40 for one. I believe factory spec is 11-13psi.

Since you state your other vehicle is quicker, you may not be getting fuel enrichment. There is a tube from the intake manifold to the top of the IP that limits fuel delivery until boost is up... this keeps smoke levels low. It also likes to become full of, well, crap over time and will not give proper signal to the IP. A simple remove, clean, and reinstall typically fixes this issue. Also the overboost solenoid on the firewall likes to plug up making the vehicle nice and slow.

I do not know if the 3.5L 603 motor has a cat under the car, the 3L did in '87. Those can and do plug up.