vacuum wastegate..........OM 602 - PeachParts Mercedes-Benz Forum

Rob90300d · #1 11-29-2007, 04:36 PM

I'm new on the scene here and already have a tech question.
My 1990 300d has the vacum line plugged off at the turbo. I read that it's a wastegate vacum pod.There was also a small oil leak at this area. I want to make repairs and prevent any problems or possible damdge. Also has a engine tap on cold warm up , goes away when warmed up.
The diesel runs great with 93,800 mi. I bought it with this cond. any advise or knowledge of correct repair is greatly appriciated.
I really enjoy this car and plan on keeping it a long time. This car is well cared for and gets Mobil 5w40 diesel formula oil changes with wix filters.
This is a great forum. Thanks again !

Brian Carlton · #2 11-29-2007, 09:01 PM

Welcome to the forum.

Need some folks familiar with the OM602 and the vacuum wastegate to chime in.

2.5Turbo · #3 11-29-2007, 09:21 PM

Yes, the wastegate is vacuum operated on the 90-93 300D. Without it connected, the wastegate is held open and you'll get no boost and 18 second 0-60. For a test, hook up straight vacuum to the wastegate and see what you're performance is like. Try not to romp on it too hard to avoid overboosting. On the 90 the line from the wastegate actuator goes to a transducer that is mounted under the air cleaner. All this must be in place for the turbo to produce boost. Everything else also must be there and working (EGR, butterfly flap valve, airflow meter, rack sensor, crank sensor, temp sensor, etc) for the computer to not throw a code and cut boost. When I first got my car from my grandparents, it wasn't producing boost and I thought it was just supposed to be that slow for about 8k miles until I did some research and found out it wasn't. That's when I found that the wastegate transducer was bad.

On the oil problem, I'm not sure...could be a bad oil fitting gasket on the turbo.

The ticking is probably either a bad hydraulic lifter or a dripping injector. To test, loosen the nut holding the fuel line to the injector. Do this for each cylinder, one at a time and note if the tick goes away for any of them. If it does, that injector needs service. If none of them stop the ticking, then it's probably a lifter that needs replacement.

Rob90300d · #4 12-10-2007, 04:48 PM

Hey Dale S,Thankyou for relying to my questions.
I followed you're advise on diag. but I didn't find a useable vacum source. I did ck. all connections and transducer. I re-connected the line to the wastegate and road tested.
The 2.5 runs pretty strong for it's size. I believe the turbo must be working.
Where I work we have the sprinters w/ the 2.7 turbo. I'm using it for drivability reference. They run strong and fast.
As for the tap it has started to go away sooner at warmup. I'm crediting the sythetic for that one so far.
Thanks again for the help. Much appriciated! Go diesel!
Robert

gsxr · #5 02-12-2008, 07:41 PM

If you ever want to ditch the computer-controlled wastegate, you can convert to a pressure-type unit. Details are in this thread.

The ticking noise is very likely valve lifters... but if new lifters don't cure it, you likely have debris blocking the oil supply to the lifters, from a failing head gasket (which is common on the OM602). Don't ask how I know this...