Progession of vacuum problems from a faulty repair / c280 - PeachParts Mercedes-Benz Forum

brookspw · #1 05-24-2006, 12:51 PM

I have a 94 c280. It would not start intermittently. They diagnosed a faulty crank sensor and replaced it.

Immediately, I knew something was wrong. 1 -- the transmission shifts were VERY harsh. Ok, I figure, they left off some sort of vacuum line. 2 -- shortly after (couple of days) the internal vacuum control flaps that control the air flow to side and center vents stop working. 3 -- Then, I start losing coolant. I see no drips and it isn't going in the oil (gasket). It has NEVER lost a drop of oil or coolant before this. 4 -- the starting problem is STILL occurring. 5 -- I seemed to note a larger than usual discharge from the A/C condensation drain pipe on some occasions.

Where is the coolant going and could it be related somehow to the vacuum issue? Car is going back in tomorrow for their diagnosis.

duxthe1 · #2 05-24-2006, 09:50 PM

The trans shift and climate issues are probably do to a vacuum line(s) off at the lower part of the intake at the back of the engine near the crank sensor There are coolant connections at the rear of the engine, too, but they don't give trouble often. Grab a flashlight and pop your hood open. Leaning over the driver's side fender find your heater hose and follow it down to the engine. Check the hose for leaks and inspect the area under the fitting for leaks too. If everything there looks dry peek down beside the dip-stick to see if the block is wet down there behind the water pump. Water pump leaks are real common on the M104

brookspw · #3 05-25-2006, 11:29 AM

Quote:

Originally Posted by duxthe1

The trans shift and climate issues are probably do to a vacuum line(s) off at the lower part of the intake at the back of the engine near the crank sensor There are coolant connections at the rear of the engine, too, but they don't give trouble often. Grab a flashlight and pop your hood open. Leaning over the driver's side fender find your heater hose and follow it down to the engine. Check the hose for leaks and inspect the area under the fitting for leaks too. If everything there looks dry peek down beside the dip-stick to see if the block is wet down there behind the water pump. Water pump leaks are real common on the M104

Thank you very much. Any other thoughts out there?

How about my starting issue? If not the crank sensor, then what? Or could the new one be acting up, too?

duxthe1 · #4 05-25-2006, 08:43 PM

Starting issue could be a leaking fuel pressure regulator. Pull the vac hose off it and check for the presence of gas. A faulty overload relay can cause a no start on that model too. I'd start with those two before trying to diagnose the more complex possibilities