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Saturday, July 22, 2023

Mercedes S600 Loss of boost fixed!

A little humor:

What is the male equivalent of: "Fuck it, I'm just going to become a stripper"?

Joining the military.
 As ex-military, it's OK for me to tell this joke ;)

 Onwards.  Oil Change.

The S600 finally got to visit a non-chain store oil service place - a shop that specializes in European cars.   Oil (9.5 quarts, full synthetic) and filter were replaced at a cost of just over $150.  No other work was needed or done.  I asked the guy about the Tire Pressure Monitoring System (TPMS) alarm.   He shrugged and informed me that somehow Mercedes has managed to set their cars up to NOT recognize third-party "universal" TPMS sending units.  He said you either buy the Mercedes sender, or get used to having an alarm light on all the time : /

Rim replacement.

After the oil change, I took the car to a tire shop - to *finally* replace the cracked left front rim.

It looks really pretty, and best of all, no leakage.  I may have to polish the others now...

 The MAP sensor.

After returning home from those chores, I set about checking the Manifold Absolute Pressure sensor, mentioned previously.  In the linked post, I suspected that the pressure sensor was malfunctioning and causing the Engine Control Unit to cut the turbocharger boost to zero.  The loss of power would usually make itself felt after the engine had warmed up and I had mashed the accelerator pedal once or twice - afterwards, the car acceleration was always very sluggish - no boost at all.

I pulled off the MAP sensor and found that the sensing line had a large crack in the rubber.

I suspect that when the turbochargers pressurized the intake, much of the air that was supposed to go to the MAP sensor leaked out of this crack .  As the car warmed up, the rubber would soften and allow even more air to escape.  Probably the ECU never saw the expected boost pressure, and immediately dialed the throttle and/or turbo boost back to prevent engine damage.

This was by far the least expensive repair I've dealt with on this car.  $2.50 for a foot of 3/8" fuel line, which I cut down to three inches and installed.

I took it for a spin afterwards, allowed it to warm up, an stomped the gas pedal over and over.  Each time the car launched like a rocket - so it looks like that was the problem, which has now been solved.  I put the spare MAP sensor in the glovebox, in the event it is needed in the future. 

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