It's nice having the local MB dealer tech be a 500E owner. He readily shares tips, especially since he know's I'm an enthusiast of the 500E.

I've been having intermittant "CHECK ENGINE" lights come on, and using the blinking-light counting method, it has always been either LH DM number 4 (Air Injection System) or number 5 (EGR).

Since the M119 engine gets SO HOT, it literally cooks/bakes everything. The rubber tube between the hard-vaccuum line and the EGR was cracked, replaced with Mercedes rubber which withstands the heat and has the correct diameters for the vaccuum lines. No more number 5 for over 5-months.

However, number 4 (Air Injection) was still coming on intermittantly, and although I could hear the clutch bearings go bad, I asked the dealer tech, and he said there is another rubber vaccuum line that goes bad on the air-pump's (aka, smog pump) diverter valve or comes loose if you had weak motor mounts.

Sure enough, I found this rubber connector off and deteriorated. I've replaced the rubber connector, cleared the codes, and hopefully it will stay off.

FWIW, he said the next things to check are (1) Oxygen sensor, (2) air-pump passages in the head (has to be taken off to clean out), and finally (3) the air-pump itself.

:-) neil
1988 360TE AMG
1993 500E