This car!! Driving along stepped on it heard a clunk like I hit something in the road. The battery light came on got home the car will not shut off, shut it off with the shut off lever under the hood. Thought the belt broke but just replaced it last fall. Everything looks fine cannot understand what the big clunk was.

Hmmm.. interesting. I'm not really familiar with your model Mercedes. Best i could do is recommend to you an excellent Mercedes shop in Rock Hill SC.

I posted already, but cannot find it so I will try here. Hope I am in the right place.
My 87 mercedes made a huge clunk like I hit something under the car but there was nothing in the road. Then the battery light came on, when I tried to turn the car off it kept running. Opened the hood and shut it off, fan belt fine so as usual stumped. Someone have any ideas I really appreciate any help. thanks

is this the first time you've experienced the not shutting off issue? now that its warmed up a bit this afternoon is it still not shuttin off? are you experiencing other vacuum related problems?

You said nothing about brakes so it appears there is sufficient vacuum. Transmission shifting, ACC vent selection and rear headrest dropping also use engine vacuum. If the transmission shifts as before, you can get cabin air from vents other than the windshield defroster and the headrests drop back, the vacuum system is fine and you have a problem isolated to the 'brown' line circuit.

If power steering works and engine coolant temp are okay, the belt must be okay too. I'd pull the belt and make sure all the pulleys spin smoothly and quietly. You might have lost something in the alternator and the pulley's just along for the ride.

I'd pull the vacuum pump as well particularly if it's the old style - no screws on the front cover - to check that the bearings are in good shape and there's no scoring on the roller coaster track cam that drives the pump.

I'm curious to see how this turns out because I can't see how the issues are related.

Sixto
87 300D

the "huge clunk" has me worried... I'll bet you lost your vacuum pump... brakes can remain working for several presses without vacuum... but I'd NOT START the car before removing the pump and investigating!

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Everything works power steering,shifting, head rest has not been working for some time(6mo) If the clunk was the vacuum pump (there definitely was a huge clunk) where is this vacuum pump and could it partially die. if it was not for the clunk I would think it was the alternator.
What is the brown line circuit?
carmen

The vacuum pump is on the front of the engine opposite the injection pump. It looks like this -



6 bolts that take a 10mm wrench hold the pump to the engine, and of course the vacuum supply lines up top. Mind you don't touch the bolts that take a 13mm head interspersed with the vacuum pump bolts. Those bolts hold the injection pump and there are blind nuts that are a PITA to get back in place.

There can be leaks in the headrest circuit. Holding down the switch for 5-10 seconds with the engine running might knock down the headrests. I don't know if it works with the engine off.

The brown line circuit is the brown vacuum lines for engine shutoff. A brown line tees off the brake booster vacuum line check valve near the glow relay, heads to the key switch, then continues to the shutoff actuator on the injection pump as a brown line with red stripe.

Sixto
87 300D

Started car this am alternator light went out but car still does not shut off. the vacuum system seems ok in that the heater fan works fine, shifts, door locks ok, even the headrest went down after Sixto's help. But when I turned off the key the alternator light came on and the car will not shutoff. Hate to replace a working vacuum pump, could it be the alternator? The alternator light is not on when car is running with the key in the on position.

Hurray! Found a worn vacuum (hole)in line that goes to the exhaust manifold. Car stops fine thanks everyone for you help,
carmen

to correct forum for answer.

Are all the belts intact? Check voltage at the battery to see if alternator is functioning. Use a mity vac to test vacuum level in the vacuum system. Report back.

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Dont know what the clunk is, but maybe you sprung a vacuum leak. Do your door locks still work? Have a look under the hood. There is a yellow valve that has two vacuum tubes going into from the firewall. Are they connected? Or.. you can disconnect it completely and put a golf tee in it to see if the engine turns off?

There's another related thread by the OP. IIRC Carmen reported a vacuum hose came loose and the clunk was the resulting hard shifting. I haven't seen anything further about the battery light which can't be related.

Sixto
87 300D

Are your belts loose? Check the alternator belt. Once I was driving and heard a load 'clunk' with a resulting battery light. Turns out one of the long bolts that fasten the alternator to the bracket had worked its way out. The clunk was probably that big bolt hitting the radiator fan or whatever else it hit on its way to the road. The alternator slumped down,(none of the bolts were tight enough) with the slack belt not turning the alternator enough-which caused a light. For whatever reason I've always had a problem with these bolts, even though I have good motor mounts...