Just bought a 84 300d. The man a bought it off of said that he was driving down the highway and the car started to overheat and knock.The car will start and run. But it does knock. The car has 199000 miles on it. I was thinking it might be the timing chain jumped time. Has anyone else ever had the problem.thanks

give us a little more detailed description of the knock. is it even always sounding the same? random? ticking noies? deep clunk, you know that type of thing.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Sorry to tell you this, but it sounds like the car might have some major issues. Such as a scorched bearings, or a burnt/melted piston.

How does the car idle? Does it vibrate excessively? Run rough?

Does the car still overheat?

I have (should you need it) a good running diesel engine listed on eBay here:
http://cgi.ebay.com/ebaymotors/Mercedes-used-parts-W126-300SD-Diesel-Engine-more_W0QQcmdZViewItemQQcategoryZ33615QQitemZ7981225198QQtcZphoto

Drain the oil and check for little bits of metal, that's a sure sign of catastrophic engine failure.

www.benzbonz.biz

marty

It is a constant knock.The engine moves back and forth when it is running,I would not think the engine would run if the piston was bad.

I forgot to add it is a deep clunk..

deep clunk? sounds like you got bottom end problems, like rod bearings.

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'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)

How hard is it to pull the oil pan off the the engine.So I can look at the bottom end?

Put the car in gear, hold it with the brakes and give it some throttle for a couple of seconds. Does the knock become more pronounced?

Loosen the injector lines one at a time. Loose enough that fuel leaks out of the fitting. Can you isolate the knock to a cylinder?

Sixto
95 S420
87 300SDL

I will not get back to work on the car until the weekend. I will try reving the engine to see what happens.If you open a fuel line going to the injuctor and the noise goes away.Then it is a piston problem. But what does it mean if the noise does not go away?

Maybe get a stethoscope or something to pinpoint where the noise is originating from as well as loosening the hardlines. Don't want to jump to conclusions but the PO's description of what happened to him doesn't sound like a precursor to injector knock. Hope that's all it is but be prepared for the worst.

__________________
'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)

lots of things. if there is a hole in the piston you should get all kinds of blowby out the oil filler when running. bottom end problems are very rare on these diesels... so bad bearings are about out unless run low on oil. deep knocking is prob mains, higher pitched knocking is rod bearings, knocking under acceleration is mains i think. ticking on decel is wrist pins, i think.

do above tests to see if you can isolate the prob to one cyl and check back.

i am not sure about chain slipping timing on a diesel. on a gas motor your symptoms sound about right for that.

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

My 300SD with 351K miles on it, must have done some injector knocking. I was sitting at a traffic light waiting for the Green, when I started hearing a knocking sound. It sounded like bearings, whether it be mains or rod???

I panicked, my baby can't do this to me yet!!!

Well, I figured I'll be parting her out soon because of this strange unwanted sound emminating from the engine compartment. Seemed like from the bottom area of the engine.

I drove the car anyways. After about 2-3 miles, the sound stopped just as quickly as it started.

Question, is it even remotely possible for bearing knock to go away? I did add a quart of oil because it was a quart low on oil, and ummmmm, I can't remember when the oil was changed last, it's got some blowby and I just keep adding oil as needed, so I figure all the oil isn't that old.

So I figure a piece of french fry might have gotten lodged in one injector and the car needed a hind lick manuever.

Well I took the pan off and my knock was #2 rod bearing.I am in the process of getting the parts car engine started to put in this car. Was also thinking about rebuilding this engine over the winter.But did not know how much I would sink in the motor on a rebuild.So I thought it would be less expensive to replace the engine.I would not think a bearing knock would go away.thanks