W124 E220 Loud ticking - worse when hot

Dickie14

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I have an 1995 E220 with the M111 engine, and it has developed a pronounced ticking/tapping noise. It started last autumn and I assumed it was one of the tappets - it is directly linked to engine rpm and seems to be coming from the top of the engine, near the back. I had the headgasket done over Christmas and the tappets were all replaced but the noise remained. It is barely audible when the engine is cold but once hot it is loud enough for people to ask ‘what’s wrong with your car?’...

As it’s now sunny enough to drive around with the windows open I’m constantly aware of it and keen to fix it, but the local Merc specialist suggest it may be a long and expensive process to find out what’s causing it. I’m reasonably competent with mechanical stuff - Is there anything I could be looking at first? A friend has suggested that as it gets worse when hot I just fill the engine with thicker oil!

Advice welcome
Cheers,
Dickie
 
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grober

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Could be a valve. Could be a little end - where the con rod fits on the piston gudgeon pin. As your specialist said- difficult to determine without an engine strip down- which takes it into swapping for a good second hand motor territory costs . One thing about using a thicker oil is to use it as a diagnostic- if its an excessive clearance/wear/bearing phenomenon then it may well quieten things down. At least then you have a better idea what territory you are in?

ps weird fault territory here- a cracked or leaking exhaust manifold but this would be an unusual sound if it was?
 
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Dickie14

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Thanks for the swift replies gents.

With regard to the valves, what would cause them to make a tapping noise? And I did wonder if it was exhaust related but the sound doesn't seem to be coming from it or the heat shields (I've got one of those mechanics stethoscope things).

Bruce - I've read through your thread (what a shocking run of bad luck you've had - fingers crossed things go up from here!). Are you suggesting that the tapping noise I have may be a knackered big end, delicately warning me that my engine will destroy itself any day now?
 

brucemillar

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Dickie

I hope I am not the bringer of doom.

Tapping/knocking sounds are so difficult to pin down. In my car it sounded top end front and ended up bottom end rear.

Anything that increases with engine speed when stationary warrants a really good look.

I have no words of comfort. Sorry. Get it up in the air and use a mechanics stethoscope on it. This may point you at the knock.

Good luck.

Sent from my iPhone using MBClub UK
 

Bellow

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With regard to the valves, what would cause them to make a tapping noise?

Failed/stuck hydraulic tappet the most likely followed by cam wear.
Valve train noise presents at half engine speed, bottom end (piston/rod/crank) at full engine speed.
 

hotrodder

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...ps weird fault territory here- a cracked or leaking exhaust manifold but this would be an unusual sound if it was?
^^ This but as said tracking down weird noises (especially over the internet) can be frustrating. Cracked exhaust manifolds (or manifold leaks from a broken stud etc) can result in a ticking noise that appears or gets a chunk louder as the engine warms up and is follows engine rpm

I had the exact same symptoms on my old s123 with the m102 engine, cause was a broken manifold bolt in my case but without getting in there with a stethoscope/for a good butchers sounded not disimilar to a horrendous top end rattle. Dunno how common cracked exhaust manifolds on the M111 engine are but they definately aren't unheard of
 

grober

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See this thread http://www.mbclub.co.uk/forums/engine/159449-tips-cracked-manifold-removal-124-2-2-m111.html
THIS MIGHT INDICATE WHERE THEY CRACK - the one in the picture has been crudely welded.
 

Bellow

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Removing the oil filler cap should let you know if the source of the noise is internal or external.
 
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Dickie14

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Counting the ticks seems to line up nicely with 1/4 engine rpm so looks like that rules out valves etc.

But opening the oil cap whilst running didn't seem to present the noise from within the engine at all (just a low humming sound, I assume the noise a valvetrain makes whilst straddling hundreds of explosions a minute?).

At the weekend I'm going to have a more thorough look at the exhaust side of things.

Thanks for the suggestions, very much appreciated

Cheers
Dickie
 

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