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1989 Mercedes 560SEC
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244 Posts
Discussion Starter #1
I have a 1991 560 sec with 107,000 miles on.
Started my car this morning and there is a knocking sound coming from the front of the engine maybe around the radiator fan, the noise seems to stop when in park and goes away after the drive to work. I am hoping it's not the timing chain as I had that done at 100,000 miles.
The only way a feel that I can describe the sound I recall from that of an old w123 diesel. Has anyone experience these symptoms?
 

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W126, R107, W210 AMG, W221
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342 Posts
Hi, I think my freshly acquired 500 has the same. Sounds like a diesel, esp.when warm. It's hydraulic tappets from what I learned. You need to check them..I'm going to open the engine next week, bought new seals today to be ready.
 

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SuperModerator
1986/1990 W126
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14,120 Posts
Quite possibly a sticky lifter as above. You can try using oil flush next time you change the oil. There is a hydraulic lifter additive available which can help too.
 

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'91 300SEL, '91 560SEC
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18 Posts
I have the same problem with my '91 560SEC.When starting the car, it sounds like a loud clanky clank coming from the front of the engine eventually goes away when driving.

I diagnosed the problem and discovered it was the radiator fan hitting the fan shroud. You might want to move the fan shroud a little to see if the clanking stops. From what I've read, this problem arises from bad motor mounts. As the mounts deteriorate, the fan lowers and hits the sides of the shroud.
 

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W126, R107, W210 AMG, W221
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342 Posts
I have the same problem with my '91 560SEC.When starting the car, it sounds like a loud clanky clank coming from the front of the engine eventually goes away when driving.

I diagnosed the problem and discovered it was the radiator fan hitting the fan shroud. You might want to move the fan shroud a little to see if the clanking stops. From what I've read, this problem arises from bad motor mounts. As the mounts deteriorate, the fan lowers and hits the sides of the shroud.
This is something else..however motor mounts should be changed every 50.000Kms if you do a lot of city driving.
 

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Mercedes-Benz 560SEL mod 91,MB 560SEL mod 90
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500 Posts
There are tow things that may cause this sound. If the sound is too loud like tuck...tuck, I think this is due to the rocker arm. If the sound like tick...tick, I may accuse the hydraulic lifer.

Here what I faced , my problem on my 91 was ticking noise on one side of the engine, I opened valve cover, removed all the hydraulic lifters, inspected them and found two of them were partially stocked : they were not moving the whole travel, they were not expanding as they should be by the spring force on them which makes a gap between them and the rocker arm " cleaned them using cleaning agent, put back and they were fine. No more tick tick .... sound.

Here is an example of a bad rocker arm.
Goodluck
 

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Registered
W126, R107, W210 AMG, W221
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342 Posts
There are tow things that may cause this sound. If the sound is too loud like tuck...tuck, I think this is due to the rocker arm. If the sound like tick...tick, I may accuse the hydraulic lifer.

Here what I faced , my problem on my 91 was ticking noise on one side of the engine, I opened valve cover, removed all the hydraulic lifters, inspected them and found two of them were partially stocked : they were not moving the whole travel, they were not expanding as they should be by the spring force on them which makes a gap between them and the rocker arm " cleaned them using cleaning agent, put back and they were fine. No more tick tick .... sound.

Here is an example of a bad rocker arm.
Goodluck
Thanks for the explanation. What mileage had yours when it happened? How hard is the job and what you need to have prepared new except cover seals?
 

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1989 Mercedes 560SEC
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244 Posts
Discussion Starter #8
super quick fix, it was the radiator fan hitting the radiator. he just lowered the radiator. nice...
The motor mounts were done a month back maybe something was misaligned after this.
 

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Mercedes-Benz 560SEL mod 91,MB 560SEL mod 90
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500 Posts
Thanks for the explanation. What mileage had yours when it happened? How hard is the job and what you need to have prepared new except cover seals?
My car has run about 157000km when I first got this problem. I usually keep some good parts as a spare. Before I start the job, I kept in mind that I need some of the valve lifter and/or valve rocker arms on had plus the valve cover gaskets. The job depends on pre-estimation of the job overview and how fast you can do it. It takes about two to three hrs.

Parts and tools needed:
1. 10mm socket wrench to open valve cover.
2. 24mm socket wrench to remove the valve lifter.
3. valve spring compressor.
4. two new cover gaskets
5. some valve lifters, valve rocker arms and 8 pieces of brass o-rings for valve cover bolts.
 

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Registered
W126, R107, W210 AMG, W221
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342 Posts
My car has run about 157000km when I first got this problem. I usually keep some good parts as a spare. Before I start the job, I kept in mind that I need some of the valve lifter and/or valve rocker arms on had plus the valve cover gaskets. The job depends on pre-estimation of the job overview and how fast you can do it. It takes about two to three hrs.

Parts and tools needed:
1. 10mm socket wrench to open valve cover.
2. 24mm socket wrench to remove the valve lifter.
3. valve spring compressor.
4. two new cover gaskets
5. some valve lifters, valve rocker arms and 8 pieces of brass o-rings for valve cover bolts.
Excellent, thanks, I saved your reply for future reference. I got somewhat inspired here but I think mine with 216,000Km won't be as bad.. have a look!
Classic Benz: W126: Top Overhaul.. That Solved The White Fume Issue!
 
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