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1981 380SL
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397 Posts
Discussion Starter #1
Back in April, I did the chain job. Replaced the chain, tensioner, upper guides along with things like cam oiler plastic bits and some gaskets, etc. cam gears looked to be in great shape, and not original (it’s still a single row).

hearing some slap (maybe) when I’m starting up the car on cold mornings. it’s my daily, and has been for two years, so it’s a little concerning.. maybe a junk tensioner? I feel relief knowing the chain and guides are new, but it’s still not a nice sound to be hearing every morning!
 

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1988 560SL
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70 Posts
I don't want to suggest what's normal, because I am still learning, but for clarification, do you hear the slap every cold start, or just after the car has been sitting for a few days? I replaced my guides, tensioner and oilers (the chain was still in spec for stretch) back in the summer, but if I let the car sit for 5-6 days I do hear a little slap for 3-5 sec on cold start. I used a febi tensioner, and have come to understand that may not hold the oil as well as the genuine MB, so I'm assuming my symptom is due to tensioner letting it's oil out while sitting for a few days. I also daily drive my car, so it's pretty rare that it sits long enough for me to hear the few sec of slap, so I'm considering that OK (knowing that I have new/non-brittle guides). I'd probably be concerned if I heard the slap every day on cold start.
 

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Premium Member
1986 560SL with M120 V12 Engine, 1988 560SL Stock
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9,867 Posts
Did you replace the lower tension rail. If not that is your problem.
 

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'79 450SL, '04 CLK200 convertible; former A124, W210, A209.
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1,389 Posts
Based on others' experience the issue you're describing is quite common with Febi or Swag chain tensioners. I tried a Febi tensioner but gave it up after 2 mins as the chain started slapping.
 

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'80 450SLC Afro RHD Ikonengold
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2,884 Posts
Can it be that the hydraulic tappet compensators are naking the noise?
My original MB tensioner goes soft after a while but i never heard chain slap. Chain was stretched too...
 

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1984 380SL
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2,301 Posts
I ran a Febi tensioner and I had occasional slap. One thing I did which helped was to run a heavy-weight oil, which I could do because I'm in a warm climate. Castrol 20W50 helped maintain tension. When I mentioned it to a lifetime Mercedes mech, he said if your guides are good, you're fine. Are your guides good?
 

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Registered
1981 380SL
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397 Posts
Discussion Starter #7
The upper guides and tensioner guide rail was replaced, if that’s what you’re asking, Ron. Lower guides were not.. I hear that’s an engine out job.

I did use the febi tensioner that came with the “kit”, so maybe that’s my issue.

I’m not sure what a hydraulic tappet compensator is, but I would say that the sound I’m hearing is more like a clicking for about .5 sec when I first start the engine.

The MB tensioner is quite expensive.. I would like to keep running the febi and maybe use a heavier oil? Maybe I’ll try 20w50 per your experience, WM.
 

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1984 380SL
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2,301 Posts
The lowers can be replaced motor-in, we did. You have to remove a lot of stuff (including the oil pan) but the front plate will come off. There's no gasket so just 'paint' one on when replacing.
 

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Premium Member
1986 560SL with M120 V12 Engine, 1988 560SL Stock
Joined
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9,867 Posts
The upper guides and tensioner guide rail was replaced, if that’s what you’re asking, Ron. Lower guides were not.. I hear that’s an engine out job.

I did use the febi tensioner that came with the “kit”, so maybe that’s my issue.

I’m not sure what a hydraulic tappet compensator is, but I would say that the sound I’m hearing is more like a clicking for about .5 sec when I first start the engine.

The MB tensioner is quite expensive.. I would like to keep running the febi and maybe use a heavier oil? Maybe I’ll try 20w50 per your experience, WM.
Yes the tension guide rail. There is one other below on the other side which does require engine removal but it very rarely causes a problem. Do you happen to know if the heads were milled on this car. Also try putting the old tensioner in if you still have it. Its not too difficult.
 

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1988 560SL
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70 Posts
So the suggestion to reinstall the old tensioner raises a question that I've had since replacing mine. Is there a way to test if a tensioner is still good? I replaced my tensioner about 6 months prior to doing the upper guides after hearing some chain slap at startup. In retrospect, I believe that slap occurred after the car had been sitting for about 6 weeks because I was not driving while recovering from back surgery (which is also why I decided to just replace the tensioner at that time to buy a little more healing time before doing the major chain/guide job). Anyway, I still have the old tensioner, which was 20 years old, but only had 55k miles on it (per PO service records). With the Febi tensioner, 15W-50 oil, and daily driving car for most part, I rarely hear the chain on startup (only after car has been sitting a week or so), so I'm not overly concerned now that the guides are new, but if the 20 year old MB tensioner is actually still better than the new Febi, it's certainly a pretty easy thing to change out. Just wondering if there's a way to test the tensioner to know?
 

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Premium Member
1986 560SL with M120 V12 Engine, 1988 560SL Stock
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9,867 Posts
Its normal for a tension er to bleed down after a few days but the chain shouldn't slap if you replaced the tension rail. That's the part that wears out and causes the chain to have enough play to slap the block. The other thing is when people resurface the heads the chain ends up gaining slack. Did you replace sprockets. My original tensioner is now 32 years old and has 165K miles on it. I don't believe in replacing tensioners with every timing chain I do unless its rapping every morning when driven daily.
 
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