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'87 190E 2.3 Manual, '81 500SEL 4whl SLS, '91 300SEL
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1,757 Posts
Discussion Starter #1
Hi all.

The '91 300SEL I've been driving around is starting to have some interesting issues.

I did an oil change yesterday, filling the car up with Valvoline 5W-30 instead of the usual Castrol 10W-30. Yesterday and today, after starting the car up cold, a tapping noise comes and goes for about 10 minutes until the car warms up. I say comes and goes because it will get quiet, and then slowly get louder until it comes up to the original volume. It will usually remain there for a few seconds, then it will get quiet again. Acceleration does not diminish the sound/problem. Any ideas?

Also, I noticed while listening to the car that when I press the gas pedal, I hear a quick "click" when pressing the gas pedal down, and another click when letting off. It does not appear to make this noise when the car is off.

Any help would be appreciated.
 

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1985 500 SEC EURO AMG/LORINSER; 1988 560SEL, 1995 S500 Sonderschutz
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3,679 Posts
Who is Edgar Allen Poe and the Telltale Heart?
 

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Registered
1985 500 SEC EURO AMG/LORINSER; 1988 560SEL, 1995 S500 Sonderschutz
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3,679 Posts
Well, I was going to suggest at first it is your auxiliary air pump which circulates your exhaust fumes for a few minutes after startup until your engine heats up, but it's more of a hissing than a tapping.

I have a rapping I fear is from chain slap on the driver's side, but I don't think it's that bad and probably is just the cams clacking.

The clicking could be a relay, your injectors, or just a clicky pedal. Spray some lube on it.

Clunks in the rear would be your rear sway bars.

Clunking on acceleration could also be motor mounts, do you have a rough idle?
 

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'87 190E 2.3 Manual, '81 500SEL 4whl SLS, '91 300SEL
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1,757 Posts
Discussion Starter #5
I know the air pump is alright, and the tapping is definitely a tapping. Directly in-line with RPMs, and all that jazz. My best guess right now is that I should be using 10W-30, not 5W-30, and maybe I should switch back to Castrol GTX.

In regards to the throttle, it is definitely a "click" on/off, but I assumed it to be too loud to be a relay. Should I just try spraying down the throttle linkage (along the firewall)?
 

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1966 200 Diesel; 1985 500 SEL (wrecked); 1991 420 SEL; 1979 280E (Home Market); 1993 190E 2.6
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584 Posts
Lifters. Perhaps....
 

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1989 560SEC
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2,056 Posts
Possibly switching to 5W-30 from 10W-30? Try going to 10W-40 and see if it gets quieter. I use Valvoline High Mileage 10W-40 and my motor seems run quieter.

Mike
 

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Registered
'87 190E 2.3 Manual, '81 500SEL 4whl SLS, '91 300SEL
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1,757 Posts
Discussion Starter #8
Yeah, I was thinking it was because of the switch. My dad thinks it's just the lifter going bad (which it could be) I don't plan on switching to 10W-40 because it runs just fine at operating temp.
 

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1990 Mercedes 560SEL
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578 Posts
My car too makes this tapping noise for the first few minutes after cold start in the morning. I thought it was the timing chain.
 
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