Engine sounds like a diesel when warm...

[Ulf]

My otherwise lovely 230 SL has a quite a bit of what sounds like valve clatter when it gets warm. When started from cold there is very little noise, but as the engine temperature rises the sound becomes more audible and slightly intrusive. The valve clearance have been set, same with the throttle linkage, there is no smoke and a compression test showed perfect compression on all cylinders.
Any ideas on what might cause this?

Thanks in advance

Ulf

[Naj ✝︎]

In my view, the engines run a lot quieter when the valve clearances are set at 0.003 inch inlet and 0.007 inch exhaust rather than the metric gaps (0.1 and 0.2 I think) recommended.

naj

[waqas]

In my view, the engines run a lot quieter when the valve clearances are set at 0.003 inch inlet and 0.007 inch exhaust rather than the metric gaps (0.1 and 0.2 I think) recommended.

The recommended is actually 0.08mm and 0.18mm, which come to 0.00315" and 0.00708". I can't imagine differences of 0.00015" and 0.00008" would noticeably change the sound of the engine, and these differences should lie well below typical valve clearance measurement error.

[230slhouston]

Ulf,
Could the clatter be the timing chain perhaps?

Maistran

[ja17]

Hello,

Check to see if the valve cover hold down straps are up against the cam shaft. This will cause all kinds of valve clatter.  See the details in the"valve adjustment tour".  Flat wear areas on rocker arms will also cause noise.  If you run across any valves that are way way out of adjustment remove their rocker arm and inspect the surfaces for wear.

Badly worn ball studs get a  "crown". This wear can make valve adjustment inaccurate and difficult. The crown can be ground off flat or the ball stud can be replaced to improve valve adjustment accuracy.

[upside2k]

I would agree with one of the previous replys:

CHECK YOUR DRIVE CHAIN FIRST! If you lose the chain it will be very costly. That eliminated, move on to the valve train components.

[glenn]

Flatbed it to The PUB Hospital in July.  Recovery rate is extremely high!!

[Ulf]

Flatbedding it to PUB is unfortunately not an option as I live in Denmark  , but I'll have my mechanic check the timing chain, tensioners etc. and set the valves once again. But if the timing chain is indeed the issue, wouldn't the sound also be present with a cold engine?

Ulf

[230slhouston]

Ulf,
My experience with timing chain clatter was; the oil is a little thicker when cold, as it warms and thins a little the clatter increases. Replaced the chain and tensioner and solved my problem.

Maistran

[Benz Dr.]

That sounds more like bottom end problems. Look for a bad pin bushing or rod bearing.

You can test for this by pulling each plug wire off one at a time. The problem area will go quiet when you take that cylinder out.

[dseretakis]

I know this sounds really obvious but did you check the engine oil level?  This happened to my parents on a 450SEL.  They failed to check oil level for very long time.  One morning they started it up and heard this awful metal on metal clattering sound.  They took it to their mechanic who told them that it needed a new timing chain and that it may have suffered expensive damage.  They then took it to the MB dealer who discovered that it had no more than a quart of oil.  They topped it off, the noise went away and the car was fine for another 200,000 miles.

[Ulf]

I've tried pulling off the cables one by one, but it doesn't change anything. The oil level i correct as well, think I'll go for the timing chain replacement once the snow melts away.

[Benz Dr.]

When the engine is cold so is the oil and it's at a higher viscosity. As the engine warms the oil thins out and the thick cushion it once provided is gone. If there's any excess play between parts it will show up AFTER the engine warms.
In my experience it usually goes in this order:
valve rocker noise
rod knock
piston slap

Valve rocker noise is the easier to fix than the other two. Setting the valves may be all it needs.
Rod knock is serious and you aren't going much further for very long.
Piston slap is caused by a collapsed piston skirt. It only takes about .005'' or less to make noise. It can bang away in there for quite a while and still run OK. In either case keeping the engine speed down is a good idea. Both require pulling the engine apart and rebuilding.