Re: Knock sound when turning car off
 

I'm with you on this one...

Mine do the same thing, the chatter occurs at the instant I kill the ignition, clutch in or clutch out... doesn't matter. The chatter only starts immediately as the engine shuts off, and lasts less than a second.

Re: Knock sound when turning car off
 

Yea, its really not an issue as the motor stops so fast, it's just a byproduct of their design, over time (100,000+ shutdowns it could cause rocker arm wear but by that point other things would have worn out) you could run an accusump to prevent the problem on shutdown, but on a stock motor there really isn't a point.

Re: Knock sound when turning car off
 

I may be missing something here, and I am not too old to learn. The oil pump is working even as the engine stops and oil is being pumped through the system as long as the check valve is working the oil will not flow backwards.:confused:
Oil pressure keeps the lifters in contact and the pressure is not so great as to lift the valves. So?

Re: Knock sound when turning car off
 

most modern automotive oiling systems don't have one way check valves. And per our FSM, none exist anywhere in the system. Oil pumps have a pressure check valve that circulates excess oil back around the pump to keep pressure in check.

All oil pumps have a minimum operating rpm (i haven't datalogged rpm vs. oil pressure so I can't give a concrete number) but lets say hypothetically that limit is 200 rpm. During shutdown as engine rpm drops past that number, the pump isn't spinning fast enough to pull oil from the pan and pressurize it when this happens. And the fact that the lifters on our cars are basically the last thing in the oil passage circuit, they lose pressure first (the most important thing to keep oiled regardless are the main and rod bearings, which is why they are almost always first in the circuit, they pretty much keep residual pressure during shutdown and the starter spins the motor fast enough during cranking to deliver small amounts of oil pressure until the motor turns over)

Hydraulic lifters use oil pressure to force a piston against a spring which pushes down on the roller taking up the lash between roller and valve.
http://www.streetsideauto.com/images...utawayCMYK.jpg

This is a cutaway of an LS v8 HLA (hydraulic lifter assembly) but they are all the same in construction and basic principle of operation.

When oil pressure drops on shutdown, the spring forces the piston in the lifter to its full retracted position. This causes excess lash between the lifter and valve, causing the chatter you hear on shutdown.

Re: Knock sound when turning car off
 

Very informative post, I'm impressed

Re: Knock sound when turning car off
 

I try to be helpful when I can lol.
Plus being an engine builder you gotta know how they work or its hard to put them back together :p

Re: Knock sound when turning car off
 

Agreed... leftover parts = :mad:

Re: Knock sound when turning car off
 

certain leftover parts = weight reduction :D
but when it comes to engines, leftover bolts and such means you probably screwed up somewhere

Re: Knock sound when turning car off
 

What do you think was the cause and how did you fix this?

Thanks

Re: Knock sound when turning car off
 

Take a look at the date of the post, six years ago.

Of course, I just checked, he was reading threads here yesterday so maybe we will hear from him.

Re: Knock sound when turning car off
 

You know, the fan motor/blades/housing is an assembly - why not just replace it?
I am 99% sure this fits - maybe 100/80 or Mr. Miata can verify.

http://www.ebay.com/itm/like/282122420819?lpid=82&chn=ps&ul_noapp=true

Re: Knock sound when turning car off
 

I'd have to agree on the fit since 2004 SLK320 is listed :
Fits Model and Year:
1999 2000 99 00 MERCEDES BENZ C280
1998 1999 2000 2001 2002 2003 2004 98 99 00 01 02 03 04 MERCEDES BENZ SLK230 , SLK32

Re: Knock sound when turning car off
 

The fan and motor and the shroud are only an assembly when fitted together, they can come as two separate parts although they could be sold as an assembly with the use of some other parts.
You can buy the fan and shroud separately.

The SLK320 and SLK32 quote different parts to what is on my Crossfire. The shroud is a different number altogether and the fan is #000 540 15 88 and #000 540 16 88 on the SRT I have.
I believe the NA and SRT use the same fan and shroud - I'll check though.

Look at the parts on your cars the Mercedes part number is on most parts, even those made by Bosch etc.

I got the SLK320 and SLK32 parts list in the documentation thread along with other lists but why did I bother if nobody looks at them.:rolleyes: I admit they may get out dated in a few places but the basics are there.

Re: Knock sound when turning car off
 

I have a spare fan/shield, I went out to the garage to look and all I could find was
333-55019-100 on the shroud, no numbers at all on the fan.

Google seems to think this is a good number for the crossfire fan assembly .....

Re: Knock sound when turning car off
 

Re: Knock sound when turning car off
 

I also have a 6spd. I have always started and stopped the engine in gear with the clutch pedal down. It stops the engine from rattling after shut down. Just my experience.