320SLK top end rattle on start up

[DaveAVT]

Hi

Wonder if anyone can shed light on this. As of yesterday, If I start the car from cold (as in left overnight) there is a rattle from the top end of the engine just after cranking for a second or two, just as if it has no oil up there, then quietens right off and runs perfect as usual. If I then turn the car off and then back on again, it starts fine with no noise, pointing to a lubrication issue.

Ive checked the oil, level was midway, and Ive topped it up a little more, and it has made no difference.

Is this a common fault, are the 320's prone to oil pump problems, or PRV problems, or sticky tappets. Are they hydraulic or mechanical?

Thanks

David

 

[smuggler]

This is normal, you'll find this on most if not every car. What happens is when the car is left, the oil drains back into the sump so there is very little oil left in the head/top end when you start the engine. So when you start it, and the oil pump runs, it pumps the oil to the top end and thats why the rattling stops. This is also why when you restart the engine after turning it off that there is no noise, as there is oil still in the top end.
Nothing to worry about really.

 

[Deleted member 6183]

Ours has always done it.

 

[lynall]

My wifes 1st merc e320 with the 104 engine never did it, her ml320 with the 112 never did it, her current c320 112 engine doesnt do it and my 430 doesnt do it.

In fact of all the cars we have owned we have only had one that started to do this an e36 bmw 140k so was entitled to i guess

So going on that i would say its not normal, if it was mine i wouldnt be happy, especially if it had never done it before.

When was the oil last changed!

Years ago used to happen with cheap oil filters with no non return vale fitted, not applicable to mb as got paper cartridge filter.




Lynall

 

[Robbo]

Dave, its nothing to worry about.

try a different grade of oil if you are worried, Mobil 1 0W40 is worse for this in both my cars than 5W40 oil.

 

[DaveAVT]

When I say rattle tho, I mean rattle like an engine with NO oil in it And on cranking you can feel a miss at it fires, as you can tell they lifter is not working. This only lasts for 2 seconds max tho, then its fine, and if I pre crank the car a couple of revolutions, not let it fire, turn off and back on again, then its fine too. In someways I wish the engine would just do a few more revs before starting! Car has been fine for 2 weeks, then this just happened over night..

Its due an oil change so Ill do that. Ive been recommended to use the 0w40 instead of the 5w40 for the simple fact its better at initial lubrication which may be my issue, and to use a fleece filter instead of a paper one.

 

[lynall]

Turn ign on but dont start, wait for fuel pump to stop ( you can just hear it with door open) then do it again, then start it and see what happens.

Lynall

 

[Sp!ke]

Its due an oil change

Most likely, there's your problem. Get your oil and filter changed with fully synthetic oil pronto.

I'm not a believer in these extended oil change intervals. I change mine every 6k.

 

[Dieselman]

Have the oil flushed at the change. Hydraulic tappest fail because they can't get oil in and adjust readily, a flush may clean them out a bit and stop the sticking.

 

[Ian B Walker]

I change mine every 6k.

As should everyone else, especially if you only do short journeys. But that is only my opinion, others will differ.