cold engine start up chatter

[Richard_Hamilton]

Very common. I found that using a 5W-40 oil almost eliminated it on mine.

 

[Mike IRL]

One thing I noticed when test driving 996s before I purchased was that when engines are cold there is a chatter for a couple of seconds when started. I presume that is purely because oil has not circulated yet but is it normal on all water or air cooled 911s? For such a nice motor, it does take away from it slightly. No issue when engine is warm.

Any comments?

 

[Mike IRL]

Thanks Richard - is this on 993s (and older) and 997s too ? or specific to 996s?

 

[Richard_Hamilton]

I think all 996/997's do it to a certain extent - some more noticably than others. I can't recall my 993 doing it - the engine is a completely different design - but it wouldn't surprise me if some did. If it only lasts a second or two, don't worry about it.

 

[Mike IRL]

yes, only 1-2 seconds and not at all when engine is warm. It's just more annoying than anything and not what you would expect from such a motor.

 

[sawood12]

On conventional engines it tends to be because the oil drains out of the cylinder head when the engine is off and it takes a few seconds upon startup for the hydraulic tappets to pressurise. I guess you could be seeing a similar effect. As far as I can glean it isn't a problem as such as the engine should be designed to accommodate this effect. Sounds nasty though. The 5w oil being slightly thicker when cold probably means the oil doesn't quite drain away fully and so pressurises almost instantly when started.