M40 start up rattle

[swindler]

Hi the latest project I've got is a facelift 316i M40. Sometimes on start up the top end gives a short loud rattle - sounds like something is oil starved. It goes away after 2/3 seconds. The car and engine have done 70700 miles from new and been serviced. It recently had (basic) oil and filter change. The engine is otherwise great - no flat spots, pulls crisply to the red line, idles steadily etc.

Any thoughts chaps - I want to nip it in the bud?

[soul4t]

Hello mate,

Mine does the same, had it since 43000 miles. I've been using a variety of oils, mostly Magnetec semi 10w-40. Done an engine flush.

I've literally just put some fully synth 5w-40 in and I'm setting off early all this week, so I can let you know if thats cured it! It shouldn't be a problem as far as I've gleaned from others, so long as you don't rev it when it's clacking!

[daimlerman]

One,or more,of the valve lifters is draining it's self of oil.

[Brianmoooore]

If it goes away in 2 - 3 seconds, then it can almost be considered normal. Not an unusual thing to happen with some much more modern engines.
Even if it happens most of the time at idle, then it's harmless and won't cause any problems, except comments from the uninformed.

[soul4t]

Hi Brian,

Just out of curiosity while we're on the ticky subject...would you say it's normal to have louder ticking at certain rpms, mine's most quiet at around 1000rpm, but then quite loud at around 1500, then eases off slightly when higher revs...I think it's mainly at low load, as when cruising...it's hard to tell when under load as the noise of the exhause and air intake interferes...what say ye?

Ta

[swindler]

Yes it's never more than 3 seconds and only when cold. Quite a metallic rattle. Would a thicker oil help?