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Matt, Mechanical Engineer
Category: BMW
Satisfied Customers: 22917
Experience:  BEng hons Mech engineering, in auto industry 22 years
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My x5 diesel sport is tapping loudly in time with the engine

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My x5 diesel sport is tapping loudly in time with the engine revs until about 1600rpm!
I have put a lifter cleaner through it and changed the oil. Also I have have had a mechanic disconnect each injector one at a time to see if it's injector knock! It also takes 3 or more seconds to fire up even when warm but it's turning over fine so the battery must be ok!!
Could it be hydronic lifters, big end bearing or something else!!!
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I'd first try removing the auxiliary drive belt and turning every pulley and ancillary ( power steering pump , alternator etc) by hand. All should turn easily (with the exception of the AC pump) with no grittyness or wobbly pulleys- If you do find a sticky pump / alternator then it should be replaced or repaired

If the engine is stone cold you can briefly run it with no belts to see if the noise changes or has gone away, this will help show if an ancillary is the issue

Examine carefully the condition of the bottom / crank pulley as these are composite construction with a rubber element and its possible this rubber is breaking up and allowing the two metal portions to move.

Another possibility is the variable valve timing system as this does rely on oil pressure to correctly synchronise your vvti pulley on the end of the camshaft. If the valve has become blocked up then its possible the pulley is rattling about and producing the noise.

Matt, Mechanical Engineer
Category: BMW
Satisfied Customers: 22917
Experience: BEng hons Mech engineering, in auto industry 22 years
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Customer: replied 3 years ago.

Tried all that today, didn't work unfortunately. Do you think it could be injector knock? Or maybe something to do with the swirl flaps?


injector knock is a possibilty, but this should have gone away when you disconnected the injectors?

I'd say the most likely cause is still the valve lifters so it might be worthwhile trying a slightly thicker oil to try and get the lifter to pump up faster?

if you can let me know what oil grade you're running now I can suggest something
Customer: replied 3 years ago.

I know it's the exact casterol gtx oil that the handbook says to use! When he disconnected the injectors I don't think he took them rite out, he just Un plugged them! Can I upload a video of it maybe?


if the injectors were unplugged then thats enough as they won't fire / inject like this

as for the oil then there are 2 specifications, a 5W -30 and a 5W40

if you're on the 5W30 it might be worht trying the 5W40