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Discussion Starter #1 (Edited)
Looking over Jacob's M5 (GA25321) at the moment

Oil has just been changed with Royal Purple 10W40 synthetic (Castrol and Mobil 10W60s not available here at the moment) , the old oil smelt of fuel contamination and was black.

A bit of a worry was a cam tick on start up when cold , this noise went for about 1 minute on the old oil and 15 seconds on the new oil.

It sounds like the noise is coming from one of the front cylinders, on cylinder 2 we found one shim that was 0.5mm gap which was replaced and back within specification.

Once the engine is warmed up it sounds normal.

Obvious suspect is the oil pump on the way out but is there any other known causes for this ?
 

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Discussion Starter #3 (Edited)
Possibly

Is there a check valve in the oil pump that keeps it primed ready for engine start ?

I just started the engine after sitting for 7 hours and no ticking sound , this morning's start the M5 had been sitting for 2 days.
 

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Sounds like a classic tensioner symptom to me - this tends to happen on the old diaphragm model (relies on a certain amount of oil pressure I believe). The S52 tension is widely regarded as a worthwhile upgrade.

Lantz
 

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Discussion Starter #5
Chain tensioner is relatively easy to get to.

Can the oil pump be replaced with the engine still in the car and the sump off or is it an engine out job ?
 

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the oil pump can be replaced with the engine in. If you go that far might be worth at least looking at the rod bearings too.

I did rod bearings and oil pump on my 93 3.8 at around 165k km. (internet myth that 3.8s go thru rod bearings got to me). They were actually in very good shape.
 
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