Engine knock at startup

I wonder if you can help.

I have a 2003 4.4 V8 RR Vogue with 125K on the clock, the engine has just started making a loud knocking on startup, only for a couple of seconds and then stops, runs like a dream after that, this it only happens on the first start of the day, all subsequent starts are perfect.

Is sounds like lack of oil, but I have checked the levels and they are fine, I have added slick50 and it has made no difference.

Any advise would be gratefully received.

Many thanks

wickets

I would guess at the VANOS but i'm sure SaintV8 should be along soon with a much more informed reply.

As Martyn says could be VANOS, but this tends to be more of a tick.

If it is closer to a rattle or slapping, could be timing chain tensioner or the timing chain guides.

One of the guides has a hydraulic tensioner fitted that is pumped up by oil pressure, if the seals are worn, the oil leaks out when the engine is stopped and the tension on the timing chain reduces causing them to rattle or slap about until the oil pressure has pumped the tensioner up again (much like hydraulic tappets).

If it is more of a knock, might be the big end bearings worn, but this is uncommon on a well maintained M62.

Thread hijack so apologies up front.
Saint, I have the same knock which stops when the oil light goes out, it's not coming from the bottom end so that leaves vanos/tensioner/guides.
I'm not 100% sure but I think mine is a non vanos and the tensioner was changed a few days ago. Is the tensioner separate to the guide it's fitted to and could the guide itself be causing the knock or would an oil and filter change help with a different viscosity oil. It has 5/40 at the moment and it seems the oil is running back while it's parked so do you have any other suggestions that might help.
Thanks and apologies for the hijack

Hamster97 said:

Thread hijack so apologies up front.
Saint, I have the same knock which stops when the oil light goes out, it's not coming from the bottom end so that leaves vanos/tensioner/guides.
I'm not 100% sure but I think mine is a non vanos and the tensioner was changed a few days ago. Is the tensioner separate to the guide it's fitted to and could the guide itself be causing the knock or would an oil and filter change help with a different viscosity oil. It has 5/40 at the moment and it seems the oil is running back while it's parked so do you have any other suggestions that might help.
Thanks and apologies for the hijack

Click to expand...

All M62's had VANOS - Single on the intake cam.

The tensioner is seperate to the guide and acts like a little hydraulic ram and pushes up against the top of one of the guides which in turn is pivoted at its base...this pushing puts tension into the chain.



If you had the tensioner changed and still get a rattle/slap it could be the guides are worn, but this doesn't explain why it goes quiet when oil pressure builds!

It could be the VANOS seals causing the cam chains to move about, but again VANOS seals I would attribute to a ticking noise as the VANOS bodies rotate around themselves and hit each other! (the VANOS unit has a series of rotating 'shells' that adjust when oil pressure is applied....knackered seals causing a reduction in oil pressure can mean the 'shells' rotate and hit their stops causing a ticking)

The M62 does have hydraulic tappets much like most other modern engines, and they can too lose oil pressure as they get old...although uncommon on the M62...they do tend to last a while!

You could try a 10/40 or 10/50 oil safely in this country as we rarely get temps below the lower threshold for these oils (-20degC).

Oil pump failure has been documented in the M62 but more often than not, it is the pump drive chain that is the issue (the oil pump is mounted very low down by the sump and is driven by a chain from the crankshaft)

I'd do an oil change with a good flushing agent, then refill and change again after a few hundred miles and see if the knocking noise is reduced....if it is the same, then it is a mechanical issue and investigation is needed....

Thank you, I'll get on with an oil change with some 10w50.

I used forte advanced formula engine flush which is supposed to be one of the better ones, you would need 2 bottles.
Worth a try but didn't cure my occasional start up rattle
According to beisan systems site the early sign of vanos failure is startup rattle as is the non return valves behind the vanos solenoid
Very common and can be caused by various faults as already mentioned

It is definitely a knocking rather than a ticking of a slapping, the service was done only a few thousand mile ago,

If it was big ends wouldn't it knock all the time?

I'll try an engine flush and fresh oil and see how I go.

Thanks

wickets

I think as Saint has pointed out there are very common issues like the vanos and hydraulic tensioners which give your symptoms
If the issue was bearings I would say it would be constant and worse when hot.
My money would be on a combination of vanos, tensioner and non return valves
Mine is generally ok when starting from cold but worse when starting from hot when the oil is thinner and I have a constant quiet tap at idle when hot.