Series 3 Loud knocking sound from the engine when running.

Snellsypu · Saturday at 14:30

My s3 blew a sump gasket a while back and stalled due to lack of oil. Once I got a new gasket on there she turned over fine but there is a loud knocking noise.

After being told it was probably the tappets, I drove her to the men's shed(men's mental health charity/social club) I attend. We checked all the tappets and the clearance is near perfect. It seems like the sound is coming from the bottom of the engine, so maybe the oil pump or a big end bearing?

There doesn't seem to be a loss of power and the noise didn't change for the 10 mile round trip to the shed and then back home, going through all gears and the overdrive and up to about 45mph(speedo doesn't really work)

Recording of the sound after I drove it home

miktdish · Saturday at 14:47

More likely to be a big end.
Be careful because that knocking may suddenly turn in a thumping followed almost instantly by parts of the inner workings getting out through the side of the crankcase.
Con rods bending and pistons hitting valves may also occur.

All a lot more expensive than not starting the engine untill it's been checked out.

Anaconda · Saturday at 16:11

When you say it stalled do you mean it broke down because there is no oil in the engine?
Best follow the advice in the post above this one.

Snellsypu · Saturday at 16:38

Anaconda said:
When you say it stalled do you mean it broke down because there is no oil in the engine?
Best follow the advice in the post above this one.

It started tapping while I was on the motorway so I pulled onto the hard shoulder and as I slowed down the engine cut out and wouldn't turn over.

Snellsypu · Saturday at 16:42

miktdish said:
More likely to be a big end.
Be careful because that knocking may suddenly turn in a thumping followed almost instantly by parts of the inner workings getting out through the side of the crankcase.
Con rods bending and pistons hitting valves may also occur.

All a lot more expensive than not starting the engine untill it's been checked out.

I've already ordered a new set of big end bearings incase it was. Per your comment I'll tow it to the shed rather than drive it. Is there anything else it might be besides big end bearings? Any part of the timing chain that could make the noise?

boguing · Saturday at 16:43

If you're very lucky it may only be the shells that are damaged and the crank may just need a polish. You didn't mention main bearings on your order?

Edit. I'd put the order on hold until you've inspected it. You don't know whether it has standard bearings now, and you certainly don't know if the crank needs a grind.

Anaconda · Saturday at 16:43

My limited experience is chains rattle and top end taps.

kermit_rr · Saturday at 17:59

Perhaps it's just a turn of phrase, but there shouldn't be much pressure in the sump to blow the sump gasket. Even if the gasket was leaking, i wouldn't expect a catastrophic loss of oil.
I think proper investigation is in order to clarify exactly what's happened and why.
If you've had low/no oil pressure for a while, did the light come on?
If you've had no oil/pressure then the rocker shaft could have been starved of oil, it's not a big deal to check the shaft for wear, while you check the bottom end which is likely where knocking will come from

Snellsypu · Saturday at 18:37

kermit_rr said:
Perhaps it's just a turn of phrase, but there shouldn't be much pressure in the sump to blow the sump gasket. Even if the gasket was leaking, i wouldn't expect a catastrophic loss of oil.
I think proper investigation is in order to clarify exactly what's happened and why.
If you've had low/no oil pressure for a while, did the light come on?
If you've had no oil/pressure then the rocker shaft could have been starved of oil, it's not a big deal to check the shaft for wear, while you check the bottom end which is likely where knocking will come from

I just meant a major leak. The gasket was a rubber one with several major cracks and it was solid to the point i thought it was abs plastic but no silicon in sight. Probably leaked out over a few days but not sure. Most of the electrics in the dash are a bit naff(on the to do list) but I don't think the oil pressure light has ever turned on since I got it.

boguing · Saturday at 18:38

Snellsypu said:
but I don't think the oil pressure light has ever turned on since I got it.

It should come on with the ignition and go off once the engine starts. That would be a very unfortunate one to have fail.

Snellsypu · Sunday at 16:06

boguing said:
If you're very lucky it may only be the shells that are damaged and the crank may just need a polish. You didn't mention main bearings on your order?

Edit. I'd put the order on hold until you've inspected it. You don't know whether it has standard bearings now, and you certainly don't know if the crank needs a grind.

It sounds like the noise is timed to one of the cylinders. so if it is a bearing, hopefully it's just one of the conrod bearings. You can see them with the sump off but i stupidly didnt think to check while replacing the gasket.

I know about lapping the bearings to fit the cap, but I wasn't aware you had to polish the crank?

boguing · Sunday at 16:27

Snellsypu said:
It sounds like the noise is timed to one of the cylinders. so if it is a bearing, hopefully it's just one of the conrod bearings. You can see them with the sump off but i stupidly didnt think to check while replacing the gasket.

I know about lapping the bearings to fit the cap, but I wasn't aware you had to polish the crank?

The crank may have picked up bits of bearing and other muck that has been hammered on to it by the dying bearing. Lst one I did looked like it needed a grind, but the guy who's been doing this for at least thirty years assured me a polish would do. They looked like new and the new bearings measured up perfectly. My driving very gently to a garage a mile away to get more oil just saved it I think.

steve2286w · Sunday at 17:53

too late now but fixing the oil pressure light should have been at top of list

.
Should be able to check main and con rod bearings with sump off on a still day

See manual and parts book here

Land Rover Manuals

smithies.co.nz

Is it a 3 or 5 mb engine
Was there much oil in when you drained sump
Oil pump should be ok as it’s submerged in oil

Series 3 Loud knocking sound from the engine when running.

Snellsypu

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miktdish

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Anaconda

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Snellsypu

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Snellsypu

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boguing

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Anaconda

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kermit_rr

Very

Snellsypu

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boguing

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Snellsypu

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boguing

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steve2286w

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Land Rover Manuals

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