Engine noise

[ChrisGadd]

Hi,

After having my car off the road for the best part of 3-4 yrs I have finally started the engine only to discover that there is a loud metallic knocking related to the speed of the engine. The exhaust is off the car and I have replaced the engine oil, filter and sump plug.

So far :-
1) Checked oil pressure on tick over and it's at 25 which seems a little low?
2) Checked valve clearance and all seems ok.
3) Taken the plugs out and turned the engine over with the starter motor and still knocking noise.
4) Removed the alternator and water pump drive belt and turned the engine over and still knocking noise.
5) Done a compression test and cylinders 1,2,3,4 at 140 cylinder 5 is 120 and 6 is 150. (This was done with the engine cold as I don't want to damage the engine any further.)
6) Partially removed the dipstick still no difference.

I can't really hear where exactly the noise is coming from but thought about dropping the sump and having a look if there is anything obviously wrong. So the question is have I missed anything to try before embarking on dropping the sump? and has anyone removed their sump in situ

Oh and it's an S3 2.9

[Scoobimax]

You've covered everything I'd do (because I'd have to ask you to do it) ;-)

Hope it gets sorted easily for you.

[tofts]

Sadly, your describing what sounds like a dodgy bearing, which could also be why 1 cylinder is down on pressure. I would have the sump off to investigate! I do hope I am wrong for you but I can't think of anything else it could be.

[Griffinr]

Is it a heavy knock or loud tapety knock? Could it be that you have hydraulic tappets and one of them has drained down and not primed.

[GreenV8S]

Seems unlikely that a bearing would choose to fail suddenly while the engine was laid up. Even if it started up with zero oil pressure it wouldn't immediately destroy a bearing. The idea of a follower that has drained and not pumped back up seems far more credible to me. I'd be tempted to turn the engine over slowly by hand and see whether there is any play ion the big/little ends, take the rocker covers off and see whether all the rocker arms are gapped about right.

[ChrisGadd]

Griffinr said:

Is it a heavy knock or loud tapety knock? Could it be that you have hydraulic tappets and one of them has drained down and not primed.

Difficult one to answer but it is definitely a loud knock. It's a late S3 but as I understand it it's difficult to know if it's hydraulic tappets or not.

[ChrisGadd]

GreenV8S said:

Seems unlikely that a bearing would choose to fail suddenly while the engine was laid up. Even if it started up with zero oil pressure it wouldn't immediately destroy a bearing. The idea of a follower that has drained and not pumped back up seems far more credible to me. I'd be tempted to turn the engine over slowly by hand and see whether there is any play ion the big/little ends, take the rocker covers off and see whether all the rocker arms are gapped about right.

Hi peter, I've already had the rocker covers off and checked the tappets which only needed a slight adjustment, although I may be tempted to take the right hand cover off again and re-check cylinder No 5 given the lack of compression. I suppose the next thing to do is remove the cylinder head and see if there is anything showing.

[phillpot]

Before taking anything apart I'd be inclined to try and find an "expert ear", or two, to have a listen



lot of talk of tappets and valve clearances, do you know for sure if you have solid or hydraulic lifters? Did you adjust any of them more than a slight amount?

Logic would say if you've done nothing major to the engine there should be nothing major wrong if it was working ok before?

ChrisGadd said:

The exhaust is off the car

Surprised you could hear anything!

[mk1fan]

I too have a tappety sound which I suspect is can end rather than valve end given the same noise was there before the head swap - yes I checked the clearances. Solid tappets on the Reserve - although Samy has hydraulic.

[ChrisGadd]

phillpot said:

Before taking anything apart I'd be inclined to try and find an "expert ear", or two, to have a listen

Good idea Mike, I'll see if I can upload some footage of the engine sound.



lot of talk of tappets and valve clearances, do you know for sure if you have solid or hydraulic lifters? Did you adjust any of them more than a slight amount?

From what I can remember it was only slight adjustments, as for hydraulic or solid lifters I believe the only way to tell is by taking the heads off ?

Logic would say if you've done nothing major to the engine there should be nothing major wrong if it was working ok before?

My thoughts exactly and I certainly don't want to disturb what has been so far a very reliable engine.

ChrisGadd said:

The exhaust is off the car

Surprised you could hear anything!

I can hear the knocking when cranking the engine over on the starter motor and plugs out.

[Alan461]

Have the plugs been out or plenum off while it's been laid up?
Something could have fallen into one of the pots and be fouling at tdc

[ChrisGadd]

Alan461 said:

Have the plugs been out or plenum off while it's been laid up?
Something could have fallen into one of the pots and be fouling at tdc

Hi Alan,

Plugs have only just been removed to try and work out what the knocking is so I doubt anything has dropped into one of the pots. I think the next thing to do is check the engine number to see if it does have hydraulic tappets.

[ChrisGadd]

Hi folks, here's an update on my knocking issue. I have looked at the Engine Numbers and it suggests from the previous posts on here that I may have an engine with hydraulic lifters. So that may explain the knocking noise if one of the lifters isn't getting the supply of oil needed.


Two things that spring to mind :-

1) When I adjusted the tappet clearance they were set to solid lifter settings not hydraulic as the hydraulic lifters are as I understand it pre-loaded so should have no gap ?

2) If I do have hydraulic lifters then if they are set to the solid lifters clearance then the valves will not open as far as they should and reduce the engine performance?

Is there any information about how to correctly set the pre-load on the lifters ? and if I set these and it's not got hydraulic lifters what damage will it do ?

Thoughts please

[h271mbk]

Could your knocking noise be from a blow in the exhaust manifold or exhaust gasket? This can sometimes sound like an engine knock.
N

[TVRees]

h271mbk said:

Could your knocking noise be from a blow in the exhaust manifold or exhaust gasket? This can sometimes sound like an engine knock.
N

I don't think so, since it was mentioned earlier that the exhaust is off the car.

[White S3]

Have you managed to locate the rough area that the noise is coming from? After a 2yr period off the road my water pump had failed but didn't show until shortly after MoT. After replacing it with hindsight there was a quiet metallic knocking before the steam train effect every time it came up to temp.

On examination, the failed water pump had about 2mm of play in the bearing and in my hands I could generate a metal on metal "dink" sound. Opening it up, serious corrosion and I had drained the coolant system before taking the body off. New pump was silent off and on the car, so if emanating front lower half of engine block check the play in the pully block.

[ChrisGadd]

White S3 said:

Have you managed to locate the rough area that the noise is coming from? After a 2yr period off the road my water pump had failed but didn't show until shortly after MoT. After replacing it with hindsight there was a quiet metallic knocking before the steam train effect every time it came up to temp.

On examination, the failed water pump had about 2mm of play in the bearing and in my hands I could generate a metal on metal "dink" sound. Opening it up, serious corrosion and I had drained the coolant system before taking the body off. New pump was silent off and on the car, so if emanating front lower half of engine block check the play in the pully block.

Hi sorry for the long delay in responding but I've been otherwise occupied, it can't be the water pump or alternator because I removed the drive belt to eliminate the possibility of these being the problem. It must be mechanical and not related to any ancillaries because I can still hear the noise when the plugs have been removed and the engine is cranked over with the starter motor. My guess is a valve that is sticking or a block in the hydraulic lifter. As said before the tappets look to me to be adjusted as though they are solid lifters and not the hydraulic lifters that this engine has.Does anyone have any advise on how to set the lifters and clear any blockages?

[Top Gear TVR]

has the sump taken a clowt from a poorly placed jack / stand or similar?

[HvdWeerden]

Search function !

http://www.pistonheads.com/gassing/topic.asp?t=376...

[The Beaver King]

On a scale of 1 - 10, 1 being whisper quiet and 10 being 'Holy crap, she's gonna blow!', how loud is the knocking?

I have a theory based on my own experience, but the knock would need to be pretty loud (7-10 range).