Diagnosing valvetrain noise

[billj]

My CSE's engine (1995 2.0LPT) is making quite a bit of noise. This follows an oil leak complicated by a non-functioning oil-level sensor and, worst of all, oil pressure sensor. The oil was very low and refilling has not got rid of all the noise.

I think some of the noise is at the big ends but there does seem to be a loud knocking from the cam cover so I've removed that and the camshafts for inspection.

There is barely-visible scoring on the cam bearing caps and none on the camshaft bearing surfaces. Also no visible wear on the cam followers and the cam lobes. The grooved bolts on the bearing caps, designed to carry oil to the followers, are clean and clear.

So, assuming the noise was coming from the valvetrain, what could it be? A faulty follower? If so, how can I tell which one? With the camshafts off, none of the followers is sitting noticeably lower than the others.

If I leave the car idling, the noise will lessen briefly, then return. No amount of running or idling will make it go away.

I want to cure any top-end noise (or eliminate the top-end as a possible source of the noise) before going to the bottom end. The good news, though, is that my specialist tells me there's a good chance that even if the big-end bearings need renewing, the crankshaft will be OK so I'm hopeful that it won't be an engine-out repair.

[cdcarlsson]

Hi Bill,
Hmm, Bourne Motors once diagnosed a hardened 'guide pad?' (never saw sight of it so can't be more helpful) for the timing chain some years ago, but it wasn't making a terrible din, just a ticking. Perhaps worth investigating?
Nick.

[billj]

Thanks, Nick. I intend to replace that anyway like I did on the Aero when I did the head gasket and timing chain. It's a rubber pad fixed to the inside of the cam cover and they do go hard with age.

However, this noise is really quite loud. It may really be down to the bottom end but it certainly seems to be coming from the top.

And let that be a lesson to others like it has been to me. Warning lights are OK but are no substitute for regular fluid checks

[sgould]

Any valve sticking and slow to return? May need a compression check or head dismantle to know for sure though.....

[billj]

Originally posted by sgould:
[qb]May need a compression check[/qb][/b]

Bu66er.

Didn't think to do that. I was convinced I was going to find something obvious. It wouldn't take long to put the camshafts back on and do the test, though.

Any measurements I could make that might help?

I might end up having to put it all back together and concentrate on the bottom end to see if that fixes it.

[mark e]

Silly question perhaps, but what sort of noise Bill?

Regular ticking? Or something else?

[sgould]

The reason I thought of it was that I had that fault with another car. The valves are supposed to rotate slowly. I think these did, but were only returning the full travel in certain positions. I only found it in desperation when I took the head off and slid the valves to and fro by hand. It was only falling short by a very small amount, but when it did it had the effect of a very wide tappet gap.

[billj]

Originally posted by Mark E:
[qb]Silly question perhaps, but what sort of noise Bill?[/qb][/b]

Not a silly question if I haven't made it clear.
It's a regular hollow knock. A bit like cam knock on an old Ford or Vauxhall. I could be mistaken, though. It does sound like it's coming from the cam cover.

[murphwiz]

Have you tried compressing each follower in turn see if one of them locked?

[billj]

Originally posted by sgould:
[qb]It was only falling short by a very small amount, but when it did it had the effect of a very wide tappet gap. [/qb][/b]

Sounds like something that would be picked up by a compression test. I think that's something I need to do.

[billj]

Originally posted by Leon [9-5 stg2]:
[qb] Have you tried compressing each follower in turn see if one of them locked? [/qb][/b]

How would I do that? I thought that would take an awful lot of force.

[wrighar]

Originally posted by BillJ:
[qb]*QUOTE

Originally posted by Leon [9-5 stg2]:
[qb] Have you tried compressing each follower in turn see if one of them locked? [/qb][/b]

How would I do that? I thought that would take an awful lot of force. [/qb][/b][/quote]Or conversly is slack.

No it doesn't take that much pressure to see if they are good or bad, just work through the whole lot after running the car, the 1 or 2 that are 'different' are the ones to look at.

Andrew

[billj]

I took the camshafts off, thereby relieving any pressure on the followers, shortly after running the engine. Does that mean it's valid to do it now (or tomorrow evening, rather)?

[wrighar]

Originally posted by BillJ:
[qb]I took the camshafts off, thereby relieving any pressure on the followers, shortly after running the engine. Does that mean it's valid to do it now (or tomorrow evening, rather)? [/qb][/b]

Nope.

[billj]

No problem. I'll do it after the compression test, having spun it plenty on the starter to get the oil pressure up. Who knows - I might even be able to hear which one is knocking, if the noise is indeed coming from the valvetrain.