Engine Knocking.....

[SADLOTUS]

A bit of background:

Recently took the car round an airfield on a Club Lotus thrash. Whenever I parked there'd be a small pool of pressurised oil under the car - about 4inches in diameter. it would stop dripping after about five minutes. I had overfilled by about half/two thirds litre to help stop the oil surge.

During the day the car started to missfire like it had done a couple of weeks before. Back home it was traced to a carburettor imbalance - the slave carb balance lever being loose on its threaded bar - so loose in fact, a new one was needed.

Replaced the slave lever, started the car, ran it and balanced the carbs over a fifteen minute period. No problems. No nasty noises.

Decided to adjust the clutch, check out the oil leak. Jacked the car two feet in the air, took the exhaust off at the lower manifold junction, adjusted the clutch. Not clear where the oil was coming from. Put a socket on the sump bolts and to my horror each one (the ones I could reach) needed a good whole turn to tighten!

Reassembled everything and dropped the car down. Soon as i started it there was a knocking noise, sort of nack nack nack noise. Seemed to be coming from inside the engine like an end. deeper than a rattle, softer than a bearing, metallic but not harsh, from the front not the back, inside the sump when I'm under the car. The noise gets drowned out when I rev but is still disernable. No noise with plugs out and turned over on solenoid (must recheck this). Ticks over smoothly with the noise always present. Increases speed with revs.

I have a theory..... doing the sump bolts up tighter has brought the sump baffle closer to the crankshaft counterweights, just brushing it (oily nack nack nack).

So.... first thing to do is to drain the oil, check for swarf (in case I'm wrong), refill, then release the sump bolts a fraction and start the car.
Next question.... is it possible to reach the sump bolts at the back, behind the gearbox/clutch thin metal cover bit, so I can take the sump off and 'remodel' the windage tray. I've only ever done it with the engine out.

Is my theory a bit far fetched? Any other theories?

[billwill]

Not a lot of help for getting them out, but long ago I sawed screwdriver slots in the head of the sump bolts so that they could be done up with a long big fat screwdriver with a tommy-bar hole in the handle.

If doing it again I would probably fit hex-socket bolts instead and if necessary make a long hex rod-spanner.

[leifanten]

On my 1969 +2 I was able to remove the sump in situ. It is a bugger of a job putting back again as you need to be in many places at once. Including in front of the car checking that you get the rubber seal seated properly. But it can be done. I would say your theory sounds a little *exotic* though. I am not sure what clearance there is between the crankshaft and the various parts of the sump, but I would be surprised if such a skinny tolerance was made that it allows contact when a gasket is compressed .... Have you tried the stethoscope on it to find out where the noise is coming from?

[1964 S1]

Yes, try the stethoscope with the long pointy rod and get back to us.
I'd do pan, block, head, and then the pan again on the opposite side. And finally, I'd put it on the front chain cover, I think you're hearing the timing chain rattle before the oil pressure build up. Tensioner issues.
Did the noise begin immediately after tightening the pan bolts?
Eric

[ardee_selby]

Just wondering if the leak & noise are not directly cause & effect. I've never deliberately overfilled....so what does the +2/3 litre look like on the dipstick? At what point would overfilling a twink cause problems?

Rohan's advice was:

"The problem comes when going hard through a long right hand corner...Overfill the sump by around 5 to 10 mm and watch the pressure through any long right hand corners and back off if you see any problems"

Has the oil leak been cured by tightening sump bolts?

When you do the stethescope test it may be something simple...Track thrashing? Noise from the front? Alternator (dynamo?) bearing noise being transmitted?

Good luck - Richard

[rgh0]

The sump bolts go loose as the cork gaskets compress overtime and this can result in leaks, especially on the track where oil is being thrown around in the sump by hard cornering. TOver pressuring the sump with increased blow by at high revs on a track can also result in oil being blown out the seals and gaskets more and it goes away in normal road use.

If your sump is standard the clearances are such that the sump should never hit anything moving inside the engine. If its been modified the anything is possible I guess. I suspect your hearing the noise after tightening the sump is coincidence.

I use hex socket head cap screws for holding the sump on so it can be more easily tightened in situ using a long ball head hex key but you can do it with a small 1/4 drive socket set and universal joint on the extension easily enough also with the standand bolts

cheers
Rohan

[neilsjuke]

Hi Paul give me a ring if you want to bounce any thoughts
Neil

[SADLOTUS]

Hi all, thanks for your replies and suggestions.

I haven't been able to investigate anything over the last couple of days but will do asap.
I don't have a stethescope but do use a length of plastic pipe and an ear to a long screwdriver.
No (unusual) noise from the front timing chest, the cams or followers, nothing from each of the chokes. Nothing from the block between the manifold or next to the distributor. A longer rod is called for to listen to the sump, I'll do that next. The nack nack nack definitely comes from the front, down low.

The sump is baffled. I have not seen it since the engine was rebuilt. Before that, I had a tray, like the diagram above with a hole in it for the oil pickup, sitting on top of the front/back standard baffle.

The noise happened immediatley on starting (first opportunity) after tightening the sump bolts.
The oil leak has not stopped.

I'll also disconnect the fan belt for a short while to see if that will isolate the noise.

What head and thread and size should a change to socket heads be? (lazy! yes I know)

[rgh0]

They are 1/4 Unc with a 3/16th hex socket
I use set screws with 1/2 thread section length for the ones into the cast iron block and 3/4 inch into the alloy front cover and rear seal carrier sections to maximise thread engagement in these.

regards
Rohan

[mr.vman]

Good idea to remove the fan belt. A bad water pump bearing can sound like a lower end problem. If the noise just started after messing with bolts, could still be a water pump problem or worse! Hope for the best, plan for the worst. Maybe the oil pan baffles came undone? Good luck.
Steve V.

[neilsjuke]

I think you should also do a compression test before restarting ,poss crank case pressure = oil leak
Neil

[gjz30075]

Wait a minute here! The simple diagnostic 'tool' would be to loosen the sump bolts by the same amount that you first tightened them immediately before the problem (one turn, per your post), give the sump a few small whacks with a rubber mallet to allow it to 'fall' back to its 'original' position and fire it up. That should tell you whether or not your theory is correct.

Greg Z

[SADLOTUS]

Ok, update time.

Been a while due to commitments and being away, gives me a chance to think over what I'm doing and what needed to be done.
Bought a proper mechanics stethescope, new sump gaskets and a set of 3/16 socket heads - and custom made a ball head allen key to get round the sump bulges.

As Greg suggested, I also thought the first diagnostic tool would be to loosen the sump off and have a relisten.

Loosened off - no noise.

At first I thought the 'clacking' noise was coming from the frontish end and was convinced the crank or a rod was touching the windage tray in the sump, but seemed unlikely because as Rohan said, it was so far down and away from any circulating parts. Chatted to the engine builder and he said I had a longer stroke Mexico crank and they have been known to touch the sides of the sump on their rotation. Took the sump off - had to bash it with a rubber mallet and it dropped nicely onto the front crossmember, bit of a wiggle and it dropped down. I couldn't see any marks but the rods were very close to the sides. Ran some duck tape along the edges, did a trial fit and turned the engine over by hand - no marks or scuffs.

On the sump sides, near the lip there are small circular (fat finger sized) indentations where the rods (normal or otherwise) need clearance. I used a steel (fat finger sized) rod and bashed with a hammer to try and increase that clearance a wee bit. Put it all back together using the original gasket as that was still OK. Filled with oil and started the car. Knocking still there. Very grumpy. Went away for a coupla weeks.

Stethescope arrived and with the engine clacking I decided the noise was in fact coming from the back middle of the sump - just as it rises to the rear seal. Sump off again. There, right in the middle where I thought, was a small polished mark, a tiny shiney spot about 2mm x 3mm, you could also see how the sump was slightly pushed up as if knocked from below and the tightening of the sump bolts had brought it closer to the rotating rod/crank web. More hammer work and the sump was ready to go back, I used the Burton cossflow gasket set, (not cork material) just the side parts, not the plastic seals and Abro black sealant.

During the previous refit the washer on the tea strainer broke loose....ggrrrr....found out they're not available anymore....ggrrr!

Mended it carefully with aeronautical metal epoxy. (thanks Neil, shoulda spot welded it really).

All back together, started, and quiet underneath. Small 2" pool of oil drained from the bellhousing where oil had dripped back into it from the sumpless engine when jacked up at the front.

mmm.... those tappets sound a bit noiser now.

[gjz30075]

Congratulations! Nice find.

Greg Z