Strange Noises.... (Rattles, Clonks & Whines!)



After 8 months in the garage, it is now time to get the Elite on the road again. But tonight as it was started I noticed a strange rattle from the engine area, at precisely 2800 rpm., and it stoped when it had warmed up. The engine was in any other respect as normal, easy to start, responsive, clean running, and with all BHP at home. Under normal conditions you don't keep the car at precisely 2800 rpm, so it might have been there for a while, with out beeing noticed. It is a 907 engine rebuilt to 2.2 ltr. and I am told that the bottom part of that engine is weak, and is likely to rattle. But what is it that rattles - is it damaging the engine, breaking the crank, or what? I have checked the camcovers so it's not that.


Almost any time a sound can be heard at a particular RPM, it means its a harmonic vibration. Something loose under the hood is vibrating sympathetically at that particular RPM, and probably isn't particularly serious. It doesn't even have to be inside the engine, it could be a loose bolt. I would poke around while its making the noise and see if it suddenly gets quiet, then you have found the source


Check the timing belt shroud. Are any fasteners broken or loose? Do you have a mechanic's stethoscope? if so, do some poking around to listen. if you hear "internal" sounds - like piston slap, it could be that you have the Nikasil liners??? There is some extra clearance until the pistons warm up. I don't remember the exact materials but it was some combination of liners & pistons.


8 months is quite a while. Has it been started on occasion, or has it just sat there? If it was the first time it has been running in a long time, maybe there was not enough lubrication. It could have been a connecting rod bearing(s). Maybe now is a good time to get rid of that old oil and put in some fresh 20W-50. Test again, but allow to idle till the oil has circulated.


Other things to check are water in the oil/oil in the water. (white creamy stuff) as this means the head gasket has gone. Check if the engine sounds rattly. This is common, and needs the shims doing.


I would be grateful for your advice about a strange 'clunking' noise which appears to be originating from underneath the front/middle of my Lotus Elite. The noise sounds metallic/clunking/banging . It is very noticeable when I am driving slowly and it sounds like it is related to the wheels when they are turning.....although it is prominent all the time now.


My Excel gives clonks & bangs at low speeds, which is the anti-roll bar moving in its mountings. No real problem there, just the noises. And after 18 years of it I suppose I'd worry if if _didn't_ clonk at low speeds.....


Check the Anti Roll bar mounting points (particularly the chassis ones) as the rubber bushes do open out allowing a certain amount of movement. Nothing to worry about if that is the source of the noises unless it is really bad.


Check that an anti roll bar bush has not come loose....

When maneouvering at low speeds and occasionally when braking hard a click/clonk noise comes from the front (left I think). What is this likely to be?


Off the top of my head: steering rack mounting bolts; loose anti-roll bar mounting bolts loose, or bushings perished; wheel bearings loose (raise car and push/pull wheel); lower control arm bushings perished (pry wheel around with Lotus Tool #1); bad shock; stone stuck in tyre tread; brake caliper mounting bolts loose; bad trunnions


Check the suspension and steering, also get into the engine compartment and give other components a good yank. I found the AC compressor mounting bolts to be loose on my car. This would cause a "clonk" under certain conditions. When checking the wheel bearings (wheel off the ground), hold the tyre at 3 and 9 o'clock and give it a good push-pull, hands at 12 and 6, repeating the actions. Be not gentle whilst performing these tasks related to the suspension parts. A broken damper is also a very good candidate for this noise, as is a motor mount. If your engine has broken through the bonnet, I'd bet on a knackered motor mount.



Cam belt slightly overtightened?


Have a careful listen at the front end of the motor and make sure your water pump is OK. Mine was on the way out, and the car started to sound more and more like a diesel as a result. A new pump has quietened things down nicely.


Do you think the noise could be valve gear? The noise can bounce around inside an engine and come out in odd places. I suggest you check the valve clearances before doing anything drastic.


I suggest you check the timing belt idler (tensioner). It just might be the problem. I think it can cause an oscillation or something that can wear or break the belt with disastrous results. So ... if you have any strange noise at the front of the engine that might be a bearing problem, change the tensioner! They are not expensive and not that hard to fit. Unless it's very new and low miles, you might consider a new belt at the same time.


Just an update on the funny noise situation....the damn thing's chewed up a timing belt after a mere 2000 miles. I haven't been able to get my torch down to get a decent look at the crank pulley yet but I'm guessing that's the culprit; I'll need to take it off to change the belt anyway so I can do more detective work then. But yes, there's a patch of 8-10 teeth that have lost their sharp edges and got very ragged indeed. Could have been nasty... Check yer belt regularly, everyone who doesn't already!

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