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MG MGB Technical - Like pinking but not pinking

Hello everyone,

I have started experiencing a ticking noise which happens under all the circumstances when you might expect to hear pinking noises. Putting your foot down hard on the gas brings it on – easing off relieves it. Driving uphill brings it on – changing down relieves it.

However it is not the (unmistakable) jingly sound of pinking, rather a metallic ticking.

Now then.. some pointers.

I have recently replaced much of the ignition system, including points and condenser (and setting the gap), plug leads, plugs and distributor cap. I also had a look at the timing and even backed it off slightly to no avail. Even when I backed it off to the point where tickover was down to 500 revs the problem didn’t go away. This made me think it wasn’t pinking.

I have also replaced my fuel pump (noisy cylindrical Facet) and I can see that there is a good supply of fuel to the carbs. The mixture is good (light brown plugs) and there is enough oil in the dashpots. Again helping eliminate pinking.

I have lost my compression tester so I can’t test this until I buy a new one but there doesn’t seem to be any oil smoke in the exhaust so hopefully I haven’t broken a piston ring.

It is impossible to check the source of the sound with a stethoscope because the problem does not occur when the vehicle is stationary. Parked up, the engine sounds lovely. It is only when the car is moving that it happens.

To me this seems to indicate either drivetrain problems or that it is actual load which induces the sound?

Also, I don’t know if I am imagining it but the sound seems to be coming from behind me.

I have seen mention here of UV joints and pinholes in the exhaust as possible contenders but are there any others?

Would you guys drive your MGs in this condition?

Thanks for any pointers,

Alec
Alec

I forgot to say, I also checked the valve clearances and they are all good.

hmmmm.
Alec

Sounds to me like exhaust manifold gasket or one of the downpipe joints. Check first to see if all bolts are tight.
Iain MacKintosh

Hi Alec.

It just might be the speedo cable.
As they wear the inner can rattle within the outer, also the outer can rattle against the rear of the engine, which might be more pronounced as the engine vibrates on it's mounts under load.

Don
Don

Iain, Don,

thanks for those. I haven't recently untightened anything which might have caused me to induce a leak into the exhaust system - I don't think - but I think you are right that it is well worth me checking this, along with the whole exhaust system. What is the best way to check for leaks?

I will also have a look at the speedo cable issue as well - at least I can check by eye to see if the outside is contacting with the engine at all. As to whether it is worn I can test by replacement.

In the long run I don't suppose I have much to lose by buying new UV joints and replacing them anyway I suppose. (Unless I really fugg it up).

Thanks again,

Alec
Alec

What you describe sounds very much like a UJ beginning to break up. Get underneath and check them both for wear - at each UJ hold one of the yokes and try to move the other, any play means the UJ is dying.
Miles Banister

In my experience u-joints will not produce the type of sound described. Worn u-joints make their appearance on initial acceleration and deceleration and make a thunk. A worn joint also is generally accompanied by a vibration which should be felt through the shifter and possibly the rest of the car. I may be wrong however.

To solve this problem you must ascertain if the noise is at engine speed or tranny (driveshaft) speed or wheel speed. Does the sound change when shifting to another gear? Figuring this out will help you diagnose where the noise is coming from.

Check your motor/tranny mounts and exhaust mounts too.

Mike MaGee

Miles, Mike,

Thanks for your help. I haven't yet got under the car to check the universal joints for wear/play. I suppose until I do I have no business driving it around. I did take it up the road earlier however to try and listen better. It certainly doesn't seem to be making a thumping sound, rather a rythmical ticking. As to whether it is at engine/transmission/wheel speed I didn't work out. Shifting down a gear, rather than speeding it up often made the sound disappear (much like pinking) so it was not possible to tell whether the speed was related to the engine speed.

I haven't discounted anything yet but for some reason I suspect that an exhaust leak may be present. Quite why this would change with engine load I don't know (hopefully someone can explain). However, another thing I noticed earlier (despite my earlier post) is that, even when the car is stationary and out of gear, when you first put your foot on the gas the engine response isn't quite instantaneous. Rather there is a brief half second of flatulence before the revs pick up and then it sounds fine. Maybe this could be related to an exhaust problem too.

It is difficult for me to tell whether this ticking problem is affecting the performance much because I have spent the whole time backing off the gas.

Thanks for your continued help. I'll give the car a good inspection tomorrow to see what else I can find.

Alec
Alec

Does this noise happen when the engine is cold, or all the time? If it doesn't appear when the oil is thick, the rod bearings could be suspect. I notice a bit of a similar sound to pinking when my car has thin oil and hot besides. The oil pressure is not enough to keep my rod bearings from clacking under heavier load if I don't put 20W50 oil in in the summer.

The noise doesn't sound like it's coming from the rear, though. But it does sound similar to preignition (pinking).
Tom

Thanks for the suggestion Tom.

The noise is there right from cold so maybe not quite the problem you describe. The engine was rebuilt a few years ago so hopefully there isn't too much wear and I have been regularly using STP oil treatment. I don't think I have over-filled the engine either although it is reading MAX on the dipstick.

I hope the engine isn't worn in any case.

I tried to buy a compression tester in Halford's yesterday and you should have seen the dumb expression on the kid's face. Like the time I tried to buy a timing light. He just said, "What for exactly?". I said, "er, to check my..................timing". He just looked blank.

With a bit of luck I will have more to report tonight.

Thanks again,

Alec
Alec

Alec, The reason I suggested a UJ was that I had something similar a few years ago. It sounded just like pinking and even went away when I lifted off the throttle. It drove me crazy for weeks and in a final attempt to fix it I ended up retarding the ignition so much that that I could hardly beleive it would still run. The breakthrough came one day when I was driving with the roof open (it's a GT and it was winter) and I realised that I could hear it faintly during left but not right turns (it might have been the other way round). Then I knew it couldn't be pinking. When I checked the rear UJ the play was barely perceptible, but it was present. When I stripped that UJ it was totally dry and a couple of the rollers had broken up. Now I have UJ's with grease nipples !
Miles Banister

Thanks again Miles.

Where exactly should I expect to see any play manifest itself? Is it missable if its there?

Thanks again,

Alec
Alec

I agree with Miles. The UJ is a very likely culprit. Without hearing the noise, it is difficult to tell but another possibility is a loose timing chain. It would also get noisy under load and the noise would go away as the load is relaxed. Unfortunately, it is not easy to get at.

Karl

Thanks Karl,

I have been looking at the prices of replacement UJs just in case this turns out to be the culprit and I see there are 2 kinds - sealed type and greasable.

Which is recommended? Miles, you went for greasable - is this a better choice?

Thanks,

Alec
Alec

OK,

I have just been under the car and had a look at the prop shaft. Shaking it left-right and up-down gave about a milimetre (maybe 2 at the most) of play. The back UJ made more of a clonking noise but the front one made a much more metallic clang, which, if my ears aren't playing tricks on me sounds similar in pitch to the sound I've been hearing.

S'pose I've got nothing to lose by ordering a couple of replacements and fitting them at the weekend If the weather holds.

I also had a look at at all the nuts on the exhaust manifold and they seem secure, although this doesn't mean there is no leak at all. I also looked under the car while it was ticking over (briefly) and could hear any strange noises coming from anywhere on the exhaust.

I'll try replacing the UJs and see where that gets me.

I'll let you know.

Thanks,

Alec
Alec

The u-joints should have ZERO play. That should cure at least some, if not all your noise, as well as some vibration.
Jeff Schlemmer

Alec I heve come across a noise like you discribe a few times over the years on early lucas starters. Is your car an early B with bendix type starter? If it is it is most likely to be a broken return spring in the bendix assembly. Its a very light spring that holds the pinion away from the ringear. Under acceleration or going up hill the pinion brushes the ring gear and tinkles. You can sometimes check it by just touching the starter while it is making the noise and it may stop for a second or two. Denis
D M HILL

Alec,
The best way to check for wear (imho) is to grasp one yoke in each hand and then try to twist them against each other, in both directions. If you can feel any play then the UJ is on the way out. Shaking the prop shaft might not pick up the earliest signs, but it sounds as though you're on the right track.

The first time I did my UJs I used the sealed ones, they only survived a couple of years and in fact it was because I'd replaced them so recently that it took me so long to realise they were the culprits. The second time I went for the greasable ones so that I could give them a squirt now and then.

When you fit your new ones, be sure to check that they move smoothly, that the grease nipple doesn't get trapped, and that when you grease them the grease comes out of all four arms. I found that after pressing in the last cup one of mine was little tight and I had to press from the other side to ease it. The job isn't too difficult and can be done with an ordinary vice, a suitable sized socket as a press tool, and a big hammer to get the old joints out. Make sure the holes in the yoke are nice and clean before fitting the new cups.

Good luck, let us know whether or not that solves the problem.

Miles.
Miles Banister

Denis, my car is a 72 and the starter is the 68 onwards model so maybe the spring you mention isn't the cause here. The sound I hear is slightly lower pitched and percussive than "jingly", if you know what I mean. Thanks for that suggestion though - it is worth bearing that one in mind.

I have to admit that I was shaking the prop shaft rather than twisting but if, as Jeff says, there should be zero play then I will go ahead and change them both. I'm away in Paris this weekend (by train, not MG) so I'll have a shot at fixing it early next week and let you all know.

Thanks again,

Alec
Alec

This thread was discussed between 30/08/2005 and 01/09/2005

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