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MG MGB Technical - Sh, sh sh noise
|Have a sh sh sh sh sound from somewhere between engine and gearbox. Increases/decreases with speed of car. The same when engine is running in gear or out of gear. Same noise when engine turned off and coasting forwards or backwards - what could this be? Spigot/pilot bearing, speedo cable? But speedo works smoothly...Moss|
|My girlfriend makes noises like that when I complain about all the dodgy drivers on the road when we're in the car....|
Does the noise go away when you engage the clutch? From your description it sounds like it is there all the time?
|Do you have front disc brake rotors with holes &/or grooves cut into them? |
I have a similar noise which appeared immediately after I installed these rotors. They came with two disclaimers: that it would take 300-500 miles to fully break-in, and that this type of rotor could always make "some" noise. I'm not through the break-in period yet so I'm hoping for better results eventually.
If a brake pad is not full retracting from the Brake rotor, then it will make the sound that you describe.
|Check the driveshaft bolts, and u-joints. Make sure that nothing|
is rubbing against the driveshaft (ie: speedo cable).
I know that the sounds seem like they're coming from the front,
but I'd also check the rear brake drums (ie: brake drums rubbing
against the backplate, or brake shoes adjusted too tightly).
|Easy way to check front or rear brakes. Apply handbrake, if noise is still there apply foot brake.|
If noise is still there it ain't the brakes
|Thanks for the comments. The noise is constant when the car is in motion - either going backwards or forwards. I have changed the brake discs, pads and wheel bearings at the front. Same with regards to rear suspension at rear (leaf springs, bushings, drop links, u-joints etc.) Rear brakes are checked and adjusted. Have checked brakes - its not the breaks!! Does not go away when clutch engaged/disengaged. Driving me crazy...It is probably something really simple - like speedo cable rubbing on something, a loose scew/bolt...|
Have you checked the tires to see if they are rubbing on something adjacent?
|J. E. Guthrie|
|My '63 MGB. Same sound. Speedo cable. Some day I'll get around to it.|
|Greg Van Hook|
|It's not in the location you suspect, but problems with the spokes in wire wheels can make some odd noises. If it will do it at a walking pace, you could walk next to it and listen.|
|C R Huff|
|Thanks everyone...tried at walking pace, had people sit in the car hanging over the doors to listen etc. Going to disconnect the speedo at weekend - determined to find problem...I'll let you all know the result. Regards Moss|
|Speedo cable would be easy to eliminate by temporarily disconnecting it at the gearbox end.|
|Hi again chaps...it is not the speedo cable...!! Unless...could it be the angle gear thingy sticking out where one screws the cable in place. A bit odd as it rotates and there is a small brass screw which one can tighten to stop it rotating....|
|Actually its more of a shk shk noise. Cannot work it out...taking out the engine and transmission in October. Rather excited about what I find. Moss Denmark|
|Tried securely raising the rear off the ground and running it through the gears?|
|Switch off the heater fan, could be a leaf or similar in the impellor.|
|Paul H, sounds like a good idea - where does one put the stands - under the side members?|
AG, not the heater fan - Hoped it was, thanks for the suggestion
I really don't mean to be insulting, but you have indicated that you are inexperienced. If you don't know how to safely block a car up in the air, you should try to find a knowledgeable friend who does to give you a hand with it.
If you have no such friends, try putting a set of axel stands under the axel tubes, and then don't get under it while it's running.
|C R Huff|
|Exactly as Charley says, particularly the bit about not getting underneath it! If you want to listen to diff, hubs etc. use a loooong listening stick!|
|No insult taken - just asking out of interest. Of course the axel tubes either side of the dif about half way acroos is the obvious place. Its where all the motion takes place(inside the tubes and out to the wheels!)Its the classic 'know lots of theory - but putting it into practice is something else' scenario...And yes I will use a loooong listening stick...very loooong|
|"either side of the dif about half way acroos"|
I'd have said right at the junctions of the tube and the diff, and the tube and the back-plate. That's where the bearings are, and I'd expect to hear more noise there than in the middle, also get a better idea of which end it is, if any.
|PaulH, I'll remember that when I go ahead and 'road test'. I was unclear in my response thread - I was refering to placing of the stands, not where the noise comes from. Its a very odd noise - still seems to be coming from the front between gearbox and engine. Just can't fathom it.|
|Ah right. Those should be as far outboard as possible to minimise the stress on the tubes.|
Just remembered a similar thing years ago. Check your rear brake shoes to see if the spring that holds the shoes in place has disappeared.
|This could be as simple as the carbon throwout bearing rubbing against the pressure plate. It might be binding in its linkage and not retracting all the way. RAY|
|The release bearing *always* rubs on the pressure plate, or it should be. It's only the pressure plate that pushes the slave piston back into its bore, and that is against a spring inside the slave cylinder. This spring takes out any play in the linkage as well as keeping the release bearing pushed up against the pressure plate. It's what keeps the clutch biting point consistent as the release bearing wears down.|
*Could* make a noise, but the original poster says the noise changes with *car* speed, not *engine* speed. Easily eliminated as a possible cause by knocking it out of gear, releasing the clutch pedeal and switching off the engine.
|While you have the car lifted up, check the stamped metal ring|
that is just behind the rear driveshaft mounting flange.
The manual calls this part a "Dust Cover".
This part is merely pressed on to the mounting flange and
once in a while (although rarely) it can wriggle loose and then
rub against the rearend casting as the driveshaft is turning.
|Thanks for all the input - yes, the noise is 'car speed' associated - whether the engine is on or not. And going forwards or backwards, in or out of gear, clutch depressed or not depressed...the noise is loud enough to be annoying in fact. At speeds of 40 mph and over it becomes a whine...for me its as though there is something spinning round and rubbing/knocking on something else. Have tried to find the dust cover but can't see it....|
|An extension to my thoughts on jacking up the rear and running the gearbox and axle, is to raise just one wheel at a time. That way if the noise stays at the same rate, and with either wheel spinning, it has to be the gearbox, propshaft, or axle input shaft. If the rate doubles, and is only on one wheel, then it must be a problem with that side of the axle.|
You don't have something wrapped round your prop-shaft, do you? :o)
|Hi PaulH, nothing around my prop. I checked almost everything apart from road test with rear on stands and the rear wheel bearings - I've had the rear drums off as well and appears to be plenty of clearence when wheels rotating. |
Have to admit not sure anymore where the noise is coming from - from the front of the gearbox or rear of the car - all very confusing!! Of course could take it to a mechanic but here in Denmark this is VERY expensive and classic cars are rare (not really a car culture as in the anglo saxon world - 180% import duty on all cars.
My help is arriving at the weekend in the form of my Dad - so two heads better than one. We're going to take the engine/gearbox out and look at a few things -the clutch/realease bearing needs changing, and while we're at it do the road test. I'll keep you updated...
If it were my car, I wouldn't remove the engine and transmission unless I had determined that the noise was coming from there.
|C R Huff|
The release bearing or spigot bush needs replacing at any rate. Rattling noise when clutch pedal comes up, disappears when pedal pushed down to the floor. The shk shk shk noise is a seperate issue...or maybe its all part of the same. I am determined to find out!! It will be a busy week in my 'workshop'...
Ah, well, if it needs to come out for other reasons anyway, then it isn't wasted work. However, once you take it out, you cant reproduce the noise. I thought you said it did it while rolling with the engine shut down, so it seems like that would eliminate the engine as the source of the noise, but wouldn't eliminate the trans. If the noise was from the trans, I would want to know it before taking things apart.
I saw the pic on the engine removal thread. That is a very pretty car. Somehow I envisioned that you were working on some old neglected beater.
Any chance that the missing engine/bell housing bolts are causing the problem?
|C R Huff|
Yes, the car is very pretty, but looks can deceive - I hope that I can find the cause of the 2 problems - the rattling from the clutch and the shk shk noise, - the latter occuring as said when engine is turned on or off when in motion.
I also think there is a carb issue (weber 32/36 dgev) - drives well up to 4500 revs (70 mph)but engine won't accelerate beyond in 4 th gear - think the vacum advance is non functioning or the second port is not opening...but this can wait til the other issues are fixed...
|Vacuum advance *should* only come into play for cruising economy. When accelerating there should be little or no vacuum advance, but if faulty it could be letting air in and so affecting the mixture all the time. Easily diagnosed, simply disconnect the vacuum advance pipe from the carb or inlet manifold port and plug that port.|
|Check the prop shaft where it passes through the tunnel, there are two bracing panels at the handbrake location. If the rear one is installed backwards, it just touches the large dia part of the shaft. Just found that out having put it in wrong sometime back. This is for the 1600 with the sliding shaft.|
|Sorry, that was for an MGA. Maybe it is the same situation though.|
|Update - shk shk noise! The cause...no bearing spacers in the hubs (between the inner and outer wheel bearing racers)...and no shimms. No wonder I could not tighten up to the required 60 psi torgue!!|
|Should be 40 ft lb minimum then to the next split-pinhole which should occur before 70 ft lb which is the maximum, and you should still have just perceptible end-float i.e. a little wobble in the hubs. Without spacer and shims you should have been able to achieve the torque, but the bearings would have been binding badly!|
|Exactly - but I did not know about the bearing spacers - or rather I did but thought they were in the hubs and were 'built in' and therefore not possible to take out. They were not in the hub. With regard the shimms I thought, well, the car was bought from a professional mechanic so he must have known what was what...as it turns out he did'nt. Far from it!|
|A professional is someone that *might* know the correct way to do something, but will probably do it in the quickest and easiest way for him.|
|Indeed- apart from the fact that the shk shk noise was so obvious that one wonders...(it was there when I bought the car). Anyway the problem is solved and I'm the wiser...|
This thread was discussed between 07/09/2010 and 13/10/2010
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