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MG MGB Technical - Whine - High Pitch

Hello Friends,
have been busy following up on all the tips last fall and have the 72 mgb roadster driving, looking and running pretty good. Got the front end re-built, all maintenance performed, tuning et. Also put in a new interior.
A couple remaining items:

1. Putting the interior in caused me to drive to car for the first time with the top up. There was an anoying high pitched sound. Can't be certain if it was rear end, gear box or engine. Seemed to be most noticeable as I took her on the highway and seemed to start at about 40 mph and get worse. Darn near give you a head ache. Seemed to be associated with hitting the gas or letting off. As you excel, more pronounced. Any ideas? What should I check?
I did change the rear end lubricant and it looked fine. No shavings or miscelaneous debris. Topped it off with new 90 weight gear oil as recommended.

2. On the carbs. Looking at the engine from the driver side, the left hand carb has a hose coming off the side that just hangs in the air? What is this and what should it be connected to?

3. Since this is hiostorically registered and exempt from emissions, is there any value or benefit from eliminating the emissions control junk? Easy to do? Any good references on what to plug and how to accomplish if you think this is a good idea?

Best regards,
Doug
DT Toms

The DIY Guide to mgb restoration has a whole chapter devoted to emissions control removal. But--before you do it--do you really want to add to the pollution already being spewed by older vehicles, trucks and busses? You might see a bit of increase in performance--but the B isn't exactly a rocket in it's best form. I'd buy or borrow a good manual, get all the hoses hooked up correctly and see how you like it as it is. As for the whine--could be anything, from a bad gear in the rear end to a failing alternator. Might even be a whistle from that open hose.
R. L Carleen

R.L.,
I agree to leave well enough alone with the emissions if there's not a good reason to remove. If you said this set of hoses and tubing is a pain to keep maintained and easy to remove, then I would remove.

On the whine, the generator could be a culprit I hadn't thought of. That would be easier to fix than a gear in the rear end.

Darn thing is, it wasn't apparent until I drove it with the top up. :-), Maybe I just drive with the top down LOL.

Do you have any idea where this hose is suppose to be connected?

Best regards,
Doug
DT Toms

The hose is probably the carb vent hose. It needs to stay open and unattached to anything. If you suck on it lightly with the engine running, does the engine stall? If so, it's definately the vent hose!

Did you grease your u-joints before you took the car out? Is your rear axle full with fresh 90w? Is the tranny full of 20W50? Are the front wheel bearings properly adjusted?

As a side note, I took my first 50 mile drive after restoring my '71 last week. I had a horrible squeek in the shifter area when I came to a stop with the clutch pressed in. Turned out to be a screw for the shift boot retainer that was too long and rubbing on the top of the transmission. I got the new screws from Moss! I guess you never know what you'll find!
Jeff Schlemmer

FWIT, driving with the soft top on my MK11 always has me hearing more of the rear-end sounds than with the top down. Having said that, its surprising how a soft top manages to magnify all sounds as well as produce some of its own.
Regards
Roger
Roger T

Yes, the soft top amplifies mechanical noises. If you think the soft top does it well, try a factory hard top. Even louder.

As far as the whine goes, you need to determine if it is rear wheel bearings or the diff itself. Is the whine consistent at all speeds and on or off throttle. If it never changes when you accelerate or deccelerate and simply varies with speed, look at the rear wheel bearings.

On the other hand, if it varies with load, i.e. the noise on acceleration is slightly different than the noise on decceleration and maybe even goes away in a no load (neither on throttle nor off throttle), I would look at the diff itself.

If it turns out to be the wheel bearings, pay close attention to the directions for installation in the Bentley's manual. You MUST pack them with grease when you install new ones, regardless of the logic that tells you there is 90 wt. gear oil in the diff and they should be OK. They won't be and you will be replacing them again soon.
Richard Smith

Engine noises can be easily eliminated when the car is stationary so the first task is to eliminate these. However the roadster is a very different car hood up to hood down and rear end noises become very apparent with it up. A Hypoid gear axle typically moans starting at about 40 mph when under load and this could well be your problem. It's very much something you may have to put up with.
Iain MacKintosh

Thanks for everyones responses.
I have addressed the differntial lube and gear box lubes during the maintenance this winter.
Also, repacked all wheel bearings.

Sounds like it could be a differential noise, but minor and something that is somewhat normal for the year and age. It does get worse with load and less without load. Since it seems minor and normal to some degree, I will leave well enough alone.
Aws far as the carb vent hose, sounds like that is ok as well. I am just used to thinking most hoses go somewhere :-).

Thanks a bunch.

Best regards,
Doug
DT Toms

It's the gears in the rear. I had the exact problem in my 66 and after installation of another pumpkin the whine disappeared. The old gears were shot.
Mike MaGee

Maybe take off the battery cover and drive the car so you can hear if it's the diff.
That's haw I discovered where the whine was coming from on my B.
Samuel Sullivan

This thread was discussed between 16/05/2005 and 22/05/2005

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