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MG MGB Technical - Noise when releasing clutch when engaged

1978 MG B GT

So I resuscitated my 78 B from my parents garage having freed up the fuel pump. Running surprisingly well as has been in there for nearly a year (thanks COVID). Brakes free too, everything seems OK. Until......

Once warm I have a grating noise while releasing the clutch/holding it on the clutch whilst it gear. Strangely only seems to be happening when warm, and it seems as though trying to wiggle clutch pedal horizontally side to side quietens it!

Having just done the clutch on my 71 sprite I have convinced myself this will likely be the throw out bearing friction plate and it mates on to the clutch plate.

Looked through the archives and it doesn't seem that I have an exact match to this symptom though

Any ideas how I can be certain its that, and how urgently I need to crack out the hoist? ;-)


JS neal

Basics first before taking the engine out.

If it's been sat for a year (or a number of weeks) it's going to need reason length journeys, at least 20 miles, of varying types of driving and conditions to get it back in condition.

How many runs and miles have you put on it since getting it out of the garage?

Obviously everything will need checking, starting with safety items first brakes, tyres, steering, suspension, lights/wipers/horns moving on to the much less important things like the engine. If the tyres were left on the car just as they were then take it easy with them until they loosen up.

Have you check the level and state of the clutch fluid, does it need bleeding or changing.

Checked the pivot of the pedal. With the help of a glamorous assist you could check checked the master cylinder push rod and it's movement and the throw of the slave cylinder and spigot arm under the car and perhaps shine a torch in to see the release bearing and clutch(?).

You should never have your foot on the clutch other than when pulling off and changing gear, no other times.

I'd also check the gearbox oil level and if it's not been changed in the last couple of years (or 24k-miles whichever is the sooner) and clean the o/d filters. (see image attached as a reminder).

Perhaps the rubber gear lever gaiter might be too tight and pulling on lever, easy to check just unscrew the retaining ring.

Got to go tea is up!



Nigel Atkins

Another thought, the flexi-hose.

With the pedal I was also thinking of the bush, and with pushrod also the clevis pin.

If you've not already looked you'll find loads of info on Paul Hunt's excellent site. - http://www.mgb-stuff.org.uk/hammertext.htm

(And I've now remembered to change my location back.)
Nigel Atkins

Thanks Nigel, all good stuff.

Been over everything else and its all surprisingly Ok. That said I serviced and lubricated most stuff that I could before it went away (I normally hibernate it oct-apr but wasn't banking on a pandemic!)
Fluid levels are all good too.

Gearbox oil - I didn't change or check so that sounds a good place to start.
Wasn't aware you can get visuals in situ on the release bearing either from under the car. Thats my Good friday sorted ;-)

In terms of the noise itself its most obvious when manouvering (i'e reversing) when you are riding the clutch somewhat

Cheers,
JN




JS neal

Is it a continuous grating noise while it's held down? Intermittent while held down? If you lift it up and press it down again is it quiet then or is it doing it every time?

Do you know if it's a graphite or bearing-type release bearing? This is my first thought, especially if affected by temperature.

The bit about wiggling the pedal could be misleading if the noise is intermittent while the pedal is held still. I could imagine the pedal pivot being dry and making a noise as the pedal is moving, but not while held still.

Personally I wouldn't be in any rush to do anything about it, I had a ball-bearing type that made noises various noises almost from the beginning for over 20 years before it finally broke up.
paulh4

JN,
sorry I might have mislead you, I'm not sure if you can the release bearing or clutch on a B (hence my bracketed question mark) but you could check all other stuff whilst under the car.

Gearbox oil (and o/d) is a 2-year/24k-mile service schedule change but often forgotten or ignored so the oil could be many years old if not decades (same with rear axle).

As the oil in the gearbox is normally engine oil it's not so robust in the gearbox so even more important for timely changes.

Best oil change is done with hot oil to get as much muck and existing oil out, and to leave draining as long as possible, cold drains as normally done won't get out as much existing oil and muck (same for engine and rear axle).

Best way to get the oils hot is to go for a good spirited drive first.

The o/d should operate almost instantly, and you don't fully lift your foot off the accelerator, or dip the clutch, when engaging or disengaging the o/d.

By coincidence a thread started on the midget & Sprite section about clutch drag basically because of possibly not being able to bleed the fluid and suggested pedal hole wear.

Hibernating the car isn't a good idea for the usual reasons plus you miss some of the best dry and sunny driving opportunities of the year and the carbs love the cooler weather.

As Paul has put and I suggested more driving may sort this or give more information but just riding the clutch can give noises anyway but especially if the clutch hydraulics or gearbox oil (gear lever bit?) aren't as they should be.

Another thought, is your tickover too high?

Have a read of the relevant Driver's Handbook, rather than a Haynes, or in this case workshop manual, and you'll get a lot of info and/or reminders.

Good luck, let us know how you get on.
Nigel Atkins

Paul - is intermittent it seems, and only really seems to be when letting the clucth back out after putting it in gear and pulling off

Nigel - too many cars is the hibernation story made worse by the pandemic meaning cant go out and drive at all let alone too little ;-)

Can't bring myself to sell this car either. I won it on eBay 10 years ago thinking I would never get it. Got it home and it had one owner since 79 and had original colour charts in the glovebox. Mechanically, it must have been maintained well as its still decent now. Body wise it had been rustproofed from new. Small hole in drivers floor and one castle rail tip had been patched. Door bottoms and bonnet tip gone so replaced those and preserved the rest.

Cheers,
JN


JS neal

That could well be a dry pedal pivot bush and spindle then, especially with waggling the pedal changing it. Not a difficult job once you have got the cover screws out!
paulh4

JN,
less (cars) is more (time with each). 😉

As Paul has pointed out a lot of servicing, maintenance and repairs just boil down to cleaning and lubing.

Give it a quick spray of something like GT85, better than standard WD40 (unfortunately GT85 was an English company but is now owned by the WD40 group as well as 3-in-1 as WD40 take over similar to Coca-Cola, Mars, McD, MS, ect.).

If that stops it or improves it you could do more there if you wanted, repair or replace parts (or just clean and lubricate and see how it goes on from that).

Guy on M&S (or is it S&M) recommends drilling and tapping for a grease nipple there (I'm not for adding any but reducing them to absolute minimum, but even less than that would be better to me).

Less cars, the more concentrated servicing and maintenance and better performance (which includes mpg, at higher speeds).
Nigel Atkins

This thread was discussed between 29/03/2021 and 30/03/2021

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.