Gearbox Leak

[Simon83]

I have this problem with my Austin, but I think it's the same as a MM so wondered if anyone could help. It's an 803 gearbox and has developed quite a leak from underneath. I took it for a run last night and am pretty sure I've found where it is coming from. I've put an arrow on the photo below to show it, but I can't tighten the nut up because somehow the threads are worn so there's no resistance.

I think I need to put a new gasket on it and then new bolts to hold it on - but am not sure if I can do it myself. has anyone here encountered this / got any advice?
Simon[frame][/frame]

[bmcecosse]

It looks like the side cover retainer ? But are you sure the oil isn't coming from the rubber bung where the clutch rod goes in - and just blowing back? The side cover is held on by studs (on later gearboxes anyway) although your's does appear to be held by screws. I suppose the thread may be stripped - I can only suggest trying a longer screw and perhaps dipping the thread in gasket goo before screwing it in. It won't be the gasket! I suggest you clean it all off so you can see where the oil is REALLY coming from![frame][/frame]

As you can see here -the later boxes have studs - perhaps because of this 'thread stripping' problem! In extremis - you could remove the cover - drill and tap a new thread hole in the box, open out the hole in the cover to match - and then refit the cover with a larger screw in that hole.

[Simon83]

Thanks for that. When you get up close it does seem to be studs with a spring washer and nut on the end. The only worry is whether the threads on the stud or gearbox casing are the culprit.

I went under the car and watched it for ages and saw the drip form and fall from that spot (in the photo) - on inspection it seems OK around the clutch rod.

I'm going to get it on a ramp tomorrow and have a good look as well as seeing if the nut is turning or whether it's actually the stud itself.

[bmcecosse]

Well - it likely just the nut has stripped. And that stud probably goes into a blind hole - the box looks very solid there. Gasket is easy enough to change - just don't lose these two springs - but I really do doubt it's the gasket.

[Simon83]

Thanks for the help - hopefully it is the stud. Bull Motif put me onto someone who does their gearboxes and he's sending me new stud. I'll have a look tonight to see which thread has actually gone and report back. (fingers crossed its the stud)

[bmcecosse]

Most likely it's just the nut on the stud!

[Simon83]

I went under it last night - had lost a lot of oil. After getting the car on a ramp, it is indeed a bolt. The threads on the bolt look fine so unfortunatly it must be the threads in the casing.

The only good thing is that the bolt isn't long enough to go right down to the bottom of the hole. If I can get a new bolt which is longer than the current one I may just have around 4mm of new thread in the casing which could possibly hold. Next problem is where to get a new bolt from? I'm sure it's a 9/16.

Have you any idea who sells them?
Many thanks again,
Simon

[bmcecosse]

Strange - because the later boxes use 1/4" UNF studs. I seriously doubt it's 9/16" !!!!!!!! I suggest that's what you do - fit a stud, with some gasket goo on the thread, right to the base of the hole (which I would have thought would be 'blind' anyway?) - and then put a washer and nut on the outside.

[alex_holden]

Perhaps someone has tried to screw a too-small bolt into it. What happens if you remove one of the other cover bolts and screw it into the hole that is leaking?

[Simon83]

Hi Alex,
I tried that - the bolt from a "good" seal is the same length as the one that's leaking and again just turns with no resistance. I'm putting faith into a longer bolt and hoping that I can pick up some unused thread right at the end. I've managed to find some and they should be here tomorrow / Saturday at the latest.
Simon

[bmcecosse]

If the new stud (better than a bolt or screw because you can wind it right to the base of the hole) doesn't do the job - then just drill and tap next size up. M8 would probably do it.

[Simon83]

Well I got two new studs and fitted them today. I nipped them up, went for a drive and it was still dripping. Then I gave them a slight 'nip' more and went for another drive - put some wood under and after 2 minutes of being back there were drips again.

I'm completely stumped now - what else could it be? It's still seaping from the stuf in the photo, running accross then dripping

[alex_holden]

I'd try replacing the gasket, perhaps with some Blue Hylomar too (belt and braces).

[Simon83]

Thanks Alex. Just been looking at how to do that - doesn't seem too difficult, I should be able to do it without taking the gearbox out I think. I'll see how that goes - can't think of anything else so hoefully that will sort it.
Simon

[bmcecosse]

Yes - you can take it off in the car - strange that it's leaking there - most unusual. Are you SURE it's not coming from the rubber bellows in front ??

[Simon83]

No it's definatly there. Every problem I have seems strange or un-common with this car haha. I will post my progress when I try the next step.

[Simon83]

I have some blue hylomar Alex - would you coat the studs in it as well?

[alex_holden]

No, just put as thin a coat as possible on the metal surfaces and both sides of the gasket, then allow it to dry tacky before assembling. I would use threadlock on the studs, to stop them coming out rather than to seal them.

[katy]

If you're going to pull the cover off to regasket it, it would be the ideal time to put a heli-coil insert in the hole w/the stripped threads. Either that or tap it oversize as bmcecosse suggested.

[MarkyB]

Might be tricky to avoid getting swarf in the gearbox which would be a bad thing.