MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Diff Leak

I noticed when draining the diff that there is oil seeping past the cover. It's not much and no oil is dripping onto the garage floor. Is it worth replacing the gasket?
Rod Merrall

Have you checked that the breather valve is clear?

Nice to see you're giving the car a full service check.

I don't know if it'd be worth changing the gasket but if the leak isn't that bad you could perhaps leave it for now whilst you'll probably find other work that needs doing on the car.
Nigel Atkins

Yes breather is clear, first thing I checked.
Rod Merrall

The gasket may have given a bit, you could check the tightness of the securing bolts, give it a cleanoff and recheck later on
William Revit

It's either leaking, or it isn't!!!
If it is replace it, it will only get worse and not a difficult or expensive job.
Removing the cover will give you the chance to clean out the bottom of the diff housing.
Allan Reeling

Rod,
if the leak isn't bad, I favour as Willy has put, a quick clean outside to be able to check it later and checking bolts because I think it's best to be driving the car as much as possible to iron out the wrinkles and find and sort any issues.

I'm all for a full 36k-mile service and checks being carried out but as a rolling thing between driving the car.

Allen's idea of sorting it now and cleaning inside is good as long as it doesn't hold you up too much from other work and driving the car and take you down a rabbit hole of distraction.

I take it replacing the gasket means the area remains leakfree for a good while. I don't like leaks but find you can soon get into diminishing returns trying to completely stop them all.

As my car is outside I have to wait for good weather to service or sort my midget but if it's good weather I want to be driving it and resent working on it.
Nigel Atkins

If it's not dripping then leave it, other than checking bolts. But don't over-tighten them or it warps the cover and causes leaks. It would be nice to have everything oil tight and spotlessly clean but with cars this old - and British dare I say - that's rare. It could be coming from the drive flange oil seal and running back, so at this stage I wouldn't do anything other than clean it off between those two area and see where it develops - if it does.
paulh4

I've been thinking about it overnight and I think I'm with Allan. I don't use the car in bad weather so it is off the road at the moment so no time pressure. I'll check the bolts first though.Thanks for the views.
Rod Merrall

I forgot you are up in the frozen north so if you have the car off the road anyway then get as much servicing maintenance work done as you can. But I think thorough oil changes need to be done with the oil hot (and left to drain as long as possible) but if your taking things apart you can at least clean inside the diff.

Not so with gearbox and o/d and engine so perhaps some sort of flushing fluid in each as the car is new to you. Even if you take the sump pan off (a bit of a PITA anyway IIRC) and rocker cover you miss the middle bits.

A good thorough clean of the engine bay and underside of the car will help with seeing when weeps and leaks appear (otherwise known as chassis preservation).

Good luck with your preparations for an early and warm spring.

Nigel Atkins

Two schools of thought with engine flushing - the second is that if the engine has suffered from poor maintenance with the PO flushing can dislodge crud that can block oil ways. The top of the cylinder head under the rocker cover is a reasonable guide.

If the gearbox oil comes out black and with bits on top of the OD sump filter then yes it probably does need flushing - at least, but not otherwise. Whereas with the engine you can use a pre-change flush treatment like Forte as far as I'm aware the gearbox needs to be drained, refilled with your chosen flushing fluid, drained and refilled again.
paulh4

Good points Paul, I should have put - some sort of flushing-fluid/oil - and perhaps expanded on explanation.

If things look really bad caution will be required but you'd probably need to do a lot more work than an flush clean and oil change.

There were different types of flushing oils but they seem to be down to just the add to engine oil types but you could use other, perhaps thinner oils and chemicals to flush clean.

For engine, gearbox and rear axle for a gentler and easier cleaning and flushing you could use a cheap (or even good quality) oil for say just 50-1,000 miles and then do a hot and leave as long as possible drain and refill with the oil you intend to use. Again this methods gets the car used and new owner enjoying and learning about the car.

On oil changes I do the hot and long drain and towards the end of the drain pour some warm(ed) fresh oil in to act as a bit of a flush and leave that oil to drain fully whilst I have a mug of tea (I'm not into doing stuff in record times). It's quick and easy and not (too?) expensive.
Nigel Atkins

In the light of all the comments I'm persuaded to leave it.I checked the bolts and they are all tight. The car is not new to me Nigel; I've had it for 5 years and it is in great condition.I bought a car that did not need work because at 76 (now) I did not fancy crawling about on my back on a cold garage floor. So what am I doing - crawling about on a cold floor!

I was about to say I have serviced it regularly but when I looked at my log (I write everything down I do to the car) I saw to my horror I haven't touched it for 3 years. Tempus fugit.

I will now go over every inch of the car before spring!

I will probably be back with more daft questions because I like to do things right; bear with me.
Rod Merrall

Sorry Rod, for some reason I thought the car was new to you, my memory isn't the best.

I got a couple of physical issues from spending hours in a very cold unheated garage this December so even I will remember never make to make the mistake of working in one again.

Three years without servicing, tut. :)

There are no daft questions. I just wish I could remember more of the answers.
Nigel Atkins

This thread was discussed between 03/02/2020 and 04/02/2020

MG MGB Technical index

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