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MG MGB Technical - MGB Race car axle breather

Has anybody got a good idea for a rear axle breather for an MGB race car?

Standard breather blows oil all under the rear of the car.

What I have fitted is a banjo fitting with a length of rubber pipe with a loop in it. It is better but still blowing oil out.

I had the same problem with my MGA race car, both fitted with plate type LSD.

What I am considering next is a longer length of pipe up into the boot, with a plastic bottle to collect the oil. Then it can drain back.

Any other ideas?

Colin
Colin Parkinson

If it's only splashing out then than your catch-bottle should work. But if a length of tubing with a loop still sprays oil out it sounds like it's under pressure, and your catch-bottle would have to allow that out - but where is the pressure coming from?

I can't really see why a race car would do that if it doesn't happen when a road car is driven with enthusiasm. It's not something I've heard of with track-day cars.
paulh4

Hi Paul, I had the same problem on my MGA race car as well. I put it down to the LSD somehow creating pressure.

Nothing to do with the thrashing it had at Anglesey the other day!!!

It is handling like an absolute dream.

Colin
Colin Parkinson

Interesting. I have had a plate type LSD for nearly 40 years in my B but havent had this problem. Use has been a bit of racing, a lot of (special stage) rallying, and even more driving with enthusiasm on many trips. And daily driver for a decade, with much road use for the other years.
The one problem I have had is the alloy diff housing spreading, after each major multi-day rally with 1000+ km of special stage. This changes the settings and results in CWP misalignment and whine. Which I figure would also increase heat production.
All of which makes me tend towards heat not being the cause. But I wouldnt rule it out. Maybe I don't try hard enough!

I wonder if cornering forces have an effect. They are higher on a track than anything legal on the road, and also higher than when rallying on gravel. In addition, most tracks have at least one turn which is lengthy, giving oil plenty of time to migrate away from where it is needed to where it might be a nuisance. And tyres now are so much stickier. Speaking of which, my track time usually doesnt involve sticky tyres as I am very happy enjoying the loose feeling of less sticky examples.



Paul Walbran

Colin,
oil low where it's required, heat, racing, and you being in Upper East Midlands for axle oil do you use your local blender in Brighouse?

My road use only Midget uses CRX (75w-90) NT+.

https://www.millersoils-shop.co.uk/motorsport-transmission-and-gearbox-oil
Nigel Atkins

Nigel, I have an account with Millers, and am using CRX with LSD additive, and there is plenty in.

I am putting it down to excessive corner speeds. Tyres are Yoko A008R. They seem to be quite sticky! So corner speeds are quite high.

I am out testing again on Monday at Blyton. Hopefully I can rig up a bottle on the breather pipe to collect the excess. At least it will drain back instead of coating the underside of the car!

Colin
Colin Parkinson

Sounds like too much oil, pipe it into catch tank and see if with that amount of oil removed it solves the problem next time. Repeat a couple of times.
Mike
Mike Ellsmore

Colin,
Mike beat me to it, (missed your post before) I find the car likes to find it's own level with fluids. I often find when I check the rear axle (all standard) cold, unran, that oil runs out of the filler/level plug hole yet it was fine at previous filling or checking (at exact same location).

Another query, you racey boys, how often do you change your car's oils and other fluids?
Nigel Atkins

Nigel, I assume the fill plug on the B is also a level plug? Some cars you have to measure. If you let it run out there is too much oil!

I must admit I havnt removed the plug when hot to drain off any excess. I might have a go at the track day on Monday.

But I have now fitted a rubber tube from the axle through the floor into the boot to a Girling brake fluid reservoir. It was what we used to do on Ford rally cars back in the day.

But I only just remembered that. It's an age thing!!
Colin Parkinson

Colin,
at least you remember, then of course you have to remember to actually do it. 😁

The filler plug hole is also the level, well on standard axles. The WSM says it's important not to overfill and to allow excess to run out. Also has that it's best to drain after a long run with oil still warm, I thought it was my unique original idea to do hot drains. 😁

Whenever I fill at the end I just need to add an ounce yet after that two ounces slowly drips out.

I don't follow the brake fluid reservoir other than as a container.
Nigel Atkins

Yep just a container Nigel.

Colin Parkinson

Colin,
I'm laughing at myself, I read the word reservoir and thought and applied it as master cylinder, even though I put reservoir (as I've just changed my integrated clutch master cylinder).

I was thinking that perhaps you'd rigged up a system to catch the oil throughh the lid of the master cylinder, measure it in the reservoir and then pump it back to the axle, and wondered how you'd done that with one tube/hose (valve). 🤣
Nigel Atkins

This thread was discussed between 11/08/2021 and 16/08/2021

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