• Hi Guest!
    If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

MGB-GT Spongy Brakes on my 70 GT

Share this page

RickB

RickB

Yoda
Offline
About a week ago (after topping up the brake fluid) the brakes went all soft & spongy so I parked the BGT and brought Frankie out of mothballs.

There's no fluid leaking anywhere so I'm afraid its the MC.

If so - what's the general wisdom?
Replace it? Rebuild it?

Where do I get parts or a good new or rebuilt MC?

I'm not in any rush, I've got a Midget that runs great and the weather is turning better.
 
It happened when you topped up the reservoir? That can't be coincidence. Did you use the same type of fluid? Regular fluid does not mix well with silicon. Was the fluid really low? You may have forced some air into the lines.

If your MC is not pitted, you can rebuild it easily yourself with a few dollars worth of parts. If it's pitted, you will need to either replace it or have it sleeved.
 
It wasn't 'really low' but maybe 75% - 80% full.
The old can of fluid the PO gave me was DOT3 so I bought new DOT3 for topping up. Maybe the old had simply sat in there too long and I upset the stability of the system.
Maybe taking the cap off (was very tight) caused something to give.
I've rebuilt them before. Replacing sounds much better unless they are made of gold plated unobtanium.
 
check the brake hoses (one at each front wheel, and one at the rear axle). They will deteriorate from the inside out. sometimes you won't notice them leaking. Also when they start going bad, they flex (swelling outward under pressure) and then the brakes feel spongey. If they are bad, replace the rear brake cylinders too - they are cheap enough. Was the reservior completely empty? Might have gotten some air in the lines.

Just a few thoughts.
 
Back
Top