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MG MGA - Brake Bleeding Problems

It's the last piece of the puzzle before my first drive and I can't put it to bed even after reading all the posts in the archive.

Let me first start by saying that John Twist did the rebuild of the master cylinder for my 59 1500 with drums all around. Therefore it's safe to assume it was done with the highest degree of quality.

While having an assistant pump the pedal I have great flow of fluid out of all four wheels and a huge burst from the clutch slave. I have been very careful to take my time at each wheel to do my best to work out all the air. No matter what I do, I am not able to build any pressure in the system.

I tried a vacuum pump system today (mitivac) without any luck. When I tried it on the clutch I was able to fill the bottle very quickly but it was as if I was blowing huge bubbles through a straw. I filled three bottles and was never able to reduce the amount or size of the bubbles. I wasnt able to draw much fluid through the brakes for whatever reason.

I'm dying to drive this car but it's tough without brakes and clutch.

Any practical ideas?
Jeff Bennett

Ditch the Mitivac (one of the most useless tools in my collection- it sucks air in from the bleed nipple threads) and get an Eezibleed. It's then 15 minutes work with a helper to bleed everything. Just make sure that you start with a full bottle, and check the level after each wheel.
dominic clancy


When I had a similar problem I had failed to snug up the brake shoe adjusting dogs. The brakes were working fine, but without the final adjustment the shoes would not reach the drums when the brake pedal was applied.

Once I adjusted the position of the brake shoes everything worked fine. I chased my tail for a couple of days before figuring out the problem.

If you are pumping out clear fluid and/or can not even pump up the brakes with several strokes of the brake pedal, it is likely that it is not the bleeding process but a mechanical or assembly issue with the master cylinder, brake shoes or the wheel cylinders.

Good luck!

jjb Backman

I agree with Dominic - I have used the gunson's Easibleed each time I have replaced a brake cylinder and each time bled most of the air out very quickly single handed - a second session with it after a day or so got rid of the last few bubbles that were trapped in the clutch line and all has been great ever since.
Cam Cunningham

Dominic & Cam,

The Gunson's is hard to find in the US. I can order it from the UK but it would cause me to keep the car in the garage for another week or so until it arrived.

If anyone can point me to a supplier in the US I would appreciate it.

John - I did install all new brake components so I am encouraged by your tip. I'll go back and tighten down the adjusters.

Jeff Bennett

I found a supplier in Florida. Should have it in a few days.
Jeff Bennett

Received the Eezibleed today. Pretty awesome tool! It worked great on the clutch but I'm still not holding pressure on the brakes. Not sure how that can be since it's all the same system.

When I have the Eezibleed hooked up and under pressure I have a nice firm brake pedal. Once I disconnect it, my pedal basically goes to the floor. If I pump the pedal once I do get some pressure. It's enough to stop the car but it's scary.

I don't know what else to do. I don't think it's a problem with air in the lines. I have bleed about 6 pints of fluid through the system. I checked all my brake shoe adjusters. I'm not leaking anywhere.

Why wont the brakes hold pressure? Any other ideas?
Jeff Bennett

I assume that you have checked the pushrod clearance at the master cylinder?
Surely it has to be the Master Cylinder?

Mick Anderson

Have you tried clamping the three flexible hydraulic hoses? If the pedal still goes to the floor it is a master cylinder problem.

Mick Anderson

Are you sure the non-return valve is installed properly on the back of the spring in the Master Cylinder? If the rubber plug isn't seated correctly fluid can bleed past it.

Joe Wiley

The pushrod clearance looks fine although I might be able to take it up a bit. I have I tried clamping the lines. I'll give that a shot today.

If the master cylinder turns out to be the problem I will be very unhappy. Paid $325 and waited two weeks for the rebuild.
Jeff Bennett

Had the same problem and it WAS the push-rod clearance. Drove me nuts till I figured it out.

Jeff, where in Florida did you order the Eezibleed from and was it less expensive than what Moss charges?
Andy Bounsall

A little dity:

If the shoes don't move
You must conclude
That the master
Is disaster
James Johanski

The Eezibleed is nice, but using the tire pressure is a pain. I rigged it up so it runs off my air compressor, setting the regulator to 20 psi. Just have to remember to disconnect the air before you unscrew the filler bottle :).

I did have this problem once, after installing a newly resleeved and rebuilt MC. I used the EZ bleed method, which has always been sucessful, and still I couldn't get solid pedal. Try removing the wheel cylinders and topiing them off manually and then re-installing them.

I ended up driving the car a bit, then letting it sit overnight, and the next day I had a firm pedal. I never figured it out, just chalked it up to "one of those mysteries". Probably just an air pocket that had to work itself out.
Mark J Michalak

Update -

I didnt have a chance to adjust the push rod today but I did clamp off the three lines. It had no noticeable effect on the pedal. I'll try the push rod tomorrow.

James, thanks for the dity BUT remember, the shoes will move enough to stop the car - in fact I can lock them up but I need to pump at least once or twice. The clutch works great.

Mark I did install all new wheel cylinders so you may be on to something. I will pull them all out, top them off and reinstall. Although I would think clamping down the brake lines would have isolated that problem.

Any logic to cracking open the bleeders just a little at each wheel and letting it sit overnight?

I'm also going to give John Twist a call tomorrow and see what he has to say.

Put 50 miles on the car this weekend with absolutely no trouble at all. It sure turns heads but I'm not sure if its the car or the look of total terror on my face as I try to stop the thing!!

Andy - check for the Eezibleed. Its about $40. I didnt realize Moss sold them.

Jeff Bennett

Do you also have new brake shoes and possibly turned the drums? I had the same symptoms with my 1500 when I rebuilt the whole braking system. I could pump it once and get a solid pedal, but if I released it and waited the pedal would go almost to the floor the next time. The problem turned out to be the radius on the brake shoes. In the old days when most cars had drums all around most brake shops had radius grinding machines for brake shoes, and the shoes were ground to match the radius of the drums. On mine I just adjusted all the brakes until they dragged slightly and drove it carefully until they wore down to the correct radius. I was then able to readjust the shoes to the correct clearance and the brakes have worked fine ever since.

Jeff Schultz


Yes, new shoes, rubber lines, etc. I did not turn the drums.

Thanks for the tip.
Jeff Bennett


Had the same problem with my 57. Spent hours trying to bleed the brakes. Turned out the old drums were worn to the maximum end of the tolerance. Put on 4 new drums, worked the first time, and was off on the road in under an hour.

From Boston to NYC Go Sox
R Egge

I'll add this important tidbit. After I did my novice rebuild of the master (but prior to John Twist doing a complete rebuild / resleeve) and prior to installing new wheel cylinders and rubber lines I had the brakes fully bled with a nice high pedal. It was easy to do. I had enough pressure to blow out a wheel cylinder with a big splash.

So the problem can't be the drums. I'll call John Twist in the next hour or so and post an update.
Jeff Bennett

The manual says the drums are 10 inches diameter and lists no maximum limit. I think the generally accepted limit is .060 oversize. New shoes are built to match the radius of the original drums. What happens when the drums are worn or ground oversize is that the center of the shoe contacts the drum first and then the shoe flexes giving the excessive pedal travel.
Jeff Schultz

So if you replaced the shoes in between when you had a good pedal and a soft pedal it could just be that the new shoes need to be radiused or bedded in.
Jeff Schultz

I talked with John Twist. He said based on everything I tried it must be the master cylinder and I should send it back to him right away. I have to give the guy credit - he doesnt mix words or make excuses.
Jeff Bennett

Please report back when John gets the the master and you get it fixed. I still have a problem seeing how master could cause your symptoms, unless the sleeve was undersize causing less volume in the cylinder. If you can pump the brakes and build pressure, that says the valve in the master is working and the holes supplying fluid to the piston are not clogged. If after pumping up it will hold the pressure, it says fluid is not leaking around the seals.
Jeff Schultz

Check the diameter of the drums anyway. Mine were fine before, after replaceing the cylinders and shoes, the drums were too small to work. I doesn't take long to look and you may be surprised
R Egge

Jeff - I still have a hard time believing John got the rebuild wrong as well. I'll be sure to post back the results and will measure the drums in the meantime.

The clutch does work fine. There is no leak in the system whatsoever.

I'll send the mc on vacation to Michigan and take a couple of days off from the car.
Jeff Bennett

Maybe a stupid question, but why are people paying $375 for a rebuild when new cylinders are available for the same cost and none of the problems? No sleeves, no leaks, modern tolerances all round, and all the other benefits of a brand new part
dominic clancy

I doubt anything was rebuilt wrong. Most likely the rubber seal was defective, and there's almost no way to know that before you install them. I have had bad rebuild kits twice before, so it definitely can happen.
Mark J Michalak

I never bothered to ask what it was going to cost. I may have bought a new one had I known. That's my fault.

It was $325. A new one is closer to $400 with tax and shipping. The new ones are probably made in Taiwan. There is something to be said for keeping English parts in the car.
Jeff Bennett

I received the mc back from John Twist on Friday. He did a one day turn around so I could have the car for the weekend which was nice.

I installed the mc, used my Eezibleed, and adjusted my push rods. The push rods took about 12 turns each!

The result was that the brakes work perfectly!

The question is was it the mc or the push rods? Wish I tried the push rod adjustment before I took the mc out in the first place.

My guess is it was both. I'm going to give John a call on Monday and ask him what he found, if anything. I'll post back here after I talk with him.

Thanks to everyone for their help.
Jeff Bennett

This thread was discussed between 02/05/2008 and 11/05/2008

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