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MG MGA - Brakes, need to pump them.

Pulling out all my hair!

Replaced the Master brake cylinder, and all the wheel cylinders on my 58 MGA 1500.

Found all the leaks (I hope). We spent lots of time Sunday trying to get the system up and running with no luck.

If we pump the brakes it will take 2-4 pumps to build up preasure (the preasure holds well) if we release and repump 1-2 to goo preasure. IF we wait a minute 2-4 for good preasure.

Do we have a leak?

Do we need to continue bleeding (if so does anyone have a bleeding procedure?)

Thanks

Russell
R Egge

You either need to bleed more, or adjust the brake clearance, or both.

The best method I found is pressure bleeding. A pressure bleeder has a cap for the master that has an air fitting. You pressurize the master to about 10lbs and then open the bleeders one at a time. Some people get good results from vacuum bleeding, but I had problems with vacuum leaks around the threads of the bleed screws.

I had the same problem after installing a complete new brake system with new shoes and turned drums. I was only able to get the proper pedal feel by adjusting the brakes so all the shoes were dragging. If I loosened them so they didn't rub, I needed to pump them like you describe. I finally adjusted them so they were dragging slightly, and drove it a while. I was then able to adjust them properly with good pedal feel and no pumping.

Jeff Schultz

I think it might have been Jeff that solved a similar problem for me several months ago. It indeed was the micram adjusters. I'd had several "issues" including a bad master cylinder and had forgotten a few other adjustments I had made in the process. Turns out the shoe adjusters had been backed off while tweaking things and resulted in some long travel of the pedal.

However, the pumping part was when I had the bad MC. I would say that if you are getting good pressure and a firm pedal after pumping it several times then there is air somewhere in the system. If it is simply long travel but w/ no firming up of the pedal, then probably shoe adjustment.

I concur w/ Jeff about pressure bleeding. Despite the voices of the diehard traditionalists, pressure bleeding is the way to go, especially with the clutch. Just make sure you watch the fluid level in the MC, otherwise you have to start over again.
Jake

Even with pressure bleeding, it is sometimes very difficult to get all the air out of the wheel cylinders. If you take a critical look at the bleeder nipple, you will note that it bleeds the lines, but not the cylinders. On both our TD and Magnette, I have had to prefill the wheel cylinders with brake fluid before the brakes would bleed all the air out. You can pre fill the cylinders either by removing the shoes and then the pistons and pour fluid into the cylinder , then replace the piston, pushing the excess fluid back into the lines and M/C (it is necessary to rotate the one front wheel cylinder until it is pointing up to do this). The alternative method involves removing the banjo bolt fromt he back of the cylinder and shooting fluid into the cylinder with a syrenge, then reconnecting the banjo bolt. Both methods are messy, but will get all the air out of the system. Good luck - Dave
David DuBois

Back when I was a young man and drum brakes were common the usual procedure in our shop was to adjust for a light drag. Because most new shoes are not radiused the same as the drums the first point of contact is usually very small. If you back off the adjustment too much it takes a lot of pedal travel or a pump or two to make good firm contact. It does sound like you still have an air bubble somewhere in the lines also.
Bill Young



Russel, If you pull the handbrake and set it does the pedal feel much better?

If so just go to the adjusters and move them out. If you run them to maximum travel and cannot get a good pedal you've probably reached the limit of the rear drums. There was recently a discussion about how much the rears can be turned but the practical reality is that if the adjusters are maxed out and the pedal is too low the drums are at or beyond the limit.

Assuming of course the rest of the system is correct. Soft or degraded flex lines? Air in the system? Pedal adjust rods correctly set up?

Let us know what you find!

Good luck !
Tom M

You may very well have air in the system. If u vacuum bleed , take out the bleeder and coat the threads with vacuum grease or very viscous silicone grease. You can use RFI (reverse fluid injection). Eastwood ,snap-on and others have this new piston pump which will move fluid both ways. pushing fluid in and up to the master cylinder moves the air ahead of it. Another item to check is the little top hat shaped valve at the far end of the m/c brake piston, these often get damaged. Don't get discouraged, this is often difficult. Bill.
w.g cook

Problem Solved (Almost)

First thing I did was buy the pressure bleeding system from Moss. Slick system, uses the spare tire for the air supply.

Got very few bubbles out, but bleed the slave cylinder while it was hooked up.

Went back and re adjusted all the wheel until they had slight drag and came to the conclusion the drums are gone. Couldn't get 2 to drag and the other 2 were at the last notch before they dragged, however the brakes worked!

So now waiting for 4 new brake drums.

Any I thought boats were expensive!

Russell
R Egge

Rock Hard Brakes!

Put on 4 new drums and adjusted them to drag oh so slightly.

And... the brakes pedel went nearly to the floor.

Put on the last wheel and went to bed.

Today I have brakes that are rock hard.

Russell
R Egge

Brake Issues on my MGA 1500.

Order of Operations.
1) Replaced front Slave cylinders, bleed the brakes, no problems. Brakes work great, only requires to put the pedal half way down.
2) Replaced Rear Slave cylinders & bleeder screws on banjo. Bleed the system, etc. It now takes two pumps to bring the car to a stop. Although, now the emergency brake engages quicker, (only requires me to pull halfway up to engage).
• All bleeding was done with the Eezibleed system (pressure @ 15 pounds)
• I have bleed the system twice now, and I almost positive that there is no air in the lines!
• Brake pads have been adjusted to allow a small degree of drag.
• There are no leaks, and the brakes worked great prior to replacing the rear slave cylinders. I am going Crazy…. Please help

Devin
DRE Devin

Dre,
The fact that your parking brake is good implies that the rear wheels are adjusted properly, as well as the fact that the front wheel cylinders are properly adjusted since they worked prior to your replacing the rear brakes. There is not much left to check. It sounds as if you still have air in your brakes. I recommend bleeding back to the master cylinder from each wheel cylinder. If you still have problems, you may have a problem with the master cylinder. Good luck
mike parker

This thread was discussed between 06/12/2004 and 19/12/2004

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