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MG TD TF 1500 - Spongy brakes on TF

Hi guys.....back again.

This time with a little more serious problem. As the title suggests, I'm having some difficulty getting a firm brake pedal feel. I had the master cylinder and wheel cylinders rebuild/brass sleeved by White Post Restorations. I also had them re-line the brake shoes and arced the shoes to fit the drums that I had turned. I removed all the lines and cleaned them out to make sure no crud was left in them, and replaced the flexible lines with new ones. After bleeding the brakes, I sprung a leak in the small brake line from the master cylinder to the 3 way connector. I just replaced the line tonight, re-bled the brakes again. The brakes work...but not all that well, and I don't have any leaks. Seems like I may still have some air in the system since when I depress the brake the pedal tends to travel 3/4 of the overall pedal range. If I pump the brakes the pedal travels about 1/2 the pedal range and then holds firm. What sort of overall pedal travel should I see? I have the pedal set at the initial 3/4" travel recommended in the shop manual.

Is there a trick to bleeding these brakes to assure that the system is purged of air? I had a chance to look at the inner workings of the wheel cylinders and all there is is a small hole in the bottom of the cylinder to allow fluid to enter and leave. If there is air inside...how is it expelled when bleeding? Are there any other things I should be considering as well?

Thanks again.......

Jim (nothing but questions) Rice
TF7022 / XPEG852

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Jim Rice

Jim - You still have air in the wheel cylinders. If you take a look at the bleeders at each wheel, you will find that all they do is bleed the brake lines. At one time, I took a syring and filled each cylinder after removing the banjo bolt from each, then put the bolt back in. Since then I have filled each cylinder prior to putting them on the backing plates and have had no more problems with bleeding the brakes. If you are using silicone fluid, things are even worse as it tends to trap bubbles as you are trying to bleed the brakes. However, if you fill the cylinders with fluid, even this is not a great problem. I have been using silicone fluid for about 20 years in my brakes and have suffered no ill effects. Good luck - Dave
David DuBois

Jim,
Had the same problem last year after re-build.....same cure as David D. describes worked for me!
Borrowed a syringe from the junkies across the street....hope my brakes don't catch aids from thess guys!
Cheers,
David # "A1"
David Sheward

Jim,

Before you get into the above, have a look at the amount of "slack" at your rear wheel cylinders. Just as a quick test, click your handbrake on a click or two and see if the situation improves. If it does, you will then know where to work. Always look for the simplest thing first.

Reed
Reed Yates

Filling the cylinders with fluid works fine, but you must bleed brakes in a sequence, starting with the brake cylinder (rear, right) that is furthest from the master cyl. Then left rear, right front, left front.
colin stafford

Looks like I'm going to be using a lot of brake fluid this weekend. If I understand correctly, pre-filling the cylinders is the way to go. I believe that means removing the flexible lines at the frame connect points first so as to be able to remove the banjo fittings, thereby introducing air into the lines.............again.

That not all that bad, just disappointing. I'm still puzzled however on how to properly fill the cylinders and keep them full during this process.

Once I have removed the fittings, the opening in the cylinders is exposed. I believe the opening is at one end or the other of the cylinder. For those cylinders that are installed so as to push the brake shoes down, filling the actual cylinder with fluid makes sense since the cylinder should remain full once filled.

However, for the cylinders installed that push the brake shoes up, it would seem the fluid would want to drain out the opening allowing air to get in?

Is my logic and understanding of the system correct here? If it is, how did you guys overcome any fliud draining out of the cylinders?

Jim
Jim Rice

Jim - You are correct regarding the cylinder that is pointing the wrong way and it is a very messy job. The last time I did this process (on my magnette several years ago), I filled the cylinder that is pointing down with a syringe and reconnected all the piping. I then removed the shoe from the cylinder that was pointing up and removed the piston and cup from the cylinder and filled it with fluid that way. The only problem here is that you have to be careful not to trap a large bubble under the cup when it is reinstalled. I put the cup in edge ways and then turned it flat after it had been emersed in the fluid (did I mention that this was messy?). Be sure that you have plenty of rags packed around things to catch the fluid that is spilled. Good luck - Dave
David DuBois

I have never personally had to hand-fill the wheel cyls. on the several T-cars I have fiddled with, but maybe have just been lucky. What about shoe adjustment? If too loose, the pedal does about the same thing (the first stroke is used up pushing the linings to the drum, and the pump stroke then applies the real force. When you first install the shoes and adjust, they are not really centered well, hence the first couple of pedal pushes after bleeding may move them a bit, causing slack. Are you using silicone fluid? It is hard to bleed. Also make sure you are not sucking air back before tightening the bleeder (ie press pedal down, hold, and then tighten the screw.) Also, bleed slowly, and refill the reservoir before half empty, slowly, so the new fluid doesn't bubble. Most important thing of all: never use your wife to help bleed brakes. They do not understand, and of course are not the one under the car in the dark being sprayed with fluid and being bitten by mosquitoes! Good luck.
GeorgeButz

Hey George.....

Are you sure your not the guy across the street who watches me work on the car every night? Your last couple of sentences could not be more correct. I hate those damn mosquitos !! True the wife has been assisting, but she's actually getting pretty good at it.

I'm using Castrol GT LMA brake fluid. It's not silicone. I also bled them in the correct sequence as Colin had mentioned earlier. I do intend to re-visit the adjustors once more, but I believe they are set properly. Full tight and then backed off a click or two until the shoes clear contact with the drums.

Seeing as how all things here are British...I've come to expect that any seemingly straight forward process can turn into a real pain in the ar*e.

Jim.
Jim Rice

Hi Jim, we dont have any trouble bleeding brakes in Australia as this being the land down under the fluid actually runs in the opposite direction. The cars being made in Britain were designed to be impossible to bleed but that works to our advantage here.

Seriously, I have never had a problem and I generally do the job by myself. The trick as I see it is to attach a piece of clear plastic bleeder hose arranged in such a way that the fluid must travel up the hose for a few inches before it then goes down the hose into the container. This ensures that if there is any return suction only fluid and not air goes back into the wheel cylinder.

Also do it just as George suggests, slowly, and give the pedal a couple of seconds wait between pumps to allow the fluid to get in front of the master cylinder bucket at each pump.

If you have any queries about the arrangement of the bleeder hose, I can rig it up and send you a digital photo.

Cheers,

Paul.



Paul van Gool

Paul...touche !!

Just had to laugh at your comment ! Reminds me of the Foster's Beer commercials we have here in the states...quite humorous to say the least.

Well I finally got the car on the road for the first time in 22 years. God !!! there's nothing like the sound and feel of an MG on the open road. Accelerates quite nicely thank you ! Absolutely great !! Despite the desperate need for a paint job and an interior, nothing but grins and thumbs-up from the neighbors and passers-by.

The driving and un-expected responses made all the work and frustration over the past two years worth it. Still not too happy with the brakes though. Of course I'm not sure if what I'm experiencing is normal, but I'll be fiddling with the adjustors some more and will bleed the brakes one more time just to be sure. I did pull the pistons on the front brakes and filled them as per David's suggestion, bled the system again (this time a Triumph owner helped), and re-adjusted the shoes.

On question....how far should the brake pedal travel before full braking pressure has been applied? Mine seems to stop a little PAST vertical when the car is not moving. However, when driving, the pedal seems to go a bit further past vertical. Is that normal? I realize these are non-power assisted drum brakes, but I was expecting the pedal to stop somewhere BEFORE reaching a vertical position.

In addition, to all of you who tirelessly and dependably answered my inquiries and questions, I'm grateful. Should you ever find yourself in the West Palm Beach area I would hope you could avail yourself to some Southern hospitality and stop by. Hell....I'll even buy you a COLD beer since my refrigerator is made by GE !!

Best regards,

Jim
TF7022 / XPEG852
Jim Rice

Jim - I am not sure how far past verticle the pedal goes when I am stopping, as long as the car stops before the pedal hits the floor I'm happy : ). Seriously, I don't think it is unusual for the pedal to travel further when the car is moving as the twin leading shoes on the front wheels cause a bit of a servo action, pulling the shoes into tighter contact with the drum will probably cause the pedal to travel a bit further than when standing still. Also, any further problem with your MG will undoubtedly be cause by allowing the dreaded Trum... influance near your car. MGs don't take kindly to being manhandled by Trium... owners ; ). Good luck - Dave

PS. Just got back from a weekend trip in the TD to the other side of the mountains for the Northwest MG 'T' Register's Mini-GoF. Roughly 250 mile round trip with nary a hick-up. Did have some problems with smoke from the forest fires burning over there (about 4 miles from the Mini-Gof site) and we had to add a judging class for fire trucks. They were all considered FIRST CLASS in our opinion.
David DuBois

This thread was discussed between 17/08/2001 and 20/08/2001

MG TD TF 1500 index

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