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MG TD TF 1500 - Brake Bleed problem
I'm currently experiencing some problems bleeding the brakes on my TD following replacement of the front slave cylinders.
The symptoms are of air in the system in that the brakes are spongy but this is after bleeding them 4 times. Also when the brake pedal is depressed during the bleed, even gently, a fountain of fluid shoots out of the filler hole, and I've not seen that before.
Has anyone any advice or suggestions please.
I'd also be interested to know of any 'one man' system of bleeding brakes. There are many kits out there (in the UK!) but non fit the master cylinder of my TD.
|Mike, the wheel cylinder design doesn't lend itself to the rgular method of bleeding. The air gets trapped in the cylinder. I'd suggest that you get a syringe and fill the wheel cylinders individually with fluid. If your not using silicone fluid be sure to get the spill( it will be messy) off right away as it will remove the paint in a short time. reconnect the lines just as soon as you get the fluid in the cylinders. You can then go on to a normal bleed method. As for the one man method, I used a rubber bungie wrapped around the pedal arm and attached foward to the chassis. But I did so before I mounted the tub. I have done some brake light testing by placing a large brick against the pedal. That method might work for a one man bleed. I believe that the "shooting" fluid is normal on these master cylinders. Just replace the cap between fills and bleeds.|
|It is really nice to have the fluid squirt in your eye-been there done that. I think they all do that to some degree. Make sure you re-adjusted the shoes to center them and remove all the slack, as that can make it feel spongy.|
I have found teenage son much better assistant than wife for bleeding- don't have to say "please" and explain why you have to do it over and over! Never tried a one person system, there are some out there that you have to drill and modify an old MC cap to use. Seems to be a common problem, but I have never had much trouble on my car. Make sure you go slowly, and have someone close the bleeder all the way before letting the pedal up slowly. George
have a look in 2009 archive "master cylinder rebuild"
this has always worked for me.
Ray TF 2884
As was suggested to me, you can clamp off the lines to work on one wheel at time. This may help you narrow down the problem.
|I did my wheels by myself and got a piece of tubing that fit over the bleeder nipple...that went into a full bottle (clear) of brake fluid (you have to keep the end submerged in the fluid). Start with the right rear and pump while looking at the bottle...when the bubbles stop, walk around and tighten the nipple...then the left rear...same thing...then the right front and finish with the left front.|
|Thank you all for your suggestions - I was worried that the spurting fluid indicated a master cylinder problem but it seems that this is normal.|
Not too sure how to clamp off each wheel line Tim, how's that done, but it would certainly help isolate a problem?
I'll check the archives Ray.
Gordon how do you see the bottle and pump at the same time??
Led do suggest filling the cylinders by removing the connecting pipe between them, and I'm not using silicone?
So with all your advice I'll try again - if I can get the wife to agree to help that is!
|Haha... you pump with your left hand and are looking across under the car....(wish I had a photo)!|
|Mike I didn't use that method myself but saw it sugested by others here. I would guess that you would disconnect the line from the cylinder and fill there. It does sound to be quite messy to me but it may have to be done as the cylinder sits higher than the bleed screw.|
Best of luck.
|I have alway used the method that Gordon describes here. I have always done the job solo and without the need to prime the brake cylinders. I have found the only awkward part of the job is getting my head above the M/C so that I can see how much fluid I need to top it up. I would think that to try to bleed brakes without using a bleeder tube would be most difficult.|
Also I only just crack the bleeder nipple instead of screwing it out much. This way there is no possibility of air getting back through the screw threads. I know when the air is out of the line by looking at the bleeder tube after every refil of the M/C.
|Paul van Gool|
|I do the solo technique also. I have a bleeder kit that includes a one-way valve that goes into the end of the hose that is submerged in brake fluid. My method of depressing the brake pedal is with the use of a long piece of 2x4 that I push against from behind the car. Just don't ever allow the fluid to get low in the master cylinder. I put the cap back on (loosely) after every topping up of the m/c so fluid doesn't squirt out.|
|Thanks again for the helpful advice. |
Gordon, you really have to get that on video!
I'm sure the best way for one man bleeding is to get someone to turn a dummy filler cap with a spout and use the pressure from the spare tyre as per the Eazybleed (sic) system.
Perhaps Moss might take up the challenge, can't be too expensive?
|I modified a filler cap and tried the EasiBleed system, but had no luck at all. It worked fine when I used to use it on an MGB. I suspect that the TD master cylinder doesn't provide a clear path to the pressure section of the fluid when the pedal is not depressed.|
|I made a bleeder from pump up garden spray (From a BMW site mentioned in the archives I think) and modified an old master cyl cap to use it. Worked well.|
When putting the brakes together it helped to prefill the wheel cylinders with fluid and then block their inlet holes with a lump of silicone grease (I used silicon fluid in the system) so that they would stay full during the assembly of the brakes. Regards, Richard.
|Thanks Bud and Richard,|
I assumed that in the 'off' position the fluid in the master cylinder could be pressurised, it seems I was wrong. Back to the wife.
|Hi Mike, |
I have a M/C cap modified to automaticaly top up the cyl while bleeding. If you need to borrow it just contact me off line and I will post it to you.
That's a very kind offer so you have mail.
Sorry I am late getting back, I just clamped the rubber brake lines - I was going to replace them anyway.
|No one mentioned if the MightyVac works for bleeding the brakes on the TD's. I understand it creates a vacuum to pull the brake fluid through the bleeder. Is that correct? Does it work as advertised on the TD? I am considering getting this.|
|Mike, my experience is that it doesn't work on the TD. Worked great on an MGB, but I don't believe that the TD master cylinder gives a straight path to the atmosphere when the pedal is not depressed.|
I am still trying to make some sense of the problem, since the brakes are still spongy.
I'm beginning to think that there may be some deterioration of the MC master rubber cup. The brakes work but the travel is quite long and can be improved by a little pumping.
The WM shows a compensating orifice in the MC which in the off position connects to the fluid supply. So why can't the fluid in the MC be pressurised allowing for one man operation?
Also the WM says (in section M4), that the level of the fluid should never be closer than 1/2" from the bottom of the filler neck, but in section M15 says that when full the fluid should be level with the bottom of the filler neck. Any thoughts on which is right?
|Mike, you have probably done this already, but are the brakes adjusted correctly? Regards, Richard.|
The compensating hole is only there to stop system heat pressurising in the off position, it is only a few thousands of an inch in diameter and will not allow fuid through quickly. The only way fluid can get through using a pressure system, it first has to collapse the main seal then get past the one way valve built into the pressure retention valve (parts 10 11 &12) in the workshop manual.
|I'm grateful for all the comments about my brake problems which, with the replacement of the MC, are now solved.|
This thread was discussed between 24/03/2009 and 01/04/2009
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