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MG Midget and Sprite Technical - 1275 Brake mystery
would really appreciate your input on something. Recently over the last few months the hydraulic pressure in the brakes has declined so much so that the pedal must be completely depressed for the brakes to work. In addition the pedal does not return to its original position and sometimes must be pumped to work at all. makes for interesting driving!
The reservoir is full and i do not appear to be losing any fluid. could this be a problem with the master cylinder do you think or do you reckon it's something else?
Many thanks in advance.
|If you're not losing fluid and have to pump it then I'd say you've got an internal (infernal?) leak in the master cylinder. As for the pedal not returning, it should unless you're missing the return spring. I'd park the car until it's sorted, you don't want to use another car to stop you. Been there, done that, got the dents to prove it.|
|I don't know but could this also be the rubber flexi hoses broke down internally?|
I assume you've also got your rear brakes set properly (pedal travel?)
Good advice from Martin if your brakes are fualty don't drive it especially now we have snow/ice/sleet/rain/standing water
|You could have at least two things that are at the root of your problem. |
One is the pivot bolt is corroded. Try pulling up the handbrake lever and then see how the pedal feels. If it has come back up then the rear brakes need adjusting. If neither of those two things do not cure it then you need to rebuild the master or replace it with a serviceable one. If you have dragging brakes then I would change all three flex hoses as they break down internally and show no external problems at all.
|It certainly could be one or more of the three flexible hoses having lost its wall strength, so when you press the brake the hose balloons rather than the brake operating. That could also account for the slow return of the pedal. Whatever is the cause, the car is un-roadworthy and if you had a collision your insurer could well disown you. Don't risk it.|
seeing as there are braided goodridge hoses on this car, I'd suggest that the master cylinder is at fault.
I'd also check the rear brake adjustment as this gives a longer pedal.
I'd also check the freedom of movement on the clevis pins,
|I wonder if this is a lovely green midget...|
Whatever Jonny, take the good advice, only use the car when it's been fixed if you don't have the diagnostic abilities.
John has given you a good start, set the rear brake adjusters then look again, it may be all you need to do.
|Thank you for your suggestions chaps. John, don't worry, I won't be driving your lovely green midget until it's fixed, as you and all the other guys have said, it isn't road worthy. I'll replace the master cylinder and see if that fixes things, if not, I'll have a look at the hoses. I'll be sure to update!|
P.S John, you'll be pleased to know that the midget is still in fine form since I bought her from you.
|Before lashing out money and time on a new master cylinder, l would most definately adjust up the tear brakes. The symptoms you describe are both consistent with out of adjustment rear brakes.10 minutes with a jack and square adjusting spanner could be all it takes to sort it out.|
|Guy Oneandahalf Sprites|
|Not only that but it sounds more like internal worn hoses than a MC failure.|
Firtst check all the cheap things before doing the expensive parts.
-adjust rear brakes
-check the pedal pivot and disasemble and grease (and do not over tighten with reasembly)
-check if the hoses are worn (pres the pedal and check if the brakes stay blocked if so check if they release when you losen the connection at the caliper, if so repeat but now losen the MC or T joint to check if it is not a blocked MC)
while your down there clean the caliper and check if the seals and piston look good.
|As usual I agree with Guy |
This sounds like 2 things the rear brakes require adjustment (simple) and secondly I think you do not have a return spring on your brake pedal otherwise I think it would return.
|Robert (Bob) Midget Turbo|
|If you've got alloys while adjusting the rear shoes you might want to check that the rubber bungs that go in the inspection holes have not pushed into the drum assembly and got inbetween the brake shoe and the drum.|
This happened to me and caused a moment of panic when approaching a roundabout and no brakes, pumping the pedal brought gave me just enough pressure to slow down for it.
Just a thought
|The failure to return may be due to a blocked/sticky vent on the master cylinder reservoir ?.....|
|Thank you for your advice everyone.|
if the rear brakes do need adjusting would this be something which would gradually occur as it has taken a few months for the symptoms to gradually worsen?
I take it rear brake adjustment can be found in the Haynes manual?
I'll follow your advice and adjust the rear brakes, inspect the clevis pins and hoses and then look to replace the master cylinder if I still have no joy.
Thanks again for your help, I am still learning! You'll be pleased to know that I refuse to give in and buy a "sensible" modern car.....I've grown far too attached!
Picture below for you John, taken in the autumn.
|Sounds like the master cylinder, the brakes would not go out of adjustment so much in a couple of months to cause the problem you describe. I'd definitely check the rear adjustment first, very easy to do if you've done it before, but can be a bit tricky if it's your first time! The adjuster is a four sided cone that pushes the shoes apart as you screw it in. It needs to be set on one of the flat sides of the cone to give the correct adjustment. Yes it is in the Haynes manual. If it's your first time, get someone knowledgeable to help you!|
|Nice one Jonny, looks better than when I had it!|
If you drop me an email to the address above, i'll put a workshop manual on CD in the post for you, that way you can just print out the bits that you need and throw themn away when they have oily fingerprints on.
You know, that car would make a good K-series conversion base as you've already got the 5 speed in place.....
|As well as Haynes (and IMO better) get the relevant owners Handbook, for £8 it will tell you how to do the rear brakes and almost all you need to know as a owner and is better for you even than the workshop manual (but don't turn that down)|
|REcently had similar problem with brakes sticking on. Needed to pump pedal to get to release. Changed caliper thinking that was the problem, but ok after changing the Master cylinder. seems the by-pass valve inside the MC gets blocked and stops the brakes returning. |
Also told that spongy brake pipes can be a cause or poor pedal pressure
There is no "bypass" valve in the master cylinder, however what there actually is is a small vent hole that allows fluid to return to the reservoir when the pedal is released. This can get blocked or more than likely the piston in the cylinder does not return far enough to clear the hole.
|Bob Turbo Midget England|
This thread was discussed between 04/12/2010 and 14/12/2010
This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.