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A question on brake bleeding

  • 16-08-2021 4:11pm
    Registered Users Posts: 756 ✭✭✭ BlakeS94

    Need to change the brake bleed screws on my car, never done this before. Is it as simple as remove and fit new ones or is there anything I need to know besides fluid loss and keeping master cylinder topped up? Should I bleed each caliper after changing the bleeder or wait till I have all 4 done and then bleed them all


  • Registered Users Posts: 159 ✭✭ XLR 8

    I really wouldn't recommend you DIY this one. Not if you haven't or aren't familiar with brake systems. Any local garage will do that job safely and it ain't gonna chew the wallet too badly. Too many folks are perishing on the roads dude. Best to be safe...

  • Registered Users Posts: 5,323 ✭✭✭ jmreire

    Whats wrong with them that you need to change them? Are they leaking? Are the rubber caps still on them???

  • Registered Users Posts: 4,163 ✭✭✭ greasepalm

    Or worse they are corroded and sheer off. I have never ever heard of changing them.

    Clamping flexy hoses with a brake clamp will stop fluid leaking out and can bleed it after.

    Some cars differ as you have not said what car is it.

  • Registered Users Posts: 756 ✭✭✭ BlakeS94

    Reason I want to change them is because they're completely rounded, a flare nut wrench isn't turning them, and the size down doesn't fit. So my plan is to break them loose with a vice grips and replace with brand new ones, there isn't any signs of rust so I don't think they'd snap off.

    It's a Ford mondeo mk4

  • Registered Users Posts: 5,357 ✭✭✭ kirving

    What size spanner are you using? It's very often not a standard size.

    Never uses a 12 pointed spanner either, far more likely to round the nuts.

    One for a mechanic IMO, it just isn't worth me spending hours on something when a mechanic will lift the car, change the nuts and pressure bleed the system for an hours labour.

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  • Registered Users Posts: 561 ✭✭✭ dooroy

    If they were tight enough for the corners to be rounded off then there is a strong possibility that one or more of them will snap off - and you are then faced with a much bigger problem.

    You may not see any signs of rust but they can still be seized solid.

  • Registered Users Posts: 200 ✭✭ MAYOMICK

    Sure if your not having problems with the brakes theres no need to touch them.If the day comes when there is a problem you can cross that bridge then.

  • Registered Users Posts: 756 ✭✭✭ BlakeS94

    They're an 11mm, and I tried using an 11mm flare nut wrench to no avail. I see your point, but I like to try do as much as i can and learn along the way, but if you think maybe it's best left to a mechanic I'll take your advice on board.

  • Registered Users Posts: 756 ✭✭✭ BlakeS94

    If I was to tackle it I'd spray some penetrating fluid every day for a few days leading up to it would that not help?

  • Registered Users Posts: 756 ✭✭✭ BlakeS94

    I tested the brake fluid in the master cylinder with a brake fluid tester and it showed all the red lights which recommends to replace immediately.

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  • Registered Users Posts: 4,426 ✭✭✭ maestroamado

    I think if you do them one at a time you will not need to bleed at all. Just break the bleeder before you remove brake hose, you may need a small grips. you should easily be able to remove, replace and tighten before master MT.

    If you put some cling-film over the master and replace cap it will reduce the flow to almost zero... you will need to put a tray under to catch what leaks and top up master after each wheel...

    Personally i would leave it "if its not broke don't fix it"

  • Registered Users Posts: 561 ✭✭✭ dooroy

    I have found that the penetrating oil does not seem to be able to reach where it is needed - and just under the part where the spanner fits the shell is quite thin and can snap easily.

    If it snaps and then you have to replace caliper most likely - and car off the road in the meantime possibly.

  • Registered Users Posts: 4,426 ✭✭✭ maestroamado

    What i have done a few times in the past is saturate a piece of cotton sheet in WD and wrap around whatever and leave overnight, also spray more oil on the rag...

  • Posts: 0 [Deleted User]

    Just remember, these are very easy to brake. These days the well supplied garages may have a specialty tool for that purpose - vibro impact. It makes only little torque, but vibrate like a crazy.

  • Registered Users Posts: 21,864 ✭✭✭✭ mickdw

    Easy job and in theory should only need a very basic bleed as little air should be introduced.... That is until you snap one of the bleed screws. Then its a nightmare job.

    If you are using a vicegrip, be very careful. You will easily snap them with that but using with care, it will do the job. If small force doesn't do the job. Leave it.

  • Registered Users Posts: 756 ✭✭✭ BlakeS94

    I think I'll give it to a garage to do. I don't want to cause unnessary stress and mess up callipers, thanks for all the info guys much appreciated

  • Posts: 0 [Deleted User]

    Keep us updated. I think it is right thing to do. Only cover your back and make a price agreement. If they took that job, you do not care how many hours it takes and you pay only fixed price. Every single garage knows there is the risk. Once it took 5+ hours to get fixed by other mechanic. I really do not know why it took so long. He not only used his work hours, waste others work hours too. My strategy is to use reverse drill bits because sometimes it can crack it loose. Extractor tools typically is garbage

  • Registered Users Posts: 756 ✭✭✭ BlakeS94

    Finally got around to this, changed all 4 bleeder screws, needed to use rounded bolt removal sockets, proving to be the most valuable tool I've ever bought.

    Wasn't too bad getting them out, just went back and forth a few times, sprayed penetrating oil once they came out a little bit.

    Put in the new ones and went back around and bled everything, put about 500ml of brake fluid through the first bleeder to get as much of the old fluid out, went around to do the rest, clamped off the brake hose with a plastic hose clamp, very little fluid came out, a few air bubbles when bleeding but I think that could have been down to not pouring the fluid into the master cylinder smoothly enough. clean fluid now though with no air, brakes are working so much better.

    There was a bit of vibration when braking that I thought was a warped disc, but seems to have gone now since I changed the fluid