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Brake booster fluid leak?

Discussion in '"Stock" Alpine' started by Durhamguy, Mar 22, 2022.

  1. Durhamguy

    Durhamguy Platinum Level Sponsor

    I was doing a job on the steering box (per Sunbeam Channel video and using Castrol SHL grease instead of the egg cup of oil left in it) and decided to check the brake fluid in the Master. Surprise, it was almost empty. I topped it up in October before storing in my garage. I read some older posts on here about possible causes. I have no fluid leak inside the car under the brake peddle. No apparent leaks at the wheels or under the car. But I have not removed the wheels yet. No leaks under the Master nor anywhere in the engine bay. I haven't checked the brake lines under the car yet. The older posts indicated probable cause of the brake booster.

    The Alpine had a brake service in a shop last August.

    How do I check the brake booster without taking it apart. I did notice the vacuum pipe from the booster to the intake manifold was sweaty on the outside last summer and fall, but didn't think anything of it. I still have braking function as I topped the Master up. Not that I am going to drive it like this and besides I have to put the carb back on.

    Any thoughts/advice will be appreciated.
  2. mikephillips

    mikephillips Donation Time

    Well, the first place it goes in the booster is to the piston chamber in front. You can do a couple things to check. First, you can remove the three bolts securing the booster to the bracket and see if the assembly is heavy at the front and you hear liquid if shaken, that will indicate it has partially filled with fluid. Or you can pack a bunch of rags under it and loosen the fasteners holding the front cover on, but beware that it could lead to a lot of fluid coming out so I recommend the unbolt method first to avoid possible paint damage from the fluid. If the seals in the booster have failed you can also look to see if you get white smoke when accelerating since if enough fluid fills the front of the booster it eventually will get sucked in the hose to the intake and burned. So no dripping leaks.

    I personally have boosters in my cars but they don't get used, they're there to fill the spot like stock. The lines from the brake master bypass them and go to T fitting that the line from the booster would normally connect at. Means higher brake pedal pressure is needed, but you get used to it, or I have at least. You could do that as a temporary measure if you find the booster has internal leaks so the car is still drivable.
  3. Durhamguy

    Durhamguy Platinum Level Sponsor

    Thank Mike for the input, much appreciated. I have not notice white smoke from the exhaust.

    Is there a trick to moving the brake master bypass to the fitting, so as to not kink it? Not sure how fragile these lines are. I guess I would have to bleed the system as well?
  4. Alpine 1789

    Alpine 1789 SAOCA President Diamond Level Sponsor

    Just to be certain, have you looked under the carpet by the master? I know others have found fluid there when the master is leaking.

    Also, a question for those who know: will the brakes function normally when the booster seals fail? This happened to me many years ago and I had the classic symptoms: a puff of smoke out the tailpipe followed by a lack of braking. I didn't drive it again until I'd replaced the booster (with the Lockheed replacement) but can't imagine that it would have functioned normally if I had just refilled and bleed the master.

    And, finally, typing the above made me think of something: if the booster seals failed, won't there be fluid in the vacuum hose? That might be a quick, easy way to check.
  5. mikephillips

    mikephillips Donation Time

    OK, so as for the booster and loosing brakes, depends on which seal has failed internally. There is a seal to prevent fluid from leaking out of the alloy housing to the vacuum canister and a pressure seal that is used to push against the fluid, just like in a master. So if the pressure seal fails and the other doesn't then it can cause fluid to move around the piston rather than push on it. If both fail a little, you can slowly lose fluid into the cannister and of they fail completely lose it quickly to the cannister. The cannister then needs to fill enough to feel it move around if you shake it before it starts be drawn into the vacuum hose. You can check the hose for wetness, it may or may not be depending on how bad the internal leak is.

    As for rerouting the brakeline, when I did it I gently bent it from the booster down to the T fitting trying to avoid sharp bends. Due to the age of the lines if they're still original, you may still need to go to a parts place and get a new master to booster length line. Or you may be able to get by with a coupling for the master to booster/booster to T to hook them together. But be aware that the bubble flare is only supposed to be compressed once and not reused so it could leak.
  6. Durhamguy

    Durhamguy Platinum Level Sponsor

    Jim, new front floor pans were fitted last August and only sound retardant material has been added back (no carpet yet). Though most of the firewall is just metal as I had to stop late Fall due to cool weather. So I see no wetness at all in the driver's side. The vacuum hose did get wet in late summer on the outside (I thought it was moisture) but has been disconnected from the manifold since October. I will totally disconnect it, hang it up and see if anything drains out. Once I finish off the steering box (by this weekend) I will focus on the brake lines and isolate the booster to see if it is leaking.

    The brake peddle has been softer. Over the winter, I fitted a LED brake light kit. It was supposed to be plug and play but wasn't for me. Grounding was one issue, now fixed, but the other I think now is the brake switch not being consistently triggered due to fluid loss.

    Again, thanks Mike for the input. The leak is slow as it is 1/4inc from top now after filling. Over winter (Oct to late March) it lost all but 1/2inch.
  7. Durhamguy

    Durhamguy Platinum Level Sponsor

    Looping back on this topic, it was the Girling booster. Once out I could hear the fluid swishing around the cannister. I then rerouted the brake line into the T-fitting and have brake peddle pressure back.

    I bought a Lockheed booster from SS and it is not clear how to fit it into a IV Alpine in the space (see pics) the Girling was in. Appreciate any thoughts folks have. Many thanks.

    Attached Files:

  8. Tim R

    Tim R Silver Level Sponsor

    When we have done this we have made up bespoke brackets to mount the replacement servo, I hope that this helps (our cars are RHD).

    Tim R

    Attached Files:

  9. Durhamguy

    Durhamguy Platinum Level Sponsor

    Thanks Tim very helpful. My booster would be in the same place as shown in your pictures even though it is LHD. What gauge metal was used? 22 guage would be too thin I imagine.
  10. Tim R

    Tim R Silver Level Sponsor

    I'm sorry David I don't know the gauge. It was just some spare mild steel that we had that seemed about right.

    Tim R
  11. Barry

    Barry Platinum Level Sponsor

    The last thing you want is a hydraulic brake booster flopping around in the engine bay. For a "two-point" mount like Tim's, I would use at least 14 gauge (0.075"). For a "single-point" mount, I would not use less than 11 gauge (0.120").

    JMO; ask three more people and you'll probably get four more answers.
    Tim R likes this.
  12. Durhamguy

    Durhamguy Platinum Level Sponsor

    Thanks Barry.
  13. Alpine 1789

    Alpine 1789 SAOCA President Diamond Level Sponsor

    Here are a couple of photos of a Lockheed booster mounted in my SV. I did this about 20 years ago when I didn't have the skills or the tool access to do anything better. But, it has worked just fine and I never bothered to improve upon it. The front mount is just a piece of scrap metal I had laying around, bolted to the booster's bracket and then to the car. There are two straps on the back, one that came with the booster and another that is just plumbing strapping. I have no idea why I used both, but probably had a reason at the time.

  14. Durhamguy

    Durhamguy Platinum Level Sponsor

    Thanks, again very helpful.

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