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brake questions

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walshja

walshja

Jedi Warrior
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ok, so I met a real nice guy at the British by the Sea car show, and he has a 1974 that he is restoring. Says his brakes don't feel right, so I offer to help him out since I had similar problems with my brakes.

I get to his garage, and sure enough the brake peddle goes right to the floor, offering minimal resistance. There are no leaks anywhere, so I decide we should flush the hydraulic system, and get some new fluid in there. I start with the passenger rear, connect my vacuum pump to the bleeder valve and we suck out some bad looking brake fluid. Repeat at all 4 corners getting the same bad fluid from each.

Same problem exists, peddle goes right to the floor like there is air in the system. So I then decide we should adjust the rear brakes to ensure the problem does not lie there. After adjusting nothing changes.

My question is where should we look next? Can I still have air in the system? Or can this be a bad master cylinder?

Using the vacuum brake bleeder, maybe we are letting air back in the system as we try and close the bleeder valve? Or would a bad master cylinder exhibit the same symptoms?

Suggestion on what to do next?

We did get his rear differential oil changed. I have never seen such dirty oil in my life, it was a thick, mud like substance that came out !!! So we did accomplish at least 1 job last night !!!
 
I would certainly look at the master cylinder next.

mark
 
I agree, sounds like bad main seal in the MC letting fluid squeeze through instead of applying pressure. Hopefully it is rebuildable.
 
walshja said:
when you say hopefully it is rebuildable, what do you mean?
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That hopefully it is not damaged beyond repair

walshja said:
what would prevent it from being rebuildable?
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scratches in the bore, pitting or corrosion

walshja said:
is it pretty easy to rebuild one?
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some say yes, others say no, myself i am in the "buy the complete rebuilt unit" camp. less to worry about when that idiot pulls out in front of me and i really need to be not worring about the binders...

mark
 
walshja said:
Mark and jvandyke, thanks for your feedback.

I will recommend that the master cylinder be replaced.

Do you think the slaves in the rear are OK?
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Have you looked at the brake lines while he pushes the pedal down? Look for any non metal lines that are expanding when you push the pedal, I've seen this balloon effect myself and yes it's weird but it does happen. (maybe there are no non metallic lines on the car but it's something to check.

Check the slaves - see if any are leaking and if they are all operating when the pedal is pushed. Some may be stuck with corrosion.
 
RickB Have you looked at the brake lines while he pushes the pedal down? Look for any non metal lines that are expanding when you push the pedal said:
I saw this with a '59 Humber Super Snipe - The brake hoses were very old (maybe original) and facing a very soft pedal issue, I had my wife stomp on the brakes while I observed while under the car - two of the hoses were actually expanding when she pumped the pedal!
Click to expand...
 
livinginthepast said:
RickB said:
Have you looked at the brake lines while he pushes the pedal down? Look for any non metal lines that are expanding when you push the pedal, I've seen this balloon effect myself and yes it's weird but it does happen.
Click to expand...

I saw this with a '59 Humber Super Snipe - The brake hoses were very old (maybe original) and facing a very soft pedal issue, I had my wife stomp on the brakes while I observed while under the car - two of the hoses were actually expanding when she pumped the pedal!
Click to expand...

Hey, I owned one of those when I lived in Alaska back in '85!!

Wow - that was some kinda straight engine wasn't it?

That was a really weird car.

Sorry - back on topic... come to think of it my spridgets don't have any non metallic brake lines so that might not have anything to do with is problem. Of course, you never can tell what an owner or PO or even DPO will do... :wink:
 
My Humber was black with a red leather interior. Yeah, that engine was like a tractor! I loved that boat. Then I gave it to my son in the late 90s.

Big mistake. RIP my old Humber friend.

But, on topic - my bugeye arrived with a mysterious brake issue - it did stop, but the pedal was consistently soft, a little too soft to drive comfortably. Bleeding didn't help - and beyond changing pads/shoes, that's where my expertise ends. So I took it the shop and it turns out that the calipers (this car has been changed to front discs)were both bad (despite having been 'rebuilt' by the PO). Apparently, all he had done was change the 0-rings, which is apparently sufficient in some cases, but not in this one! I haven't seen the complete work up yet (there are acouple of other mysteries under investigation), but I'll post as soon as I get the details.
 
I vote for rebuild - easy to do and cheap enough that if it doesn't work you won't feel bad
 
I rebuilt mine 3 times before I realized the bore was pitted and chewing up the seal, can have it sleeved but I just put on another one (also rebuilt). You should have three rubber sections of hose, one at each front caliper, one at the rear where it attaches to the axle, right? Those can go bad and start collapsing and acting like a one way check valve. Rear slaves=rear cylinders? Replace them as they are dirt cheap new ($15 each or so?).
I'd tear the MC down, examine the bore closely for pitting or rough areas, if it looks okay, maybe hone it very lightly, then put new seals in it. Rebuild kits are only $18 or so. New MC very very much more than that and if you've examined and rebuilt your MC, it should be as good as any other replacement.
 
Before digging into the master cylinder, one more possibility: I'd suggest trying to bleed it once the old-fashioned way: one guy pushes the pedal down, another closes the bleeder, first guy lets the pedal up. Open the bleeder and repeat. Do it fairly fast so you force out the bubble that tends to stay in the high part of the brake tubing.

I have a Mity-Vac, and I've never bled anything successfully with it. It sucks air in around the bleed screw, so it comes in as fast as it goes out. Now, I always do it as above, and it always works. Even with the clutch.
 
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