Leaking bleeder plugs
Thread Starter
Instructor
Joined: Jun 2010
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From: Fritsla Sweden
Leaking bleeder plugs
Hi,
I have rebuilt all four calipers on my 1968 after sandblasting and painting semi gloss black. Reused front pistons, new rear pistons. All news lip seals, dust covers and O-rings, pads etc. New bleeder plugs and blind plugs on the rear.
Yesterday I refilled entire system with fresh brake fluid, and bled out the system. Seems fine (I will probably regret saying this). But I noticed small leakage from the bleeder screws. I will tighten them further tonight and hopes this stops, but I do not like the idea to overtight. The bleeder plugs are brand new from Corvette America.
Perhaps it's normal on these calipers to tighten the bleeder plugs fairly aggressive? Any other suggestions? I noted that on one of each rear caliper halves the bleeder plug seems to "bottom out". A bit strange I think...well well...hmm...
/Martin
I have rebuilt all four calipers on my 1968 after sandblasting and painting semi gloss black. Reused front pistons, new rear pistons. All news lip seals, dust covers and O-rings, pads etc. New bleeder plugs and blind plugs on the rear.
Yesterday I refilled entire system with fresh brake fluid, and bled out the system. Seems fine (I will probably regret saying this). But I noticed small leakage from the bleeder screws. I will tighten them further tonight and hopes this stops, but I do not like the idea to overtight. The bleeder plugs are brand new from Corvette America.
Perhaps it's normal on these calipers to tighten the bleeder plugs fairly aggressive? Any other suggestions? I noted that on one of each rear caliper halves the bleeder plug seems to "bottom out". A bit strange I think...well well...hmm...
/Martin
Race Director
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Unfortunately they should close fairly easy, they always have for me and this is my third set of calipers. They just close with what I would say 1-2 lbs or so of torque, I can look up the specs. The rear ones that "bottom out" maybe the plugs are supposed to go there I don't know. I have 3 bleeders and one plug on each rear caliper...I think
Others might have a different experience
*Edit : it is 90 in/lbs for the bleeder valves or about 7 ft/lbs which is pretty low
Others might have a different experience
*Edit : it is 90 in/lbs for the bleeder valves or about 7 ft/lbs which is pretty low
Last edited by MotorHead; Jun 28, 2010 at 12:56 PM.
Team Owner
Joined: Mar 2002
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They shouldn't take much torque at all to seal off. I seat them finger tight, and then just snug them up with a wrench maybe 1/16th of a turn or less. I think it's more likely you over torqued them rather than under torqued. Hopefully you only screwed up the bleeder and not the caliper itself.
Bottom line is you aren't going to fix a leaking bleeder by cranking it down real hard.
Bottom line is you aren't going to fix a leaking bleeder by cranking it down real hard.
Race Director
Joined: Mar 2006
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From: Florida
Both the bleeders and plugs have a taper that seals on the tapered seat (45° or close to it) in the caliper when tightened.
Sometimes the new bleeders or plugs don't quite seat properly and a little extra torque is required. You may have to deform the taper on the new bleeders and plugs a bit by repeatedly opening and closing them until they seal. Your seats should be good, since you are reusing the old calipers. Carefull not to break them off. Both the bleeders and plugs should bottom out.
Any parts store handles the replacement bleeders, but maybe not the plugs.
I always put a little antisieze on the threads.
Sometimes the new bleeders or plugs don't quite seat properly and a little extra torque is required. You may have to deform the taper on the new bleeders and plugs a bit by repeatedly opening and closing them until they seal. Your seats should be good, since you are reusing the old calipers. Carefull not to break them off. Both the bleeders and plugs should bottom out.
Any parts store handles the replacement bleeders, but maybe not the plugs.
I always put a little antisieze on the threads.
Thread Starter
Instructor
Joined: Jun 2010
Posts: 173
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From: Fritsla Sweden
Thanks for your inputs. I have the same impression from all other brakes that it never is a problem and only snugtight do just fine. I do realize the risk of braking them off or deform the caliper seat so I have not used any significant force yet, just a tad harder than usual.
I think the point with a slight seating issue between caliper seat and taper on bleeder might be the root cause. I actally had some issues on my Yamaha YZF R1 when changing bleeder plugs a coupleof years ago. That was also brand new bleeders in used calipers, and it was a bit problematic before it was 100% dry.
Hmm, I will try to exercise the bleeders by opening/closing a number of times. I will also compare the taper on bleeder seat with the ones that was on the calipers before disassembly.
My worst nightmare would be if the seats in the calipers is deformed. Argh. I hope this is not possible to do easily without using excessive force...
I think the point with a slight seating issue between caliper seat and taper on bleeder might be the root cause. I actally had some issues on my Yamaha YZF R1 when changing bleeder plugs a coupleof years ago. That was also brand new bleeders in used calipers, and it was a bit problematic before it was 100% dry.
Hmm, I will try to exercise the bleeders by opening/closing a number of times. I will also compare the taper on bleeder seat with the ones that was on the calipers before disassembly.
My worst nightmare would be if the seats in the calipers is deformed. Argh. I hope this is not possible to do easily without using excessive force...
Thread Starter
Instructor
Joined: Jun 2010
Posts: 173
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From: Fritsla Sweden
Just got back from todays recreation session with my 68. Removed bleeder plug on front right caliper. Conical area on bleeder plug looked very good, no scoring, distortion what so ever. In the caliper the conical seating area looked good also. Looked nicely conical.
One thing however, the new bleeder plug is 0.5mm smaller in outside diameter, 7.5mm when measuring across threads. The original one was 8.0mm and fits MUCH more snugly in the caliper. The new plug sort of "wobbles" down in the caliper, which leads me to suspect that it might land non centered in the conical recess leading to my small, small seepage of brake fluid. I cleaned up the original bleeder screw and installed (one thing good with this 68 is that it's almost rust free). Will see how this goes, but it feels much more snug and tight.
0.5mm feels a bit much I think in difference...?
/Martin
One thing however, the new bleeder plug is 0.5mm smaller in outside diameter, 7.5mm when measuring across threads. The original one was 8.0mm and fits MUCH more snugly in the caliper. The new plug sort of "wobbles" down in the caliper, which leads me to suspect that it might land non centered in the conical recess leading to my small, small seepage of brake fluid. I cleaned up the original bleeder screw and installed (one thing good with this 68 is that it's almost rust free). Will see how this goes, but it feels much more snug and tight.
0.5mm feels a bit much I think in difference...?
/Martin
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Thread Starter
Instructor
Joined: Jun 2010
Posts: 173
Likes: 0
From: Fritsla Sweden
Hi,
I will probably need to take both rear calipers off and inspect the bleeder plug sealing area carefully. Something is not right over here. Annoying.
Perhaps corrosion on the seat surface...?
What is the correct total length of the bleeder valves? 1"?
Thanks.
/Martin
I will probably need to take both rear calipers off and inspect the bleeder plug sealing area carefully. Something is not right over here. Annoying.
Perhaps corrosion on the seat surface...?What is the correct total length of the bleeder valves? 1"?
Thanks.
/Martin
