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914World.com _ 914World Garage _ Brake bleed valve seat....calling all brake gurus
Posted by: raynekat Nov 10 2018, 06:16 PM
Just trying to get an answer over the weekend to a question I have.
I've got some new rear calipers going on the car and one of them is weeping some brake fluid.
Hard to see exactly where it is coming from.
Could be a bleeder valve or possibly a defect in the caliper casting.
I have a question about the brake bleed nipple seat.....actually the very bottom where the end of the bleed valve bottoms out.
See pic below:
To me, the correct bottom of the bleed valve seat should be beveled to match the beveled point at the end of the bleed valve....such as the example on the right.
My particular caliper has a seat bottom that is square like the example on the left.
Not only do you get less surface area for the bleed valve to seat against possibly causing a leak even when the bleed valve is closed or tightened up....but if you tighten the bleed valve even a moderate amount, the square bottom will put a nice "step" in the bevel of your bleed valve.
I don't believe that is an optimal situation or even wanted.
Any thoughts or knowledge on this?
I'm thinking I have an incorrectly machined bleed valve seat.
I was thinking about taking a proper sized drill bit and putting a bevel down there, but the angle is not the same on the drill bit.
On Monday I'll check with Eric at PMB for his take on this.
Posted by: 914Sixer Nov 11 2018, 07:11 AM
Are these the reproduction -6 calipers?
Posted by: raynekat Nov 11 2018, 08:19 AM
Yes they are the reproduction six calipers ...interesting question.
Posted by: mobymutt Nov 11 2018, 09:07 AM
My guess is version 'B', but with a very small chamfer to match the cone. I don't think you'd ever get version 'A' to seal with that much surface area.
Posted by: 914Sixer Nov 11 2018, 09:12 AM
I have a set for the rear of my car. Looks like I might have the same problem. I have not got them installed yet.
Posted by: Krieger Nov 11 2018, 09:18 AM
I have found the fit has to be right on. I have an old pair of calipers. When I bought new speed bleeders they leaked. Both are tapered, but not quite the same.
Posted by: raynekat Nov 11 2018, 01:59 PM
The point on the bleeder valves is right at 90 deg.
Ordering a 3/16" countersink bit with a 90 deg tip to chamber a bit of that square seat on Ebay right now.
I'll loan it out to anyone who wants to use it (hint hint wink wink Mark Heard).
Posted by: raynekat Nov 11 2018, 02:02 PM
My guess is version 'B', but with a very small chamfer to match the cone. I don't think you'd ever get version 'A' to seal with that much surface area.
The problem with version B....it puts a big step or dent in the end of your bleeder valve.
Pretty sure that's not cool or optimal.
Posted by: Jamie Nov 11 2018, 02:59 PM
The point on the bleeder valves is right at 90 deg.
Ordering a 3/16" countersink bit with a 90 deg tip to chamber a bit of that square seat on Ebay right now.
I'll loan it out to anyone who wants to use it (hint hint wink wink Mark Heard).
Its very easy to grind a point profile on a drill bit with a bit of practice and a grinder.
Posted by: Jamie Nov 11 2018, 03:00 PM
How do I delete duplicate posts?
Posted by: rgalla9146 Nov 11 2018, 03:49 PM
The point on the bleeder valves is right at 90 deg.
Ordering a 3/16" countersink bit with a 90 deg tip to chamber a bit of that square seat on Ebay right now.
I'll loan it out to anyone who wants to use it (hint hint wink wink Mark Heard).
This is not a job that should be trusted to a hand held tool.
You'll be inviting a more difficult repair.
Is this is quality control issue that the supplier might be best equipped o remedy ?
Posted by: raynekat Nov 11 2018, 05:19 PM
The point on the bleeder valves is right at 90 deg.
Ordering a 3/16" countersink bit with a 90 deg tip to chamber a bit of that square seat on Ebay right now.
I'll loan it out to anyone who wants to use it (hint hint wink wink Mark Heard).
This is not a job that should be trusted to a hand held tool.
You'll be inviting a more difficult repair.
Is this is quality control issue that the supplier might be best equipped o remedy ?
I'll be attempting this with a drill press.
Not sure it's that tough if you're careful.
In my case....I've got nothing to lose really.
Without a successful outcome, these calipers are going in the dumpster.
Posted by: sixnotfour Nov 11 2018, 05:36 PM
The point on the bleeder valves is right at 90 deg.
Ordering a 3/16" countersink bit with a 90 deg tip to chamber a bit of that square seat on Ebay right now.
I'll loan it out to anyone who wants to use it (hint hint wink wink Mark Heard).
This is not a job that should be trusted to a hand held tool.
You'll be inviting a more difficult repair.
Is this is quality control issue that the supplier might be best equipped o remedy ?
I'll be attempting this with a drill press.
Not sure it's that tough if you're careful.
In my case....I've got nothing to lose really.
Without a successful outcome, these calipers are going in the dumpster.
If you get it square inline to threaded hole ...turn the chuck by hand to produce desired chamfer width...or get your money back...
Posted by: raynekat Nov 12 2018, 03:06 PM
This bleed valve seat affair is turning into a non-issue.
Put some new bleeder valves in today and the caliper is still weeping from the thru bolt threads 2nd from the top.
This is the bolt just beneath the upper fluid passageway that connects both caliper halves together.
The area around the bleeder valve is bone dry.
So either there is an issue with the square O-rings (or their mating surfaces) that seal both caliper halves or....
what I really believe.
I think this caliper has a casting defect such that there is a micro fissure or void allowing fluid to travel from the brake fluid gallery directly into the thru bolt bore or hole.
If so, it's terminal for this caliper.
Posted by: mobymutt Nov 12 2018, 03:45 PM
My bet is on the damaged or missing o-ring. Are you going to split the caliper apart?
Posted by: raynekat Nov 13 2018, 12:44 AM
My bet is on the damaged or missing o-ring. Are you going to split the caliper apart?
Already split apart multiple times.
The square O-rings are new (each time) and the O-ring seat and flat mating surfaces look fine.
If you look closely inside the thru bolt bore, something in the wall doesn't look good.
And if you go in with a small pick, you can feel a roughness to the wall.
That's the casting defect, fissure or whatever that causing the leak I believe.
Posted by: raynekat Nov 14 2018, 12:10 AM
Ordered some different rear calipers today from PMB....still 914-6 GT.
I threw in the towel (or waved the white flag) on the others.
Posted by: mepstein Nov 14 2018, 07:07 AM
Ordered some different rear calipers today from PMB....still 914-6 GT.
I threw in the towel (or waved the white flag) on the others.
Real ones?
Posted by: raynekat Nov 14 2018, 12:24 PM
Real 914-6 calipers with the spacers so they will fit over vented discs.
As real as I'm gonna get with this. 
Aren't the GT calipers just the six calipers with a couple of spacers thrown in between?
Posted by: mepstein Nov 14 2018, 01:19 PM
Real 914-6 calipers with the spacers so they will fit over vented discs.
As real as I'm gonna get with this.
Aren't the GT calipers just the six calipers with a couple of spacers thrown in between?
Yes. The spacers are easy to find but I think the bolts are a special size but I could be making that up.
My GT calipers are Ferrari 308 calipers that Eric machined for a second bleeder. They are the same ATE casting and come with a spacer but oriented 180 degrees on the red cars. Got the first set for $250 before the Ferrari guys caught on.
Posted by: raynekat Nov 14 2018, 02:15 PM
Real 914-6 calipers with the spacers so they will fit over vented discs.
As real as I'm gonna get with this.
Aren't the GT calipers just the six calipers with a couple of spacers thrown in between?
Yes. The spacers are easy to find but I think the bolts are a special size but I could be making that up.
My GT calipers are Ferrari 308 calipers that Eric machined for a second bleeder. They are the same ATE casting and come with a spacer but oriented 180 degrees on the red cars. Got the first set for $250 before the Ferrari guys caught on.
Eric is using more "common" type bolts on these....not the impossible to find Ribe sized bolts.
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