28 replies to this topic

[73SUNBURSTEXYOUWON]

Hi all,
I am having a little issue when re-bleeding my brakes. All i am doing is a fluid change. Car has been driven and stops. Nothing has been pulled apart on brakes in some years though.

I dont get full brake clamping pressure at my front calipers/rotors after the first bleed attempt to the next. EVEN the rear brakes when i began the bleeding process, from LHR > RHR, was a bit sus.

> Now at LHF,It takes about 3-4 pumps of the pedal to build more pressure in the front brake circuit before the calipers will lock onto the rotors again. And thats checking both sides for clamping force, only when bleeding at LHF.

Also fluid flow out of the LHF caliper bleed nipple/bleed hose can be minimal, after the first initial bleed attempt.(caliper nipples are at the top b4 u ask ).

My M/C was resleeved (about 9 years ago) and in the attached images, you can see the small orifices drilled into the sleeve, which are way smaller than the holes drilled into the reservoir base which i believe are factory size, so why should the sleeve drillings be way smaller?

Could that be the problem, not enough fluid getting through the small orifices??.

I have checked my pushrod protrusion from the booster face, which is now re-adjusted to 28mm (*was 30mm).
Maybe it could be shortend a bit more yet but in doing my maths on my setup (attached scrawl),that i work out my pushrod maybe now 1mm clear of bottoming into piston when all fitted up.

Where as before (*at 30mm) i thought maybe i was not getting full piston travel/effort because the pushrod had already partially pushed the piston in by 1mm, sounds F-all, but had to check.

I have not removed my pushrod from the booster, but can feel it sitting against the reaction disc, feels and sounds like the head of the pushrod is seating against something rubbery.

With the engine running and bleeding, still no different really to the above description. And that was with the booster pushrod at *30mm. Which was not self applying any brakes either.

So additionally... could i have an internal issue within my M/C like perished piston seals?

My gut feel is to bust the M/C into pieces and answer my own questions, but wanted to share the issue all the same.

Cheers
Jaso.

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[TOERUNNER]

Just had mine resleeved also and it is the same as yours, mine works fine,pretty sure there is only a small orifice originally, i would be checking that the piston cup is coming back past the orifice because if the drilled hole is in a slightly different position the cup may not be clearing it.

[73SUNBURSTEXYOUWON]

Hmmm, when i have someone pushin the pedal, i can see the pistons moving but can quite see the piston cups.
Looking at where those orifices are drilled almost centre, one would think they should be in the right spot.
Must be a fine line, between pleasure n pain. Let me do some more homework.

[S pack]

Now at LHF,It takes about 3-4 pumps of the pedal to build more pressure in the front brake circuit before the calipers will lock onto the rotors again. And thats checking both sides for clamping force, only when bleeding at LHF.

Also fluid flow out of the LHF caliper bleed nipple/bleed hose can be minimal, after the first initial bleed attempt.(caliper nipples are at the top b4 u ask ).

Cheers
Jaso.

3 to 4 pumps of the pedal to bring the pedal pressure back up sounds pretty normal when bleeding brakes.

I would be more concerned about the very slow fluid release from the bleeder nipple. I had a similar thing with the right rear wheel cylinder on the LJ some years ago.

Eventually this almighty blob of thick gooey brake fluid was discharged through the bleeder nipple and after that the brake fluid was flowing like beer on tap.
 

[73SUNBURSTEXYOUWON]

Im going to bust my M/C apart. Rekit it.
There's gotta be somethin not quite right in there?

Check'n first if kits are available. I've seen em somewhere for $195.00, if thats a current listing/price.

https://www.earlyhol...nut-square-top/

And just looking/ thinking, the primary piston has a new spring in the kit, but the secondary piston does not have a new spring in the kit.

So could the spring under my big nut be tired, and not pushing the secondary piston back enough to allow the front cup to pickup fluid?

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[S pack]

If your brake pedal pumps up after 3 or 4 pumps and stays that way (no more bleeding) and your brakes are working properly (road test) then your master cyl is working fine.

If the cup in the m/cyl was swollen to the point that it is blocking the compensation port then no fluid would be able to drain down into the cyl bore forward of the cup and your brake pedal would not pump up

Don't fix what isn't broken.

[73SUNBURSTEXYOUWON]

3 to 4 pumps of the pedal to bring the pedal pressure back up sounds pretty normal when bleeding brakes.
I would be more concerned about the very slow fluid release from the bleeder nipple. I had a similar thing with the right rear wheel cylinder on the LJ some years ago.
Eventually this almighty blob of thick gooey brake fluid was discharged through the bleeder nipple and after that the brake fluid was flowing like beer on tap.
 

Thanks Dave, noted.
I didn't notice anything thick n gooie so far...

Also the connector switch is another area i will look at too. But they are quite basic, fluid in one side out the other.

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[73SUNBURSTEXYOUWON]

If your brake pedal pumps up after 3 or 4 pumps and stays that way (no more bleeding) and your brakes are working properly (road test) then your master cyl is working fine.
If the cup in the m/cyl was swollen to the point that it is blocking the compensation port then no fluid would be able to drain down into the cyl bore forward of the cup and your brake pedal would not pump up
Don't fix what isn't broken.

I am really liking your above closing comment "Don't fix what isn't broken."

You are beginning to talk me down off the ledge.

Id rather not pull the M/C apart. And yes eventually when i build the pressure backup the brakes are working - After all, they were prior to the fluid change/bleeding.
I never thought then that i had any issue. NO leaks no lights on etc, have been driving car without a care in the world.

The fluid flow.. like having an enlarged prostate, is at times a dribble i guess come with age.

Let me do some more homework....I hated school BTW.

[RallyRed]

Haven't seen it on the front, but on the back,  have had it on the back of 2 Toranas in recent years, virtually no flow at all out of hose ( body to rear axle) when brake pushed, brakes virtually not working.  $25 for a hose and away again.

Maybe crack the hose off the caliper and hit the pedal....see what comes out?

[73SUNBURSTEXYOUWON]

Thanks Col, yeah, i could open up the LHF brake line to brake hose joint, check flow out of pipe,then check flow at caliper end out of hose too.
Its added to my homework.

[RallyRed]

Yes, the hose just seems to "grow" inside until it blocks up.

Maybe not your issue, but a quick thing to do.

[dattoman]

Looks fairly familiar

The little compensating port holes are only .7mm

 

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[73SUNBURSTEXYOUWON]

Looks fairly familiar
The little compensating port holes are only .7mm
 
big nut1.jpg
big nut.jpg

Thanks Datto

[Indy Orange]

I have two big nuts that need restoring.😏

[claysummers]

Not interested in yer nuts. Show us yer donk...

Sent from my SM-G781B using Tapatalk

[73SUNBURSTEXYOUWON]

Well, after cringing - reading bout Indys big nuts, and clay wanting a look at his Dong-K.

I have my own show n tell again.
I removed the M/C and having a close look at its piston cups, the Very front cup of the Secondary piston has some defect. Whether that was there from manufacture of the cup or not, could be my issue.

Also found a bit of fluff (BiG Nuts hair) in the cup of the Primary piston....dunno if that was causing anything much either in the rear.

I took a random pic too, of the little stop bolt length, is it correct length?
I guess it only needs to just protrude into the M/C bore enough to touch the forward shoulder of the Secondary piston.

Finally the Primary piston, trying to measure n work out the cups in relation to the bore sleeve drillings.

So gunna source sum new seals and try it all again.

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[73SUNBURSTEXYOUWON]

+1 image

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[Indy Orange]

Not interested in yer nuts. Show us yer donk...

Sent from my SM-G781B using Tapatalk

Unfortunately the whole assembly needs re kitting.But here ya go.

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Edited by Indy Orange, 27 August 2022 - 05:08 PM.

[claysummers]

Choice indeed

Sent from my SM-G781B using Tapatalk

[S pack]

At the end of the day finding this defective seal has been a good result however I doubt that it has been causing any problems, yet.

[73SUNBURSTEXYOUWON]

Back again, (above, thanks Dave)

I got my tip drills out. Checked the compensating port drillings on the M/C for size, 0.69mm as Datto advised about 0.7mm.

So then i refitted the Secondary piston and spring back into the M/C bore also pushing it in to refit the stop bolt.
Then Got my magnifying glass out and operated the Secondary piston and can observe the port is clear before the forward piston cup moves forward to cover the port, simulating brake application.

Did same also with rear Primary piston fitted too.

So i am satisfied that both front and rear circuit compensating ports are drilled in the correct spots.

Then next, set up a brake fluid bottle and Vaccuum bled from that to LHF caliper. It bled without hesitation. Free as.
Yesterday with the M/C fitted i could not get the Bastard(LHF) to VAC bleed hardly any fluid. (Is that because the 0.7mm drilling is so small??)

I am going to recheck my Booster Pushrod measurements again. Measure Twice cut once again to rule out the piston cups not pushed too far to cover ports.

Just another observation when i fitted the pistons, they went in relatively easily. Not a real lot of resistance from the cups.

I am dropping into BHSS Capalaba Brisbane with the M/C during the week, they did the resleeve originally so will get them to check it out and supply/fit/test new cups.

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[73SUNBURSTEXYOUWON]

The brake fail pressure differential switch I have is not creating a circuit when testing as pictured.

I do get an Intermittent circuit, when testing from the plunger to the threaded body, as i wriggle the plunger.

The plunger is moving in and out, but seems to have some binding resistance like there must be a rubber seal inside?

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[73SUNBURSTEXYOUWON]

Looking for an alternate solution to these brake fail warning switches. Given ebay sellers have em listed $110 upwards to $249.

The thread appears to be 3/8unf and the shape of a JIC hydraulic fitting.

Anyway, thinking about it as below link, something similar to an oil pressure switch could work. With a pin that simply pushes switch contacts open, until the pin drops into the shuttle valve groove and simply turns on the dash brake light?

https://www.google.c...=PrgSBDnsQMJUkM

[dattoman]

Not sure what you are trying to achieve with the switch

 

Its a dry area... no fluid

All it does it activates the light in the case of a circuit fail...assuming the shuttle moves

[73SUNBURSTEXYOUWON]

Not sure what you are trying to achieve with the switch
 
Its a dry area... no fluid
All it does it activates the light in the case of a circuit fail...assuming the shuttle moves

My acheivement was to attempt to come up with a future alternative to a switch that is becoming less available.

I totally understand the no fluid area the original switch operates in.

If a switch similar to an Oil pressue switch which in theory works the same way, only with a detent pin inserted into it instead of fluid pressure, then it would seem like an alternate solution.