Brake problem and vacuum readings

[Bloodyaussie]

I have had a problem for a little while now and yesterday day I noticed my vacuum gauge while sitting out the front of my house with my foot on the brake drop pressure after only a moment...then noticed my foot sink a bit more till it felt like it was touching the floor.

Now when I hold my foot on the clutch the gauge moves only a touch and holds that pressure.

Is this a sign that my brake booster is stuffed???

Matty has the single pot calipers and his car stops very well where as mine is bloody terrible.

[Sir Roofy]

has it a diaphragm if so probably perished or its your master cylinder

[billyj]

id be looking for any extrenal leaks, check the sliders are moving freely. sounds like your loosing pressure somewhere, either extrenally or through the master bypassing internally. that or you have some air trapped in the brake lines, the twin piston brakes are great when working right, good firm pedal and really make the old patrol pull up in a hurry, but they are a dead set bitch to bleed. think it took about 3-4 hours of stuffing around bleeding and test driving to finally get all the air out of mine when i had the calipers reco'ed and fitted a new master

[Bloodyaussie]

Cheers mate I just got back from a brake specialist and he said my discs have glazed over and so would the pads plus the moisture meter went off the chart when he tested it.

They did not try to up sell me and I offered from the start to pay for driveway service but he refused and looked at it for free.

[Winnie]

Would that be because they weren't working properly and have now overheated? I am not confident new discs and pads will fix the problem, it did not fix my problem.

I have been looking for twin piston calipers but they are too dear for me... so I am just going to put a seal kit through all my calipers

[Bloodyaussie]

My calipers have been rebuilt and the discs are near new but will now need to be machined.. Pads are Bendix and the longer hoses were added so the only spot is the calipers that would need replacing.

[nissannewby]

Sounds like your master/booster. Are all vac lines to this point in good condition and free of obstruction?

[billyj]

they might be so called professionals but pedal dropping is from a pressure loss be it a leak, sticky piston, sticky slide or stuffed master. id bet the glazed pads/rotors are a by product of the front brakes not working properly.

figure out where your loosing brake pressure, fix that then just remove the front pads and if they still have plenty of meat left give them a good sand with some emery to remove the glazing and refit they will soon mate nicely to the rotor and good as new, no need to spend a couple of hundred on parts that are still going to work perfectly

[BillsGU]

Had a similar problem on my Patrol for ages. Had it looked at by many "experts" and "specialists". In the end in frustration I replaced the LPV and the brakes are now perfect.

[Bloodyaussie]

Funny as I started to look at new pads and stuff so I could begin the process I have been hit with another out of pocket expense and not sure if I can manage to get the parts just yet.

I think there are a few issues and with the wheel off the hub is very firm and not that easy to turn.

Also in the last couple of days and only sometimes I noticed a weird clunk on the drivers side as I first go to take off.. makes me think the caliper is sticking.

I have to find the card for the bloke that machined my discs last time (my old discs) and only charged $65 for both fronts.

Also I have to bleed out the brake fluid with all new fresh fluid... fun.

One other thing I have noticed and that is my rear pads still have bloody heaps to go even though they were what I changed ages ago but my fronts are getting very low.

[liftlid]

Reco ing single pots only gives you good brakes until you go 4x4 ing again it's not really worth it.
If you have a hand vac gauge test booster and associated parts separately to isolate fault.
Sounds like your brake bias is up the put!
Try the de glaze route and swap fluid check sliders

[Parksy]

My understanding is that glazed rotors don't need to be machined, only scuffed up to remove the glaze.

As for bleeding brakes, I used to hate bleeding brakes, but now do gravity bleeding which is dead easy, and, the only method so far that has given the patrol a solid pedal. Put a hose on the bleed nipple, other end into a jar and crack it open. Have the reservoir open so it can be topped up, but about 10 mins per corner(including proportioning valve) is all it needs. If you have a clear hose, this makes it easier to see if you still have air inside. I even tried gently tapping the caliper while the fluid was dripping out and I did manage to make a little more air escape.

If the slides are sticking, the fronts are easy to remove and clean. Use an appropriately sized drill bit by hand to clean the holes that the sliders sit in and re grease.
I did try cv grease on the pins at one point, but this stuff dried up within a few months and was useless. Only used it because I was worried about the incorrect grease eating away at the rubber seals. I've since just used wheel bearing grease. Rubbers are still fine months later and the pins don't dry up anymore. And the brakes are amazing.

[Alitis007]

remove the air out of the booster then clamp each wheel to find the area that's at fault. Clamp 1 at a time and try the brake pedal each time.

I've tried everything to improve my spongy pedal but after everything I have done still the same thing. There's 1 more thing on my list but I'll leave that for later down the track anyway let me know when you're going to bleed the fluid and we'll smash it out in 10 mins. Ask Darren how fast and how well we bled his gq