Seized Brake Pistons!

thebluboy, Jan 28, 5:25am
Brakes Have been pretty s**t on my 92 hilux since I bought it about 3 months ago, took it back to the yard and they said they had a look and it was a burst valve of somesort and told me the brakes SHOULD be better. i got my truck back and they werent.So today I had a look myself to see if it was the pads, it wasnt, but I put new ones in anyway. As I fitted the new ones, one of the pistons wouldnt retract back in. So I took it out and it seemed pretty seized to me I had to put it in the vice and apply a moderate amount of pressure to get it to retract. took them into the mechanics and asked them to service them and told them they were seized and must of been over looked last time. He then went on to say they were not seized at all and it is a common thing that you have to put them in the vice to free them up. Is that true or is he just covering up!

mechnificent, Jan 28, 5:32am
Vice!

"burst valve"!

Cover-up.

bitsy_boffin, Jan 28, 5:39am
Somebody will know, but are you sure that there's not a screw on the calipers to wind them back!

If you force the pistons back on a caliper like that, screwed caliper results :-)

thebluboy, Jan 28, 6:08am
nope self adjusting, ones on passenger side were fine. the seal had cam off the worst one which made me think they were seized.

carkitter, Jan 28, 6:21am
Your talking about rear disc calipers which I very much doubt a 92 Hilux has. This issue will be with the front disc calipers.

I agree with #2, covering up incompetence. Brakes are not rocket science yet so many 'so-called technicians' seem to get it all wrong.Any real mechanic knows you've found the source of the problem. You can strip down the caliper, clean it up and put new seals in it if you feel confident, or just pick up a replacement at a wreckers. Look for terminal wear or pitting on the caliper bore. Make sure you lubricate the mounting pins top and bottom too.

carkitter, Jan 28, 6:27am
If a front caliper is seized, then an inspection of the rear wheel cylinders would be a good idea too (checking for leaking seals).

thebluboy, Jan 29, 9:21pm
o.k, thanks for that guys.

elect70, Jan 30, 11:54pm
Boot splits & the cast iron edge of the cylinder rusts & as pads wear it sticks . Best take it off sand off rust cleanthoroughly & put in new seal kit. cheap as from BNT .

intrade, Jan 31, 12:06am
your brake fluid is probably more water by now. sounds like huge bulls to me I got a special mesuring tool to mesure moisture in the brake fluid. brake on a hilux should be real good as you can tow and need to stop heavy unbraked trailers down hills.

http://www.ehow.com/how_2111457_change-cars-brake-fluid.html

marte, Jan 31, 12:26am
Now. If theres water in the brake fluid, it probably got there from the reservoir.
If its got past the master cylinder, which is normally cast iron, the water would have made the master cylinders walls rust.
Not where the seal rubs against it, just a bit past that.

So when you go to push the foot pedal past where it normally travels, it rubs past the rust, dislodging the rust, ruining the seals, lifting rust into the brake fluid which will travels down the lines (forever) untill it gets to the brake seals, where it rusts the walls of the cylinder there (iron rust + water).

& all of your brake system is now ruined & you need to start at the master cylinder, relining that, putting in new seals, cleaning the lines, replacing all the slave cylinders & seals before running new brake fluid thru it.
Might as well replace all of the brake hoses, machine or replace the discs (warped thru running hot discs into creek streams.its a 4WD) & replace & clean the disc piston seals etc.

Once thats done, you will never have to look at it again.

marte, Jan 31, 12:30am
Oh, if during heavy braking downhill, the vehicle starts pulling hard to one side, the water in the brake lines has boiled & now your brakes are 'steam powered'.
Stop & wait for them to cool down or undo the brake bleeder nut to see all the steam escape & wait till thats gone & do it up again.

The answer is simple.
Just use a vacuum powered brake fluid bleeder, or get Midas to do it for you.

mechnificent, Jan 31, 12:56am
Crikey, someone has been reading a lot of books.

therafter1, Jan 31, 2:30am
But not the book that tells you that brake fluid is hygroscopic !

marte, Feb 2, 2:18am
Nah, thats all found out by experience.

I had a Cortina, several if you count parts.

petemun, Feb 2, 3:24am
lol I always thought it was called "hydro"scopic but nah you're right

scuba, Feb 2, 10:44am
so do you work for Midas or just get sucked in to sevicing your car there

carkitter, Feb 2, 11:21am
In my experience, no-one who works for Midas would know all that. They just come up with an excuse to replace everything and charge $700+

skin1235, Mar 3, 1:00pm
is it just hilux's, I've had to pull both callipers on both of mine in the last year, took a hell of an effort to get the pistons out of them, ( one side of one I had to tap a thread in the galley and pump them out with a grease gun - and a G clamp to make sure one didn't pop out before the other was free enough to pull out) and a lot of work with a hone to clean the bores, plus some serious work with fine wet and dry to clean the gunk off the pistons just to get them to fit the bores with no 'ring' on them
twin pots and double acting so 4 pistons per wheel
new seals and covers and they appear to be as good as new now