Ae82 uneven rear brakes

[dxtawagon]

hey,
wof time and the GT has failed on uneven rear brakes.
first time round both the handbrake and footbrake were low on the rear left. This made me think it may be something with the caliper. got a new caliper and fully bleed all brakes. this time round handbrake is sweet but footbrake still low on left rear.

Must be something to do with the valving?

what should i do next? is there just 1 valve that proportions the rear brakes? is this located on the firewall?

Cheers

[Rick]

When you say you got a "new caliper" was that brand new or as in new second hand?

If it was a problem with the proportioning valve it would affect both rear brakes

It sounds like its a blockage or damaged brake line (if the caliper is new or recond), the rear brake line "T"s off to the left and right rear brakes under the car, trace the line from the T to the dodgy caliper for any damage, if there isn't then it maybe something in the line, you may have to undo the line at the T and at the caliper and blow compressed air down it to clear it.

[dxtawagon]

yeah its actually a second hand caliper. i don't think that's the problem as the brakes failed for the same thing with the original caliper.
might be the line - ill have to take a look. I just changed the engine so there may be a chance that the line has been squished somewhere.....

i didnt know how the valves work so i thought there may be a valve that separates the left and right rear. as opposed to just proportioning between front and rear?

[Bling]

If it was a problem with the proportioning valve it would affect both rear brakes

Not in my experience, granted not with this model of car, so this could be irrelevant. I had the issue on my car though and found it was commonly a problem with the proportioning valve.

More info on the board if you search.

[matt dunn]

If it was a problem with the proportioning valve it would affect both rear brakes

Not on FWD cars,

it will be a split diagonal system so there is no front and rear split,
and so will have basically two proportional valves in one unit,
so probably is the problem.

[Rick]

Yes sorry thinking of my AE85 yes it could very well be the proportional valve which is on the firewall. I have had proportional valves in the past stick/not work I am not sure on the AE82 one but my AE85 one I could pull it apart and clean it out.

[dxtawagon]

cool cheers.

that pic is exactly what it is. RF goes from booster straight to brake (through splitter that also feeds LF, LF runs through valve however. And a separate line comes off the booster straight to the valve which i assume runs the two rear pipes.

Is it worth pulling the valve off to try and clean it? or should i look to find a second hand one? or can you buy these new from repco/partsmaster etc?

Also, if i pull it off, is there a clean way to do this? looks like it could get pretty messy as there are like 5 pipes into/out of the valve unit....

Thanks again

[Bling]

When I did mine I put an old hose on the feed from the master cylinder / feed / whatever. So the pipe leading into the P valve I undid first and tightened the old hose onto the inlet pipe then just tied it above the height of the master, so it didn't drip.

Then just undid the rest, pulled the P valve to bits, gave it a good clean out and put it all back together. In mine I could see a thin line of corrosion / muck, only tiny but cleaning all that out gave me pretty much perfect balance. Bleed the brakes and should be all good to go.

If you get a second hand one make sure its exactly the same and clean that one out as you never know its condition. Fiddly / messy as f**k job (first timer) but not very hard if you have experience with brakes / mechanic type stuff. If you're worried though, wouldn't cost tooooo much to get it cleaned out by a pro. It can be a pain to do. I got a spare one off a wrecked car I had, so cleaned that out and made a mint job. Then found even though it was the same shape car, it was slightly different (one was 4 port, one was 5 IIRC), so had to do it all again with the one already on my car.

[dxtawagon]

got the valve out without much hassle.
Doesn't look very easy to pull apart though? has pressed in caps on the bottom.......i dont think these are going to come out very easily without wrecking them......? anyone done this before?
can you buy these valves new from toyota?

cheers

[Grrrrrrr!]

You probably can get them from toyota, but i'm guessing the cost will make your eyes water, and chances are it'll be ex japan. Take it into your local brake and clutch specialist and see what they can do for you.

[xsspeed]

Not much you can do to them but flush, reinstall, bleed, and hope it works.

[dxtawagon]

sweet,
yea i gave the proportioning valve a good spray with carb cleaner then blew it out with a air compressor. I had an after thought that maybe i shouldn't have used carb cleaner? does anyone know if any residue carb cleaner will affect the brake fluid?
just need to try blow out the brake line to the left rear as well to make sure there are no blockages. i checked the line front to back and cant see any areas that have been squeezed or anything...

[Bling]

Don't take this as the correct method... it's just how I did it. (on a 96 corolla though)

Grabbed a really fine flat head screwdriver and worked my way around those pressed in caps till they pop out. Memory is going fuzzy now..... but there are probably circlip springs holding the pistons in the cylinder too, they can be a nightmare to get out. Once again I got out the tiny screwdrivers and eventually levered them out. I think I then tapped a small allen key into the opposite end of the valve (where the line fits to the valve) and tapped the pistons out. Then I gave them a good clean out, making sure to keep everything in the right order. I found a tiny as build up in one of the cylinders so cleaned that all out, and flushed the whole lot with brake fluid and put it all back together.

My guess is you'd be lucky to have fixed anything by doing what you've done. But who knows. The build up in my cylinder wasn't going to budge with just a flush out that's for sure. It was a minute ring of build up that sat between the "piston" and the cylinder wall.

As I say, that's just what I did and it may not be the correct / best method.

[TRD Man]

There's an old theory (old ones are usually the best) that when looking to fix any problem for which you do not know the cause you should start by doing the simple, and cheap, jobs first.
So before you race off and buy a new caliper, or a proportioning valve, or rip half the car apart, look at your hoses.
At the age of your AE82 these can have a tendency to collapse internally and effect the braking on that side. Replace both sides whilst you're at it.

[allencr]

Post with some info on that valve & cleaning.
viewtopic.php?t=81619&start=20

[dxtawagon]

cheers for the link, some good info in there! looks like a pig of a job to do though!
valve from toyota is $255 and 3 weeks EX japan! haha

looks like ill be trying option 1 - cleaning the valve.....dammit.

[dxtawagon]

managed to pull the valve apart and as stated previously getting the little circlips holding the pistons in was a NIGHTMARE, managed to bend a pin to get in behind the clip to lever it out. really really fiddly job though, had to relax, have a cuppa and stare at it (and what tools i had) for a couple mins to work out how best to go about it haha.

was actually a reasonable amount of crap built up in there so fingers crossed that was the problem.

It appears to me that this valve separates the balance of the rear brakes completely, i.e. not dependent on each other at all. I think rear left is taken off front right line and vice versa?

anyways, sorry the photos are crap, couldn't find batteries for my proper camera so they just off phone.

[matt dunn]

It appears to me that this valve separates the balance of the rear brakes completely, i.e. not dependent on each other at all. I think rear left is taken off front right line and vice versa?

Yes split diagonal system and almost all FWD cars have it,

there is two feeds from the matser cylinder
one feeds left front and right rear
the other feed is right front and left rear.

so the two rears are on completly different circuits once they leave the master cylinder.

One of the first things we learnt on pre-trade course years ago.

[dxtawagon]

It appears to me that this valve separates the balance of the rear brakes completely, i.e. not dependent on each other at all. I think rear left is taken off front right line and vice versa?

Yes split diagonal system and almost all FWD cars have it,

there is two feeds from the matser cylinder
one feeds left front and right rear
the other feed is right front and left rear.

so the two rears are on completly different circuits once they leave the master cylinder.

One of the first things we learnt on pre-trade course years ago.

Haha, that shows that i have zero training haha! but im glad i got the right answer haha