Brake issues - the never ending adventure

[Bannisterr]

Howdy everyone, second post so please be easy on me

Hoping to get some knowledge on a brake issue which has me chasing my tail.

My 2005 kun26r is refusing to brake well, hitting the pedal will slowly bring the car to a halt. In an emergency I wouldn't be able to stop in time. Solid brake pedal with the car off however once the engine is started the pedal drops about 2 thirds down and is very spongy. Pumping the brakes builds pressure for a split second until it droops back down.

So far I have replaced/done-
-Master cylinder (new bosch)
-New front and rear pads/shoes
-New front rotors
-Adjusted proportional valve
-Adjusted rear shoes
-Torn apart calipers and they're in good condition
-Bleed the system several times

I've isolated the new master and clamped it off, it holds pressure which baffles me as this seems like a simple MC issue. After removing the clamps one by one, it seems to come from the front brakes.

I also tested the rear brakes by jacking up the back and they were able to stall the engine although the pedal went quite low while doing this.

Any advice would be much appreciated, I was unable to find any answers using the search. My apologies if I have made any mistakes in this post.

[martynvella]

Has the car had a lift with larger wheels and tyres?

[hiluxxury]

^^x2 larger wheels greatly reduce the effectiveness of the standard setup.

You could also check the system is bled properly - the proportioning valve has a return line to the master cylinder which has caused me a number of headaches.

[Gipsy]

From others here who have early model kun26 the brakes were not outstanding, so many have put larger rotors from later models in and get much better results. Search here for brake issues and you're sure to get some real life stories.

Read through this thread

viewtopic.php?f=12&t=3663

[Bannisterr]

Hey guys thanks for the replies!

It only has 265/70/17's, has a 2 inch lift so nothing too crazy. I know the earlier models have less brakes than a runaway train, just seems too slow at stopping. Not comfortable driving it how it currently is

Ill have a another full system bleed including the return line mentioned today and report back

Thanks everyone

[Gipsy]

The 265/70/17 tyres are bigger than standard for your Hilux so that may be the problem, only bigger discs will fix that. Check that thread.

[hiluxxury]

x2 32in tyres are a fair bit bigger. Get the bleed done first to eliminate that before you take on a brake upgrade.

[241steve]

the booster is rooted.
you did have the key on when you bleed the brakes.

[Bannisterr]

Afternoon everyone,

Just a quick update and info for anyone who ever has the same issues I did.

Braking power is back, still a little spongy but that may just be in my head. Only issue is im unsure what exactly I did to fix it as I did several things at once before road testing it

Spent a good part of today religiously bleeding it, I used several techniques from gravity to the simple push and hold method. Although there still seems to be a small amount of air while bleeding which refuses to go away (possible air leak?) The pedal also seems to sink a little after pumping but it doesn't feel too terrible.

I replaced the proportional valve in conjunction with constant bleeding. I have a sneaking suspicion that the old one may have been sending too little pressure to the front brakes. (please correct me if this is wrong, just an observation)
I'm now able to get my brakes to lock up when emergency braking and my car to slow down. Rear end may need adjusting in the near future.

I didn't bleed the brakes with the key on Steve, was unaware that was a requirement on these cars. Worked on hundreds of landcrusiers and never heard of that. I will have another look at my manual and check that out.

Thanks everyone for the information much appreciated!

[241steve]

i say that as a lot of Prado ive worked on have an electric component to the booster and need the key on to bleed them i haven't touched any hilux brakes yet.

[Bannisterr]

Would be worth looking into Steve thanks mate, just as a side note my car doesn't have any ABS. Not sure if that's related to having the key on