Do I remove and keep the calipers upside-down when replacing brake fluid?

[Antipodes4WD]

I have no record of the brake fluid ever changed, so it was the time. After watching countless Youtube videos I settled on the vacuum pump method. Strangely enough, only a single line goes to the rear axle and another to front brakes. I always thought ABS works on individual wheels...

The available videos are either a disassembly, or just adding liquid to the master cylinder and sucking from bleeding screws.What worries me is that (especially at the front calipers) the bleeding screws are at the top. I see no way the old fluid will leave the caliper's cylinders to be replaced with the new fluid. Likely the fluid in those cylinders is as old as the car. Even if I hold the caliper with the bleeding screw down I am not sure it will help. The proper job would be disassembling the line and draining the caliper.

Am I missing something?

 

[Shayne]

Long time ago I decided to replace brake fluid on a 90 series , i just opened all the bleed nipples until they dripped and kept topping up the reservoir until the full bottle was gone .

Then bled like usual .

 

[Towpack]

I changed the brake fluid using one of those pressure bleeders (Gunsons I think) that pushes fluid through from the reservoir rather than sucking it through from the caliper end. I've never actually split a caliper but I assume they are designed so the fluid flows through the entire caliper before exiting the nipple. I've even bled the system dry by blowing air through from the reservoir, followed by new fluid and the system bled easily so, in answer to your question, I don't believe it's necessary to remove the calipers to bleed out all the old fluid.

 

[Antipodes4WD]

I changed the brake fluid using one of those pressure bleeders (Gunsons I think) that pushes fluid through from the reservoir rather than sucking it through from the caliper end. I've never actually split a caliper but I assume they are designed so the fluid flows through the entire caliper before exiting the nipple. I've even bled the system dry by blowing air through from the reservoir, followed by new fluid and the system bled easily so, in answer to your question, I don't believe it's necessary to remove the calipers to bleed out all the old fluid.

Yeah, I think that comes to the definition of the 'replace brake fluid' in the Toyota Land Cruiser 'Warranty and Service' manual. What is seen on the Youtube is mixing old and new brake fluid (and if I flush a gallon through the system mostly new) down the pipes and calling it done.

If I read the ellery.com.au manual (a physical book), they also have 'Brake fluid replacement' chapter page 261. They go into trouble of bleeding dry the master cylinder, holding calipers upside-down, removing cylinders.. etc.

If I have to follow Toyota schedule of every 24 months and do it at the workshop manual suggests, perhaps I start looking for an electric vehicle option... But as the mainstream Youtube goes it is clearly a half-arsed job.

Some suggest that 'In Toyota we trust' and the caliper chambers are designed to be flushed in the process, but I have serious doubts about that.

 

[Shayne]

ABS is electric when it sees one wheel lock up it reduces braking on all 4 to prevent you losing traction .

 

[Towpack]

I'm inclined to trust the Toyota FSM rather than any third party workshop manual.

 

[uHu]

Good point, Antipod, especially for the 4-pot calipers.
As water, and any particles dissolved in water, gathers at the bottom; and that both the inlet and the bleeder are at the top of the inner chamber of the caliper; there must be a bit of crud left over at the bottom after a normal, thorough bleeding.
I see that the bottom pistons corrode faster, or more often, than the top pots; which I take as an indication of more water at the bottom. I think I change three bottom pistons for each top one when servicing calipers.
Otoh, it takes only a few minutes extra to block off the hose, remove the caliper completely and drain it, before putting it back on for a normal bleed through.

 

[Shayne]

If the truck is new to you then its worth pointing out that despite not feeling it necessary rebuilding all 4 calipers on all three of my cruisers resulted in a significant improvement .

Mind you i replaced all the discs with M-Tek drilled and slotted at the same time .

 

[Towpack]

When I overhauled the brakes a few years ago with new rear callipers, a bit of new copper line and new flexy hoses I rebuilt the front callipers with new seals. I emptied the front lines with the pressure bleeder before removing the callipers and there was very little fluid left in them when I took the pistons out. The rear callipers were very crusty which was the main reason for the overhaul. The fronts were still working OK, as in the pistons weren't actually seized but braking was improved after the whole job was complete. Still easier than adjusting the flippin' hand brake IMO!

 

[Juddian]

Bleed the brakes out by whatever method you prefer, it makes sense to have the pistons pushed as far back into their bores as possible, new pads is the obvious time to do this.
If you were so minded you could jam the pistons fully closed which would see all but the smallest amount of old fluid left in the calipers also so little inside the bores that the swirl effect during bleeding is more likely to push out any nasties, i had to use the clamping method to get any sort of successful bleed on a series Landrover, used G Clamps to hold the slave cylinders closed, no reason it wouldn't work for pistons too.

The last time we bled the brakes on the 120 was by the age old up/down on the pedal method with wifey doing the pumping, brakes are superb.
I've never used the vacuum method, the good old Gunsons easibleed as far as i know doesn't fit the master cylinder cap on our vehicle, be annoying to find out i could have used it all along.
I think there's a brake flushing action if you have techsteam where the brake pressure pump will do the work for you, happy to be corrected if that's wrong.

When i service the brakes, ie strip clean lube, annually usually, i make a point of exercising the pistons in their bores, this is so easy on multiple piston designs, as you push one piston in its oppiste will slide out.
From my experience its usually the inner lower piston which suffers first on the 4 piston designs we have.

I've never had much sucess refurbing calipers myself, re-sealed dozens of slave cylinders in the past but generally calipers have had bores too corroded to seal properly again.

 

[Towpack]

As the reservoir on the 80 isn't the screw down type I made a cap that clamps down on the rim so I use the Gunsons pressure bleeder.
I've also just bought one of these...Piston Tool....ready for the fitting of some new pads instead of using an adjustable wrench like I've done in the past.