Fading Brake Pressure, no fluid loss

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Replaced the soft lines and did not get rock solid brake pedal. I think now I may never had had it. Bought the wife a new car and am now driving the LC again. I can't tell if anything is wrong with the brakes at this point, but I can still pump them up and feel pedal fade, however the truck stops fine.

Like CDan told me, there is no silver bullet for this one.
 
Scooter said:
Replaced the soft lines and did not get rock solid brake pedal. I think now I may never had had it. Bought the wife a new car and am now driving the LC again. I can't tell if anything is wrong with the brakes at this point, but I can still pump them up and feel pedal fade, however the truck stops fine.

Like CDan told me, there is no silver bullet for this one.
Click to expand...



Cool. My brakes suck. The PO had them dome at Midas with the Lifetime pads. Just ordered some OEM ones from Beno today. Hopefully this will fix them.
 
Scooter said:
Replaced the soft lines and did not get rock solid brake pedal. I think now I may never had had it. Bought the wife a new car and am now driving the LC again. I can't tell if anything is wrong with the brakes at this point, but I can still pump them up and feel pedal fade, however the truck stops fine.

Like CDan told me, there is no silver bullet for this one.
Click to expand...

I saw (read) that your brake pedal sinks when you hold the pedal as you would at a stop sign.

This is a classic symptom of a failed brake master cylinder.

"It was fine before the brake pads were replaced"
"did not open any brake bleeders"

all signs point at the brake master cylinder itself.
 
Having calipers with stuck pistons will also give this neg. effect.
 
Ok here goes my first post, I hope this is helpfull

I have the same issues as described in this thread

I have just completed an overhaul of the brake system in my 81 series
I removed all four calipers and reconditioned them using OEM calliper kits
I had the rear brake rotors machined, they were well within spec and still measure over 1mm of minimum thickness (I think 18mm is new 16mm is minimum so mine are around 17mm) and front rotors were machined last time I did pads less than two years ago and rotors still look perfect.
I left the hand brake shoes as there was still plenty of material left on these.
I've used new Toyota pads front and rear and put everything back together.
The brake fluid has been flushed with new DOT4 (I do this every second year anyway as my truck doesn't do that many Kms).
After bleeding the system including the proportioning valve everything was finished and like a completely new system.
I'll add here that I haven't touched the master cylinder during this round of servicing as it was replaced three years ago and I'm happy it is still working fine. Also haven't replaced rubber brake lines.

Now the brake pedal was the problem

It is firm, very firm when the motor is not running however with pressure applied I start the motor and the pedal sinks as boost comes on (normal) then... I can continue depressing the pedal so it slowly sinks almost to the floor.

I re-bled and checked for leaks as well as checking rubber lines for bulging and everything was perfect.

At first I questioned whether my master cylinder was the fault.

The interesting part is that on first road test the brakes are great. Plenty of bite and could lock a wheel if I had to (pre ABS model)

I was stumped as to why I could get so much travel from the pedal at idle, where was the fluid going? Absolutely certain there was NO AIR left in the system.

When I got home I found an interesting write up regarding brake boosters and specifically diesel powered heavier vehicles.

http://www.nbsbrakesupplies.com.au/technical-information/creeping-brake-pedals.html

I am more than happy with the braking performance of my truck on the road, and I would never find that I'm applying such heavy pressure under normal driving, I'm still yet to tow the boat anywhere so will find out how it really stops soon.

I also bought a new handbrake cable from Toyota which I still have to fit so hopefully that sorts the lack of handbrake when parking.

Sorry if this post is too long but I hope it helps anyone who is scratching their heads like I was but like I said I'm happy with how it is now
 
No guarantees but something that has worked for me for vehicles that have long runs of brake lines (Suburban).

Park the truck so that the bore of the MC is level. If you don't have some incline in your driveway then use boards or whatever is safe to get the bore level.

I use a squeegee but you can use anything similar and I put it so that the handle is on the brake pedal and the soft part is on the edge of the front seat. Then I use the power seat to move it forward until the brake pedal is about 1/2 travel. I leave it there over night. Then I remove it.

The theory is that there could be air in the line near the MC. This lets the air get into the MC and then into the reservoir when you let the pedal go.

I am not saying this will fix the problem but it is a no cost low effort move.
 
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