1991 Brake Issues (1 Viewer)

[pavell]

Hey guys I have a 1991 LC with 233,000 miles. New to me.

I had an incident a 1 week ago where I overheated the brakes coming down a mountain. (rookie mistake I should have been engine breaking).

I basically lost brakes coming down the mountain and I shut the car off and the pedal came back a bit more mushy. Now 1 week later the pedal goes to the floor and there is hardly any brakes at all. I flushed all the fluid out (it was almost black). The pedal was still spongy; I flushed the whole system again.

I pulled the rear drums off; wheel cylinders look good no leaks. The front calipers also look good no leaks.

It doesn't seem like there is any leaks in the system. I've going to try to replace the master cylinder and bleed again. Any thoughts or tips to check before I'm throwing too many parts at it?

 

[ppc]

If the Japanese models are like the US then there is a proportioning valve above the rear axle that needs to be part of the bleeding sequence.

 

[pavell]

Sorry I forgot to mention I did bleed that too

 

[pavell]

Just an update, I replaced the master cylinder and front calipers with new units. I bled the brakes with rear valve included. Still no brakes.

I got a brake pressure bleeder with speed bleeders and bled the brakes 2x more. The pedal is a little better but still goes to the floor.

Any thoughts/troubleshooting help ?

Thanks

 

[gnarlytoes]

Booster?

 

[pavell]

Booster?

the pedal goes all the way to the floor and is still soft. if it was a booster wouldn't the pedal be hard to push in ?

 

[gnarlytoes]

When the booster went out on my '92, the pedal felt spongy and would go to the floor. If I held it down, it would then start pushing my foot back up.

 

[pavell]

When the booster went out on my '92, the pedal felt spongy and would go to the floor. If I held it down, it would then start pushing my foot back up.

Yea the pedal feels very spongy and goes to the floor. If I hold it down it just stays down.

 

[Mark W]

You have not made mention of adjusting the brakes. The rear drum brakes are not self adjusting. They (are supposed to) adjust when the parking brake is used. If it is not used regularly, or if the self adjusting function is not working (not uncommon), then the shoes will be out of adjustment and excessive travel will be required. This increases pedel travel, and also causes the pedal to feel soft.

Mark...

 

[pavell]

You have not made mention of adjusting the brakes. The rear drum brakes are not self adjusting. They (are supposed to) adjust when the parking brake is used. If it is not used regularly, or if the self adjusting function is not working (not uncommon), then the shoes will be out of adjustment and excessive travel will be required. This increases pedel travel, and also causes the pedal to feel soft.

Mark...

Hey Mark, thanks for the idea. I did in fact have to adjust tighter both shoes when I removed both rear drums for inspection in order to get t back on. I will check the adjustment on the drums tomorrow. Is there official procedure to do this?

Meanwhile I have a booster on order if this doesn’t fix the issue. I’m open to any other feedback or ideas. Thank you all

 

[Squash]

If time is of no concern then try gravity bleed.
Start the process one bleeder at a time and just ensure you are getting clear BF.
I often open up lid and invert a fresh brake fluid container because you don't really want to run the reservoir dry.
While doing this you also have time for other things.
Like love making this is a long and thorough process which can leave you satisfied.

 

[ppc]

@pavell ,

Speed bleeders are garbage unless you use them properly. Most likely you still have are in the system. You may have damaged the bore/seals of the Master Cylinder during your bleeding process.

 

[pavell]

I am using speed bleeders with a pressure bleeders that is applying 15-20psi through the master cylinder.

What is the issues with speed bleeders ? I figure it would be extra insurance with a one way valve to not let air back into the system ?

I will try adjusting the rear shoes tonight.

 

[ppc]

Yea the pedal feels very spongy and goes to the floor

Pedal to the floor meant the master cylinder seals have been pushed past the normal range of travel. Beyond normal range there is going to be corrosion, debris etc. that damages the rubber seals. Time to replace the master cylinder.

The problem with speeders they leak air back into the system. Do some reading you will find see it's common.

 

[pavell]

Update from the shop I took it to. They have not proposed any solutions yet. See report below:

Finding:
Checked master and it holds pedal . No pedal fade or drop . Bleed system with power bleeder and noticed fluid was coming out really slow from the front bleed valves , but no air in the system . Pedal seems a little better on test drive , but brake pedal seems to have an excessive travel and feels like the brakes don't really grab . Booster seems to be fine .

Any recommendations?

 

[pavell]

The shop is telling me it may be the rubber front lines. I will replace those and report back to you all. Let me know if you have any thoughts ?

 

[Malleus]

EDIT: never mind, just reread. I got nothin'

 

[pavell]

The shop replaced the front rubber lines and told me they finally got the bakes to lock up. But the pedal is still a little spongey. Any feedback from the LC guys ? Is this a trait of the 1991 LC brakes ?

The shop told me they will try a new proportioning valve tomorrow. To see if it fixes the spongy/soft pedal

 

[gnarlytoes]

The shop replaced the front rubber lines and told me they finally got the bakes to lock up. But the pedal is still a little spongey. Any feedback from the LC guys ? Is this a trait of the 1991 LC brakes ?

The shop told me they will try a new proportioning valve tomorrow. To see if it fixes the spongy/soft pedal

Did they replace all three rubber lines, or just the two going to the calipers?

 

[jonheld]

Your truck is 33 years old. Every single piece of rubber is past its due date.
The 91 with drum brakes has 4 soft brake lines.
One for each of the front calipers and one for each axle drop to the frame. The shop should have replaced all of them.

As Mark already stated, proper adjustment of the rear shoes is crucial for brake performance. There is an adjustment procedure in the Toyota factory service manual (FSM) that you can download from the resources section. That will get you in the ballpark. The handbrake lever should have 5-6 clicks to set the brake. Frequent use of the handbrake keeps shoes in proper adjustment assuming the adjusters are working properly.

A faulty booster/check valve will give you a rock hard pedal.

Looking at calipers and wheel cylinders and saying "no leaks" is not a real diagnostic.
Are the pistons frozen due to internal corrosion?
Do they move easily?
Are the rubber outer seals intact?

There are OEM rebuild kits available for both calipers and wheel cylinders.
04479-60020 caliper rebuild kit
04474-35100 wheel cylinder rebuild kit
Brand new OEM wheel cylinders are still available (47550-60120) around $50.

The vacuum system will also affect brake performance.