Soft/spongy Brakes

[876 Cruisers]

Hey all,

I'm having the common brakes issue with my 80. I've changed / rebuit everything and somehow the brakes dont feel right. My other cruisers brakes have a more responsive feel but my 80 somehow is always soft and requires a further pedal travel to slow down.

I have changed the front and rear disc rotors. Rebuilt the front and rear calipers, new brake lines and the changed the mc and booster to a late model one. I have bypassed / deleted the lspv and it doesnt have abs.

We have bled the system multiple times. Checked the pin on booster for proper clearance.

I dont get a proper bite on the brakes until the pedal is half way. And it seems to go to the board before it is fully engaged.


Thanks in advance
Dan

 

[Azca]

This is a common problem with the 80 series. Most likely culprit is air bubbles trapped in the anti lock break system. There is a way to activate it to help bleed it, others go to a dirt road and lock up the breaks to get the system to cycle. Search on this forum and you will find the threads relating to this.

 

[876 Cruisers]

This is a common problem with the 80 series. Most likely culprit is air bubbles trapped in the anti lock break system. There is a way to activate it to help bleed it, others go to a dirt road and lock up the breaks to get the system to cycle. Search on this forum and you will find the threads relating to this.

My cruiser never came with ABS. I'm wondering if even though I rebuilt the calipers they are somehow taking in air

 

[Azca]

My cruiser never came with ABS. I'm wondering if even though I rebuilt the calipers they are somehow taking in air

Okay, non-us model. Did you bleed the LSPV?

 

[876 Cruisers]

We bypasses that and disconnected it. So I dont have it connected anymore

Okay, non-us model. Did you bleed the LSPV?

 

[NeverFinis]

When was the last time you checked your bearings? Front and Rear.

 

[876 Cruisers]

When was the last time you checked your bearings? Front and Rear.

They all new. Front and back completely overhauled on last 1k miles

 

[NeverFinis]

They all new. Front and back completely overhauled on last 1k miles

Did you bench bleed the new M/C?

 

[876 Cruisers]

Did you bench bleed the new M/C?

I dont think we did. May have ti try that

 

[NeverFinis]

 

[876 Cruisers]

Thanks I'll try that

 

[876 Cruisers]

If not will just change calipers to new ones

 

[jpoole]

Did you set the length of the rod that pushes down on the MC internal plunger when you installed the new MC? It should have a bit of free-play when the pedal is fully at rest/retracted but the tip of the rod should hit and start moving the plunger inside the MC very quickly after pedal travel starts. If that rod is too short then you are wasting some of your pedal stroke without moving the MC at all until the rod tip makes contact. If that rod is too long then your brakes won't release and will drag as you drive.

Are you sure that the MC is compatible with the calipers? Broadly speaking there are variants in terms of the volume of fluid that the MC moves per travel and the size of the wheel cylinders/calipers and if you get the combination wrong you can run into:

• if MC bore is too small relative to the rest of the system you get a pedal that is too soft and that causes you to run out of pedal throw before full braking power is met.
• if MC bore is too large relative to the rest of the system can have a pedal that is too hard and that doesn't travel very far but also doesn't yield strong brakes.

Compatible MC and calipers result in a pedal with proper throw and braking power.

If you have to pump the pedal a few times and then the brakes feel great, until you let off of them for a bit, then you may have pads binding on the slider pins or loose wheel bearings causing the pads to be retracted/pushed out too far so that the first pedal strokes are just getting the pads back to the rotors.

Some have reported a variety of issues with booster problems and of course 80s can be hard to bleed (don't know if that applies to non abs models) so you could have air in the system as well.

 

[876 Cruisers]

The MC I'm using is an Aisin from the 96 landcruiser. I had changed from the 92 4 bolt to the later 2 bolt mc. I'm also using the 93+ disc and calipers. Also using the stock jdm rear disc brakes. As its a 92 fj80

 

[876 Cruisers]

The only parts on the braking system that I reused was the calipers. Otherwise everything else is new

 

[876 Cruisers]

I also have a 97 80 series that the brakes feel soft but stops lovely. Po had changed calipers Ave mc but used a j90 prado mc. I had bypassed abs on that one.

 

[BILT4ME]

How about brake hoses?
Have they been replaced from original?

Believe it or not, I've had really good luck with gravity bleed just opening a bleeder to a drip and let it sit for a couple hours and keep the reservoir full. Then move to the next. Longest run on rear first, then other rear, then longest front, then last

Since no ABS and no LSPV, there are less places for air to be trapped unless you have a fitting that is leaking somewhere.

As long as your MC is matched to your calipers, you should be ok. But if your MC is too small (from a 92) then it won't have enough volume or pressure to activate the larger calipers properly. I realize you said you updated it, but I didn't quite follow your list of procedures.

 

[876 Cruisers]

How about brake hoses?
Have they been replaced from original?

Believe it or not, I've had really good luck with gravity bleed just opening a bleeder to a drip and let it sit for a couple hours and keep the reservoir full. Then move to the next. Longest run on rear first, then other rear, then longest front, then last

Since no ABS and no LSPV, there are less places for air to be trapped unless you have a fitting that is leaking somewhere.

As long as your MC is matched to your calipers, you should be ok. But if your MC is too small (from a 92) then it won't have enough volume or pressure to activate the larger calipers properly. I realize you said you updated it, but I didn't quite follow your list of procedures.

Only thing original is the rear disc brake which is smaller than the 93+ models. But the mc and booster matches the bigger front calipers though the rear calipers are all the same.