Mushy Brakes = long stopping distance

[powderpig]

There is a link from the brake booster that is adjustable and needs to be adjusted jsut right for the master cylinder to work properly. If this gap is too big it will not put the right amount of pressure on the MC, if too tight then too much pressure on the brakes thus hot front brakes, burned rotors etc. You really can not just swap out a new MC and expect it to work right with out doing the adjustment. That may be your problem currently. later robbie

 

[Cruiserdrew]

The adjustment Robbie is referring to is tricky. There is an SST to set the small gap between the pushrod fron the booster and the master itself.. In an ideal world, you want about .001 clearence between the pushrod and the surface it pushes on.

The work around that Mudrak told me about is cool. Put a tiny dab of grease on the rear cup of the MC. Then assemble the MC to the booster. Then take it apart-you can tell by the impression of the pushrod in the grease how close it actually is. Aim for a tiny gap, so there is no brake pressure when you let up on the brake pedal. This method worked like a charm when I put the new MC in my FJ40 last year. You could buy the tool, but you really don't need to.

 

[rockclmbr]

The Australian "Gregory's Manual" has a very clear description and drawing showing the measurements along with the formula to determine this. I took the MC off this mornign and measured with calipers. I had a gap of approx .015". This could also be due to the fact that I used an off the shelf thicker gasket instead of the toyota one between the booster and MC. It was difficult to break the stuck pin, but once I did, I advanced it about 1/4- 1/2 turn and remeasured. It is now about .001" clearance, but there could be error in measurement in such a tight space.

I tried the grease trick and everything looks good. I'm going to power bleed now. Cross your fingers

 

[rockclmbr]

To conclude this "Braking News Story":

The new master cylinder was an improvement, but not the one I was looking for. The brakes still felt mushy, and the pedal traveled too far.

I tried the power bleeder to no avail.

I tried Speed Bleeders only to find that I couldn't get them tight enough without stripping them and/or removing all of the thread locker.

I finally gave up and dropped the truck off at the local shop in which they connected a vacuum to each bleed valve and sucked the air/fluid out. This helped tremendously!

My brakes have never felt better. So in the end, I don not believe that I needed to replace any parts, I just needed a better method of bleeding. And for $49 I am not going to attempt to try it myself next time. I spend far more than that in fluid, time, and other contraptions. Not to mention my wife's leg is sore.

 

[Darwood]

Glad you got that sorted out. These things suck to bleed.

 

[knorrena]

I wonder if one could install a 100 series booster and mc?

Karl

 

[Brian894X4]

After going through the same problems you described and bleeding 12 quarts of fluid myself, thinking I was still having air problems with the LSPV, I gave up and had the dealer power bleed it.

That actually didn't solve anything, much to my surprise. But the dealer suggested that the master cylinder to brake booster might need adjustment, so they removed the MS, cleaned and adjusted and low and behold, that made a significant improvement.

The brake is much firmer down low, stopping is much improved, but the overall pedal feel is still fairly long travel. I''m going to check the pedal adjustment and if that's good, then I'm done. This is probably as good as it's going to get.

I've been told that OEM calipers (PO put in aftermarket ones before I bought it) and steel braided lines up front will probably help even more, but after 5 days of bleeding the brakes, I'm in no mood to open it back up anytime soon.

 

[robmir]

Replace all the lines with the braided and you will notice right away a better pedal feeling.

Vacum power bleeding is a must also, you will save a lot of time and will remove all the air pockets.

 

[4WD Toyota Owner Magazine]

I've had the same complaint as others here, mushy brakes on the 80. I've read the threads, took them to heed--vacuum flush/bleed, keep engine running, the 80's brakes just aren't up to snuff, etc--but I'm looking to go a bit deeper.

We replaced all rotors (DBA), front calipers (OEM Toyota), all pads (PBR), and front steel brake lines. Pedal feels mushy. Gravity bled, same. Vacuum bled with engine on (including LSPV), same. Mushy, long travel to action.

At one point we had the rear lines clamped off, and the pedal felt great! Unclamp them, back to the mushy feel. Which suggest the rear calipers may be the problem? Can a brake guru give a reason for this?

 

[NaterGator]

Where did you clamp off the rear lines when the pedal feel improved so much?

 

[dfmorse]

Rockclmbr;

I noticed that u don't have DBA's in the front. Odd, because that is where they really help. I use DBA's all round and FJ100 pads in front. That combo really helped; not perfect, but 10x better than stock.

Proper pad bedding is important!

http://www.zeckhausen.com/bedding_in_brakes.htm

...

 

[FDNYCRUISER]

dfmorse:
I'm new to the thread.
I purchased a set of oem rear pads for my '96 today, I asked the counter person to look at a set for a 100 series because I had read that a few guys were using them with better results.
You had said that you use them in the front, do the 100 series fit only in the front? The 2 rears I compaired today were definitly different sizes. The 100 was larger then the 80.
Thanks for any input.

 

[dfmorse]

FDNYCRUISER;

The FJ100 pads will fit the front of the FJ80, however, some of the shims may not have to be used.

Here's some other info; although the pic seem to have been lost.

https://forum.ih8mud.com/showthread.php?t=13758&highlight=fj100+pads

Use new DBA slotted/drilled new rotors for max benefit.

...

 

[robmir]

I've had the same complaint as others here, mushy brakes on the 80. I've read the threads, took them to heed--vacuum flush/bleed, keep engine running, the 80's brakes just aren't up to snuff, etc--but I'm looking to go a bit deeper.

We replaced all rotors (DBA), front calipers (OEM Toyota), all pads (PBR), and front steel brake lines. Pedal feels mushy. Gravity bled, same. Vacuum bled with engine on (including LSPV), same. Mushy, long travel to action.

At one point we had the rear lines clamped off, and the pedal felt great! Unclamp them, back to the mushy feel. Which suggest the rear calipers may be the problem? Can a brake guru give a reason for this?

Any reason why you didn´t replace also all the rear lines with steel ?

Take in mind the old rear lines expand as the pressure increases, and this wasted pressure doesn´t end in the calipers.

In the rare case that replacing the lines doesn´t correct your mushy feeling, you shoud try to hook a pressure meter, raise front brake pressure up to 1138 psi and check/adjust the rear proportioning valve for 869 + / - 86 psi as per OEM specs.

Also pads should be correctly breaked, at first rounds they tend to feel mushy, but once set pedal start to feel hard.

 

[knorrena]

The other day I had some crap from ikea in the back - about 400lbs (bookshelves) and the braking was better. I got to wondering if maybe our load sensing valves are poorly adjusted?

Karl

 

[robmir]

The rear proportioning valve was suposed to be a blessing, but if it´s poorly adjusted or needs to be replaced, you end asking the front brake to do all the braking job and as you noticed it´s not enough.

 

[EricE]

Resurrecting this thread only because it has some good info. This is the first place I have seen a description of how to bleed the master cylinder.

Quote:
The new MC will need to be bled. Clamp gently in a vise (horizontal) and fill the reservoir so that the fluid is above the interior baffle at least. Take a large phillis screwdriver and pump the MC while gently holding your fingers over the two holes where the brake lines attach. Alternate holes while pumping until air is replaced by fluid.

Also the only description I have seen of adjusting the Power assist properly.

Quote:
The adjustment Robbie is referring to is tricky. There is an SST to set the small gap between the pushrod fron the booster and the master itself.. In an ideal world, you want about .001 clearence between the pushrod and the surface it pushes on.

The work around that Mudrak told me about is cool. Put a tiny dab of grease on the rear cup of the MC. Then assemble the MC to the booster. Then take it apart-you can tell by the impression of the pushrod in the grease how close it actually is. Aim for a tiny gap, so there is no brake pressure when you let up on the brake pedal. This method worked like a charm when I put the new MC in my FJ40 last year. You could buy the tool, but you really don't need to.


I am also taking note that bleeding needs to be done with the engine on. I have never done it that way. DOH!

My question:
I know in the past I have let the master cylinder run dry when working on the brakes. The description above on how to bleed the MC seems like it would happen automatically just using the brakes. So if I let the MC run dry when working on the brakes six months ago, then all I need to do now is re-bleed the brakes, right?

 

[FirstToy]

My question:
I know in the past I have let the master cylinder run dry when working on the brakes. The description above on how to bleed the MC seems like it would happen automatically just using the brakes. So if I let the MC run dry when working on the brakes six months ago, then all I need to do now is re-bleed the brakes, right?

take a bottle of brake fluid and turn it upside-down into the resivoir before you bleed. This way you will never run dry.