Help with first gen brakes

[cowsinblack]

My brakes on my 1982 Toyota have been extremely spongy recently. So spongy that that I feel they are getting too dangerous to drive. If I compress the pedal a few times, the fluid will build up and make braking easier but after holding the brake for 5-10 seconds, the pedal sinks down really low. I've tried bleeding out the air bubbles but didn't feel any difference after. The brakes in the front are new discs and the ones in the rear are original drums. Thanks for your input!

[HogCanyonHopper]

bad mc

[jssgbsn]

Sounds like air in the system still.  I just had a similar issue after flushing my brake system for the first time.

Were they working fine before the new discs?  Did you flush all the old brake fluid?  Did you follow the order that was recommended for bleeding the brakes?

http://board.marlincrawler.com/index.php?topic=96452.0

That is the thread I made and got help.  Everything is good to go now.

[cowsinblack]

So my LSPV is there but its smashed and clearly doesn't function at all. I bought the truck 4 months ago and havn't done anything to the brakes besides bleeding out the air bubbles to try to fix the sponginess. What does MC stand for? Thanks for the link!

[jssgbsn]

MC = Master Cylinder

Also, if you scroll down a little on the list of Forum Threads you should see a Tech Section that gives year ranges 79-92, etc...

Prob have more people see your post there than in the General Section.

What did the fluid look like?  Brown and polluted?  If so, it might be a good idea to do an entire flush.  My prob was fixed when I bled the MC first, then the brakes, then the LSPV.  I was kinda flying blind on bleeding the MC, I am positive I sucked air in through it when bleeding the brakes for the first time.

You may have a different issue.  But I am sure other people will want to know if they were bled in the correct order.

[jssgbsn]

And better safe than sorry.  I would be very careful driving on the road.  Make sure the parking/emergency brake works just in case.

And this would be the name of the thread section I would recommend.

"Toyota Pickup/4Runner Tech 79-95"

[cowsinblack]

When I bled them, all the fluid was a mucky brown. I will flush out all the old fluid once I get back to the West coast. So you recommend I follow the bleeding order that you did? MC, brakes, LSPV. If the brake fluid reservoir is opened during the bleeding process does that suck in air? I havn't touched the MC whatsoever so I'll need to learn more about it before I do the bleed. As I said before, my LSPV is shattered and definitely non functioning. When I get home I'll do a full inspection of the LSPV and see where all the lines are leading and post photos. I was thinking I would just remove the LSPV cuz I a lot of people on here say its pretty worthless. Especially considering I rarely have heavy loads in the bed. I have 37s and I've been reading that with 33s or larger, the LSPV doesn't really affect much.  Once again, thanks!

[jssgbsn]

Yes, Master Cylinder 1st then...

     "1. Drivers side rear
      2. Passenger side rear
      3. Passenger side front
      4. Drivers side front
      5. LSPV (Load sensing proportioning valve)(if you still have it)

      If you look at the LSPV you will see three lines going to it, two in the front, and one in the rear. The one in the rear feeds the rear brakes. One of
      the lines on the front comes from the MC, the other is a return line the goes to a "T" for the front brake system. It is a bias line that changes the
      bias on the front brakes as the valve works up and down. That is why the front brakes still get air in them if you do not bleed the LSPV. The
      reason you do it last is the LSPV is the seconded highest component in the system and air travels up, hence the reason you bleed it last."

Yes.  I did everything solo.  Pretty sure when I was bleeding the brakes I let the Master Cylinder get to low and this let air into the system.

I'm still learning about the LSPV, but I have read the same things about either eliminating or holding the arm all the way up (bolting/zip tie, etc) if you have 33's or larger.  I didn't do this yet...but I will eventually.  For now my brakes are working fine.  I'm guessing they will work better once I eliminate/tie up my LSPV "bar".

Wish I was more of an expert.  I saw you posted in the Tech Section.  You'll prob get some similar responses at first.  In any case, this is the most helpful forum I have been with.  Especially when it comes to hard to solve technical problems.  Since I very recently just went through this, other people might hope you have read through my post or others.  But brakes mean safety and again, I am not an expert.

I never had to bleed a MC before.  You can bench bleed (which is supposed to be easier) or bleed it mounted in vehicle still.  You will need a 'MC Bench Bleed Kit' autoparts stores carry them (bunch of fittings and a few hoses, about $10).  If you doing solo, bench is probably easiest, mounted seems to be easier with two people (i did it solo, but I trusted the process and was able to visualize what was happening without being able to see the MC fully bleed).

If you have not done that before check youtube for 'bench bleed master cylinder'  you'll prob see some videos for bench bleeding or mounted bleeding.  When they talk about pushing the plunger in with a screwdriver that is the same thing as pressing the brake peddle (if it is still mounted and not in a bench vise).  I just hooked up the fitting and hoses, made sure they would not pop out and pressed the brake peddle over and over slowly, pausing between each press.  I couldn't watch the bubbles eventually stop, figured after doing it about 20 times it must have been bled completely.  I would watch a few different videos just to help the process be more familiar, especially if you're doing it solo.

Then I very slowly bled the brakes, topping the fluid off after each wheel. 

Prob a lot easier to have more than once person there.  Doing it solo took awhile.  But i recently moved and don't have many people to ask to come over as a second hand to help.

Good luck!!

[cowsinblack]

I luckily have a buddy who does all the repairs with me  . I've been watching bench bleeding videos on youtube and have found a few methods. The one that seems easiest is to use a syringe to pump fluid from the two brake line ports up into the master cylinder reservoir. Has anyone else on here used this method?