OK, I'm posting this for my cousin. He's got an '87 runner & his brakes are really spongy. We bled the brakes, twice, and still just as spongy. Thinking maybe the master cylinder is bad, but thought I'd ask around here & see if anyone else has any thoughts/ideas/recommendations. Thanks, guys!

 

Air in the lines is probably the #1 cuprit, and bleeding is the answer.

Inspect carefully all the flex lines, look for a bulge or anything that looks odd.

 

One other thing to check out would be the rear axle seals.... because if they go it'll leak back and forth and you will notice liquid all over the rear drums. I found this out the hard way. Everytime I'd come back from 4x4'n My brakes would be really spongy. One reason I thought was because when you're braking over long periods of time, it'll eventually warm up a bit so I thought the brake lines were expanding. Logical to say the least, but after closer inspection I found my real culprit. The axle seal. Check you're drums see if there's any fluid being spat out and go from there. Hope this helps....
Cheers, Lee Hathaway

 

I had the same problem and it was the residual valve in the master cylinder. A new master will fix your buddy up.

 

the 3 most likely problems have been mentioned....I would pull the rear drums before replacing the master cylinder, then inspect everything....if you cant find anything then its most likely going to be the master....good luck....

 

Thanks, guys. I guess he's just going to take it in & have it checked out. Thanks for the help!

 

I'm having a really odd problem here. About a week ago I took of in my truck before it was warmed up. About a mile down the road my pedal just went to the floor and didn't have any grab at all. After that she locked up normally and functioned like it should. Two days after that I had the same exact problem. I just figured it had something to do with the 20 degree weather.
Now just today the brakes got cosistently worse until I had total brake failure and had to use the E brake all the way home.
I bled all the lines including the lspv until all the air was out. I did this after noticing the release bolt on the bottom of the MC was loose and wet. Apparently a ton of air got sucked in at that bolt because the brake lines were FULL of air! I tightened the bolt and bled everything again.
Now I have intermittent break pressureabout every third time or so that I hit the breaks I get full grab, the rest of the time the pedal goes all the way to the floor with no pressure orit grabs a bit halfway down then loses pressure the rest of the way to the floor.
This is a really strange problem since it works sometimes then doesn't the very next time I brake.
I need some help here please guys. I'm completely stumped now! Thanks for any advice or knowledgable info in advance.

 

Did you bleed the master cylinder? This would be needed in this case in addition to (or rather before) the wheels and LSPV.

 

holy 5 year thread bump!

 

How do you bleed the mc? I don't see anywhere to bleed it. The only way I've heard of doing so is to bench bleed it but I was hoping not to have to pull it all apart lol.

 

Per '99 4Runner FSM page BR-4. I don't know if yours is different.

Then reconnect brake lines and proceed to rebleed wheels and LSPV. This is what you have to do if you let the reservoir go dry when bleeding. It would seem to apply in your case as well.

 

Yeah, I know--but no one is going to give him the snarky "use the search button" noise.

 

Thanks Durk. I'll give that a shot shot tomorrow.

 

I once had a similar issue with a "non toyota" vehicle. Turned out to be the brake booster........in my case, the hose came off the brake booster....easy fix.

 

Update: I bled the mc then bled all the lines again until I had clear fluid and no air bubbles at all. I also changed the rear shoes and adjusted the rear brakes while I was at it.

Verdict: the brakes are tighter and less spongy but I still have the same problem, just not half as bad. Everyother time I hit the brakes it still goes to the floor with no pressure. I have no leaks anywhere so I'm still stuck. I'm going to try another entire system bleed an see if there's any change. After that... I'm lost

 

Well, in general, you are looking for any fluid/air leak, booster problem, bad MC, LPSV or a bum cylinder, somewhere. You should know you are technically in the wrong forum, you have a 2nd gen rig. (I don't think you had a sig before). Most of us 3Gers have ABS type systems with no LPSV. You may have better luck in the 2G forum for specific troubleshooting help on that type system. At least look at the 'spongy' threads over there, if you haven't already. There seem to be a bunch of them.

 

ok you said the drain screw was loose did you open that and giv e a gravity bleed and see if any mor air came out??? when you have some one push down on the brake pedal about half way break the brake line and gravity bleed there as well...

on my sisters beetle we had a similar issue and the vacuum bleeder was ineffective so we developed an air attachment to push the fluid through and this worked on the bastard and bastard it was never had such an issue with a bleed till then. remember never let the fluid empty or you will have to start over!!!