DeadGame420

Well heres the issue. Was wheel'n the other weekend and lost brake pressure coming down a hill. Yeah it was alittle scarey. Pressure came back after what seemed like 100 pumps of the pedal. I was able to drive it home and the brakes work but pedal pressure is never the same. sometimes it will go down real far and after a pump or two gets alittle better.

I checked for booster pressure and air tight check both were fine. None of the lines are leaking but it did leak some from base of master to booster and would have to top off every few weeks.

I just changed master cyl.,bench bled ofcourse and bled all the lines. Took it for a spin and its still the same. Could it be the proportioning valve or what I'm stumped now.

Thanks in advance.

Bigblock

I've had this prob,Did you buy new M/C or reman?Always buy new.I recomend Toyota.Also sometimes they are hell to bleed but it has to be done right.
Bigblock

DeadGame420

It is a reman. I bench bled it the right way and the lines aswell. So the m/s is the only thing that would cause this problem?

DeadGame420

42 views and 1 reply,,,nice.

abecedarian

well all sarcasm aside, did you bleed the LPSV too?

Bigblock

Reman M/C's are NG!Anyway I wouldn't spit on one if it was burning.Also you need to check the clearance between the M/C and the adj. rod sticking out of the booster.Especially on a reman.I did away with my LSPV and ABS but I don't recommend it on any thing driven on the street.Although I do at my own risk.That eliminated a lot of BS and stuff to bleed.
Bigblock

DeadGame420

lol. No I did not. I did not know about it until after I done it. Where is this thing at and should I bleed all the lines after bleeding the LPSV?

I tend to come off as a d**k sometimes I know, but I mean no harm.

Thanks for the help.

abecedarian

bleed the wheels: right rear, left rear, right front, left front then LPSV.
It's the thing above the rear axle, that has the lever that comes across the frame and bolts to the side of the differential.

muddpigg

iTrader: (1)

Assuming you used the correct bleeding method. What type of fluid are you using? DOT 3 will boil in lines and lose pedal. The newer DOT 4's can go up to 500* or 600* I forget which. Don't mess with DOT 5 it'll eat your seals.
Good luck.

Or maybe a vacuum issue.

abecedarian

depends on which DOT 5 you're speaking of...
DOT 3 is basically not available anywhere...
DOT 4 is the replacement for DOT 3, and most off-the-shelf brake fluid is DOT 3 & DOT 4 compliant.
DOT 5 is silicone based and is not compatible with DOT 3 or 4... or 5.1
DOT 5.1 is glycol based like 3 & 4, and can be mixed with DOT 3 & 4, but can't be mixed with DOT 5.

muddpigg

iTrader: (1)

Yep that's probably why I stated DOT 5, don't use. Military and BMW, maybe one or two others. Read about DOT 5.1 never seen though.

abecedarian

yeah, silicone DOT 5 never really caught on, since the silicone base was more compressible than DOT 4, so it only helped avoid spongy feeling brakes at high speed, and didn't really do anything else... and then DOT 5.1 came out, with a boiling point higher than DOT 5, and was compatible with DOT 3 & 4.
And besides... unless you're driving a race vehicle with sustained speeds above 80 MPH, DOT 3 is enough... but you can't buy it and have to get the even better DOT 4.

muddpigg

iTrader: (1)

Toyota recommends DOT 4, just don't remember if that is in my 4rnr or Corolla

DeadGame420

Is the vac. line from the booster to intake mani. the only vac lines in the brake system?

blacklabel

also, DOT 5 is not hygroscopic, unlike DOT 3 or 4 it doesnt not absorb moisture at all.
spongy pedal feel is usualy a symptom of air in the system.
your proportioning valve is used to controll front/rear brake distrobution, so I doubt thats your problem.
--did you open the metering valve when you were bleeding the brake system? if you didnt, you arent getting a good bleed, and theres probably still air in the system

DeadGame420

What and where is the metering valve?

lilred86

okay im having the same problem, but here's the thing. i replace my m/c, bled everything and had ecellent brake. then i put it on the lift without straps and the suspension sagged down and stretched my rear line. the lines were disconnected for a week or so. put my rear end back together and everything else bled and bled and bled and bled still no pedal. changed the rear line still no air in the front air constantly in the back. pump it up a few times and you get pedal. then nothing. bled LSPV gets brake one time after then picks up air again. no leaking hoses or lines or anything. and only air in the rear. has to be LSPV right? took it off dirty as everything but i think the bar that activates it got over extended on the lift. sound about right? new LSPV and rod should fix it right?

yota_newbie

Well when speaking of that mysterious valve I just like to call it the "combo valve" due to its two jobs. However, I remembered that I vastly overloaded the rear end and probably shortened the life of that little booger. I replaced just about everthing in the brake system (242K + miles and much needed, not to see if that fixes the problem) and still the pedal would sink lower after a few secs. Thought for days that there was air hiding in the system. Well I talked to a few guys and the signs seem to point to damn combo valve. Replacing it on monday lookout for the official write up afterwards.

DeadGame420

I replaced booster, master, rear cylinders and bled and bled bleeding the LSPV also. I too get air in the rear. Is there a way to rebuild/clean or anything to that valve. Also is the LSPV the same thing being referred to as the "metering valve". This sucks!!!!