bigtiki Posted November 3, 2011 Share Posted November 3, 2011 My back brakes were not working well, and while bleeding them I discovered little pressure was getting to the rear. Now it appears the proportional valve is leaking. Junk yards may not be a good source, as the parts are old as mine. I adjusted the number two rear shackle as described in the manual on page 687 of 1025. The shop manual is found on this site, I really need to just shunt it. I found previous posts where members did this with good results. How do I rebuild it? Anyone seen parts? Does anyone know haw to rig it "wide open" for the back brakes? One post said there was a fix on the site but i can't find it. Should I go to a machine shop and have them mill out a block of aluminum? Thanks Chuck Quote Link to comment Share on other sites More sharing options...
Maineah Posted November 3, 2011 Share Posted November 3, 2011 It can be bypassed with no adverse effects it was designed for pickups to keep the back brakes from locking up with light loads. Brake lock up with the MH is not going to happen. A simple brake line union is all that is necessary no need for machining just bypass the entire valve. Quote Link to comment Share on other sites More sharing options...
bigtiki Posted November 3, 2011 Author Share Posted November 3, 2011 It can be bypassed with no adverse effects it was designed for pickups to keep the back brakes from locking up with light loads. Brake lock up with the MH is not going to happen. A simple brake line union is all that is necessary no need for machining just bypass the entire valve. So can I buy a three opening union at Napa? The unit has an intake, return to the front brakes, and the feed for the rear. Is there a toyota part? I have never done a brake bypass before. Thanks Quote Link to comment Share on other sites More sharing options...
bigtiki Posted November 4, 2011 Author Share Posted November 4, 2011 So can I buy a three opening union at Napa? The unit has an intake, return to the front brakes, and the feed for the rear. Is there a toyota part? I have never done a brake bypass before. Thanks Never You mind. I removed the proportional unit, and tied the two incoming lines together with a T fitting that has a flex line on it. All are 10mm. I had it made up at Carquest for $30 bucks. Looks like it will work fine. NAPA wanted me to convert everything to SAE fittings, and it was not as simple, with more possibilities of leaks. Quote Link to comment Share on other sites More sharing options...
bufbooth Posted November 4, 2011 Share Posted November 4, 2011 After doing the brake valve bypass, any noticable rear braking improvement? Thanks, Dennis B. Quote Link to comment Share on other sites More sharing options...
bigtiki Posted November 5, 2011 Author Share Posted November 5, 2011 After doing the brake valve bypass, any noticable rear braking improvement? Thanks, Dennis B. The job is not finished. The new lines will be in on Monday, and as soon as i bleed the brakes I will let you know. May be mid week. Quote Link to comment Share on other sites More sharing options...
bigtiki Posted November 8, 2011 Author Share Posted November 8, 2011 After doing the brake valve bypass, any noticable rear braking improvement? Thanks, Dennis B. I had to get an adapter to go from the two lines that come from forward to go into a block, t. The third leg of the t went into the transaxle via a flex hose. I hooked it up anjd it got dark so I quit. Then I realized in the middle of the night, that the return line that goes forward, had to be blocked to get maximum pressure to the rear brakes. \ I had a helper pump the brakess. Fluid came out one of the lines way more than the other. I logically figured this one to be the feed line. I had a new fitting , male on one end and female 10 mm on the other. I inserted this new loop on the return line. It makes a loop, and in the middle of the loop I crushed the line with vice grips. This time when bleeding the rear brakes I got a stream that seemed as strong as the front wheel cylinders. I bled all the brakes. The pedal came up high, and when I tested it at slow and high speed , it worked GREAT. The nose no longer dives and it stops quicker than ever. I can only assume that the rear brakes were not working at all, and my unfamiliarity with the vehicle prevented me from realizing the rear brakes were not working AT ALL. I hope this helps others. I couldn't get an explanation from anyone here how to do it. Maybe there is a simper way. This seemed to work for me. Quote Link to comment Share on other sites More sharing options...
twoblocked Posted November 9, 2011 Share Posted November 9, 2011 The reason your nose no longer dives is you have now equalised the front and rear brake pressures. One of the reasons manufacturers' put proportioning valves in their systems is to exert more pressure on the front calipers than on rear drums. Calipers require two to three times more pressure to equal the braking power of drums. The empirical evidence I have read suggests this solution works on quite a number of Toyota Motor Homes because of the constant highly loaded rear ends. I'll be curious as to how fast you go thru rear drums. Please keep us posted. The nose no longer dives and it stops quicker than ever. I can only assume that the rear brakes were not working at all, and my unfamiliarity with the vehicle prevented me from realizing the rear brakes were not working AT ALL. Quote Link to comment Share on other sites More sharing options...
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