86 4runner odd brake issue
03-12-2011, 05:17 PM
#21
before you replace the master cylinder, adjust the pushrod - if the master cylinder pistons aren't coming back all the way it will hold residual pressure in the system. Brake pedal should have a slight amount of play (not related to the MC push rod), but also make sure you're brake light switch isn't holding the pedal down.
The pushrod adjustment trick I learned was to put a dab of grease on the end of the shaft and then put the master cylinder in place. Remove the master cyl and look at how much grease is left on the end of the shaft. If there is zero clearance when assembled, the grease gets completely squeezed off the end of the shaft.
The pushrod adjustment trick I learned was to put a dab of grease on the end of the shaft and then put the master cylinder in place. Remove the master cyl and look at how much grease is left on the end of the shaft. If there is zero clearance when assembled, the grease gets completely squeezed off the end of the shaft.
PS> Good tip, I just read that a couple months ago
03-12-2011, 05:20 PM
#22
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yotarob2005, Googling around picked up some saying that the rubber brake hoses can break down internally and cause a condition similiar to yours. Never experienced it myself though.....others?
03-12-2011, 06:49 PM
#23
Registered User
My money's on the booster. There should be a little play in the rod which connects your pedal linkage to the rear of the booster. Try adjusting that rod out, so more thread is showing inside the cab. May also be able to troubleshoot by just pulling the vacuum line in the engine bay.
03-12-2011, 08:43 PM
#25
not that the booster is bad, but the pushrod isn't adjusted properly. See the fluid intake and return port? if the piston doesn't return all the way because the pushrod is keeping it forward, then there is a very good chance of residual pressure in the system. I've also seen brake light switches adjusted too tight INTERMITTENTLY cause this to happen
03-13-2011, 08:36 AM
#26
Registered User
Thread Starter
Thanks for all the input guys. I am heading to the parts store to get my core $$ back on the MC and get some clear tubing to bleed brakes, then I am going to get busy and hopefully get this resolved today.
Corax - You very well might be right about the push rod. My brake pedal does NOT have much if any slop at the top. This will be one of the first things I check into. When I do the grease trick, what should I adjust it to? 1/8"or so?
Corax - You very well might be right about the push rod. My brake pedal does NOT have much if any slop at the top. This will be one of the first things I check into. When I do the grease trick, what should I adjust it to? 1/8"or so?
03-13-2011, 10:11 AM
#28
"Suweeeeeet! WHAT'S MIIIIIIIIINE SAYYYYYYYY!?!?", HEHE..... now, .....GET'EM, ROB! lol.
Hope all is well, otherwise, buddy! This is great info for many who will possibly hit a hurdle when doing the Master/Booster upgrade.....
Brandon, ..... did you just get that clearance thing right by chance?..... Or, did you use the method in FSM for clearance of the Pushrod, etc.?
Hope all is well, otherwise, buddy! This is great info for many who will possibly hit a hurdle when doing the Master/Booster upgrade.....
Brandon, ..... did you just get that clearance thing right by chance?..... Or, did you use the method in FSM for clearance of the Pushrod, etc.?
03-13-2011, 10:34 AM
#29
Registered User
thanks corax, that makes more sense then saying a problem with the booster. as I said earlier, I didn't know how they work internally, but that rod there is two adjustments, one for pedal play at the pedal and then the one at the booster as well. Come to think of it, when I put my dual booster on I had to adjust that rod at the booster a little as well.
03-14-2011, 05:23 AM
#30
Registered User
Thread Starter
I think I have the brake locking up issue resolved, I drove it around for about 20 minutes and it did not give me any problems. Not sure what did it since I changed several things at once. The new master cylinder is installed, I checked the clerance like Corax suggested and it already had about 1/16" of clerance at the booster push rod. However I did adjust the pedal from in the cab of the truck quite a bit, it very possibly could have been not allowing the pedal to release pressure from the booster. While I was at the parts store getting the core back on my MC I asked about new brake soft lines and they had them in stock for $12 each so I went ahead and bought / replaced those aswell. Mine looked pretty rough and they where cheap enough.
I don't think it is related but might be worth mentioning that I did find another issue while swapping out the brake lines. One of my hubs is not unlocking properly so that axle was spinning the whole time.
Here are the new parts I installed.
I don't think it is related but might be worth mentioning that I did find another issue while swapping out the brake lines. One of my hubs is not unlocking properly so that axle was spinning the whole time.
Here are the new parts I installed.
Last edited by yotarob2005; 03-14-2011 at 06:59 AM.
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