Cruzn620 Posted January 6, 2008 Report Share Posted January 6, 2008 ok, i got the new drums on my truck today and we did a total system bleed. the pressure would be building as we bled from each point, then all of a sudden, we couldn't build good pressure any more. any ideas? the truck has new brake hoses, wheel cylinders, brake shoes and drums (discs up front) the reseviors are all full of fluid, and i can't find any leaks in the system. any ideas would help a ton!! Quote Link to comment
DanielC Posted January 6, 2008 Report Share Posted January 6, 2008 First guess, you let some air get into the system. Second guess, fluid is leaking somewhere, you just have not found the leak yet. Third guess, bad master cylinder that is letting fluid leak around the piston. Quote Link to comment
SHADY280 Posted January 6, 2008 Report Share Posted January 6, 2008 fourth guess, you ran it a bit too low, or pushed the pedal too fast allowing air to get in. fifth guess, tap the calipers with a wrench and "dislodge" any air hanging around. sounds dumb, but it works. gravity bleed them for a bit, it helps too. and bleed the master cylinder, just to make sure. Quote Link to comment
yello620 Posted January 6, 2008 Report Share Posted January 6, 2008 I bet that the third guess nailed it right on the head. Stop pumping the pedal to do all the brake bleeding. Let gravity do all the work for you. Good luck Jason Quote Link to comment
Cruzn620 Posted January 6, 2008 Author Report Share Posted January 6, 2008 sounds like a good idea. i mean, the resevior did run dry on us a couple of times, but we filled it over and over. i'm still in town (where my datsun is) so i will run over there later and just do a bleed without anybody pumping the brakes. this is what you are talking about doing right? thanks for the help guys! oh yeah...i'll get some pics of things too Quote Link to comment
yello620 Posted January 7, 2008 Report Share Posted January 7, 2008 Yes, thats it. Do Not let the reserivoir go empty for any reason. That very well could be the whole problem, but my bet is still on a bad master cylinder from all the pumping on it. Pick a corner of the truck, open bleader screw, KEEP res. full. Let gravity do the work now. Find something else to clean or work on while gravity works for free for you, just dont sidetrack yourself and forget the res. Have your brakes been adjusted? This should be done first. Jason Quote Link to comment
Cruzn620 Posted January 7, 2008 Author Report Share Posted January 7, 2008 im guessing i have a rotten M/C too...and i have a new one, but i thought id do the simple stuff first. i did the gravity bleed, but i just opened them up and closed them, not knowing that i needed to just leave one of them open...see, i did it wrong!!! LOL!! also, i did not adjust the rear drums. here is my reasoning...which, as usual, is probably wrong. i put new pads and drums on the truck, so if anything, it should be CLOSER to being correct than it was. if they were too close, it wouldn't have slid together...right? sorry that im such a noob on this stuff! it might be a few weeks before i can make it down that way again, but i think im going to buy me a reverse brake bleeder so i can just push the air out of the system all by myself...and i also think i will change out the m/c while i am there. let me know your opinions! Quote Link to comment
DanielC Posted January 7, 2008 Report Share Posted January 7, 2008 Hydraulic brakes depend on there being no air in the whole system, anywhere. When you bleed brakes, you are trying to get rid of all the air. If you let the master cylinder go empty enough to expose any of the ports in it to air, air gets in, and you have to start the whole bleeding process again. If you are doing the two person, one pumps, and the other opens and closes the bleeder screw, method, you must keep the master cylinder full of fluid. No more than three times opening and closing the bleeder screw without adding more fluid to the master cylinder. One person applies pressure to the pedal, and the other person opens and closes the bleeder screw. You must close the bleeder screw before the brake pedal bottoms on the floor. That way, there is always some pressure in the brake system when a bleeder screw is open. If you let the brake pedal go all the way to the floor, and the system pressure goes to zero, air can be sucked in the brake system through the bleeder screw. Quote Link to comment
Cruzn620 Posted January 7, 2008 Author Report Share Posted January 7, 2008 thanks daniel...we were screwing it up from the start because we were letting it go to the floor. i guess i'll put like a 2x4 or something in there next time so it won't bottom all the way. that...or purchase this self bleeder!! Quote Link to comment
DanielC Posted January 7, 2008 Report Share Posted January 7, 2008 I think I will try those speed bleeders, if you do not beat me to it. Putting a 2 x 4 on the floor will not help, because if the pedal hits something and stops, the pressure in the brake system drops back to zero because a bleeder is open, and then air gets back into the system. The bleeder screw has to be closed while fluid is still coming out. Quote Link to comment
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