new master cylinder - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Benrs86 · 11-11-2002, 10:37 PM

i replaced my leaking non power master cylinder on my 69 with a new master cylinder. i did as the instructions said and pumped fluid through the cylinder by hand then hooked up the lines and put it back in and now i press the pedal down, the fluid in the resoirvoir doesnt go down, and when the pedal gets down it stays down?? what do i do? i quit for today, and am going to fix it tomorrow, just thought id get some advice and whatnot before, maybe somebody here can help me get it fixed quicker than i could alone. thanks, Ben

Longhorn Man · 11-11-2002, 11:50 PM

When the pedal stayed down on the one ton...it was a kerfagled booster.

*Piston* · 11-11-2002, 11:57 PM

Can you manually pull the pedal back up?

There's a spring inside the master cylinder that pushes the assembly back out. If the spring is missing or broken, or the pedal/linkage is binding... your pedal will stay down.

When bleeding brakes, your resevior wont go down until your pedal comes up. This is when the cylinders replenish with fliud from the resevior.

If the M/C felt ok and would return ok on the bench, chances are the spring is ok. Double check your linkage/pedal. Also, are you getting a good flow of fluid from the lines where they connect to the M/C? This should be the first place you start to bleed after a M/C replacement. Then begin at the furthest wheel from the M/C and work your way in. Reason being, if there is air trapped at the MC, you dont want to try and pump that all the way through your system.

11-11-2002, 10:37 PM	#1
Benrs86 Registered User Join Date: Feb 2000 Location: Brandon, SD, USA Posts: 1,292	new master cylinder i replaced my leaking non power master cylinder on my 69 with a new master cylinder. i did as the instructions said and pumped fluid through the cylinder by hand then hooked up the lines and put it back in and now i press the pedal down, the fluid in the resoirvoir doesnt go down, and when the pedal gets down it stays down?? what do i do? i quit for today, and am going to fix it tomorrow, just thought id get some advice and whatnot before, maybe somebody here can help me get it fixed quicker than i could alone. thanks, Ben __________________ Brandon, SD 69 GMC 1/2 ton 2wd wide long bed with wood 3 on the tree 350 engine 4 bolt main rv cam AIM = Alphray04

11-11-2002, 11:50 PM	#2
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	When the pedal stayed down on the one ton...it was a kerfagled booster.

11-11-2002, 11:57 PM	#3
Piston Account Suspended Join Date: Oct 2002 Location: Olathe, KS Posts: 2,300	Can you manually pull the pedal back up? There's a spring inside the master cylinder that pushes the assembly back out. If the spring is missing or broken, or the pedal/linkage is binding... your pedal will stay down. When bleeding brakes, your resevior wont go down until your pedal comes up. This is when the cylinders replenish with fliud from the resevior. If the M/C felt ok and would return ok on the bench, chances are the spring is ok. Double check your linkage/pedal. Also, are you getting a good flow of fluid from the lines where they connect to the M/C? This should be the first place you start to bleed after a M/C replacement. Then begin at the furthest wheel from the M/C and work your way in. Reason being, if there is air trapped at the MC, you dont want to try and pump that all the way through your system.



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