2nd Gen Non-Engine/Transmission Spungy brakes

[Otts Machine Shop]

I replaced my master cylinder because I had a bleed down situation with steady pedal pressure.

Same old story afterward. Pedal still bleeds down. Still good braking power. Now the yellow brake light is blinking. I bench bled the Master cylinder & bled all four wheels. No leaks anywhere.

Is there other places to bleed?

Dick Ott









96 25004x4 5sp st cab

 

[Andy Redmond]

Is the reman master cylinder from a reliable source (napa, dodge vs autozone)? My brother "sings" the praises of a faulty autozone master cylinder for his girlfirends Saturn. He wasted most of a Saturday bleeding to no avail.



Also make sure the vac. pump will make 20 inches or so and you don't have a leaky booster, leaky check valve at the booster etc. .



Finally, try bleeding once more unless you are certain they are well bled.

Good luck

Andy

 

[azgearpro]

vacum

How and where do you check the vacuum for the brakes? I have the same problem except when I let off the brakes the drag sometimes and the peddle can be pushed almost all the way to the floor, Jim

 

[sam peterson]

Dick---You need to check the RABS valve. If you have a fax machine I can send you a bulletin on how to check it. ---Sam

 

[illflem]

Sam, is that what's also known as the proportioning valve?

 

[Andy Redmond]

I agree with Sam it could be several things.



Onto vacuum. . disconnect the rubber boot at the vacuum pump outlet, a vac. gauge should show 20-25" at not much off idle. Mine will put out 20-25" at idle (950 rpm's).

 

[fest3er]

Originally posted by Otts Machine Shop
I replaced my master cylinder because I had a bleed down situation with steady pedal pressure.
Same old story afterward. Pedal still bleeds down. Still good braking power. Now the yellow brake light is blinking. I bench bled the Master cylinder & bled all four wheels. No leaks anywhere.
Is there other places to bleed?
Dick Ott




96 25004x4 5sp st cab

You didn't say if you tested the wheel cylinders. If the brakes are not spongy (which would be air in the lines) and the master cylinder is good, I would then suspect the rear wheel cylinders.

Offhand, I can't think of any other place fluid could be seeping past yet not showing evidence of an external leak. You mighta got a bum rebuilt unit.

Fest3er

 

[keimmmo]

I went through the same basic problem on my '92... twice now. Yea, I know the system is different, but the symptoms are the same and I have no doubt that it is the same basic problem... the anti-lock valve! If it is bad, it will act just like a bad master cylinder even if the cylinder is good and there are no leaks.



Check that TSB above. I'll bet it will tell you what you need to do.



Steve

 

[sam peterson]

Bill---The RABS valve is for rear antilock systems and is just below the combination valve on the 2nd generation trucks. The line out of it goes directly to the rear brakes. It also has an electrical harness plugin. On the end of it is a rubber plug. This is wear the check proceedure is done. ----Sam