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Brake system upgrades/replacements

Metalhead47

Metalhead47

1/2 ton status
Joined
Nov 30, 2007
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Location
Whidbey Island, WA
Well this new rig sure is turning out to be more of a project that I was planning for. First the tranny dies a week after I bought it, got that dealt with, now I finally get a chance to pull the wheels off & find out most of the brake system is shot. Found most of the info I need with some forum searches. 1990 3/4 ton Suburban 4x4. Here's what I know is bad and must be replaced:

Master cylinder, rotors, drums, pads, shoes.

While I've got everything pulled apart, here are some might-as-wells I'm going to throw on:

Braided SS lines, manual hubs, wheel cylinders, maybe calipers.

And of course a good thorough fluid flush. Which brings me to my questions. All this carnage was caused by the rear circuit on the MC leaking as far as I can tell, dunno what kind of moisture got into the rear brake lines. Is there any way to flush the lines beyond pushing fresh fluid thru? I'm definitely investing in a pressure bleeder for this job. I plan to go with EBC pads & some drilled/slotted ebay rotors.

While everything is torn apart, anything else I should consider upgrading/replacing? Haven't pulled the rotors yet so I don't know how the bearings are. Any simple master cylinder upgrades for a 3/4 ton? I think hydroboost would be overkill on this rig.
 
Check the booster real close while you're at it. If the mc leaked any fluid at the back( at pushrod), it swells up the rubber diaphram and eventually causes a vacuum leak/poor boost.
 
throttleissues said:
Check the booster real close while you're at it. If the mc leaked any fluid at the back( at pushrod), it swells up the rubber diaphram and eventually causes a vacuum leak/poor boost.
Click to expand...

Ah, thanx. That looks like it's exactly where the leak is. I plan to pull the MC & rotors tomorrow so I can continue checking stuff. If the booster is still OK it should hold vacuum from a vacuum pump, right?
 
Yes it should hold vacuum. It is had to tell if brake fluid got into it though. If it did it might be fine today, & not tommorrow.

If you buy braided brake lines, be sure to get some that are longer than stock so that if you lift it latter you will not have to replace them again.


I know of no other good way to flush a brake system. I would prolly start by forcing all the old fluid out w/ an air compressor & then flushing w/ fluid. Apex Performance sells a nice entry level power bleeder that would work well for that. I have one & am very happy w/ it. http://www.apexperformance.net/

If your calipers are not leaking fluid they are probably fine.
 
Hey thanx. That power bleeder is actually the same one I was looking at. Far as checking the booster, how MUCH vacuum should it hold? I hooked up the soon-to-be-retired-from-bleeding-duty Mityvac but it only holds about 4 inches (mmHg, whaterver) of vacuum. Pump more and it jumps up and right back down to 4. Chilton's is useless of course.

boz42 said:
Yes it should hold vacuum. It is had to tell if brake fluid got into it though. If it did it might be fine today, & not tommorrow.

If you buy braided brake lines, be sure to get some that are longer than stock so that if you lift it latter you will not have to replace them again.


I know of no other good way to flush a brake system. I would prolly start by forcing all the old fluid out w/ an air compressor & then flushing w/ fluid. Apex Performance sells a nice entry level power bleeder that would work well for that. I have one & am very happy w/ it. http://www.apexperformance.net/

If your calipers are not leaking fluid they are probably fine.
Click to expand...
 
Do a search, there are several people who make brackets here as well on E bay, Calipers are off a caddy if you want parking brakes.
 
Yeah, but for a 14b semifloater? I know there's lots of disc kits for the full floater but I thot the semifoating version just got passed over:confused:

slider said:
Do a search, there are several people who make brackets here as well on E bay, Calipers are off a caddy if you want parking brakes.
Click to expand...
 
The power bleeder I linked to has good instructions. Keep in mind it does not use vacuum, It pressurizes the MC, & pushes fluid through. I can't pump mine over 12-15 psi. The Mc adapter will start to leak. 10 psi is plenty though.
 
Metalhead47 said:
Hey thanx. That power bleeder is actually the same one I was looking at. Far as checking the booster, how MUCH vacuum should it hold? I hooked up the soon-to-be-retired-from-bleeding-duty Mityvac but it only holds about 4 inches (mmHg, whaterver) of vacuum. Pump more and it jumps up and right back down to 4. Chilton's is useless of course.
Click to expand...
It really should hold about 16" vacuum. Your engine is probably giving it a 12- 14" vacuum signal. 4" sounds really low.
 
Hmm, well I've already pulled the master cylinder so I can't test it properly with the vehicle running. With the leaky circuit and no front brake pads I can't really judge the pedal feel before I pulled everything apart. Guess this one item will have to wait until I have everything else put back together, it looks like there should be enough play in the hardlines to remove the booster without removing the MC later on if I need to.

throttleissues said:
It really should hold about 16" vacuum. Your engine is probably giving it a 12- 14" vacuum signal. 4" sounds really low.
Click to expand...
 
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