A '91 likely already has the upgraded "v6" brakes. Look for the step in the booster to verify that its a dual-diaphragm booster and a "1" somewhere in the master cylinder casting.




As for your brake problems, I'd be looking for brake pad/shoe contamination by oil or brake fluid. I'd also check the rear prop valve rod adjustment as kewlynx mentioned. And then the last thing might be that you have either some cheap pads up front, or some hi-performance pads that need to be warmed up to work well (like carbon metallic pads). OEM pads are generally the best, but if you want an upgrade, Hawk HPS or Raybestos Brutestop are pads that have higher friction properties, but don't need to be hot to work well.

Yes I did.

& slipping i mean that as you push the pedal hard, the disc keeps spinning for a while (pedal now max out on the floor), until the calipers finally grabs the disc from spinning.

Just like cantilever brakes on wet bicycle rims...);

I'll try to bleed it again. Maybe i have some air in the mc?

Yes, it's still original 91. Not leakage found anywhere.

Question:

What's the visible size difference btwn a V6 / 4cyl front caliper?

Could I have luck in buying a reman v6 caliper & returning my 4cyl core?

Also, what brand/model of manual proportioning valve would everyone recommend? Where? (cheap is best!) <img src="/forums/images/graemlins/notooth.gif" alt="" />

Pedal should never go all the way to floor. Check for air in the system or a leaking MC. If you put your foot on the brake pedal with medium pressure, does it gradually go to the floor? If so, your MC is bad.

Here's a pic comparing my old 4cyl calipers(red) to my new(remanufactured) v6 calipers. notice the difference in the piston size.

Finally took the truck in for brake inspection yesterday for the 1st time. MC is not leaking. Turns out my right rear cylinder is seeping small amount of brake fluid at the rear seal & Dust seal rubber is holding the fluid back. <img src="/forums/images/graemlins/scared.gif" alt="" />

Should I R&R the cylinder seal or get a new cylinder?

Are the cylinder welded/bolted/pressed to the backing plate? Is removable possible without undoing axle?

i've never heard of anyone replacing the seal on those. mine went bad a while back and i just got new ones from napa. i think both were only like $30.

all you have to do is take off your drum, unbolt them from the backing plate, unbolt the brake line, and put the new ones in. really simple. this is of course implying that your brake shoes are removed already. probably a good idea to replace those too while they are off if they're worn.

oh, and make sure you clean everything real well and apply fresh grease to the contact points. you can also check out the articles section for more info.

I know my 91 front calipers have those ~6 ribs on the outer side as shown in pictures, does that confirm I already have v6 calipers?

Also, does v6 calipers use the same rotor size as 4cyl?

they both use the same size rotor. to see if you have the "v6" calipers just take a look at the pistons on them. if they are both the same size, you have them.

btw, having already remounted my lspv rod end/axle attachment higher after a longer shackle/aal, the inspection from yesterday tells me that my brake pad are used at 75% rear & front at 33%.

So that means I get too much pressure from the back, or sticking drum brakes. (My left drum shoes are even crack longitudinally along the middle of the pads!)

If I really have too much pressure in the back, should I try angle the lspv rod downward a bit more? (or give up on the lspv and use a manual proportioning valve?)

(fyi, i have not been able to lock the front tires on wet pavement lately during hard braking, just slow stop.)

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