Uhh...Anyone else running hydroboost???

[Tdubbyount]

Ive got a 79 k10 swb that came factory with hydroboost brakes (came w/ 5.7 olds diesel) and the brake booster needs replaced...But im having a little trouble finding the correct one. Niether Napa or Orielly's had the part listed under my truck, so i came up with a part number for a '79 and had one ordered. However, it wont work. As you see in the picture, the new one came without the piston spring and baffle and spring retainer, so i pulled it out and tried to re install it on the new unit, but there was a substantial bore size difference between the two. Like 3/8 of an inch. Makes no sense. How many different units are there? Anyway...I have a different one on the way, no clue if it will work, i just found one that had a different part number. So we'll see. I'll try to get more pics up. Any help is appreciated

[68Timber]

Try rockauto.

[Tdubbyount]

Same PN as the one i already bought. The other one came in today and its wrong too.

[csb#356]

The only difference I knew of was when they switched from flare fittings to o ring fittings sometime around 80'. Maybe there is a difference in bore size from 1/2 to 1 ton. Are the ones your getting to small or to big.

[Tdubbyount]

The ones im getting are too big. All of the fittings are the same and it bolts right up on the firewall side, but the rod assembly for the master cylinder is too small for the new one.

[Tdubbyount]

Screw it. I'm converting to vacuum.
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[68Timber]

I'd dig a little deeper to figure it out. The hydraboost works better plus you'll have to create a vacuum source to swap.

[Shyguy]

We just picked up a '75 C-30 and it has hydro boost brakes.

[Tdubbyount]

Originally Posted by BRUISER

I'd dig a little deeper to figure it out. The hydraboost works better plus you'll have to create a vacuum source to swap.

I've already got parts on the way. A new p/s pump, vacuum booster and master cylinder, and hoses. I may need a different pushrod but I'm not sure yet. I got tired of trying to chase down parts for that system. The diesel 350 was pulled out years ago and I recently put a fresh 350 in it, so it will have all the vacuum it needs.
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[Tdubbyount]

Swapped everything over today. Still have no pedal. Darn. Did a complete flush of the brake fluid and power bled all four corners. Very little improvement. Booster and master cylinder work fine. Last thing I can think of is calipers?
It also pulls hard to the right under braking. New problem that just came up today.
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[68Timber]

This is really hard to diagnose with that many changes going on at once. Unfortunately China is making it worse for us, lots of master cylinders are bad out of the box.

[Tdubbyount]

We disconnected the brake lines from the master, plugged the holes and tried it and the pedal was very firm while running. That rules out a bad cylinder or booster. Power bled everything. Still no pedal. I'm absolutely sure there's no air in the lines. We have good pressure at all four corners so the proportioning valves are fine. I'm thinking calipers. Wheel cylinders aren't leaking either.
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[68Timber]

Pulling hard right makes the left front brake line suspect.

[Tdubbyount]

I recently put on skyjacker stainless brake lines, and there's good pressure on either side.
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[csb#356]

If the whole system was open like that, you're probably better off just letting it gravity bleed for a while. Having air in the lines could make it pull like that.

[INSIDIOUS '86]

Rebuild kit http://www.piratejack.net/index.php?...emart&Itemid=6
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