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#1 Old 10-28-2011, 09:07 PM
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LSPV Bleeding

89 22re pick-up

Installed all new brake lines from right front to rear as well as new LSPV.

Bleeding the lines with pnuematic vacuum, The bleeder on the LSPV has gobs of air.
Is this to be expected?
Should the LSPV have been bench bleed somehow?
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#2 Old 10-29-2011, 07:26 AM
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To clarify why I ask -
There is a chance I connected the lines from the front right T fitting incorrectly i.e. to the wrong ones on the LSPV.
Would this make bleeding the LSPV impossible?
The best I've gotten is about 25% fluid and 75% air.
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#3 Old 10-30-2011, 07:07 PM
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Connecting the lines wrong could definetly be a problem.
Also, are you bleeding in the correct order?
Should be-
LR
RR
RF
LF
LSPV

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#4 Old 10-30-2011, 10:47 PM
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I've now tried the lines both ways. And attempted to bleed in the correct order. Get no blood from either of the front brakes in both cases.
Had previosuly bled in the wrong order i.e. LR, RR, LSPV, RF, LF.
Have cracked the MC and bled that 3 times in 4 steps each time.
Disconnected the rod on the LSPV to see if the piston will drop, it does not.
Plenty of fluid to both rear brakes with no air after bleeding.
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#5 Old 10-31-2011, 07:30 AM
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My latest thought is to:
Lower the LSPV mounting on the frame as low as it will go, right now it's as high as it will go.
I surmise the LSPV setting is too high and this is not allowing fluid to the front brakes.
Make sense?
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#6 Old 10-31-2011, 08:28 AM
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That's not your problem. The LSPV doesn't control front brake pressure, just rear brake engagement time and pressure.
Once you have the brakes bled/sorted out you want to start with the valve as high as it will go and see how your rear brakes feel. You may need to adjust it down some, every truck is different. But starting at the very bottom will probably cause early rear brake engagement.

I've done many of the frame replacements under recall, so I've had plenty of experience bleeding these brake systems from scratch.

Gravity bleeding is your friend when you replace brake parts. Especially long lines. You can also give the brake pedal a few pumps before you open the system to help force fluid through. And while you're at it, it's a great idea to flush the brake system at the same time. You're already doing half the work anyways. On an old truck it's a good idea to go back in a month or so and reflush, to get rid of more of the crap in the system.

If you're still getting air through the LSPV, you probably have a leak.
If you're getting air through a bleeder and can't get rid of the air, you have a leak. It doesn't matter what order you bleed them or if the lines are hooked up wrong. If everything is tight you WILL eventually get everything bled. Your brakes may not work right [if you have the lines hooked up wrong], but you should still be able to bleed them.

Bleeding in the wrong order will only slow you down, it won't stop you from bleeding the brakes. Don't get me wrong, you should do it in the correct order, and it will get done faster, but it's not 100% necessary to get the job done.

If you're not getting any fluid out of the calipers you may have clogged up bleeder screws. If that's the case you may get lucky by just removing them and cleaning out the port [replace with new ones if you can find them]. Otherwise you'll have to replace your calipers.

You also may have a bad master cylinder. They tend to go when the system is drained and someone bottoms out the cylinder pumping the pedal on an old system.

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#7 Old 10-31-2011, 01:25 PM
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Now I’m thinking this instead-
Since I have not seen a leak and I am sensitive to them, I always check and re-check.
Replace or clean the front bleeder valves.
Bypass the LSPV, although I trust what you are saying Alltracman, I just want to take the LSPV out of the equation completely for now.
To bypass the LSPV can I take a T fitting connect the LSPV return line and F line to the one side and the single port side to the rear brake feed ?
Re-bleed see if I get peddle.
If I don’t get peddle does this tell me the MC is gone? If not how can I test to see if the MC is no good?
I have noticed very little fluid discharging from the front fitting on the MC when I opened to bleed it perhaps it is clogged or inefficient.
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#8 Old 11-01-2011, 01:10 PM
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The LSPV could be bad, unlikely but possible.
Usually a bad MC the pedal goes soft, but if you have air in the lines.....
I can usually still tell, but it's a feel thing, hard to describe without being there.

Have you tried bleeding with someone pumping the brakes?
Or just the air bleeder?
Air bleeders are great but if you have a lot of air [or vapor lock] they don't always work well.
I usually gravity bleed first, then have someone pump.
I usually use an air bleeder more if I'm trying to flush a system [and even then on occasion it won't pull the fluid].

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#9 Old 11-01-2011, 05:44 PM
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We were trying to pump the brakes for quite awhile.
We'd get good peddle, I'd start the truck roll down the drive, do a few test stops and feel the peddle fading. I could pump the brakes and the peddle would return a bit.
Was able to lock up the front brakes a couple of times but the peddle will fade right after that.
I figured there was so much air I needed to power bleed or be at it the rest of my life.
Bled from the rear left first and got gobs of air out. It would have took forever by pumping and dumping.
Perhaps pumping and dumping the fronts will be the right approach.
The MC is only like 4 years old maybe 30-40,000 on it, calipers are about the same, just don't want to accept they died already, but I had the whole system emptied back than and bleeding was such a challenge maybe that bleeding along with this one did the MC in.
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