Pump for Hydroboost?
- Thread starter srgould41
- Start date
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the hydraboost pumps have 2 return barbs on the housing (1 for P/S and 1 for hydraboost) other than that they look like any other chevy pump
- Thread starter
- #4
Thanks for your replies guys. I am aware of the return fitting differences. I was more interested in the pump pressure and flow rate. I have read stories of issues of too little steering response with the brake pedal pressed and want to make sure I am not fighting the steering just to get better brakes.
My hydro set up needed custom hoses made but works great. I do not have a problem with pressure on the steering and brakes at the same time but it provides less boost than my vacuum set up on my FJ40. I prefer the Hydro. I did have a slight leak and let it get low. Lost power steering and brakes at the same time....
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- #6
Ouch, that would suck to lose both. That is partly why I have been seeking to resolve my braking issues without using hydroboost. I need MORE assist than my vacuum booster.
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- #8
Because it isn't enough to stop. 
I had another post in the 40 section asking for advice, but I have tried everything short of finding larger custom calipers for the front. I did the 4 wheel disk swap. The rears will stop me hard at the expense of the rear doing all the work. With the bias dialed all the way the rear still locks and the front wont. Even in dirt. The front is 4 Runner calipers. I have a 10" dual diaphragm booster, but only 15 inHg vac at idle. I am currently running a 7/8" master off an MR2. My original 1" was scary to stop. I need more assist pressure.
I had another post in the 40 section asking for advice, but I have tried everything short of finding larger custom calipers for the front. I did the 4 wheel disk swap. The rears will stop me hard at the expense of the rear doing all the work. With the bias dialed all the way the rear still locks and the front wont. Even in dirt. The front is 4 Runner calipers. I have a 10" dual diaphragm booster, but only 15 inHg vac at idle. I am currently running a 7/8" master off an MR2. My original 1" was scary to stop. I need more assist pressure.
You've unbalanced the system (front to rear). Pedal is kinda mushy in the front as well huh..
I'm interested to see how you like the hydroboost over the stock system. I'll bet that it won't be much change honestly.
Also, if you pump the brakes, it will be harder to steer. Even my F350 which was designed to be hydroboost will steal power from the steering for the brakes..
I'm interested to see how you like the hydroboost over the stock system. I'll bet that it won't be much change honestly.
Also, if you pump the brakes, it will be harder to steer. Even my F350 which was designed to be hydroboost will steal power from the steering for the brakes..
- Thread starter
- #10
I started with a 1" GM master. Nice short throw and hard pedal. Could not stop without two feet on the pedal, though. I even moved the attach point on the pedal for a 7:1 ratio. Finally a 7/8" master worked, but yes long travel and soft.
Part of my change will be smaller calipers in back. Wilwood makes a 2" GM caliper (pn 120-9333). Should help with bias and allow me to use less of the proportioning valve. I would be happy to use a bolt on larger front caliper but none exist as an easy swap. I though about fabbing a bracket to fit the GM Metric calipers. Wilwood has a 2.75" one (pn 120-8924). I don't know how well it would fit the rotor, though, or if I could make it fit at all.
Part of my change will be smaller calipers in back. Wilwood makes a 2" GM caliper (pn 120-9333). Should help with bias and allow me to use less of the proportioning valve. I would be happy to use a bolt on larger front caliper but none exist as an easy swap. I though about fabbing a bracket to fit the GM Metric calipers. Wilwood has a 2.75" one (pn 120-8924). I don't know how well it would fit the rotor, though, or if I could make it fit at all.
My hydroboost does great. I have no problems with it. I don't think GM would have put it in thousands of vehicles if it was failure prone. You still have brakes and steering should the worst happen, just no assist.
It's a great solution to not cutting the firewall on an early rig.
It doesn't sound like the booster is the problem with your truck.
It's a great solution to not cutting the firewall on an early rig.
It doesn't sound like the booster is the problem with your truck.
- Thread starter
- #13
I read up on that route a while back. Sounds good at first, but most people say to skip it and go with the 4Runner calipers. For the cost involved I still think more line pressure with my current setup would do the trick. If I had a stock cam the current booster would probably solve it. I could not find a larger booster than I have.
if you want more line pressure and you've already done the dual diaphragm booster swap what we do down here is install a second remote VH40 booster, they are line pressure driven not mechanically driven off the brake pedal, they give you up to 4x the line pressure from what your existing booster is pumping out, have a google or have a look on ebay for PRB VH40 boosters they are made in Aussie. I've got them on both of my trucks and the increase in braking ability is outstanding
- Thread starter
- #15
I read up on these before. They seem like a very good product. It's a shame there are no dealers in the US. Getting one here, plus lack of access to parts and support, make them just a bit too expensive. Nice product, though.
- Thread starter
- #17
I did try that route way back. The best vac pump spec I could find was good for about 15 inHg. I could not find higher rated specs.
we need to talk in person.... but before we do - to answer your question, everyone is spot on, the pump portion of the power steering pump is the same part number whether it's hydroboost or not.
But they're also right about vacuum should be more than enough.
Unless you have a whooper of a cam (you need 15 Hg of vacuum to properly operate a vacuum reservoir - though you can get away with as little as 7 Hg and a vacuum reserve canister).
Reasons why you don't have brakes:
1) glazed pads
2) glazed pads
3) and when you're sure it's not, glazed pads
before I go to number 4 - here's what happens. Someone replaces the brakes and doesn't bed them in properly. They glaze because the off-gassing of the glues in the pads cause too much heat and glazing. Then they replace only the pads without turning the rotors.... of course, rotors are glazed as well.... and the cycle continues.
4) your proportioning valve wasn't properly bled and it does #1, 2, and 3
5) you have a stuck caliper or slave cylinder
6) your runout is improper on the rotor (assuming it applies) - then 1,2 and 3 apply again
7) you didn't properly bleed the master cylinder
8) the master cylinder was chinese junk
9) your master cylinder is chinese junk
10) you have air in the system
and honestly, any of number 4-10 can do 1-3. Worst part about that is once you've glazed the pads, fixing the other things seem like they didn't fix the problem.
When you don't have good brakes - replace the entire system in a systematic and thorough fashion. I'm so guilty of this so that list above is from mostly my experience - I used to replace just pads unless I couldn't get the pad over the lip. In that case, I'd go to a wrecking yard and get a used rotor.... it worked fine, but starting about mid-90s it started not working as well. Roll forward to today and admire the shelf-full of brand-new, yet defective master cylinders. I use them for parts.... but there's at least a dozen of them that simply didn't work out of the box.... pads are about the same, it used to be you didn't really need to bed the brakes and they'd work fine. Not anymore....
now, if all of that fails, then we do need to talk because you've got something weird going on like plugged lines.... and I don't live that far from you....
and if anyone wants to try a vacuum pump, I have one for them to try.... they don't work for brakes... with that said, if you're in the 7 Hg of vacuum, they can make a marginal system marginally better.
But they're also right about vacuum should be more than enough.
Unless you have a whooper of a cam (you need 15 Hg of vacuum to properly operate a vacuum reservoir - though you can get away with as little as 7 Hg and a vacuum reserve canister).
Reasons why you don't have brakes:
1) glazed pads
2) glazed pads
3) and when you're sure it's not, glazed pads
before I go to number 4 - here's what happens. Someone replaces the brakes and doesn't bed them in properly. They glaze because the off-gassing of the glues in the pads cause too much heat and glazing. Then they replace only the pads without turning the rotors.... of course, rotors are glazed as well.... and the cycle continues.
4) your proportioning valve wasn't properly bled and it does #1, 2, and 3
5) you have a stuck caliper or slave cylinder
6) your runout is improper on the rotor (assuming it applies) - then 1,2 and 3 apply again
7) you didn't properly bleed the master cylinder
8) the master cylinder was chinese junk
9) your master cylinder is chinese junk
10) you have air in the system
and honestly, any of number 4-10 can do 1-3. Worst part about that is once you've glazed the pads, fixing the other things seem like they didn't fix the problem.
When you don't have good brakes - replace the entire system in a systematic and thorough fashion. I'm so guilty of this so that list above is from mostly my experience - I used to replace just pads unless I couldn't get the pad over the lip. In that case, I'd go to a wrecking yard and get a used rotor.... it worked fine, but starting about mid-90s it started not working as well. Roll forward to today and admire the shelf-full of brand-new, yet defective master cylinders. I use them for parts.... but there's at least a dozen of them that simply didn't work out of the box.... pads are about the same, it used to be you didn't really need to bed the brakes and they'd work fine. Not anymore....
now, if all of that fails, then we do need to talk because you've got something weird going on like plugged lines.... and I don't live that far from you....
and if anyone wants to try a vacuum pump, I have one for them to try.... they don't work for brakes... with that said, if you're in the 7 Hg of vacuum, they can make a marginal system marginally better.
on adapting, mine took custom hoses too... I ordered a complete set for an 87 hydroboost truck, and cut the end off that went to the PS pump then flared a new, SAE fitting for it.... if you have the wrong pump, the correct adapter is a direct replacement of the SAE fitting.
- Thread starter
- #20
You must have a lot of trouble with glazed pads. 
Had a chance to pull all 4 calipers off to inspect them. Go glazed brakes. I did note that the rear pads are about 25% worn and the fronts look almost new. I ran a vacuum can for a while. Makes no difference. The booster manufacturer recommends 23" in their literature. Your items 4 through 10 were not the case.
I am gathering my parts now for an entire brake overhaul.
Had a chance to pull all 4 calipers off to inspect them. Go glazed brakes. I did note that the rear pads are about 25% worn and the fronts look almost new. I ran a vacuum can for a while. Makes no difference. The booster manufacturer recommends 23" in their literature. Your items 4 through 10 were not the case.
I am gathering my parts now for an entire brake overhaul.