Chevy Hydroboost Conversion

[Spargman]

for anyone interested, here are the part #'s from my install!

I have a '99 Tahoe and this system was mocked from a '99 Suburban w/6.5l diesel. The PS cooler is from a 1ton diesel pickup.

Part #'s:
Power Steering Return Hose - AC Delco 36-368640
Power Steering Pressure Hose - AC Delco 36-365460
Power Steering Pressure Hose - AC Delco 36-365490
Master Cylinder - AC Delco 174-722
Hydroboost Unit - AC Delco 178-578
Variable Bypass - GM #19168825 (you need this to bypass variable assist)
OEM PS Cooler (from gmpartsgiant) - 26041420 & 15655032 (bracket)

The hard part is finding a hydroboost pedal!

 

[Revco]

What truck did you do this to?

Thats good info to have the part numbers.

 

[FellowTraveler]

Variable power steering bypass is a great mod!

Spargman, Great job there with conversion.

I had done this variable orifice power steering pressure valve bypass elimination years ago as it was prone to failure and steering issues like wandering. If I remember right there is a fixed power steering pressure valve that comes in the kit too. The variable steering box remains in place.

Hydroboost brakes is a jump in brake performance with three (3) levels of braking available for full sized vehicles. Most common failure of hydroboost unit is the power piston seal leaking from dirt scuffing power piston or excessive heat carried in power steering fluid. I rebuild my own hydroboost units bought all the tools to do it right. Use pure synthetic power steering fluid and a big fluid cooler (fin/plate design is best) with filters on both return lines for hydroboost brakes/power steering.

 

[Spargman]

I had done this variable orifice power steering pressure valve bypass elimination years ago as it was prone to failure and steering issues like wandering. If I remember right there is a fixed power steering pressure valve that comes in the kit too. The variable steering box remains in place.

It comes in the box with the PS pump? I had one with mine but assumed it was the variable...

Hydroboost brakes is a jump in brake performance with three (3) levels of braking available for full sized vehicles. Most common failure of hydroboost unit is the power piston seal leaking from dirt scuffing power piston or excessive heat carried in power steering fluid. I rebuild my own hydroboost units bought all the tools to do it right. Use pure synthetic power steering fluid and a big fluid cooler (fin/plate design is best) with filters on both return lines for hydroboost brakes/power steering.

Yup, my new AC Delco unit leaked from there...had to get a second one under warranty. I forgot to add the PS cooler part #, now updated! I second the PS cooler, definitely a worthwhile investment b/c the PS fluid will get extremely hot very quickly if you don't have one.

I personally held off on the filters, but I did see some aftermarket companies included them...any research that discussed the pros/cons of those filters?

 

[Spargman]

Here is a post I put together for another forum regarding data from my upgrade:
Due to me being solo for this and a lack of any scientific equipment other then a wheel with a built in counter (no idea what it's called), these numbers have a high chance of error...so please don't take these stopping distances as gold. What I think is important is the changes between and overall average of each setup.

Vacuum, 1/2t calipers, 1/2t pads, 265 tires, stock height
1st pass - 138ft
2nd pass - 136ft
3rd pass - 135ft

Vacuum, 3/4t calipers, 3/4t Hawk LTS pads, Slotted rotors, 265 tires, stock height
1st pass - 146ft
2nd pass - 148ft
3rd pass - 142ft

HYDROBOOST, 3/4t Master, 3/4t PS pump, 3/4t calipers, 3/4t Hawk LTS pads, 285/70R17, 4.5" lift
1st pass - 134ft
2nd pass - 130ft
3rd pass - 129ft

Surprisingly, each day I did the testing, it was about 50deg.

Additional info:
- My shocks were not setup correctly when I did the hydroboost passes, so with firmer valving, I have a feeling a few feet will be knocked off
- During the hydroboost test, my truck was a few hundred pounds heavier with the lift kit, bigger tires and tools in the back

Some observations:
- DO NOT BUY 3/4T CALIPERS UNLESS YOU HYDROBOOST - you're stopping distances will INCREASE. Also, the 3/4t master will not bolt up to you vacuum system
- Hydroboost was able to finally lock the tires and create a small patch of rubber...my vacuum was not able to do that

Some negatives:
Using all new AC Delco parts (do not buy cardone), expect to spend $750+ and three days doing this for first timers. You're upgrading the master cyclinder, PS pump, hydroboost unit, GM variable assist bypass, three lines and possibly adding a Power steering cooler...this stuff adds up really fast. You can always go used and ppl have had a lot of success, but for brakes, I personally always buy new.

Hydro units have a propensity to leak and are expensive to have rebuilt. If you buy used, definitely get some kind of guarantee that if it leaks, you can return. My first (new AC Delco) unit leaked and it took a week to get another one...

Also, you will need to cut and re-flare brake lines...so definitely know what you're doing before you rip into your truck's braking system. This is a job that is straightforward, but definitely requires someone who is comfortable working on multiple components and understanding when something is installed correctly (i.e. always replace orings, use line wrenches and torque to the correct settings!)

Everyone has a different preference, but I really hate that i lost variable steering. My rig rode like a boat prior, once I bypassed my variable assist, steering got even softer. With the months of research I did, I could not find a hydroboosted truck that had variable assist....so plan on bypassing it b/c otherwise you will restrict the amount of fluid your hydro unit receives.

I hope this helps everyone in the endless quest to stop these rigs! Please feel free to ask any question you may have!!

Part #'s:
Power Steering Return Hose - AC Delco 36-368640
Power Steering Pressure Hose - AC Delco 36-365460
Power Steering Pressure Hose - AC Delco 36-365490
Power Steering Pump - AC Delco 36-517137
Master Cylinder - AC Delco 174-722
Hydroboost Unit - AC Delco 178-578
Variable Bypass - GM #19168825
OEM PS Cooler (from gmpartsgiant) - 26041420 & 15655032 (bracket)

A good writeup for the install - http://www.gmfullsize.com/forum/showthread.php?t=156800

 

[FellowTraveler]

My inline return filters are not the best way to go a high pressure filter in system feed line is best protection!

The damage is almost always from sand entering through power steering fill cap one way or another, rarely some debris like metal chips entering from poorly cleaned rebuilt parts is an issue. I quickly tired of rebuilt units and changing them out way too often.

Inline filter on the high side is the best protection so it's my next mod. I went to inline filters for the dual return lines because of a grain of sand that entered system and found its way to the hydroboost power piston damaging it "elongated scratch" then that damage led to the seal leaking. I keep hydroboost hard part spares, complete rebuild kits and a complete unit redundant but I like redundant. The filters I use are FILTRAN composite units inline.

Any cooler in system when it fails needs replacement if it can't be properly cleaned of any debris that found it's way into it.
Another mod is to attach a vent line and filter to the p/s pump fill cap and mount the line/filter away from dirty area in engine bay. The factory p/s cooler was not enough for my system as I used a high pressure p/s pump from PSC, so my additional cooler "actually a transmission fin/plate design" into hydroboost return.

 

[Larry]

Hydroboost is a great upgrade. My buddy and I upgraded my old ’78 to hydroboost last year while it was under the knife for a NV4500 swap. Didn’t even have to change the pedal on the old trucks as it mounts to the brake pedal the same as the vacuum booster rod. You hear all of the hoopla about rear disks, well after doing hydroboost I see no need to bother with the expense of a rear disk swap plus if you are running a manual trans the rear disk swap leaves you in a pickle to figure out a park brake setup.

Probably not new news, but a hydroboost specific power steering pump is not really needed for doing a swap like this. The hydroboost P/S pump only has one additional port for an extra return line. This can be achieved by putting a T in the return line between the cooler and reservoir. Older GM vans, stripped chassis did not use the dual return line pumps and current stripped chassis still run T’s in the return line today.

This is the system layout on one of the trucks my company builds. I used this as a map to plumb mine. I tried to use this ZF powersteering pump as well but it interfered with the ORD steering brace so I ended up using the original GM Saginaw pump.

Hydroboost is amazing! When you step on the brakes the truck actually STOPS! :sombrero:

 

[Spargman]

My inline return filters are not the best way to go a high pressure filter in system feed line is best protection!

The damage is almost always from sand entering through power steering fill cap one way or another, rarely some debris like metal chips entering from poorly cleaned rebuilt parts is an issue. I quickly tired of rebuilt units and changing them out way too often.

Inline filter on the high side is the best protection so it's my next mod. I went to inline filters for the dual return lines because of a grain of sand that entered system and found its way to the hydroboost power piston damaging it "elongated scratch" then that damage led to the seal leaking. I keep hydroboost hard part spares, complete rebuild kits and a complete unit redundant but I like redundant. The filters I use are FILTRAN composite units inline.

Any cooler in system when it fails needs replacement if it can't be properly cleaned of any debris that found it's way into it.
Another mod is to attach a vent line and filter to the p/s pump fill cap and mount the line/filter away from dirty area in engine bay. The factory p/s cooler was not enough for my system as I used a high pressure p/s pump from PSC, so my additional cooler "actually a transmission fin/plate design" into hydroboost return.

High side filter is adventurous...i haven't seen that done yet, but if you know how to rebuild them, go for it! My guess is the current filters on the market may have a tough time dealing with that kind of pressure. Any idea what pressure is in the cooler lines on trans? (maybe an inline trans filter)

Why did you choose Filtran? Ever look at Magnefine? http://www.emergingent.com/subpage1Magnefine.htm

I don't have a preference in filters, just thought i'd throw out an option i found to get your thoughts.

I'm going to put one on the low side out of the hydro. Where did you put your second one? (return on cooler?)

 

[V30CREWCAB]

are the hydroboost pistons all the same size or are they different sizes? got a rebuild kit for a k5 blazer and wondering if it will work on my k30. got any pictures or a writeup on rebuilding your hydroboost?

 

[toddz69]

are the hydroboost pistons all the same size or are they different sizes? got a rebuild kit for a k5 blazer and wondering if it will work on my k30. got any pictures or a writeup on rebuilding your hydroboost?

Power pistons are different sizes for different units.

Todd Z.

 

[Revco]

I just did new brake pads on my Suburban today. While I was at it, I changed the plugs, wires, cap, rotor, and cleaned the TBI to clear up a little rough idle when cold. There has always been a leak from what I thought was a hose to/from the factory Hydroboost, because the frame rail on the driver's side has always been coated with PS fluid, but there is no leak from the pump or the gearbox. I would just add fluid every few weeks and ignore it. But when I was doing the brakes today, I noticed the rear upper control arm bushing has deteriorated, probably from the leaking PS fluid (previous owner used ATF as PS fluid), since that bushing is always saturated. That wasted control arm bushing explains the metal on metal "clunk" that I hear when going over a rough patch in the road. (I figured the noise was a loose skid plate this whole time) So I picked up some new control arm bushings and a new pitman arm to cure the slop in the steering and will be addressing those issues sometime this next week.

Anyhow, the Hydroboost unit looks to be leaking from the round canister on the left side of the unit, I assume it's the reservior (facing engine from front of vehicle) All of the lines are clean and all of the fittings are clean, but the saturation seems to come from that canister area. So, what's the best way to fix this...new hydroboost unit ($$$!!!) or is there a rebuild kit or what? I've never had to dig into a unit so I don't know much about them. I don't want to replace this bushing without fixing the leak but I don't want to go broke tackling the leak either.

Thanks

 

[FellowTraveler]

I just did new brake pads on my Suburban today. While I was at it, I changed the plugs, wires, cap, rotor, and cleaned the TBI to clear up a little rough idle when cold. There has always been a leak from what I thought was a hose to/from the factory Hydroboost, because the frame rail on the driver's side has always been coated with PS fluid, but there is no leak from the pump or the gearbox. I would just add fluid every few weeks and ignore it. But when I was doing the brakes today, I noticed the rear upper control arm bushing has deteriorated, probably from the leaking PS fluid (previous owner used ATF as PS fluid), since that bushing is always saturated. That wasted control arm bushing explains the metal on metal "clunk" that I hear when going over a rough patch in the road. (I figured the noise was a loose skid plate this whole time) So I picked up some new control arm bushings and a new pitman arm to cure the slop in the steering and will be addressing those issues sometime this next week.

Anyhow, the Hydroboost unit looks to be leaking from the round canister on the left side of the unit, I assume it's the reservior (facing engine from front of vehicle) All of the lines are clean and all of the fittings are clean, but the saturation seems to come from that canister area. So, what's the best way to fix this...new hydroboost unit ($$$!!!) or is there a rebuild kit or what? I've never had to dig into a unit so I don't know much about them. I don't want to replace this bushing without fixing the leak but I don't want to go broke tackling the leak either.

Thanks

Proceed with caution and at own risk, if undertaking the following understand all liability is yours! STRONGLY SUGGEST; getting detailed instruction from web and study.

FIRST: Make sure your accumulator works properly, w/engine off depress brake pedal 4 or 5 times "this dumps units pressure" then keep foot on pedal w/o excessive pressure re-start vehicle the pedal should now kick back and up by itself this is the accumulator re-pressurizing as it should if it's checks ok then proceed with engine off.

EXTERNAL ACCUMULATOR SEAL can be changed out w/o dis-assembly of hydro boost. Make sure accumulator pressure is dumped by depressing brake pedal 4 or 5 times after this make sure the brake pedal is not depressed during the following;

The seal for the accumulator can be found in kits from http://www.piratejack.net/ (I have no connection or interest in pirate jack) you need KENT MOORE J-TOOL J-26889 or equivalent to contain accumulator. Large c-clamp can be used too if j-tool can't be had by slightly compressing the accumulator into it's seat in hydro boost unit this can be done on vehicle w/o dis-assembly of HB and using small pick to remove the snap ring "a small hole is drilled at side of hydro boost (looking from front of truck at accumulator the hole is at 10/11 o'clock, leaning over fender and straight down it's an easy see to engine side) in area of hydro boost that accumulator is mounted insert the pick into hole pry out snap ring, you may need a small screw driver to grab snap ring as it comes out to the side of unit" once snap ring is removed slowly and with caution back off c-clamp remove accumulator making sure everything is clean (clean out side of unit before dis-assembly) lube w/PS fluid and install new seal on accumulator install is reverse of removal.

 

[Revco]

Thanks, it sounds like simple fix. I'll build the J-Tool myself. Is the O-Ring made of a special material or?? No sense in buying a complete "kit" just to use one o-ring.

 

[toddz69]

Thanks, it sounds like simple fix. I'll build the J-Tool myself. Is the O-Ring made of a special material or?? No sense in buying a complete "kit" just to use one o-ring.

You may be in luck. I have one of the kits from piratejack sitting on my kitchen table (yeah, I'm single) awaiting installation into a hydroboost I have out in the garage. I won't be replacing the o-ring in my booster because the one I have is still fine. The instructions are a bit cryptic as to which seal to use on the accumulator but I think I know which one it is. I'd be happy to stick it in an envelope and send it to you if you'd like it.

Todd Z.

 

[Renntag]

I am preparing to convert from Vac to Hydro on my 91 V2500. I am curious what range of trucks I can pull a hydro unit from and if the mount to the firewall is the same. (?)
The next concern is the attachment to the brake pedal, will that be compatible?
So many more questions as I am beginning to gather parts. Searched this subject (hydro boost conversion) and am coming up short with part cross overs.

Larry: Your burb and pick up are very well prepared. Nice work. Do both have Hydro-boost?