NOTE: This conversion alters one of the safety devices (brakes) on your vehicle. If you decide to
perform this conversion, it should be done by personnel who are competent to conduct such
alterations to a vehicle. This conversion can result in changes to your vehicle’s handling and
braking ability. This is not a step by step set of instructions on how to do it, but rather an outline
of the various things I did to accomplish my conversion. Any similar conversion work performed
on your vehicle is done at your own risk. If in doubt, consult the services of a professional.
Here is the stock setup. It doesn’t leave much room to change or check plugs. This we found painful each time due to cuts from frayed stock stainless brake lines.
Here is the hydro-boost setup we will be installing. It comes from a 90’s model Astro/Safari mini van.
I have cleaned it up and getting it ready to paint. The master cylinder and proportioning valve will not be needed in my application. I will be reusing the stock master cylinder.
This setup will require yet another cooler but this time it will be used for the power steering fluid. Late
model GM PS pumps recommend using the PS cooler on the return line between the steering box and
the pump. It is also recommended to help eliminate backpressure to the hydro-boost system. Back
pressure could cause the brakes to be applied while cruising at the higher speeds due to higher pump
pressure. We had this extra cooler around the house and plan to put it to good use.
There are 4 nuts that have to be removed. These are 15mm in the 2nd gens and while you’re under the
dash remove the bar from the brake pedal. I believe this is held on by a spring clip.
Remove the master Cylinder from the booster. We zip tied this off in a convenient place out of the way.
Once all the bolts are removed from inside and the Master cylinder is secured, we removed the booster
from the firewall.
So now with both in hand we thought. What could be the weight difference?
Hydro-boost section weighed in at 13.12 lbs
The vacuum booster weighed in at 11.112 lbs
OK, so no weight advantage here but there will be plenty of extra room under the hood to change and check plugs.
Now it’s time to verify the rod lengths for the brake pedal.
To do this you measure the distance from the back of the mounting plate on both boosters and compare.
You want the distance on the hydro-booster to match the existing distance on the vacuum booster. You
will also notice the hole in the hydro-booster shaft is smaller than what is required to install this back on
the pedal. Therefore, while you are cutting off the ends of the booster to swap the vacuum booster shaft
hole section to the hydro-boost shaft section. At the same time make sure the center of the hole is at
distance you measured on the vacuum booster from back of the mounting plate to the center of the hole.
Be careful and measure this correctly you only have one chance to get this right.
Stock 2nd gen Donor hydro-boost
After you cut the shafts grind the ends to be welded on an angle for a good weld. Weld the 2nd gen shaft
to the hydro-boost shaft with a good butt-weld. You could place a sleeve over the weld area to reinforce
the shaft at this location.
Shaft distance is now the correct length for attachment to the brake pedal along with the proper diameter
of the hole for the pedal post.
Once the hydro-boost is in place and mounted to the firewall. Connect the stock master cylinder to the
hydro-boost. If your vehicle is equipped with ABS you can keep the abs without modifications. However, if
you elect to delete the hydro-boost you will need to purchase a disk to disk proportioning valve or a
manual proportioning valve for the rear brakes.
Now you’re ready for the hose routing. (Figure 10)
The high pressure hose (red)routing flows from the PS pump to the left side of the hydro-boost. It exits
from the right side of the hydro-boost to the high pressure side of the steering rack. The low pressure side
from the steering rack flows to a cooler. The low pressure hose exits the cooler and joins with a tee fitting
as close the PS pump as possible. A hose off the top of the hydro-boost (vent) connects to the bull of the
tee in the return line from the cooler. The cooler provides added resistance with preventing back-pressure
to the hydro-boost unit. You would not want the brakes to be applied as your speed increases.
Those with LS/Vortec conversions using the truck accessories have the option to get the 1500HD
2500HD, PS pumps. Some of the Silverado’s came from the factory with hydro-boost so the “T” would not be required and the cooler would only be used for the PS return as recommended by GM.
Will a Diesel hydro-boost unit fit the 2nd gen S10? I have heard a 2002+ unit will work. We elected for the 2007.5 unit as a test.
Here is what we found.
The blazer is a 2001 so these finding are based on that vehicle. You would need to measure and
compare rods and the mountings in your application.
1. Silverado mounting plate has one offset hole. This can be modified by drilling a new hole in the correctlocation and using a nut and bolt to secure. We elected to remove the mounting plate from the Astro unit we had and mount it to the Silverado unit replacing the Silverado backing plate.
2. The rod style and length matched perfectly for our application.
The conclusion for the Silverado Hydro-boost unit will be that it works for 2nd gens. However you will need to purchase the large bore master cylinder from a first gen. If you own a first gen you need to verify the pedal rod hole size and length as mentioned in the previous sections.
Both of the Silverado hoses will work with a little massaging for your routing.
These are the part numbers:
Pump to hydro-boost available at Advanced Auto:
Powercraft -16MM Male O-Ring x 18MM Male O-Ring. Part No.80337
Hydro-boost to steering gear available at Advanced Auto:
Powercraft -16MM Male O-Ring x 18MM Male O-Ring. Part No.92083
Here is a good article on hydro-boost system and how it works. Inside this article is also two procedures
on how to bleed the system if needed. hydro-boost systems are usually self bleeding.
DO NOT FORGET TO REUSE A SPRING FOR THE BRAKES!
If you forget, you will have nothing but BRAKES! You will notice this goes between the hydro-boost and the master cylinder within the bore.
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