1991 Chevy Suburban hydroboost swap

asmith

Observer
After locating a hydroboost from a 1989 chevy. I decide to undertake the swap. Now I will be learning as i go so please bear with me.

This is the hydro unit i picked up. What is not pictured is the master cylinder which ill pulled off after cleaning it.
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1. Disconnect the battery.

2. Locate the brake booster on the driver's side of the firewall inside the engine bay. It will be just behind the brake master cylinder.


3. Disconnect the vacuum line from the power booster by pulling the bung out of the vacuum booster.
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4. Then slide the rear abs computer off of the bracket. To allow for easier access to the two bolt that connect the master cylinder to the power booster. I opted on leaving the computer plugged in due to the brittle connecters.
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5. Remove the two bolts that connect the master cylinder to the power booster. Be careful not to put any stress on the brake lines connected to the master cylinder. Slide the master cylinder forward and secure the master cylinder so it is not resting on the brake lines. I used a wire coat hanger for this.
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6.Disconnect the brake pedal pushrod from the brake pedal from inside the passenger compartment by removing the retaining clip and unbolting the 9/16 nut. Then slide the pushrod off from the pedal. Careful not to loose the two washers.
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asmith

Observer
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7. Remove the six nuts that connect the brake power booster to the vehicle's firewall. Then remove the booster from the vehicle.
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Note mine was covered with a rubber spray from the factory. So i had to scratch off the spray before i could get to the nuts.
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Now with the vacuum booster removed its time to figure out exactly what needs to be done.
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After putting them side to side they look the same length which is a plus :wings:
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Now on the 89 booster i has two bolts that need to be knocked out. Then i used a 7/16 drill and a hand file to open up the holes that i knocked the bolts out of.
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Next will be a trip to the auto parts and see if the 6.2 diesel MC will bolt up to the 89 booster.
 

asmith

Observer
So a trip to the auto parts showed the pin from the hydroboost unit would make things more difficult.
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The pin on the hydroboost unit was a 1 5/8ths too long. So i cut it down and beveled the edge.

Then just reverse the process and install the hydro unit. I used the trucks original MC which was still in good order.
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Pressure hoses are on order so more to come.
 

Larry

Bigassgas Explorer
Great swap! Hydroboost was one of the top 5 upgrades I’ve ever done to my K10. Between swapping on the huge 13 x 3.5 rear drums (yea, drums….I don’t buy into all that rear disk swap bs) and hydroboost, the heavy old truck stops like an anchor was tossed out of the back of the now. I can’t wait to convert my Polar Bear Burb to hydroboost as well but the priorities currently lie with swapping out the gutless TBI 5.7L to something more substantial. Might do hydroboost at that time.

Not sure if it is true or not for all years of square body trucks but, there is talk that the brake pedals are different between vacuum and hydroboost trucks which can affect your brake pedal throw. You might consider looking into that.

Your swap is looking great! While you are there, I would recommend replacing the master cylinder to a true hydroboost master cylinder for the best braking performance. Adding hydroboost to your existing M/C will be a huge improvement but moving to a larger M/C will yield that much more gain.

If you haven’t done so already when doing a hydroboost swap it isn’t necessary to swap on a hydroboost type dual return port power steering reservoir. If you look back in GM truck history, G-van’s and P-chassis in the 70’s up through the 90’s (and some heavy and medium duty trucks still today) didn’t use a dual return port reservoir. They just used the tee fitting to tie all of the return lines together. That said, there is nothing wrong with using a tee fitting rather than going through the hassle and expense of adding a dual return port reservoir.

Here is my tee fitting on my K10 near the return port at the steering gear. Return fluid comes from the booster to a tee fitting at the steering gear return then goes out to the cooler then back to the power steering pump reservoir.
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The other side where the return lines come to the cooler. From the cooler, the return goes to the reservoir.
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Looking good so far. Looking forward to more.
 
Looking at the pics of the cooler mounting it would seem that it is higher than the reservoir. Just wondering if any air bubbles get trapped in the cooler? The reason I ask is because here at my work on the newer G37s the radiator cap is not the highest point in the system. Because of this the technicians have to pressure burp the system to work the air bubbles out when they do a coolant flush otherwise the customers come back complaining about gurgling sounds. Not trying to second guess you I am just wondering if you have had any experience with this :)
 

Larry

Bigassgas Explorer
Looking at the pics of the cooler mounting it would seem that it is higher than the reservoir. Just wondering if any air bubbles get trapped in the cooler? The reason I ask is because here at my work on the newer G37s the radiator cap is not the highest point in the system. Because of this the technicians have to pressure burp the system to work the air bubbles out when they do a coolant flush otherwise the customers come back complaining about gurgling sounds. Not trying to second guess you I am just wondering if you have had any experience with this :)

Danimal,

I assume you are directing that at me since I had the pictures. You’re right, cooling systems can be a bit of a challenge to burp out the air bubbles when the fill hole is not the highest point in the system. Heck, many manufacturers these days require vacuum filling cooling systems where the cooling system is basically filled from the bottom (radiator drain) by drawing a vacuum at the radiator cap opening. The manufacturer I work for is one of them were we require vacuum filling to prevent EGR cooler failures from air bubbles.

As odd as it sounds, it seems power steering systems don’t always care too much if the reservoir is the highest point or not then other times certain vehicles are practically impossible to bleed until the reservoir is mounted as high as possible. I am a service rep for Navistar and we saw issues on some RV chassis (Workhorse) we built over the years where the reservoirs definitely had to be at the highest point but we also have several vehicles running around where the reservoir is not the highest point. Odd that sometimes reservoir height it is a big ordeal and other times it is not.

To be honest, I think I just got lucky with the cooler location on my K10 being higher than the reservoir without causing any issues. It was easy to bleed when I put it together and has worked flawlessly for the past 3 years even in 115 degree temps in Utah Canyonlands last summer. I basically copied the power steering hydraulic circuit and flow diagram that we used for several thousand UPS trucks we’ve built with GM engines over the past few years.

At the end of the day, I agree in that it would be the best practice to always have the reservoir at the highest point if possible.
 
Larry,
That is very interesting how that works. I knew you would be able to explain this to me as well so thank you. Like I said I was just noticing it and I am always looking to learn from others more knowledgeable than I. This is now one of the mods I will be doing to both of my Suburbans when we, (hopefully soon), move to Las Vegas. I would love to hear your thoughts on ways I can keep them running cool in the desert heat. Not on this thread of course but maybe sometime we can chat about it? :)
 

Larry

Bigassgas Explorer
I would love to hear your thoughts on ways I can keep them running cool in the desert heat. Not on this thread of course but maybe sometime we can chat about it? :)

You bet, feel free to send me a PM sometime.

I wonder what became of asmith’s project anyway?

Paging asmith….asmith please. Asmith to the hydroboost thread please
 

asmith

Observer
Well being in the Army, they felt the need to send me to Fort Bliss, TX for training. Now that i back im going to get back to it. When i left the problem i had was the hydroboost unit i had was the older style threads. Im thinking about using it for a core and just order the one for my truck from autozone.
 

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