R&R and repair GM Hydroboost

[Flyin6]

The subject vehicle is my 2500 series Chevrolet Suburban.

I noticed some fluid accumulating on the floor mat some months ago. Not knowing what it was, I continued to drive the truck and as time went along, the leaking was getting progressively worse, but not all that bad

(Except that any potential brake leak is no good)

[Flyin6]

Start with a prayer.

It is a good practice to pray about all things

And I do not wish to be politically correct, but, rather, pleasing to the Lord!

After that, remove the two nuts holding on the master cylinder then just pull the MC forward

[Flyin6]

Pull the return line by loosening the clamp then pulling upward

[Flyin6]

Then disconnect the two steel lines from the hydroboost unit

[Flyin6]

The typical leak point is in the front, a large bore seal that allows fluid to run out the front, as you can see here. In this case it is possible the fluid also made its way aft to the firewall, then inside the cabin due to being wind blown, or so is the theory at this point with respect to this repair

[Flyin6]

Moving inside, upside down, on your side, twisted into a horrible position, time to pray for peace and a little less pain from the front of the seat mount grindin' into your ribs and back.

Find the little clip that holds the pedal onto the shaft from the hydro boost and pry it off. Then slide off the brake switch

The pedal will now swing free like some hippie at a modern day woodstock reenactment concert!

[Flyin6]

Not the best pic, but there are four 15mm nuts that hold the hydro boost unit to the firewall. Some are hard to get to, but with using various combinations of a 3/8" universal and various lengths extensions, you can get them out

[Flyin6]

Then the thing can be worked out of its mount and free to continue working on

[Flyin6]

Here is the el-cheapo mostly seals and O-rings kit used to freshen up this long life unit

[Flyin6]

Now, it may not be necessary to remove the sheet metal mount, depending on how far you are going, but should you need to do so, and you own the most common type, use a punch and ball peen to tap against a flat of the big not to loosen it

[Flyin6]

Now if you are removing the piston, input side, and you have this style of plunger which crimps or stakes on the rod, then you will have to cut the rod, then at some later point reweld it. I have elected to leave this alone, hoping that this is not my leak point

[Nate]

Talk about an abrupt stop.....

[Flyin6]

I'll finish this with the next installment

But for now domestic family guy stuff is driving the train.

[Nate]

I'll finish this with the next installment

But for now domestic family guy stuff is driving the train.

 

[KensAuto]

Good write up boss.
Where did you source the kit?

[Flyin6]

Good write up boss.
Where did you source the kit?

Just keyed in hydroboost rebuild kit into Amazon, compared pics and part numbas then hit the order button

Did I mention somewhere in the past, we piluts like buttons?

[KensAuto]

Rog

[Flyin6]

So for the nature of the repair I am doing, not a great deal of disassembly is required

Place the unit in a vice, with five each bolt heads facing upward. They are 10mm.

Remove them to split the halves of the unit

[Flyin6]

As the unit comes apart, note the orientation of the various plungers, springs, and gasket

[Flyin6]

At this point I thoroughly cleaned the inside and outside with brake cleaner and clean rags

[Flyin6]

Inside the large bore is a seal. This is the source of the leak in this unit and probably 99% of all the other leakers out there.

Use a pick to work the seal out of the slot in the bore. Note the orientation of the lip. Putting the new seal in backwards will not seal properly and cause you to have to do over.

[Flyin6]

I used a light coating of grease to lube the bore prior to sliding the new seal into the recess.

[Flyin6]

In fact, I used grease on everything as I slowly pulled various parts off the casting to check/replace O-rings

I installed a new figure-eight O-ring, then reassembled the case halves. I finished by sliding this star spring washer unit that centers the rod in the bore to align with the master cylinder.

It got greased too, then pushed down into the bore with a big deep well socket

[Flyin6]

I finished it with two coats of black epoxy. Paint will likely slough off should you spill brake fluid on it in the future so I used the good stuff