Canadian Hummer Club Forums

My peddle hit the floor, no leaks anywhere,.... fluids still full in master, so figure it's an internal leak

I gotta master cylinder coming from our local parts store..... But was wondering in any tricks to it?

Looks fairly straight forward, but lol nothing ever is, I noticed the two brake line different nut size, and master cylinder seems like it VERY little working room, verrrry little

Loosen off the lines coming out of the master, make sure the nut spins around the line. If not, you will need heat.
Only use a line wrench. This is a special wrench for brake lines. Once lines are loose,undo all the way,
then loosen/ remove the 2 nuts holding the master cylinder off hydro boost.
Make sure both parts are identical as best that you can,
Put new master into a vise without marking the ears, hook up the plastic fittings to the ports and route lines back into the reservoir.
Fill m/c with fluid
With a large philips, or similiar object, push the plunger in and out until no air bubbles come out of the return lines.
Fasten cap with lines still in reservoir, fasten m/c to hydroboost. Then fasten lines.Last operation takes 2 people.
One pumps the pedal 3 times and holds it halfway down.The other will open the line at the m/c to let the rest of the air out of the line.
Do this a few time on each line without having the level get too low. Test pedal for firmness. Then try cautiously to check brakes while running in gear.
The pedal should be up high and firm. If spongy, rebleed. If pedal goes to the floor, call a mechanic to look at it.
 
Good luck my friend

Pump 5 times then hold!


Start on the right rear, then left rear, then front right then finally left front!


Also use only DOT 4 brake fluid in trucks that are 1999 and up with ABS/TT4 and use only DOT 5 in all 1998 and down trucks


The master cylinder is a fun job to do and can realistically be done in under 2 hours without stressing yourself out. It is tight but the right tools make all the difference!

[quote="Polar Bear"]
Pump 5 times then hold!


Start on the right rear, then left rear, then front right then finally left front!


Also use only DOT 4 brake fluid in trucks that are 1999 and up with ABS/TT4 and use only DOT 5 in all 1998 and down trucks


The master cylinder is a fun job to do and can realistically be done in under 2 hours without stressing yourself out. It is tight but the right tools make all the difference!
[/quote]
This is good for a complete bleed, I do the half bleed with a good success .

You guys are the best! Thanks