GMT900 Hydroboost Conversion How-to
 

Hello Friends, First of all, :jest: I'm not used on hard braking, you should have seen me braking all the way to work. Guys with vacuum, trust me trash it you will thank me later. Was running on 9 in/vac @ idle wth ?

(¼) Pedal travel = Nice Bite.
(½) Pedal travel = omg-abs-skid.

You won't need a full pedal anymore. "Broblem" is check brake system on message console, no lights what so ever, any electrician please chime in. :hmmm:

But anyways, I would like to thank Pl4yboy and Robert91RS.

Got my whole unit from a scrap yard from Maine for $290 shipped, 2008 40~k miles wrecked express van.

• Booster# 20940395
• P/S Pump# 20756715 (has an extra return port)
• P/S Hose# 15295853 (pump to booster)
• P/S Hose# 15804952 (booster return to pump)
• P/S Hose# 15295840 (booster to gear)
• Pedal# 15906961 (non adjustable)

http://oi47.tinypic.com/2njgjtx.jpg

1. Disconnect the battery.
2. Locate the bolts on the firewall, knee bolster + bolts are going to be P.I.T.A., stupid loctite.

(1) = Bolts
(2) = Brake lights sensor.

http://oi50.tinypic.com/35i5g9i.jpg

3. Carefully disconnect the brake pedal light sensor, Loosen the bolt and remove it. Then unbolt the whole brake pedal.

http://oi47.tinypic.com/biph6g.jpg

Okay, got a slight problem lol.

http://cdn.memegenerator.net/instanc...x/24624930.jpg

The hydroboost seem to have a different pattern. :sigh:
Didn't want to drill the firewall up, sooo...

http://oi47.tinypic.com/2a4nxch.jpg

I re-welded the bolts up to match the existing one. Thanks GM.

After re-locating the bolts.

http://oi48.tinypic.com/29gczyq.jpg

5. Get a power steering removal kit / installation kit for $30, don't use air tools on this lol. Loosen the drive belt, remove the pulley, remove the 3 bolts (front) 1 bolt (back). straight forward.

6. Connect the high pressure line from pump to booster, low pressure line from booster to PS pump.

7. Remove the clip + bolt attaching 2 lines, one coming from the PS cooler, one from PS pump.

http://oi46.tinypic.com/30blksn.jpg

You could splice this but I preferred to go with a hydraulic hose.

http://sphotos-a.ak.fbcdn.net/hphoto...51999577_n.jpg

^ Ryan @ Nitrous Express could make you one. :usa:

I made a small illustration on how to connect the other high pressure line.

(1) Cut the end of the steel line leaving the Hydro.
(2) Cut the end of the steel line going to the PS gear box.
(3) Hydraulic press the two ends with a 3/8" line IIRC.
(4) Optional, you could add fittings to adjust the hose path and weld them to the lines.

http://oi48.tinypic.com/rll007.jpg

http://oi46.tinypic.com/2rzt40g.jpg

http://oi47.tinypic.com/v4p14z.jpg

:hail: ½ line, 4,000 psi burst point.

8. Broblem? No Broblem! :jest: Found out my master cylinder lines are bigger for some reason. 2x Custom male to female fitting for $20.

http://oi47.tinypic.com/1zc0588.jpg

http://oi47.tinypic.com/2m5j9t4.jpg

9. Bleed PS, Bleed brakes.

http://oi49.tinypic.com/ykpiq.jpg

10. Attach and install everything else including the pedal lol, CHECK FOR LEAKS. Enjoy your beer.

Simple and straight forward, any questions hit me up.

where did you get the adapter fittings??

do you know the size fittings for the hydroboost an rack an pinion? id much rather run SS line vs a chopped up pressure line :)



nice write up :thumb: lets make this a STICKY

I am busy right now and not on my laptop, PM me a reminder and I will sticky it when I get home.

Stuck!!!

Thanks bro, I took the same line that goes in to rack, the hydraulic shop used water to cool it off, checked for burr, nada, perfect cut. Everything was done with big *** machines pushing threw lines, once squeezed it's done.

You could ask your local metal workshop for the adapter, It was done with a lathe I believe. :hmmm:

Can you do me a favor and resize the first and last picture so it doesnt make the post so wide? Thanks a lot for thev ery detailed write-up. I need to do this on my truck ASAP.

id have too much in machine work.

too bad no one works in a part store that can get use 2 new fittings vs hacking up ours :(

You can get new fittings, you just need to know what size they are. In his part of the country it is near impossible to find that type of little stuff.

It's also important to note he used the set up from a Van. There is often small differences between a Van and a Truck platform.

It's also important to note you can sometimes reuse your existing Master Cylinder. The bolt spacing on the end of the hydroboost will determine that.

http://oi48.tinypic.com/2gw9xl2.jpg

Final look.

http://oi50.tinypic.com/o8s2dj.jpg

Lubed up. :jest:

http://oi46.tinypic.com/2dc9ye9.jpg

Centric goodness.

Will this cause issues with my factory trailer brake controller? I've heard that the trucks with factory trailer brake controllers have option-specific master cylinders I believe.

My trailer brake controller is functioning, doesn't bother me as I never used it and have the hitch off. I tried to remove the dash message "Service Brakes Soon" which seems to appear when switch is on ignition, trick didn't work.

Thought pl4hboy fixed the brake message prob? Read somewhere all you do is tie both outside wires on the vacuum sensor connector together and message should go away. Any more info on this or can anyone post up a diagram to show what each wire does?

That works perfectly on NBS. Tried it on mine, wasn't lucky. :(

what about reflashing the bcm with a truck with the same options as yours but has hydroboost?

Hmm, thats an idea... But isn't reflashing the BCM is simply by disconnecting the battery terminal? Or you mean using HPTuners?

Any updates on the service brake light?

x2 I'd love to do this to my tahoe before buying my wilwoods!
But if I have a dash light on my head will explode!

Would imagine a bcm reflash would work... Let me talk to my buddy at the dealer and see if its possible. I don't have the parts to do the swap yet but would imagine the flash can still be done and connector just be disconnected. Will see what happens.

Alright awesome thanks cant wait to hear back from you!

http://sphotos-a.ak.fbcdn.net/hphoto...51999577_n.jpg

Where does this actually go and what did it replace?


As for the master cylinder having different size flare fittings....couldnt you just reuse your factory master cylinder, replace whatever gasket/ o ring and buy the power brake booster for the hydroboost swap?

As for the feed hose and cooler hose setup did you cut and extend the hoses using hydro line or did you go a different route?

Any luck with the message?

Alright, just got everything swapped in, attempting to bleed the steering, not sure if I'm getting it though. The brake pedal isn't getting any stiffer though. I thought since the brake and steering hydraulics are now tied together that bleeding the steering would bleed the brakes too. Am I wrong? Do I need to bleed the brakes seperately?

I think so, I am pretty sure the fluid for the master cylinder is different than the hydroboost.

Did you do this on an nnbs? Did you make any progress on the dash light/warning?

Yep, 08 VMax. I haven't bothered with the SERVICE BRAKES SOON message yet though, no. I also have an extra electrical connector that was plugged into the booster, and an unused plug recepticle on the right side of the pump. Anyone know what these are?

Yes sir, nnbs, fluids are different and I couldn't remove the warning too.

Attachment 96344

Factory fitting at the Rack. Def a bad GM design for us that want hydroboost :jest:

Any chance anyone found out how to disable the "service brakes soon" yet? Mine still says it, but it doesnt bother me

Can anyone confirm if you can reuse the original master cylinder like you could on the nbs trucks? I am thinking you can avoid the extra headache of the different size fittings on the brake lines by just swapping over the master cylinder.

Also, no one has had any luck with the 'service brakes soon' message?

Idk if you can find a booster that has the same "spread" for the master. I have not had different boosters in hand to compare to my oem master.

I have not figured it out yet, but i do know that no matter how you jump the harness it does not clear the code like the old swap. You do have an ABS plug, that all you have to do is wire together to keep it from throwing the ABS lights.

I am planning to compare ohms on am oem setup asap

i got mine to work without saying the service brakes soon message. I just capped off the end that went into the brake booster and left the sensor connected to the intake.

Do you have a part number for the master cylinder you used, and did it require any funky fittings to get your brake lines to work with it?

So, you just capped it with a rubber cap and left it dangling where it was originally by where the booster was?

Did you jump the wires on the abs sensor like iamkeniff said?

Thanks for the help guys. I am trying to figure out all of this crap before I start ordering stuff to do the swap.

I didn't have a sensor connected to my intake. I did use the vac hose for the booster to put the sensor in that was in my booster, but that didn't help cancel the read out.

If i cant get it to ohm right then i'm thinking about having my bcm flashed finally.

Yes i have the whole write up with what p/n i used and how i spliced the high pressure hoses. The master i bought used the same lines without adapters.
I would look at your master to see how wide it is then go to the part store to compare. I used all AC Delco parts on mine which i ordered online for a lot cheaper

https://www.performancetrucks.net/fo...st-how-534308/
Not trying to thread jack, just figured all the info in one spot would be better

I just finished a hydroboost conversion on my truck which is a 07.5 and it turns out i dont have any "sensors" to deal with on my vacuum booster. The master cylinder off an 08 2500HD gas truck was a direct fit in thread pitch and line spread. I also installed a T fitting for the return lines instead of replacing the pump which i also have from the HD truck. I must have gotten lucky on mine but it is basically a W/T trim model so that may be why lol.

Great write up ! Just did mines . Was very helpful . Like the guy above mine was pretty plug and play . Everything match up great .got everything from a 2500HD. Hydroboost was a great choice for me since I’m turbo . Truck feels way better and stops in a dime . Thanks again !!

Can pictures be uploaded again ? Please and thank you in advance

Please add pics back in this thread.

I would think a sticky would retain pictures.

07 Avalanche hydro boost / service brake light
 

Anyone figure out the service brake warning light yet? I can't do this swap if the warning is going to stay on due to state safety inspections.

Well, I believe that I figured it out, and posted instructions here: https://www.performancetrucks.net/fo...-c0299-559296/

This fix may only apply to the rotary brake sensor trucks (2012+); as someone with an '07 was unable to get this to work for him. It could also be that the voltages to the EBCM just need to be slightly higher or lower for the earlier GMT900s.

I'm happy to help, and you could certainly try my "Service Brakes Soon" fix before doing a hydroboost conversion.

07 Avalanche brake warning, stabilatrac
 

If anyone comes up with a solution for this, please let me know. Thank you