Hydro-Boost RPO Code

[OhFourChevy]

does the JH2 RPO code for Hyd Power Brakes mean that I have Hydro-Boost?
I am getting a brake flush tomorrow and I would like to know because the difference in brake fluid cost.

Thanks y'all

 

[Rocket Man]

Looks like that's a yes:


JH5 11948 P BRK M BRAKE HYD POWER, 4 WHL DISC, 7,300 LBS 10921 E

As opposed to mine which is non Hydro-Boost:


JC5 11768 P BRK M BRAKE VAC POWER, 4 WHL DISC, 7,200 LBS 940211

Hydraulic power brakes are Hydro-Boost. Congrats!

 

[OhFourChevy]

Nice, so what is so great about having hydro boost vs standard?

 

[OhFourChevy]

Other than my resivoir is smaller so I spend $20 less on a brake fluid flush

 

[Rocket Man]

You have Hydro Boost. It uses the power steering pump to increase braking pressure so you have more stopping power. Better braking is a huge plus for these big vehicles, especially if you tow. Edit: I'm not sure about the size of the reservoir. I thought there would be more brake fluid but I just read the how-to in the tech section about flushing the hydro-boost system and it talks about power steering fluid. Someone who has this system will know more than me! But there are those who do a hydro-boost conversion for better brakes so consider yourself lucky.

 

[nharkey85]

^^^ Correct. To fully flush a hydro boost system you would need to flush the power steering as well as the brakes


And I'm due for this unfortunately. Spongy pedal with plenty of pad/rotor left. Lines look good

 

[retiredsparky]

Spongy pedal is probably from trapped air in the system or I suppose it could be old brake fluid that has moisture. I took my tahoe to a shop and asked them to pressure bleed the brakes and the ABS system (ABS requires a tech tool to activate the ABS while bleeding). The spongy feeling went away. I have not flushed the power steering yet, but I do plan to do that to get fresh fluid in there.

Another possible cause is old brake hoses.

Another cause is installing a right hand caliper on the left side or vice versa (this does happen). This places the bleeder screw on the bottom. No way to get the air out if the bleeder is on the bottom.

 

[Archer04]

So I did a full flush of my power steering today, was an experience as it does have hydro boost. To do it yourself firestorm you have to drain the pump, then drain the gear box and hydro boost system. So I disconnected the low pressure lines and then with the vehicle on jack stands turned the wheel all the way to the left and then right several times to fully drain the gear box. As for the hydro boost I had to pump the brakes several times to drain that. Once fully drained I refilled the pump, now I wanted to flush the system but could not get the fluid to go back into the hydro or gear box without reconnecting the low pressure lines. Then pump the brakes and turn on the wheel again and continue to fill the pump until the system was properly filled. It did help solve the spongy brake feeling the tahoe had. Look at the oil I pulled out and you can see why I had to change and definitely needed to flush.

 

[rockola1971]

My 05 Denali has Hydroboost (JH2) brake RPO code. They brakes are tons firmer feel than my 03 Tahoes with non Hydroboost. This thread is good information on the system. Ive never owned anything with hydroboost so I did not know the system used power steering fluid for the hydroboost portion of the brakes. Mine will probably need a flush this summer since previous didnt take care of anything on this SUV so I can imagine how black my fluid is.