Having just purchased an 08 SUT I am in the process of changing all the fluids. One thing that I was surprised about is that GM abandon their tried and true Hydroboost braking system for a Toyota (or at least I think it is) ABS system. A friend of mine has a FJ cruiser and was surprised to see the same unit. I know back in 08 GM was scrambling to remove all items that robbed power and possibly decreased gas mileage for the H2, and thus the reason for electric fans and more then likely deletion of the powersteering/hydroboost unit. Other then a variant used in the H3 I am not aware of any other GM vehicle that uses this unit. I was also considering stock piling one of these but was jarred back to reality when I found out what a replacement cost so that will not be an option.

Now that I have digressed, back to my original issue, fluid change I would like to replace all of the old DOT 3 fluid and replace it with DOT 4 but now I am a little gun shy. Replacing old brake fluid with new is very important as it gets rid of deteriorated and fluids that are compromised with moisture. I can just suck out the fluid from the master and replace it with new fluid but would like a complete fluid replacement right down to the wheel cylinders. I have a suction tool that could actually vacuum the fluid right down to each wheel cylinder but know nothing about this new braking system and do not want to cause any problems. I do have a tech 2 and imagine I could cycle the unit but not really knowing this unit we are in uncharted territory,

Anyone with experience with this system I would appreciate input on this.

 

My guess is you are trolling, obviously you have never owned an H2 Hummer as you are totally ignorant about the design, composition or capabilities of the H2 vehicle. Perhaps you can go over to the Jeep forum and share your vast knowledge of premium off road vehicles there, my guess is you probably don't know squat about them either. Feel free to leave and not come back, you and your unfounded stupid comments are not welcome here.

 

Can't really help with your Brake question...

Most of my wheeling has been in the woods of the upper Midwest. H2s/SUTs are capable off road, but have a limitation. Has zero to do with off road ability, and has everything to do with trees being so close together that the H2 can't fit in between. About the only place I have seen trouble for the H2s/SUTs. H3s can also be stopped by those obstacles that a Jeep can squeeze through but the H3 is too wide. IDEA: mounting chainsaws on the outside edge of the front bumper to resolve that issue. Similar to feeding mayonnaise to tuna fish.... or not?

Having said that, I am please to report that a certain antagonist is now on long term vacation from HF.

 

Is it really from an fj? I have an 08 and have been wondering about this for a while. Does this system have a name like hydroboost? Id really like to find more info about it. I guess it's pretty reliable. Mine hasn't had an issue in over 14 years.

 

I checked a number of Toyota forums and, yes its called hydroboost (or HBB) as well. It's also used on a number of 4 runners and on some year GX470 Lexus SUV's. Its funny the Toyota guys say its a pain in the wallet when it fails and can be difficult to find.

My guess is GM was looking to take an electric approach rather then continuing to use the hydraulic power steering pump. They probably dropped a couple of pounds and took some of the parasitic drag of the engine.

Unfortunately this new unit is complicated and expensive plus since it is not as widely accepted and used as the original version used in GM vehicles. This removes the possibility of purchasing a re-manufactured unit.

Finding replacements for these units in 08/09 H2's might be a real problem in the future, unfortunately it is not cost effective to purchase one of these now and put it it on the shelf incase of a future failure.

 

I wonder if it would be more cost effective to replace the whole system with the hydraulic hydroboost and abs module from an older h2. That would be interesting.

 

Great idea but I seriously think it would be very difficult to accomplish, the 08 had a lot of safety improvement including some active handling which I imagine works with the breaking system, and maybe another reason why GM went with the electric system. Perhaps MixMan and HummerZ can shed some additional comments on this.