After replacing two burst brake lines, I was attempting to bleed the system, the brake pedal had no pressure at all, possible due to air in the system but there were no leaks.

I used the TECH2 to try and help bleed the system, now I have a massive amount of brake fluid pouring-out from beneath the driver position, could the Tech2 have over-pressurized the system?

Have to say my lines were pretty rotton all-round, so it could be I've ruptured yet another line OR perhaps something has happened to the Pump/ABS unit.

In the documentation there is an EBCM and BPMV which seems to comprise/form the "Brake Pressure Modulator Valve" assembly, could this have blown?

At the moment I haven't had a chance to investigate, I'm just trying to get a feel for the possible issues.

Any thoughts most welcome.

 

"A chain is only as strong as its weakest link". I use copper/nickel rolls, (easy to bend and rust resistant) and replace the line from fitting to fitting(Never use compression fittings, Never repair part of the line). Cut both ends at the fittings, remove the fittings, clean/reuse fittings depending on the condition, may need to replace the fittings, then route a new line, install the fittings, double flare, secure, then check for leaks. Your replacements may still be good, yet may have had another line burst. Best part, you found this out, while not driving. With the proper tools and a couple rolls of brake line tubing, it's cheap yet time consuming to replace them all, and prevent any further failure and potential damage to your rig. Over the years, I've had most customers that accepted my recommendation, yet there were a few that were only willing to repair what's broke, however when their vehicle was towed back into my shop for another failure, they changed their mind. Simple math, all lines with the same age and condition will fail.

Different vehicle yet to the point--> S.U.R.&R.

 

well better to have happened under your watch then to have happened on the road. your lines where most likely already compromised and by working the abs pump they gave up.

 

Indeed... still investigating.

 

hummerz
In anticipation, I already bought a complete SS kit from classictube.com, for better or worse.

Well the good news was not not the ABS Pump/Module, but a ruptured line between the master cylinder to the pump. 3rd broken line in matters of days.

It was definitely time, just didn't get the chance to get the truck to a shop rather than out in the open.

 

Get into the shop. The beer is the only thing that needs to be cold.

 

Agreed and yes that is the only thing I can think of as well. I've used that function on both my GMC and Blazer which has it under the 4WAL section on the Tech2 when I flushed the brake system on them. Hold the brake pedal down and it pushes it back hard about 8 times. I need to do that to the H2 as well, I'm quite sure the brake fluid in it is probably 10+ years old too, its pretty much black. Made a noticeable difference in braking on the other two after I flushed the old fluid out for new. On my GMC I also replaced the reservoir itself as the fluid was so old that there was sludge in it that I couldn't even get to. Cardone sells a replacement reservoir only which is fairly reasonable (like $25 US) and easy to replace. Just have to be sure you get the right one. One is sort of oval shaped while the other is more pill shaped on the full size GM trucks and SUV's. Not sure offhand which one our H2 uses.

 

Would dearly love to get it to a shop, but it going to be a struggle without brakes, very few places in the UK can take a Hummer and getting there is difficult, so I'm pretty much stranded.

MixManSC
On the reservoir I concur, I also noticed the horrible sludge. I did think about removing the reservoir and cleaning it out somehow. One thing for sure is all the old brake fluid will be flushed-out.

So a few questions, if I may :-

1. Does the fuel tank need to be moved or removed in order to access the rear brake lines (looks like it does)?
2. The ABS Brake Module needs to come out, given that access is limited and all the line fittings are seized solid, only one came out but broke the line at the same time (just had to be the rear) So my plan is to cut all the lines, drop-out the ABS unit and remove all the fittings on the bench. Now to get the Brake Module out, there are three bolts which go through the chassis frame, the lower one is easy access, but the top two are hidden by the evap unit, does this have to be removed or just undone and pushed to one side?
3. There doesnt seem to be an accurate diagram of the ABS Module port assignments, Front Right/Left lines look easy, but the two Master Cylinder ones look easy to get swapped as do the two rear ones. The preformed SS lines may help but it's a little risky, so does anyone have a diagram?
4. On brake fluid the Hummer call's for Dot3 however the experts here tell me that Dot4 covers all previous fluids, is this true? (I asked because Dot3 is harder to obtain here)

Now I have some lines on my bench I'm both horrified and mortified at the state they are in, the bottom line is they are rotten to the core!
To echo hummerz concerns on safety, this has to be top of the list of must do's to anyone who owns a Hummer, dump the GM lines ASAP.

It was my plan to video as much as I can, however working at ground level is tough and makes this difficult especially single handed.

 

You are flushing the fluid when replacing the brake lines. Yes, DOT 3 brake fluid is compatible with DOT 4 brake fluid. However, DOT 4 offers a higher boiling point. DOT 5.1 is used in high-performance and heavy-duty applications due to its high boiling point. It's compatible with DOT 3 and DOT 4 fluid.

Brake fluid

 

to do the lines properly the body mounts need to be un done on the drivers side and the body lifted up to gain clearance. but what usually happens is they cut out as much line as is accessible and just throw the lines in wherever they can. usually not clipping them back into the plastic line holders on the chassis.
here is an example he is doing a pickup so he lifts the bed. in our case its the body mounts.