Bleeding Hydroboost brakes

[Z71paramedic]

I think I may have a bad MC but wanted the gangs opinion before buying one even though they're only about $30. My axles/hydroboost came from the same truck. Not sure how long they sat. I forgot to bench bleed it, but now that it's in the truck the pedal will throw about 1" and then is rock hard. The calipers have all gravity bled except the LF which I know needs replaced. So my question is, does the truck need to be running to bleed hydroboost brakes? Thanks in advance guys.

 

[76zimmer]

The truck does not need to be running, but you do need to bench bleed the m/c if new, probably should anyway if its been empty. You could do the procedure on the truck by making a couple tubes to go from the ports back into the reservoirs also.
Also make sure the engagement of the pushrod from your pedal to booster is right, and the pushrod from the booster to the m/c is the right length. I bought a replacement m/c and the piston was a different design than the original h/b unit, so we had to make up a pushrod extension to get a full stroke on the m/c piston.

 

[pblaze725]

I bled mine with it running because I thought the hydro-booster system needed to be powered up for the brakes to work properly.

 

[imiceman44]

I think I may have a bad MC but wanted the gangs opinion before buying one even though they're only about $30. My axles/hydroboost came from the same truck. Not sure how long they sat. I forgot to bench bleed it, but now that it's in the truck the pedal will throw about 1" and then is rock hard. The calipers have all gravity bled except the LF which I know needs replaced. So my question is, does the truck need to be running to bleed hydroboost brakes? Thanks in advance guys.

You might have a bad accumulator, that canister that looks like a capacitor.

 

[Z71paramedic]

Thanks guys, I'll pull the lines and try to "bench bleed" it on the truck. I'll keep you posted on how it goes.

As for the pushrod zim, it's all out of the same truck. I used my old pedals and drilled a new hole and used a clevis. It's not binding or anything, just stops. We'll see...