I was heading to work today, and when I had to press the brakes, my truck pulled to the right really bad. Luckily my work is an auto shop, so we pulled it in and determined that the right caliper was sticking. For preventative maintenance, we decided that both calipers and front hoses should be replaced. I installed the calipers myself, but I had to get someone else to install the lines due to one of the nuts being rounded off (the whole job took a total of 5 hours).
Since this is a hydroboost system, we add fluid and open the bleeder valves and let it drain until it had a good stream coming out. When I go to start the engine, the brake pedal has virtually no resistance until about 50% down. With the engine off, it will go all the way to the floor with some resistance. The brakes worked very well before we did this, now they're pretty weak. We end up bleeding all four brakes multiple times, but there is no improvement.
I drove it home like this so I could get some rest and do more tomorrow. The thing I noticed while driving is you have to press it pretty far to where it's almost touching the floor. It has no-where near the braking power it use to have. I'm unsure if the guys at work know how to work on these hydroboost systems. Can someone help me out?
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I'm unsure if the guys at work know how to work on these hydroboost systems.
They better! Cars still have them. Otherwise I would question the legitimacy of this shop.
Did you install the calipers right-way-up? Are the bleeders facing up?
It's a 36yo truck. It wouldn't surprise me in the least if the master cylinder is bad.
And how are those brake lines doing? Rusting apart?
Have you inspected the rear drums?
I believe cars have vacuum boosters, not hydro boosters.
Yes, calipers are installed correctly. They can only go on one way due to how they're held in place.
Brakes were working perfectly fine before this (other than the pulling to the right), I'm not sure how the master cylinder could just go bad like that.
The metal brakes line appear to be in good condition.
We didn't remove the rear wheels. All we did was bleed the rear. But the thing still worked perfectly fine before we touched it.
Most trucks now use hydraulic boost. So your shop only works on small cars?
Speaking of which ... how is the power steering pump doing?
brake systems can be very flaky on old trucks like that, especially if your pumping the pedal into the floor.
You said all we did was bleed the rear. You have to bleed all four corners, not just the rear. The correct order is right rear, left rear, right front, left front.
I was referring to rear when I said that. @mmj asked if we had checked the drums, I said no. The only thing we did to the rear was bleed them. We did all 4 corners, though not sure what order my coworker did.
He is supposedly ASE certified in brakes, but I really have my doubts about his knowledge on the hydroboost systems. He worked at a Honda dealer for many years, so it's not likely he saw a lot of those hydroboost systems at that time.
You really need to find someone who actually knows what they are doing in the first place. These are your brakes, after all. Take it to a pro, not a chain store, ie Pep Boys, Firestone, etc.
I have another question about this. Do I have to bleed the power steering after changing calipers? I've heard some sources say it's self-bleeding, but I've also heard others say do this and that. I really want to try and solve this myself if I can.
We do have one master tech at our shop who knows it all. I couldn't get him to look at it today, so maybe tomorrow we can get him to take a look.
no you don't need to touch the PS.
Yes it is self bleeding
The power steering has nothing to do with your brakes.
Like I said in my last post, you have to bleed all four corners to get all the air out of the system. If your pedal is still going to the floor, you have air in the system or your vacuum operated booster is bad. Air CAN be compressed, fluid CANNOT.
Correction - The Hydroboost system does in fact use power steering pressure instead of vacuum pressure to operate the system. See this -
https://www.youtube.com/watch?v=3PqEW2Pf90I&ab_channel=BustedKnuckleOffRoad
My apologies for the incorrect information.
He said he has hydraulic boost. Not vacuum. Rockauto seems to confirm this.
that's right. Big engines don't make enough vacuum to stop a big truck. More power was needed.
See Doc eating crow above.
hey Doc learned something today.