Wonky hydroboost

[MarkB_MI]

A couple weeks ago the brake booster on my 2017 Chevy 2500 Duramax started leaking, so I replaced it. A new AC Delco booster is over 500 bucks, so I opted for a reman unit from O'Reilly for $210. Since replacing the booster, my brakes MOSTLY work OK, except when they don't. Every so often, maybe once a day, I lose boost and have to mash down hard on the brakes to get stopped. It only happens once, then the brakes are fine on the next stop. Initially I thought there was a little air in the system that would eventually work out, but I'm beginning to think the reman hydroboost unit is defective.

Is it possible this problem will clear up, or should I bite the bullet and replace the reman hydroboost with a new OEM unit? We're taking our fifth wheel camper on a trip in a few weeks and I need to get it resolved before then. It scares the bejeezus out of me just stopping the truck with no boost and I sure don't want this to happen pulling the camper.

 

[dick1234]

I would go back to O'Reilly for a replacement. They certainly must have a warranty of some sort.

 

[Steve in VA]

A couple weeks ago the brake booster on my 2017 Chevy 2500 Duramax started leaking, so I replaced it. A new AC Delco booster is over 500 bucks, so I opted for a reman unit from O'Reilly for $210. Since replacing the booster, my brakes MOSTLY work OK, except when they don't. Every so often, maybe once a day, I lose boost and have to mash down hard on the brakes to get stopped. It only happens once, then the brakes are fine on the next stop. Initially I thought there was a little air in the system that would eventually work out, but I'm beginning to think the reman hydroboost unit is defective.

Is it possible this problem will clear up, or should I bite the bullet and replace the reman hydroboost with a new OEM unit? We're taking our fifth wheel camper on a trip in a few weeks and I need to get it resolved before then. It scares the bejeezus out of me just stopping the truck with no boost and I sure don't want this to happen pulling the camper.

I had a similar problem years ago on a Land Rover and it was not the booster but was a vacuum leak in the hose feeding it. Not sure if yours is vac powered but may be worth consideration.

 

[Brown David]

I had a similar problem years ago on a Land Rover and it was not the booster but was a vacuum leak in the hose feeding it. Not sure if yours is vac powered but may be worth consideration.

Hydroboost uses hydraulic pressure from the power steering pump to boost braking power, no vacuum is involved.

Sure sounds like a defective unit to me.

 

[Jeff NWOH]

A couple weeks ago the brake booster on my 2017 Chevy 2500 Duramax started leaking, so I replaced it. A new AC Delco booster is over 500 bucks, so I opted for a reman unit from O'Reilly for $210. Since replacing the booster, my brakes MOSTLY work OK, except when they don't. Every so often, maybe once a day, I lose boost and have to mash down hard on the brakes to get stopped. It only happens once, then the brakes are fine on the next stop. Initially I thought there was a little air in the system that would eventually work out, but I'm beginning to think the reman hydroboost unit is defective.

Is it possible this problem will clear up, or should I bite the bullet and replace the reman hydroboost with a new OEM unit? We're taking our fifth wheel camper on a trip in a few weeks and I need to get it resolved before then. It scares the bejeezus out of me just stopping the truck with no boost and I sure don't want this to happen pulling the camper.

I've replaced a few of those. Always used the reman units from wherever. I've never had one need any special bleeding or not work right. I'd say you got a dud. I'd try another one from O'Reillys.

 

[MarkB_MI]

I would go back to O'Reilly for a replacement. They certainly must have a warranty of some sort.

I would go back to O'Reilly for a replacement. They certainly must have a warranty of some sort.

Thanks for the suggestion, Dick, but if I'm going to go through the aggravation of replacing the booster a second time, it will be with a new unit. I'd rather eat the two hundred bucks I paid for the reman rather than risk a second bad unit. Brakes are too critical to be messing around with suspect parts.

 

[MarkB_MI]

I decided not to change out the reman booster. The problem seems to be resolved since I went through a process that's supposed to purge air out of the system. Starting with the steering wheel straight ahead, you very slowly turn the wheel back and forth in ever-increasing arcs until you hit the steering stop. Then hold the steering wheel against the stop for about 30 seconds. Then turn back to the other stop and hold it there for another thirty seconds. I did this three days ago and haven't lost brake boost since then.

 

[DoubleO7]

I decided not to change out the reman booster. The problem seems to be resolved since I went through a process that's supposed to purge air out of the system. Starting with the steering wheel straight ahead, you very slowly turn the wheel back and forth in ever-increasing arcs until you hit the steering stop. Then hold the steering wheel against the stop for about 30 seconds. Then turn back to the other stop and hold it there for another thirty seconds. I did this three days ago and haven't lost brake boost since then.

I was gonna say maybe the anti-lock braking system had to have some sort of procedure done when replacing the hydro unit.......

 

[wore out]

I was gonna say maybe the anti-lock braking system had to have some sort of procedure done when replacing the hydro unit.......

Replacing the Hydroboost unit should not affect the "brake fluid side" of the braking system only the "power steering fluid side" would get air in it that needs to be "worked out", IMHO.

 

[Brown David]

Replacing the Hydroboost unit should not affect the "brake fluid side" of the braking system only the "power steering fluid side" would get air in it that needs to be "worked out", IMHO.

Agreed.

 

[MarkB_MI]

I was gonna say maybe the anti-lock braking system had to have some sort of procedure done when replacing the hydro unit.......

I was gonna say maybe the anti-lock braking system had to have some sort of procedure done when replacing the hydro unit.......

I haven't found anything to suggest that. Note that the ABS can't tell if the pressure on the master cylinder is coming from the booster or the driver's foot. Note that I was able to replace the booster without removing the brake lines from the master cylinder.

 

[MarkB_MI]

Apparently I spoke too soon. After four days of no problems, the booster started acting up again when I was stuck in a traffic jam. I first noticed the smell of hot hydraulic oil, then several minutes later I started losing boost. I realized then that the problem only happens after driving in traffic for a while. The problem cleared up immediately as soon as I got out of traffic, presumably because of air flowing over the power steering cooler.

Either there's still air in the system, or the fluid is contaminated. I'm going to flush the fluid out, which is quite simple on the hydroboost. There's a return line that goes from the booster to the PS reservoir; you just take that line loose and replace it with a long hose going to a drain pan. Then exercise the system. Whether the problem is air or contamination, flushing the fluid should fix it.

Why am I seeing this problem after the booster replacement? My guess is the reman booster is generating a lot more heat than the old unit.

 

[Sprint 6]

Your reman booster is junk. I only use OE boosters at the shop for these reasons. Had to replace reman boosters too many times for leaks and inoperative conditions. Same thing with power steering pumps, new OE only. The problem with Hydroboost is they are all basically the same (minus the bracket), but the internal valving can be different depending on the application, so who's to say the one you installed is actually for your truck, or is it a close enough is good enough situation?

I think the problem today with a lot of remanufactured parts is that the cores are worn out. 30 years ago, cores only had maybe 30-50K miles on them. Now, those same cores have 100-200K miles on them.

 

[MarkB_MI]

Your reman booster is junk. I only use OE boosters at the shop for these reasons. Had to replace reman boosters too many times for leaks and inoperative conditions. Same thing with power steering pumps, new OE only. The problem with Hydroboost is they are all basically the same (minus the bracket), but the internal valving can be different depending on the application, so who's to say the one you installed is actually for your truck, or is it a close enough is good enough situation?

I think the problem today with a lot of remanufactured parts is that the cores are worn out. 30 years ago, cores only had maybe 30-50K miles on them. Now, those same cores have 100-200K miles on them.

Your reman booster is junk. I only use OE boosters at the shop for these reasons. Had to replace reman boosters too many times for leaks and inoperative conditions. Same thing with power steering pumps, new OE only. The problem with Hydroboost is they are all basically the same (minus the bracket), but the internal valving can be different depending on the application, so who's to say the one you installed is actually for your truck, or is it a close enough is good enough situation?

Thanks for the input. If flushing the fluid doesn't fix the problem, I'll definitely spring for a new OEM booster. But the reman unit doesn't leak, and acts OK 99% of the time.

The reman booster is supposedly the right one for my vehicle, according to O'Reilly. Even if it's not, incorrect valving wouldn't explain the intermittent nature of my problem. And it also wouldn't explain why the fluid overheats in traffic.

 

[BarnyardEngineering]

Replacing the Hydroboost unit should not affect the "brake fluid side" of the braking system only the "power steering fluid side" would get air in it that needs to be "worked out", IMHO.

Yes, and on hydroboost systems that I have experience with, no boost, no brakes.

Dad had the classic GM "power steering pump seizes and spins the pulley on the shaft" on his 2000 Silverado 2500. He took it out of gear and... SURPRISE... he went sailing down the driveway with no brakes. Pedal right to the floor. Nothing. New power steering pump, and brakes worked fine.

I have a 2002 Silverado 3500 dually also with hydroboost. One day I jump in, put it in gear, and head down the driveway. Got to the end of the driveway, push the brakes, and NOTHING. Pedal to the floor. Not only that, the steering wheel was locked solid when I tried to jerk it to keep from sailing across the road into the neighbor's yard. Then all of a sudden the steering wheel freed up and the brakes came back. I took it to the mechanic. They couldn't find anything wrong. I flushed the system with new fluid and it hasn't happened again.

 

[MarkB_MI]

I flushed out the old power steering fluid, and the brakes seem to be much better now. I had no problems yesterday, even in stop-and-go traffic and 85 degree ambient temperature. The fluid I removed was dark and smelled bad. That said, if the booster acts up again I'm ordering a new one. But if I don't have any problems over the next week I'll flush the fluid a second time and call it good.

My theory is the PS fluid has been bad a long time, but the old brake booster was so loose it didn't care. But the seals in the reman unit are tight and can't tolerate any foaming in the fluid. Stay 'tooned!

Brakes Cut Light

 

[Geo-TH,In]

Thanks for the suggestion, Dick, but if I'm going to go through the aggravation of replacing the booster a second time, it will be with a new unit. I'd rather eat the two hundred bucks I paid for the reman rather than risk a second bad unit. Brakes are too critical to be messing around with suspect parts.

Mark,
My dad had a cabover IH truck with a flat bed we used to haul hay.
Sometimes you tapped the brakes and everything worked well.
Sometimes you would have both feet on the brake pedal and pushing as hard as you could to get stopped.
I suffer from BPSS. Brake Pedal Stress Syndrome.
Replace the booster if you wake up in the middle of the night with BPSS especially if you use the Chevy 2500 Duramax to pull your camper and you have your grandkids in the truck.

 

[MarkB_MI]

Mark,
My dad had a cabover IH truck with a flat bed we used to haul hay.
Sometimes you tapped the brakes and everything worked well.
Sometimes you would have both feet on the brake pedal and pushing as hard as you could to get stopped.
I suffer from BPSS. Brake Pedal Stress Syndrome.
Replace the booster if you wake up in the middle of the night with BPSS especially if you use the Chevy 2500 Duramax to pull your camper and you have your grandkids in the truck.

Replace the booster if you wake up in the middle of the night with BPSS especially if you use the Chevy 2500 Duramax to pull your camper and you have your grandkids in the truck.

George, you can rest assured I won't pull the camper until this issue is resolved. And the only passenger I've had in the truck since this started is my BIL, who routinely does more dangerous things than ride in a vehicle with bad brakes. He likes to hop out of my truck while it's still rolling, so if it looks like we're going to crash he can just bail out. He's had plenty of practice.

 

[MarkB_MI]

Well, it acted up again this morning. Just once, briefly, and I was only going about 5 mph. A new OEM brake booster is now on order. Amazon price is $467 plus tax, roughly double what the O'Reilly remanufactured booster cost me. Free shipping, and it should arrive by Friday.

 

[MarkB_MI]

Hopefully this will be my last post on this subject. I got the new booster installed Friday and so far it's working fine. I did take a lot of time trying to purge air out of the system by slowly turning the steering wheel back and forth while pumping the brakes.

I do think there was something wrong with the reman booster, even though it gave no problems AFTER I ordered the new booster. Flushing the PS fluid sure seemed to help, and I plan to flush it again soon.