Hydroboost problems

[Matahoe]

Hey guys I think my hydroboost isn't working correctly. I was on the road going about 45mph and put the truck in neutral. I then stepped on the the brake a few times to deplete the reserve canister for the hydroboost. As expected the brake pedal became hard and the pedal force required to stop the truck was hard.

I then started the truck while still in neutral and put it in drive. I drove down the road at 45 for a half mile or so. Then came up to a light and needed to stop but the hydroboost brakes wouldn't work at all. It was as if the reserve was depleted but this time the engine was running.

I was unable to find anything similar to this scenario while reading online troubleshooting steps. I am left scratching my head on this one. If anyone can help or point me in the right direction that would be great.

 

[clandr1]

Free bump, I have no experience so I'm unable to help.

 

[swathdiver]

So did the pedal come back up?

 

[Matahoe]

So did the pedal come back up?

Not exactly sure. I will test it again.

I might have confused having booster reserve with the engine off and on. I did come to a rolling stop with the engine off I know that...but I will make sure and list the scenario step by step.

 

[Chubbs]

If you are attempting any kind of DIY repair or replacement, even diagnosis of hydraulic assist braking, aka hydroboost, at least buy a workshop manual. I looked up braking diag procedures and there is just a vast amount of literature there. I pulled up this Chiltons online library and highly suggest that you invest just so you have a starting point.

I can tell you right now you are going about this all wrong if you are cutting the ignition while driving down the road and attempting to stop the vehicle. Prob get somebody killed if you continue. Regardless, a manual instructs with the steps & techniques relevant to diagnosing specific symptoms so that you aren't doing random shit as documented in the original post.

 

[Matahoe]

I've already looked in the manuals and also online in other forums. The reason I posted the question is because there is no directly comparable scenario in the troubleshooting literature or elsewhere that I have found. I'm not going to kill anyone being in neutral with the ignition off. Its all pretty controlled. Been doing vehicle mechanics for over 25 years. I am still able to steer and brake....it's just harder. Also, there is no one else on the road at the time as well of the tests. The only person with a remote chance of being killed would be myself but Im 99.99% sure that isn't going to happen at 45 mph less.

 

[Rocket Man]

There's no comparable scenario for a reason. Who tries to test a power steering and brake system with no power? That would fall under an emergency scenario where your engine dies and you need to get stopped without crashing which is possible but requires a lot of effort. I don't understand what you're trying to do.

 

[swathdiver]

I haven't driven a hydroboost braked car since the 1990s with my '80s Olds and Buicks. Now if memory serves, if the car were to stall the pedal and steering would get hard but could still stop with great effort. Once the engine was restarted, I'm trying my best to recall here, I think it took a few pumps of the pedal to get firm again.

Get yourself an AllDataDIY subscription for your truck and get access to the shop manual and trouble shooting guides.

 

[ezstriper]

there is no reserve that I know of, hydro boost uses P/S pressure so as long as the engine is running and belt is on system charges as long as parts working

 

[Rocket Man]

there is no reserve that I know of, hydro boost uses P/S pressure so as long as the engine is running and belt is on system charges as long as parts working

That's what I would think too. The power steering pump is used for hydraulic pressure assisted braking as oppoeed to vacuum assisted and I know from experience that the power steering quits when the engine dies so I would expect the power brakes quit also. The systems are tied together.

 

[M1Gunner]

The accumulator is there to hold reserve pressure like a vacuum brake booster. It’s just holds p.s. fluid under pressure in case you have a pump failure or belt break. With the engine off you should still have enough power assist to stop the vehicle.

 

[Matahoe]

That's the whole problem. It acts like it has reserve and sometimes it doesn't. Usually only when performing tests. According to the service manual my hydroboost could either be good or bad depending on how you interpret the instructions.

I turned off the engine, pumped the brake pedal 4 times (per service manual) and it depleted (pedal got hard) on the 5th pump. This is normal.

But here is the real kicker. The service manual then says to start the engine again and idle (for an unspecified amount of time). Then to turn off the engine and retest reserve. It says I should be able to get 1 reserve application right away. But I don't. The pedal is still hard from the previous test. However I might have not let the engine idle enough because the damn service manual doesn't specify!! You guys see my problem?

 

[HiHoeSilver]

That's the whole problem. Sometimes it has reserve and sometimes it doesn't. According to the service manual (which is vague on a number of isses) my hydroboost could either be good or bad depending on how you interpret the instructions.

I would definitely concur that it is either good or bad.

 

[Rocket Man]

I would definitely concur that it is either good or bad.

Agreed 10-100%.

 

[Matahoe]

Just found another hydroboost test proceedure. After doing the first test it says to turn the wheel to one of the stops for 5 seconds while idling. Then turn off engine, depress brake pedal and see if there is any power assist.

If this works I am going to call it good.

 

[mattbta]

Agreed 10-100%.

That's better than 10-200% right?

 

[Matahoe]

Figured it out. I'll leave you guys to imagine my outcome pending removal of the belittling remarks by the admin. However funny you thought they may have been ...they added nothing to this rather important discussion.

 

[Matahoe]

I would definitely concur that it is either good or bad.

Nate/Mark. I ammended my post while you were replying. Please read it again and you will think differently.

 

[Rocket Man]

Nate/Mark. I ammended my post while you were replying. Please read it again and you will think differently.

I was just lightening things up since it got a bit heavy earlier. I don't have hydroboost so I couldn't offer any help. I've just never heard of anyone driving at 45 and purposely turning the engine off to test the brakes so I was following in order to see why you would do that. Doing it while stopped makes sense. Sorry for being a smart ass, humor isn't my strong point.

 

[swathdiver]

Sorry for being a smart ass, humor isn't my strong point.