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Discussion Starter · #1 ·
I have read hours worth of threads on this with no solution in sight. When I hit my brake pedal in my '01 EX bydroboost it is firm at the top then immediately fades almost to the floor before stopping. I have flushed the PS fluid. I have flushed, pressure bled, manually bled, and even bled the abs with a scanner. No improvement. 3 days ago I replaced the master cylinder, which I bench bled first, then manually bled the system again. No improvement. My pedal returns extremely slowly after depressing. While I had the master cylinder off I lubed the travel area of the piston in the hydroboost and at the firewall in the cab. The pedal return was normal after I lubed it, but then began returning very slowly again after it was all back together. I can't figure out the slow return, but on the second stroke of the pedal I have great brakes. But the return is so slow that a second stroke is nearly impossible to do when attempting to stop for a light or traffic. Please help!!
 

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Start by FULLY identifying the vehicle you want help with. Each component & option. Click this & read the caption:



Then focus on the BRAKES; not the hydroboost. If the calipers, pads, e-brake cables, & drum mechanisms aren't moving freely, the pedal will never feel or work right. Are yours all clean & lubricated properly?

. .

Once all of that is RIGHT, the pedal should have a relatively-normal feel even when the HB is disabled. But this caption & the PREVious several describe the HB system:

 

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Well, he has an '01 with hydroboost that's name starts with EX so the only HB EX vehicle in '01 was the 2001 7.3L Excursion. No drum brakes in the service system, only the parking brake.

Xsv, it's most likely an issue with the hydroboost. The connection between the HB and the master cylinder is by push rod and I don't believe the '01 had a lock ring in the MC piston that locked onto the pushrod. If the master just easily came off the HB once it was unbolted, then it's not locked. If that's the case if something in the master cylinder or brake hydraulics restrained the master cylinder from returning, the HB would just pull back normally as would the brake pedal, leaving a gap between the pushrod and master cylinder piston until the master cylinder piston fully returned. That is not the way your describing the situation.
 

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Hydrobooster

In couple months you will have oil coming into cab.
I big on putting fresh components like that at that 10yr.-150k period anyway. It's going to go, replace on your time and terms before a breakdown is my philosophy.
 

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Discussion Starter · #5 ·
Thanks for the response Steve83, yes I tried unplugging and plugging it back in lol.
Seriously since I described it as an '01 EX with hydroboost and I'm on dieselstop I thought that was enough info to know we're dealing with a diesel ford with hydroboost, most likely an '01.
I have ensured all slides are free, no calipers are hanging, no leaks, no damaged hoses. I have gone through all of the preliminary checks, flushes and had no improvement. New master cylinder, a new power steering pump, and it looks like a newer or reaman hydroboost from the previous owner.
FMTRVT I tend to agree with you, but I am not terribly interested in throwing parts at it as a guess. I was hoping for someone who had seen this before for a more definitive diagnosis.
 

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Steve83,

Thanks for the diagram of the HB.
 

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Hydrobooster

In couple months you will have oil coming into cab.
I big on putting fresh components like that at that 10yr.-150k period anyway. It's going to go, replace on your time and terms before a breakdown is my philosophy.
Nick,

I have oil dripping into the cab at the Input Seal, where the rod going to the brake pedal exits the firewall into the cab.

And the only way to fix this is to get a new HB ?

Where do you recommend getting a replacement?

Thanks
 

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I'll pretend I'm Nick, well for one post only.

There are kits out there but the success rate on the rebuild doesn't seem to be good even with good mechanics I've known. The Motorcraft rebuilt unit one is the only one I would trust for a part as safety critical as this. But they sure have gone up in price.

I'll now go back to being Jack.
 

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Xsv,

Does it show on the rebuilt HB where it came from?
 

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Jack,
I heard there was a guy some years back who tried channeling Nick but he exploded on re-entry.
You're a lucky man.

Thanks for the advice. I had tried finding an HB on Tousley website but it indicated in bold letters that it can not be shipped and other Ford Parts counters were about $500.

However, RockAuto has the same NEW Motorcraft "Power Brake Booster" P/N: 5C7Z2005-B (aka: BRB-33) for $311 + Shipping.

Not sure about the EX being the same.
 

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Ahhhhhh it was killin Jack to agree with the ol Nickster.lol it's alright buddy know it doesn't happen a lot as brakes are your world, I usually don't dip into brake threads and
by what I have read what you written, you are good at that.

Being a hydro guy for same length of time as diesel, I can tell you certain components mainly safety related components should not be rebuilt unless you know what your doing, having experience and the proper tools. Ok so your an ace. Without him the proper seal protectors and driver's, you will most likely being it again for free with an upset customer you migh just be buying new carpet for the guy.
Have I been in one? Nope not expensive, if not expensive it does not make financial sense for me to go in.
If you see hydraulic leaks after rebuilds 99percent is inexperience and or no application specific seal protectors and drivers.
If you see repeated hard component hydraulic failures after component replacement 99 percent is a contaminated system that was never properly cleaned out.

BTW thanks Jack, you're a good egg.
 

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I installed a FoMoCo hydroboost unit in a customers truck that he bought from Rock auto. I wouldn't hesitate buying from there.
 

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I have no problem agreeing with you Nick. But who's agreeing with who? >:)

I can't figure out why they won't ship. I understand seat belt or airbag parts that have explosive charges, or radiators that get banged up in shipping, but the accumulators should not be charged up in a HB. Back around 2007 we bought a F series HB for $125. No inflation there.

RockAuto is fine for buying Motorcraft parts. I had a rebuilt PS pump that had to go back and they not only took the item back but because it was defective they paid shipping both ways. I couldn't ask for more. FICMRepair (Ed) sells Motorcraft parts and he might ship one. His prices are about the same as RockAuto, but RAs warranty I can't argue with.
 

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I have no problem agreeing with you Nick. But who's agreeing with who? >:)

I can't figure out why they won't ship. I understand seat belt or airbag parts that have explosive charges, or radiators that get banged up in shipping, but the accumulators should not be charged up in a HB. Back around 2007 we bought a F series HB for $125. No inflation there.

RockAuto is fine for buying Motorcraft parts. I had a rebuilt PS pump that had to go back and they not only took the item back but because it was defective they paid shipping both ways. I couldn't ask for more. FICMRepair (Ed) sells Motorcraft parts and he might ship one. His prices are about the same as RockAuto, but RAs warranty I can't argue with.
I will call Tousley...maybe their website is in error.

But Rock Auto price is lowest I have found yet.

Thanks for the help.
 

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Discussion Starter · #15 · (Edited)
Ok Jack, if I can call you Jack lol, here goes everything.
Bought the 2001 ford excursion 7.3l 2 months ago. It needed a lot of work. I knew that going in. The pedal issue, fade and slow return, has been there since (my) day 1.
Installed new front axle.
New pads and rotors. Obviously I made sure everything moved freely when assembling the brakes.
Right rear caliper replaced. Right front appears to be new also.
New right front hose.
Bled manually. Bled with pressure bleeder. Bled ABS with scanner. Bled manually again. No improvement.
The RWABS unit appears to have been removed prior to my ownership. The ABS pump obviously works as I bled it with a scanner and heard/felt it run. The ABS system does not work and I am not concerned with that in the least.
I then replaced the master cylinder. When I got the MC off it appeared to me to be a new(er) MC. I then flushed the power steering with fresh MercV. In my inspection of the PS I found that the PS pump is also a new(er) reman pump. I'm now curious enough to inspect the hydro boost more closely. It is shiny painted black and far too clean to be the original unit. So I now believe that all of these parts have already been replaced in an attempt to cure the illness that I am now trying to eradicate.
While initially bleeding the sytem after new MC (I sprayed a dry lubricant in the hydro boost chamber inside and outside while MC was off) was installed the pedal return was perfect, quick. Finished, pulled the truck out of my shop and bam, slooowww return again.
I am a service manager at a private shop in Pittsburgh. I have been a tech for 28 years. I know what this feels like. Air in the system. the second stroke (if you get one) is firm, good feeling brakes with good stopping. You can not get a second stroke most of the time because you can't wait the (literally) 3 count for the pedal to return before having to stop for traffic or a light. When sitting still with normal pressure on the brakes the power assist steering is nearly non existent. Light on the brake and the power steering is fine.
This is my first go round, surprisingly, with any hydro boost system. Mine or anyone else's.
I am considering bypassing the ABS unit all together and running lines straight to the four corners to eliminate all complications. I have considered wether or not the sensor at the front of the MC could be internally leaking on the return stroke and allowing a constant supply of air into the MC.
I think that covers absolutely everything.
AND I have considered removing the hydro boost installing a booster vacuum pump and activation solenoid off of a 2007 Saab 9-3 2.8 turbo and the Vacuum booster from a gas Excursion. Drastic? Maybe. Desperate? Yes lol
 

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Before I think about this more, you've mentioned both RABS (had been removed) and described 4WABS using its bleed function. Your going to have to explain this some more 'cause they are totally different and never together.

And thanks for explaining your mechanical ability as that will help.
 

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Discussion Starter · #17 ·
Well, I am not familiar with the abs system on the excursion so through all of my research I found a lot of talk about a RWABS unit along the frame under the cab causing spongy brake problems. So I looked for this. There is not one on my truck so I assumed it had been eliminated by someone else.
If there never was one that's fine also. The ABS unit is intact beneath the airbox in the engine compartment.
 

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Discussion Starter · #18 ·
In my defense, until January '16 when I became the service manager I spent the last 12-13 years specializing in European cars. They don't make anything resembling a truck let alone an excursion lol. And certainly no hydro boost setups.
 

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There's only a RABS unit or 4WABS unit on your rig. Either one would live below the driver's side headlight bucket. Nothing on the frame rail like you've described.
I doubt there's a possibility that air is getting back into the MC thru the pressure switch on the nose. If it were leaking, it would be leaking worse under pressure when you mash the pedal.
Other than that, I can't help you much. Jack is the expert when it come to brakes.
 

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I was just happy to know you wrenched to know how to discuss this.

Yeah, there would not be two systems. No Excursion should have a RABS so I was just trying to figure out how much someone could have played with this truck. And from everything replaced it sounds like this truck has history. Given your background I would walk into a Ford dealer and get a printout of this vehicles history from the VIN to see what dealerships have done with this vehicle.

I wrongly thought you didn't still have a dropping pedal. You homed in on the common cause of a dropping pedal, but a failure with the ABS can also cause this. I'll post the service manual check. Due to the frustration level I can understand the thought of bypassing the ABS since it's not operational. Any codes about the failure or know why it doesn't work?

Where did you get the M/C from?
 
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