6.0 brake booster help needed

photographix · 05-22-2014, 12:42 AM

I think my brake booster vacuum pump is on the way out. I'd like to fix it myself if I can.

I have a 2008 Ford E350 with the 6.0 PSD, with a little over 47K miles.

Symptoms:
Driving for several minutes or longer, the brake pedal is fine, and can stop the van easily. Feels like I have normal brakes.

Shortly later after a full stop, as in driving in stop-and-go traffic, the brake pedal then gets really hard after the initial stop. I almost have to stand on the pedal to get the van to stop, even at low speed.

With the van at a full stop, but tranny in Drive and with my foot on the brake, I can feel it getting harder to push to keep the van still. It's like the boost is there, and then drops off. The power steering is easy to turn the wheel all the time, and I never get a brake warning light on the dash.

When I feel the pedal getting hard to push, I found that if I two-foot it on the brake and gas pedals, I can rev the engine a little to about 13-1400 RPM and the brake boost returns.

I noticed this behavior after my last trip, some of which was on badly washboarded dirt road. Could my vacuum pump be starting to bite the dust, or could I just have a loose vacuum hose or a leak? I don't hear any squeaking, rattling, or an air/vacuum leak, but I have diesel, so it's hard to hear anything out of the ordinary. Prior to my last trip, the brakes worked just fine.

I have a vacuum reservoir drum behind the master cylinder, so I don't believe I have HydroBoost.

If it is the vacuum pump, how do I get to it? I've been searching here, and on Diesel Forums, and FTE. The best description I have found is that I have to loosen the serpentine belt, remove the air filter assembly, and move the power steering reservoir out of the way.

I took the doghouse off, but everything is so tight, I can't see much. I also crawled under the van and identified the A/C compressor and power steering pump (I think), but can't see what looks like the vacuum pump.

Any help or insights are appreciated! If I haven't been clear, about the problem, please ask all the questions you want. Thanks!

Tapatio · 05-22-2014, 08:34 AM

Sounds like a pump failure based on your symptoms. Mine went out suddenly at 111k miles, on the freeway, had to go all Hulk like on the brake pedal, almost slammed into a car. You can further diagnose by testing the AC vents, they are also vacuum controlled.

If memory serves correctly it's on the drivers side, lower portion of the engine and driven by the serpentine belt. It was more work than I wanted to deal with. Mechanic who I trust intimately charged $450 ($150 parts + $300 labor).

oldbonesclimber · 05-22-2014, 10:28 AM

Changing the Pump is easy. Only 15 min. Getting to the front of the engine takes 4hrs. Radiator and Intercooler out, Fan off ( takes a special tool ), fan shroud off. Then you can change the vacuum pump. Not really difficult but it takes TIME. I'm even going to start carrying a spare. you also have to have the tool to remove the pulley and reinstall on the new pump. I think when they did it on our work truck it was $850. I changed it the second time.

Paul

photographix · 05-23-2014, 02:03 PM

I took the air filter housing off to see what I could see. Man, it's tight in there! Even had to unbolt the coolant reservoir to get the AF cover out!

Looks like I would have to remove the turbo intercooler pipe. Not sure if I would have to take out the fan shroud. Then I would have to work around what looks like a brake line manifold.

Is it easier to go in from the bottom? If so, looks like the PS pump would have to be removed. Neither way is going to be fun.

For those of you that have done it yourself, are there any tips or tricks? As for swapping the pulley, I have read that a special tool is needed, but no mention or pictures of this magical mystery tool. Would a standard pulley remover work?

oldbonesclimber · 05-23-2014, 05:09 PM

You can probably borrrow the Pulley puller from Autozone. I don't know if they have the fan clutch wrench.
You also have to detension the serpentine belt. After trying to work on that motor without major disassembly I have just Accepted that it is a lot less frustrating to forfeit the 4 hrs.

Paul