My 01' F350 with a 7.3 has had a whiny power steering pump for about a month now. Didn't think too much of it til yesterday when I pulled up to a red light and the brake pedal hit the floor. I had known the power steering pump boosted the brakes in these newer trucks (my previous Fords were an 85 and a 97) so I replaced the P.S. pump this morning expecting it to solve my problems. Well, the whine is gone, but still a very mushy pedal that grabs at the very bottom of its travel. The truck has 192k on it. Any thoughts before I go poking around? I need to send this truck out on Monday with a trailer behind it. Thanks in advance guys!

 

did you properly bleed the system. if you look at the fluid while running it should not be frothy at all...

 

No, I didn't. How do I do that? When I had the engine out of my 02 dump with a 7.3, I just hooked it up and after 3-4 miles everything was back to normal. The pump isn't whining anymore, so I thought I was all set with it.

 

lift the fron off the ground. with the engin off, crank the steering lock to lock. then check reservoir. if low fill to proper level. turn lock to lock again and repeat. do this three to four times befor starting engine.

start engine turn lock to lock and pump brakes, shut off engine, check reservoir, fill if neccessary, repeat this two to three time, at the finish fill to proper level and you should be good.

if still mushy i would say to check for brake fluid loss

 

Ok, Ill try that. I did turn it lock to lock a bunch of times while running, but not with the tires off the ground. I filled the res. 2 x and it stopped drinking fluid. Also, no brake fluid loss. I will try your suggestion and let you know results. Thanks.

 

the problem with that is that the fluid gets frothy, airaited if you will, and it keeps pumping air filled fluid around the system, air in hydrolics translates to mushy... like i said, hydro boosts dont fail mushy, they either leak or get hard as a rock, so if bleeding does not fix i would start looking for air in the brakes... btw did you open the brake system? if so then i bet you need to bleed them better too

 

No, I haven't open up the brake system, and the fluid is good, and no leaks. I actually checked the brake fluid level a couple weeks ago and topped it off a little. That was before this, and the level is still at the same level. I will lift it up and try that though. Sounds like that could be the fix.

 

then its got to be air in it from somewhere.... give what i said a try and get back to me,
Good luck

 

Sounds like a cup in the master cylinder is compromised, especially if the travel is long with the motor shut off and hydroboost accumulator exhausted.

 

ya now that i think of it... you were just sitting at a red light when it just went mushy... i think its got to be in the master cylinder itself

 

Agreed about the master cylinder. The good news is that it's not an expensive part. For an OEM part check www.tousleyfordparts.com, they typically have the cheapest prices around for Motorcraft parts.

For aftermarket I'd check out www.rockauto.com. They have them as cheap as $42 for a remanufactured master cylinder.

Good luck!

 

How dirty is the brake fluid? I would start with a good flushing and brake fluid change before throwing parts at it.

 

Ok, tried the bleed on the P.S. pump, makes no difference. Also, pedal goes to the floor with the truck off as well. Thinking master cylinder. Catches just fine at the last 1-2" of pedal travel. On the older Fords, the master cylinders used to have two compartments in them, one for the front brakes, one for the rear. I know the res. on this truck only has one compartment, but I'm thinking that I'm probably only grabbing on the rear brakes. Feels like my trailer brakes do when they're cranked up and I'm only pushing the pedal enough to kick the brake lights on. Guess I'll grab a new M.C. at Advanced Auto in the morning since they have it is stock. It comes without a reservoir though. How do I take my old one off to put on the new one?

 

good to know you got the P/S sorted out thow... yea it sounds like an o-ring went away.

For any maint that i have never done, i turn to youtube. people video everything

try this one, if not keep searching Superduty 1999.5-2004+ 4x4 front brake job - YouTube

 

Make sure an bench bleed the new master good before putting it in the truck.