I have noticed thru the cold months after I start my 2001 F250 7.3L 4X4 after it sits about a minute "warming up" that it goes into a high idle. The high idle will stop once I press the brakes. Is this normal?

I think this is a unrelated issue, but just started over the weekend. Was riding home, and pressed my brakes and the pedal moved almost to the floor. Not normal conditions for my truck. Usually the pedal is very stiff. I have noticed that my power steering pump has had a hum for months. I changed the fluid (ATF Mercon) within the last 6k miles and that calmed it down a bit. After the pedal went to the floor, the hum seemed to quieten down even more. The power steering still works and the reservoir has adequate fluid and so does the brake fluid reservoir. I haven't noticed any leaks around the truck. I'm going to bleed the brake in an hour or so, but has anyone had this happen before? The brakes pedal seems stiff when I press it after the high idle, but then it gets soft after a pump or two.

 

Yes, the idle coming up is completely normal.

Taken from another post by Shake-N-Bake...

Fast idle requirements....

Vehicle in Park (or parking brake set if manual trans)
EOT below 158 F
IAT below 32 F for 1000 RPM or 14 F for 1100 RPM
Brake pedal must not be depressed
Accelerator pedal must not be depressed

 

Thats good to know. Was wondering what the scenario was for that. Any idea about the second part of the post?

 

Based on what you wrote, I would think you have air in the lines somewhere, but I am not an expert by any means on these trucks. I flushed the system on my truck when I first bought it and that changed the way the steering felt and sounded.

I followed this video for the most part.


I am inclined to think that your brake lines and fluid are OK and your problem is related to the hydro boost and power steering area, but hard to tell for sure.

 

Bleeding the brakes from the caliper didnt help. I can try the PS pump tomorrow.

 

cpye2 your issue sounds somewhat similar to mine. Pedal feels normal right at the top but then fades to floor before stopping? I have flushed PS, bled brakes SEVERAL times and now replaced the master cylinder over the weekend and no improvements.
I also have a very slow returning brake pedal after depressed. Not sure of related or completely coincidental. I'm stumped. Let is know if you make any progress and if your symptoms match mine.

 

Have you checked your brake lines going to the wheels? Sometimes these soft lines can break down internally which causes them to collapse on themselves (think about punching a drinking straw) causing all kinds of issues.

 

I bled the hydroboost today. After working on it for a while, this what I am noticing. Brake pedal is stiffer but still not as stiff is before, and power steering is still working. However, if I press the brakes and then try to turn the wheel, the wheel is very difficult to turn. Can only get about 90 degrees at best. The noise levels are way down, but there is still noise. It will bleed when I press the pedal or turn the wheels. One time when I went to put it in gear while holding down the pedal, the pedal gave. Any ideas?

 

I bled the hydroboost again so more today, this time with it on the jack. End result was the same. If I hold the brake pedal down, it has good tension, but the steering wheel is locked up. As soon as I let off the brakes, steering wheel frees up. Can anyone give me guidance? Thanks

 

After rebuilding my motor I decided to put a new pump in and new lines, mine is doing the same damn thing and has so sense October and I'm about to just take the damn truck in! . I have bleed it countless times and swapped back over to the original pump.

 

Im almost ready to take mine in also. I was about to buy a new pump also. Glad I havent yet. Sucks not being able to drive it, but I will need it in a few weeks so I got to do something.

 

I don't know, I just can not figure it out and have done everything that is suppose to be done. I already put 4K miles on the truck sense the rebuild. Pretty scary when I get into the city with stop and go traffic. I leave a lot of room in front like I do in the semi until another 4 wheeler cuts in front.

 

Sorry to hear that. I just put about $3k into completely rebuilding my front end. Drove about 3 months and now I'm dealing with this. I have another vehicle so I don't have to drive the truck daily, but I will need it for 2 trips in April so I have to get squared away by then.

I have a fellow on another F250 forum recommending a PS Pump replacement, and perhaps that is the problem. I'm doing some searching now and it seems that this problem can be common on other trucks that use the PS/Hydroboost setup.

Reading here: http://www.plowsite.com/showthread.php?t=68647 perhaps our problem is may be the hydroboost. Since you have already replaced the PS Pump with no luck, I may try the hydroboost first. I found one by AC Delco, PN 14PB4347 or Cardone, PN 52-7374. Both are re-manufactured. The AC Delco is $120 on eBay with no core charge. Thats cheaper than a Motorcraft reman PS Pump, so I may start there and replace it.

 

What power steering pump are you using, and was it remanufactured? I have been doing some reading today. Not just about our trucks, but all hydroboost / PS systems. I have a long list of things to check / trouble shoot, but before I replace parts I think the hoses should be taken off and inspected. Check the seals and connections, and also check if any teflon lining is coming out the end of the hoses. This can cause blockages. With the hoses, off blow compressed air thru them and see if any debris comes out. Also check the connections for any blockages around the hoses.

Next, there is a pretty good write up here for checking what could be wrong the system:
| Repair Guides | Brake System | Hydro-boost (hydraulic Boost) | AutoZone.com

If a a PS pump needs to be replaced, spend the extra money use a NEW OEM pump. The reman and aftermarket pumps only lead to premature failing, not enough pressure out the box, or dead out the box.

I read also that there could be debris / blockages in the steering box, so clean and blow that out too if you can.

I know a lot of people recommend using ATF fluid. Some people have said use Synthetic PS fluid. Mine worked fine for a long time with Merc ATF, but its not working now. So I don't know what the reasons are for recommending either.

I am going to do some of the tests and see about diagnosing a little further when I get home.

 

I did some further testing. Before I start the truck, the pedal goes down all the way faily easy, but does return also. No matter how many times I press it, this always happens.


I found a trouble shooting guide here: | Repair Guides | Brake System | Hydro-boost (hydraulic Boost) | AutoZone.com


So I began the Hydro boost test:
Vehicle in neutral and engine off, I pressed the pedal all the way down 5 times
While holding down the 5th press, I started the engine
The pedal did drop but then kicked back up and was firm.
That should confirm that the hydro boost is good


Took the truck around the block since pedal was firm, but everytime I went to slow down, usually while making a turn, the pedal was going to the floor. Power steering was working great though.


After parking, using the guide mentioned above, next was the accumulator test
While running the truck at idle, I turned the wheel to the stop and help it there for a few seconds
Then returned it to center and turned off the engine
When I pressed the brake, the pedal went all the way to the floor
When I started the engine and repeated to turn the wheel to the stop, I never heard a hissing sound while I was in the cab with the hood up and door open, but maybe with 2 people I could.


After stopping the engine, I think I should have gotten atleast one power assisted brake according to the guide, but I got nothing.


I am thinking the accumulator may not be filling or its leaking out the air(?) immediately.


After running the last test I sat in the cab and turned the wheels a few times with the truck running. For the most part the steering felt normal, but sometimes it would be a little more difficult. After turning the wheels and pressing the brakes softly but quickly I would fill a slight dip and then kick back from the hydroboost.


Any one got any recommendations?