Once again I come to you guys/gals for your wisdom. If I am going over 40 mph and I have to brake hard my truck pulls really hard to the right. I mean so hard it will take me off the road.
My truck is a 2004 f250 with 147,000 miles.
In the last six months I have replaced both hubs, rotors and brakes. I really drive like an old man so I don't know how long I have had this issue. Just someone pulled in front of me on the freeway and I had to brake hard and I found this out.
I have checked both front capilers and brake lines and those are fine. I have brand new tires on it. I really have no clue what is going on. I have pulled the brakes off three times and checked everything out and it looks good. If slowly push the brakes everything is great, it is only when I have to really slam on them.

Thank you for your help.
Jason

 

Pulls can happen from both the front or rear brakes.

You said you checked the brakes hoses. How?

 

Brakes hose are not worn or stretched out. I measured each one and they are the same size. I pulled the slider pins out and greased and cleaned them and I am still getting the pull.

 

Brake hoses can collapse internally and still look fine. You also can't see air in the system.

 

When I pump the brakes I can see the calipers extend so I am assuming the brake fluid is going into it

 

I had the same thing happen to me on my '06 at 95k. I checked all the calipers, hoses and etc. I also started to notice a vibration and found that the left rear caliper was sticking so I went ahead and replaced both along with rotors and pads. Problem solved. I took the offending caliper apart before turning it in for core and found some corrosion in the cylinder bore. So another thing I did was install Russell speed bleeders on all and then pumped new fluid through the system. Its amazing how little moisture in the system can causer internal corrosion and foul up the pistons in the calipers.

 

How can the back brakes make the front end turn hard? My brain isn't working. I feel like I have been going in circles on this stupid thing . I did just look at the back brakes but I haven't taken them off yet

 

When one grabs harder than the other it swerves to the same side. If it tracks straight down the road until you hit the brakes, then your alignment and steering part of the suspension is probably good. How old is your brake fluid?

 

I have had the trucks three years and never had to add any. I guess I could give that a try. Going down the road it does pull the the right just a little bit.

 

If it has moisture in it adding will not help. It will need a complete flush. Brake fluid is hygroscopic and can pull moisture out of the air.

 

The speed bleeders really make it easy and no need to have the wife help me bleed the brakes.

 

While a front pull develops a hard tug in the steering wheel, a rear pull has a second or so in developing the pull.

Air in a line causes a quick, minor tug on the wheel if front brake related, but then wheel stays straight as does the vehicle.

There are some instances with multiple piston calipers can have a frozen piston that causes a pull at high pressures, so it's worth a check when someone has a high pressure pull.

An internal tear in a brake line can occur at different pressures, it depends on the internal tear of the interior sheath. A slow flow, low to moderate pressure can leave the tear partially out of place while a fast flow, high pressure balloons the sheath out to act as a valve. Depending on the separation's location relationship to the tear, the balloon can act either as preventing flow to the caliper, or preventing release of pressure from the caliper. If preventing release, often a higher pressure application with a slow release of pressure allows the trapped fluid to bypass the flap.

The only ways of checking for a internal tear of a hose is by installing pressure gauge's on both ends of the hose and compare delta, or cut the hose apart. It's rare to be able to see an internal tear unless you have a borescope that will fit in the hose, but it is a third way.

 

On any vehicle (ford, chevy, chrysler) I owned that exhibited this pull tendency I always ended up with new hoses to fix the problem. After going through all the things the op did.
These days when doing the brakes I also buy new hoses and skip the mysteries. Fortunately most hoses are relatively inexpensive.

 

Hoses could be the problem and with the miles you have it would be a good idea just to replace them, be carefull not to let the master cyl run dry or you will have to have the brakes bleed by someone with a scanner that is capable of a "service brake" bleed to get the air out of the ABS solenoids. I suspect however that you have a sticking piston in the left front caliper or possibly the left rear either one can cause it to pull right under hard braking. Also when TooManyToys talks about brakes pay close attention He knows His stuff.