Non-TJ Brake Booster Question

[gasiorv]

This is on my Ford E350 van but brake systems are brake systems and general knowledge about brakes should apply so I figured I would ask here after not being able to find anything on the Econoline pages.
I have bled the piss out of the brakes on my van. With engine off and no boost, the pedal is at the top and hard (doesn't budge with 215lbs standing on it). When I fire it up and boost comes into play and I depress the pedal it travels about 1/2 way with a loud air whooshing sound (atmosphere air entering booster, not vacuum leak) and then gets tight. It doesn't fade at all past 1/2 way it is tight and you can't pump it up. it is not like there is air in system, the brakes are there and feel good once you make up that travel. I bled and bled and even bled the abs module with scanner multiple times.

With the tight pedal with engine off and with the pedal not fading once it gets tight at the 1/2 way point, and the fact that it doesn't pump up when at the 1/2 way point it does not seem like an issue with air in system or with swelling lines, etc... it seems like an actuator rod length and brake pedal travel before rod hits master cylinder issue; however, when engine is off the pedal is hard at the very top so I don't think I need to adjust engagement length of rod.

Is there is anything in the booster that could possibly add travel? It is a solid rod between pedal and master correct? Or is there two rods (one on atmospheric side and one on vacuum side) and if so what is in between them? Could that fail when vacuum is applied and allow travel?

Hopefully the above makes sense. I just bought this van so not sure how the pedal felt before, I just know I don't like how it feels with it going approx 1/2 way down before engaging and I have made sure caliper slides were free, rubber hoses look good, installed brake pads, and bled, and bled, and bled. It just doesn't feel like air in the system. So I am considering booster, but the booster is actually working (minus the travel concern the booster is adding boost)

Any input or help is appreciated and I have thick skin so feel free to rip on me if I am missing something obvious. I just want to get this brake pedal feeling right.

 

[Apparition]

Not sure if @mrblaine ventures into the off topic much but he’s the one for brake knowledge

 

[mrblaine]

This is on my Ford E350 van but brake systems are brake systems and general knowledge about brakes should apply so I figured I would ask here after not being able to find anything on the Econoline pages.
I have bled the piss out of the brakes on my van. With engine off and no boost, the pedal is at the top and hard (doesn't budge with 215lbs standing on it). When I fire it up and boost comes into play and I depress the pedal it travels about 1/2 way with a loud air whooshing sound (atmosphere air entering booster, not vacuum leak) and then gets tight. It doesn't fade at all past 1/2 way it is tight and you can't pump it up. it is not like there is air in system, the brakes are there and feel good once you make up that travel. I bled and bled and even bled the abs module with scanner multiple times.

With the tight pedal with engine off and with the pedal not fading once it gets tight at the 1/2 way point, and the fact that it doesn't pump up when at the 1/2 way point it does not seem like an issue with air in system or with swelling lines, etc... it seems like an actuator rod length and brake pedal travel before rod hits master cylinder issue; however, when engine is off the pedal is hard at the very top so I don't think I need to adjust engagement length of rod.

Is there is anything in the booster that could possibly add travel? It is a solid rod between pedal and master correct? Or is there two rods (one on atmospheric side and one on vacuum side) and if so what is in between them? Could that fail when vacuum is applied and allow travel?

Hopefully the above makes sense. I just bought this van so not sure how the pedal felt before, I just know I don't like how it feels with it going approx 1/2 way down before engaging and I have made sure caliper slides were free, rubber hoses look good, installed brake pads, and bled, and bled, and bled. It just doesn't feel like air in the system. So I am considering booster, but the booster is actually working (minus the travel concern the booster is adding boost)

Any input or help is appreciated and I have thick skin so feel free to rip on me if I am missing something obvious. I just want to get this brake pedal feeling right.

What were the circumstances surrounding the purchase? Did you know it had a brake problem? If so, did they relate what they had done to solve it?

You say the brakes are there and good when you make up the travel but then you say you can't pump them up. Which is it?

Yes, there is a solid connection between the pedal rod and master push rod. Too many folks would crash if there wasn't.

 

[gasiorv]

Yes, I knew it had a brake problem when I bought it. The fact that the van is 20 years old is a problem that is relatively easy to deal with, the big problem with this purchase is that the previous owner did a lot of modifications himself and now I am dealing with all his stuff as well. See below picture for example of his type of modification.

Back to the brakes - Thanks for the input. I was able to do some more troubleshooting this afternoon and I have it narrowed down to the front calipers. If I isolate the fronts by putting vice grips on the rubber hoses I get significant improvement. The brake pedal is solid if I crimp off both front calipers at the same time. I thought it was just the rubber hoses, but if I crimp off the hose closest to fitting at the frame (thus taking out the hose and caliper) and if I crimp it off close to the caliper (thus leaving the rubber hose in the system and taking out the caliper) I get the same result, so I am thinking it must be the calipers, but I am going to replace the rubber hoses at the same time since they are 20 years old. Calipers aren't leaking, and they have been bled to death with no air present (and yes the bleeders are on the upper side) so not sure where the fluid is bypassing but if I take them out of the system, everything is good.

 

[mrblaine]

Yes, I knew it had a brake problem when I bought it. The fact that the van is 20 years old is a problem that is relatively easy to deal with, the big problem with this purchase is that the previous owner did a lot of modifications himself and now I am dealing with all his stuff as well. See below picture for example of his type of modification.
View attachment 627814

Back to the brakes - Thanks for the input. I was able to do some more troubleshooting this afternoon and I have it narrowed down to the front calipers. If I isolate the fronts by putting vice grips on the rubber hoses I get significant improvement. The brake pedal is solid if I crimp off both front calipers at the same time. I thought it was just the rubber hoses, but if I crimp off the hose closest to fitting at the frame (thus taking out the hose and caliper) and if I crimp it off close to the caliper (thus leaving the rubber hose in the system and taking out the caliper) I get the same result, so I am thinking it must be the calipers, but I am going to replace the rubber hoses at the same time since they are 20 years old. Calipers aren't leaking, and they have been bled to death with no air present (and yes the bleeders are on the upper side) so not sure where the fluid is bypassing but if I take them out of the system, everything is good.

If you have it isolated to the calipers, then the most common thing that creates the symptoms you describe above is over retraction of the caliper pistons. That should be easy to see and then try to figure out why it is happening. Over retraction causes the dead spot in the pedal at the top of pedal travel and then when the pistons make contact, the pedal firms back up normally. If this is what is happening, something bad is causing it because you can't make it happen without boosted pressure. Have someone get on the brake pedal with the engine running while you watch the calipers.

 

[gasiorv]

Thanks for the info. Would whatever bad is happening be within the calipers themselves? If so, I am just going to replace them. I had the calipers off earlier today and the slides were free, pad wear wasn't even on both sides (more wear on piston side), but other than the fact that they had surface rust, nothing seemed out of the ordinary. Since I am planning on eventually taking this van on some long distance trips, I have no issue with replacing old 20 year old parts with new parts if it will solve my problem.

 

[mrblaine]

Thanks for the info. Would whatever bad is happening be within the calipers themselves? If so, I am just going to replace them. I had the calipers off earlier today and the slides were free, pad wear wasn't even on both sides (more wear on piston side), but other than the fact that they had surface rust, nothing seemed out of the ordinary. Since I am planning on eventually taking this van on some long distance trips, I have no issue with replacing old 20 year old parts with new parts if it will solve my problem.

That is why you have to watch it while the pedal is applied and released. If you are accurate, something is pushing the piston in but you should be able to pump the piston back out and mash the pads onto the rotor with the engine off. You say that can't be done which is odd but the best thing that fits is the piston over retracting. You need to watch it. Normal is a sense of the caliper expanding slightly with no movement of the body. Anything other than that needs to be investigated.

 

[gasiorv]

I had my son push the brakes with boost and I didn't see anything out of the ordinary with the front calipers. Everything seemed to move correctly and I didn't see anything abnormal. I went ahead and replaced the calipers and the rubber hoses and bled the system (using partner with open bleeder, push brake to floor, close bleeder, release pedal.........) and I even bled the ABS with scanner and I get the same exact issue. With boost the pedal travels about 3-3.5" before it gets tight. When it gets tight it is tight, it does not continue to floor. The pedal is not "spongy" once it gets tight, it is just the pedal travel before getting tight is excessive. If I crimp off the front calipers, the pedal does go high and tight without the excessive travel. It is like there is a void in the front calipers like Blaine indicated earlier, but I don't see anything moving out of ordinary which requires the pistons to make up the space, the system is bled, the fluid is new, the rubber hoses are new. I measured the rotor thickness and couldn't find min thickness stamped anywhere on the rotors themselves, but found the min thickness via an internet search and rotors are good. Wheel bearings seem to be adjusted good and thus no excessive movement, etc....

With Front calipers isolated the pedal is good so that should take everything out of the equation except for the calipers (and everything related to those calipers), correct?

 

[gasiorv]

Well I had a little time this afternoon to do some troubleshooting and I measured the brake booster push rod and it was a little shallow for the master cylinder (it was a real bear to measure since the push rod is not easily accessible on this booster). I made the adjustment and it took about two full turns to get it to eht 0.020" gap and my pedal felt much better and I thought I had it fixed. Then I took it for a drive and it was like I had no boost when I applied the brakes in a hard/quick manner, I really had to stand on the brakes to stop. If I was just driving normal, the brakes seemed good, but when I hit them hard to simulate an emergency stop it was like I had no boost and I had to really stand on the pedal to get it to stop. Funny thing is that the booster passes all the typical tests. Anyway, I will see about getting a booster installed and then will go from there. It is like everything I have done has made little improvements but hasn't fixed it overall. Maybe it is just a combination of things being 20 years old. Having basically a brand new brake system will be a good thing since I will be using the van to do some towing so I don't mind buying and installing the parts, I just want to make sure I am fixing the actual problem.

 

[B1Toad]

By any chance is it hydroboost? Do you have dual rear wheels on your E-350? What year/engine?

 

[gasiorv]

Single rear wheel. 2006/5.4L. Not hydroboost.

 

[gasiorv]

Ended up being the brake booster. Installed new brake booster and pedal feels great and it stops great.