Some brake issues...

[jperecko]

So I am working on a new crossmember to support the NV4500 and I came across a pinch in the brake line running to the rear axle. It looks like it was there from somebody installing the skid-plate one time. Check out the picture and tell me what you think. Should I do something about it? If so, what? It is a little worse than it looks in the picture...

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Also I was trying to pull the master cylinder and booster and have been having issues with that. I undid the brake lines and the 4 nuts holding the studs to the firewall. Am I missing any fasteners because the brake booster is not wanting to separate from the firewall. Any ideas? Thanks

 

[argve]

Seeing as how is a safety item - ie brakes.... that is a system I want to work everytime without failure or quirks.... I would replace it. Brake line is cheap - just time consuming (have to bend it and then bleed it)...

So replace it.

 

[jperecko]

Thanks

Any ideas to get the master cylinder/vacuum assist off the firewall?

 

[LCAM-01XA]

IIRC one of my studs for the booster had one of those retarded retaining spring-washer things on it, you know, the kind they now put on the wheel studs on most any vehicles so rotors don't fall on the idiot's foot when they remove the calipers for new pads install. So look for those things...

 

[jperecko]

I finally got the booster off... turns out that the vacuum chamber was just nicely rusted to the firewall and some time with the BFH fixed that.

 

[LCAM-01XA]

There should have been a rubber-ish gasket on the booster, then a plastic boot-thing that sits between the rubber gasket and the firewall and that carries the seal for pedal pushrod - did you not have those?

 

[jperecko]

Well yeah there was the boot and gasket... but all around that (and even through a little?) it was all rusted and... ugly. Luckily I have a brand spankin' new hydroboost setup to replace it with. I think I'll take some abrasives to the firewall and at least shoot some primer before I install the new unit.

If I remember, I'll shoot a pic to share what it looks like before the cleanup.

 

[LCAM-01XA]

That sounds like a very good idea, paint is your friend when it comes to fighting rust issues. For the hydroboost, are you running the factory pump, or you're using an F450 pump? I'm thinking it's possible the two have different springs in their pressure control valves, I know for sure the Explorers (and probably other rack-and-pinion steered vehicles) run higher pressures than fullsize cars and trucks (which use a steering box setup), but the springs swap between them so if you can lower the pressure of an Explorer pump by using a car/truck spring you should be able to raise it in a truck by using a rack-pinion vehicle spring...

 

[jperecko]

Lets just say that my hydraulic system will not really be stock to anything...

First off I am working with a Cummins here... with its silly shaft-driven pump. You can only do so much with it but it is tweaked for volume as well as pressure as far as you can go without going to a bigger belt-driven pump. The hydroboost unit itself has the internals tweaked to allow (almost) full flow to the steering even with the brakes on (a stock hydroboost unit severely limits flow to the steering when braking). This is not much of an issue for most but I am also running a hydraulic ram cylinder assist for steering which needs volume.

 

[LCAM-01XA]

Interesting... what inlet pressures are you having at the hydroboost? And would you happen to know what's the internal pressure drop across the hydroboost between the inlet from the pump and the outlet to the steering box? I have an Explorer I can rob the steering pump off, and I do feel I can do better in both brake and steering assist (as compared to my old hydroboosted Chev and my buddy's pinky-steering '86 F250 diesel)... Also, what are the internal hydroboost mods needed to accomplish the full flow thing? I'm not really planning on them, I'm just being curious.

 

[jperecko]

I have no idea as to actual numbers but I am guessing that I am well over 2k PSI. It is not an exact science (stretching/shimming springs for pressure and drilling out holes for volume...). I should hookup a hydraulic gauge as that would be neat to know.
The drop experienced with the brakes activated is with volume... as it goes from a 1/4 to 1/8 orifice (from memory here...) so if you actually use the volume (like when steering) you will experience a drop in pressure.

As far as the specifics of the mods I have no idea... I sent the system to Vanco PBS as that is the main thing they do. They will setup your pushrod for you for $50 and do crazy stuff like mine for more. You really should not need any mods to the hydroboost unit if you are doing a conventional steering setup... plus you should not really be doing much steering while braking for on-road driving. It is more of an offroad/technical driving thing.

...Not sure if any of that really helps <shrug>

 

[LCAM-01XA]

If you do have a pressure gauge you can use, that would be real good to know some exact numbers. I was told by my boss that the Explorer puts out something like 2800 psi, while the steering box only needs 1500 or so, and that additionally to the Explorer we have a few Mk7 pumps I can scavenge for springs and valves (the Mk7 also uses rack and pinion steering so it runs higher line pressure). And yes, your info does help some, I'll report with my findings soon

 

[LCAM-01XA]

Okay, took apart some pumps:

- '90 Lincoln Mark VII: valve stamped "A." with a 50mm long spring
- '90 Ford Crown Victoria: valve stamped "B" with a 42mm long spring
- '90 Ford F350 dually: valve has no stamped marks, 42mm long spring

All valves look identical, I did not notice a single difference between them. All springs are made of the same wire so they have about same stiffness constant, the difference in force exerted on the valves comes from the different length - all springs have to fit in the same space, the longer spring needs to be compressed more to fit in that space, so the whole F=k*x thing with "k" being equal and "x" being different suggested that if I put the Mk7 spring (and valve, to keep things consistent) in my F350 pump I will end up with a higher line pressure - yeps, I sure did, steering feels a bit easier now, and brakes definitely feel more powerful. So overall I'm happy for now, still gotta dissect the Explorer pump and compare it to the other three... but that requires me actually finding the darn thing first, lol

 

[jperecko]

So I took some pictures... You can see where the gasket was seated and the rust all around it which was holding the cylinder to the wall. SO I took a putty knife to it and scraped some junk off, then a wire-wheel, and finally some sandpaper. I then threw a coat of primer over everything. Check out the pictures...

Oh and the square hole where the clutch master cylinder should be is for the dodge master cylinder which mounts a little different... and I added a couple holes for my custom brackets to add some rigidity.

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[LCAM-01XA]

Good work, I think you should be fine now for years to come.