To change that valve
can be a wicked pain in the butt - mainly just because it involves making up 5 tubing connections in a limited amount of space.
You know how difficult it can be to get the threads of tubing fittings to engage (without cross-threading them). Well in this case, because you have five fittings get started, it is way worse. As each fitting is threaded into the valve body, the entire assembly becomes more rigid and the operation becomes more cumbersome. By the time you are trying to get the final fitting to engage, you feel like throwing your tools down and just drinking beer.
A handful of things I would suggest from experience:
1. Make sure the threads on the fittings are meticulously clean
2. Any paint/rust on the ends of the tubing (at least the last inch or so) is removed
3. BY ALL MEANS -
resist the temptation to mount the valve block on the
crossmember first. Doing so will exponentially increase the length of time required to
do the job. Make up all the fittings to the valve body before bolting the valve to the
member (at least get a few of the threads engaged on each fitting).
4. Wear safety glasses - there is a ton of crap just waiting to fall into your eyes.
5. If you don't have any, it is money well spent to buy the necessary sizes of line
wrenches. Open ends will slip and strip the fitting nuts.
6. After you have made up all the fittings, loosen the two inlet lines that lead from the
master (or just leave them loose during assembly). This is your chance to bleed
whatever air you can from those sections. That is where the vast majority of air will
be. Very little brake fluid will be lost from (and very little air will get into) the 3 outlet
lines. I have always found these trucks to be extremely forgiving about reasonable
amounts of air in the brake lines after replacing a component. Within a day or two any
trace amounts of air will bubble out and migrate to the master cylinder - and vent to
atmosphere. I never bleed brakes anymore unless a long section of brake line has
been replaced.
7. When you have all the fittings made up tight (and the air has been bled from the inlet
lines). You still need to mount the valve body to the cross member. It can be a bitch
to line up the mounting bolts. They barely are long enough to get the nuts started
under the best of circumstances - never mind with 5 lengths of steel tubing fighting
against you. I don't usually ever replace OEM fasteners with standard hardware but in
this case I make an exception. I buy two stainless bolts that are just about 1/2"
longer than the OEM (and SS nuts) ones and they make the job of securing the valve
to the member way easier. They just show a few more threads:
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Many of these hints will not even apply to you - because you are not replacing the brake lines. I have never removed a BPC valve for the purpose of renewing it. It is always the brake lines that I have had to renew - pulling the BPC valve just makes that job easier. Your brake lines will presumably still be bent just as they came from the factory and so will most likely line right up and thread in without a struggle.
