PB distribution block on '72

[Ted Z.]

This is my second discussion entry today. <br />
1. Why do so many C3 vette owners complain of pressure switches leaking on the distribution block?<br />
2. I put a new distribution block from Inline Tube. It took hours to break loose and realign brake connections. Since the only leak is at pressure switch, can I replace just the switch? I have searched all afternoon. I cant find a seperate switch for a 1972 Corvette.

[Joe L.]

Re: PB distribution block on '72

This is my second discussion entry today. <br />
1. Why do so many C3 vette owners complain of pressure switches leaking on the distribution block?<br />
2. I put a new distribution block from Inline Tube. It took hours to break loose and realign brake connections. Since the only leak is at pressure switch, can I replace just the switch? I have searched all afternoon. I cant find a seperate switch for a 1972 Corvette.

ted-------


The switch component of the distribution block was never available as a separate part from GM. It was only available as part of the brake distribution block and pressure differential switch assembly. I don't know if it's available in the aftermarket but I doubt it.

[Ted Z.]

Re: PB distribution block on '72

Thanks for responding Joe.
I was trying to avoid a second removal and new install (hours).
I have been considering the idea of eliminating the switch and plugging the switch opening with a plug/bolt of same thread size. Pressurized brake fluid does not flow in or out of this opening.
Any thoughts about eliminating switch and plugging off opening?

[Joe L.]

Re: PB distribution block on '72

Thanks for responding Joe.
I was trying to avoid a second removal and new install (hours).
I have been considering the idea of eliminating the switch and plugging the switch opening with a plug/bolt of same thread size. Pressurized brake fluid does not flow in or out of this opening.
Any thoughts about eliminating switch and plugging off opening?

ted------


Well, the most obvious one is that you'd be eliminating an important safety warning device. However, the car would still have dual braking circuits which in-and-of-itself provides a measure of safety. The switch only informs the driver that one of the circuits has failed which should be otherwise apparent to the driver.

[Mark E.]

Re: PB distribution block on '72

Ted,

Bad replacement parts are unfortunately not uncommon. Consider asking the supplier for a replacement. Or search for an NOS part if you think quality is an issue. This is the braking system so avoid monkeying around by bypassing and plugging stuff.

I'm surprised R&R of the distribution block took hours...it looks like a straight forward job. Was it due to difficulty with breaking loose rusty lines? Hopefully the second time will be easier for you.

[Ted Z.]

Re: PB distribution block on '72

Dear Mark. My mechanical skills and tools are limited. The block is in a very conjested area. The fittings are very tight and there is little wrenching room. the fittings must be precisely aligned or you crossthread. The brake lines are prebent and tough as nails (alignment is a bear). the bottom fitting is near the frame and you need to access by feel only. You get the idea. Stong fingers, wrists, and patience is needed.
I'm going to hold off plugging until I get more feedback. I believe in safety. But I still dont see a well sealed bolt interupting the performance of the block. The pressure switch is a seperate part that screws in like a 7/16 bolt.
Thank you for comments. Hope to get more.

[Bill B.]

Re: PB distribution block on '72

Ted,

Perhaps consider obtaining a good used block, removing the pressure switch from it and replace your leaker with it if the brake line alignment is a difficult one as you described. You do run the risk, however, of stressing the used switch (and thus causing a crack) of that 50 year old part during removal and the subsequent replacement of it into your brass block.

[Patrick H.]

Re: PB distribution block on '72

Ted,

Is your car a big block?
I've swapped these on cars, or at least taken them off, cleaned and reinstalled, and not had nearly so many issues as you describe.
But, they were all small blocks.

You made a comment about a lack of room, which is why I ask.

Patrick

[Ted Z.]

Re: PB distribution block on '72

It's a 350. Entering from the top, the brake lines are very rigid and the alternator needs to be moved to access the d-block. A BB probably wouldnt make a significant diff in removal or install. The block is very close to wheel well, attached to frame.
For those who didnt find it a diff job, I wonder why. My fittings were extremely tightened and diff to access with bigger tools for leverage. I could take up a lot of space explaining but it really needs more discussion then I think you're seeking.
I feel blessed that I got the fittings together without leaks. In short, the block and brake lines are not well aligned so it takes a little twisting and turning of block to get things going.
Lastly, the level of difficulty would be less now that the old lines have been broken loose.
Regarding Bill's comments on swapping in a used switch, that wouldnt seem likely unless you installed with super force which I wouldnt do. NOTE: the block and switch are sold as one part. I think separating would be ill advised; plus it uses o-rings; EPDM I assume.
I'm wodering why my new switch was somewhat lose when I removed it from package. Inline Tube has not answered my calls. I think my switch was compromised (sold and returned and someone messsed with it).
I have googled my situation and read many scenarios about leaking switches and fittings on 70-73 blocks and switches. I'm holding out hope to get it right with NCRS BOARD expertise.
Sorry for all the verbage. I do need to plug off switch opening as it loses fluid just sitting there
FYI: The bolt/plug will not go in deep enough to interact with shuttle.

[Patrick H.]

Re: PB distribution block on '72

Where in MI are you at?

[Ted Z.]

Re: PB distribution block on '72

Rochester (near Oakland University)

[Patrick H.]

Re: PB distribution block on '72

Ok. I thought I would check in case you were close.

[Ed D.]

Re: PB distribution block on '72

Ted,
I feel your pain. The 5 rigged lines going into a small distribution block are very challenging. On my 72 sb the switch stopped working some time ago, with no brake problems. I decided to replace the block with a new one. After struggling to get the lines to line up, the last line would not screw in. After spending an hour working with the last line. I pulled the new block and found the treads were wrong on the last line. I reinstalled the old block and switched the sensor from the the new block into the old block. It works as designed now. The sensor was not leaking, just not working
Ed

[Owen L.]

Re: PB distribution block on '72

In short, the block and brake lines are not well aligned so it takes a little twisting and turning of block to get things going.

Not sure if this will help with what you're encountering...
As I recall for my '72, for installation alignment, loosely attach the driver's front short line to the block, then loosely attach the front cross-over line and the rear line, and only then, mount the block to the frame. Once the block is secured to the frame, tighten the three lines to the block all the way. For the master cylinder lines, attach them loosely to the mounted block then to the master. Once the threads are started at each end, tighten the rest of the way.

[Ted Z.]

Re: PB distribution block on '72

Dear Ed and Owen, It makes me feel a little better knowing others have had the same alignment issues and felt the pain. Good news is that I did make all connections before I bolted block to frame (a must) . No leaks at connections, only switch.
I'll try supplier (Inline Tube) again. I need a switch as the new one was compromised. Thanks for making me feel I'm not crazy.
Looks like Im out the 85 and I may have to have the car towed to a shop for an expensive epair that was basically done.
Any recommendations on where to buy a blister pack of EDPM Orings. I suppose I could try reusing original switch.
So, as a last alternative, has anyone eliminated block altogether and replumbed? My email is tedzywicki@hotmail.com should any have a picture going the route of non-stock. (A sinful request for a NCRS member; sorry.)
Thanks to all. Ted 64289