[1750GT]

69 Dual Pressure Warning Assembly - Piston Seals

for latest and greatest solution for these seals...see post # 201 (link below)

69 GTV Brake Pressure Sensor Manifold - Piston Seals

Bingo All Hope brakes use Dot 4. The seal I'm using is Hope part HBSP109 - used on most Hope brake models. You can find exploded views of all Hope brake master cylinders, as well as other tech support at https://www.hopetech.com. The lip seal HBSP109 should be available as a single...

www.alfabb.com

I could use some assistance on this one.

I've taken a bit of break away from the bodywork part of the restoration and decided to have look inside the Brake system Pressure Manifold. Now the sensors and the threaded end cap came off surprisingly easily, however the inside pistons were a different story. I had to heat the housing up about 3 times with the propane torch and slammed the open end on a block of wood....eventually the pistons dropped out.

However quite a bit of goop and remnants of the one seal was found inside along with some minute corrosion spots here and there. The plating on the pistons has also come off in many places.

Has anyone else had a go at reconditioning these? If so, where can these seals be purchased from? BTW...so far I've only checked suppliers' Web sites and have not come across them.

 

[ossodiseppia]

Seals are not available for these. Some Porsches of the same vintage have a master cylinder with this device "built in". I'll bet $20 the pistons and seals are the same as what is in our cars. Search Fleabay for Porsche or Ate cylinders. You might be able to find a used one.

 

[1750GT]

Osso, for now I'd rather not go down a long investigative path only to find that the Porsche ones are bigger/smaller by .020 or so. So I'm crossing my fingers here and hoping that someone on the BB has already done some leg work and found a source for these.

 

[gattia86]

What does this part do?

Sorry to butt in here, but... what, exactly, does this pressure sensor manifold do?

I'm rebuilding/replacing the brake system on my GTV and fabricating new lines. I'm hoping to simplify the plumbing and do without this manifold... but I'm not sure if it provides a critical function.

Any ideas?

Thanks,
George

 

[ossodiseppia]

Sorry to butt in here, but... what, exactly, does this pressure sensor manifold do?

I'm rebuilding/replacing the brake system on my GTV and fabricating new lines. I'm hoping to simplify the plumbing and do without this manifold... but I'm not sure if it provides a critical function.

Any ideas?

Thanks,
George

It's called a differential pressure warning device. It's function is to detect a drop in pressure (a leak) and isolate that circuit so that you still have brakes. So if one of the front brake lines starts leaking, it shuts off the flow of brake fluid to the front brakes. You'll still have the rear brakes. Oh, it also turns on a light on the dash to warn you of the drop in pressure.

 

[1750GT]

This particular device is only used on the 69 GTV with the dual booster set-up....(if I'm not mistaken). It is quite a sophisticated arrangement...albeit expensive due to the number of parts involved...floor petal assembly, 2 boosters and this manifold/pressure warning device. It's no wonder they opted to go with the simpler (cheaper) design as offered by ATE with the drop down pedal configuration.

Osso FYI, I found a seal supplier (Parker-Hannifin) that has an existing seal that may fit the geometry of the piston groove and housing bore. It's their C2 series piston seal....but I need to investigate the material compatibility further.

 

[1750GT]

...deleted duplicate of previous post (sorry about that)..

 

[davbert]

osso

Do people often have trouble bleeding the 69's brake because of this device?

I hear the trick is to bleed both (cross-opposite, ie LF and RR) calipers at the same time.


d

 

[1750GT]

Well, looks it like the lead for possibly finding a seal manufacturer has dried up rather quickly! I'd have to order more than 1,000 pieces so that they could justify starting up production in Germany.

So I guess I'll now have to look into the Porsche lead that Osso suggested.

 

[ossodiseppia]

osso

Do people often have trouble bleeding the 69's brake because of this device?

I hear the trick is to bleed both (cross-opposite, ie LF and RR) calipers at the same time.


d

Yes, it's a PITA.. Papajam and I used a pressure bleeder while pumping the master cylinder. We didn't do two calipers at the same time, we did only one at a time. Papajam prefers to prime the master cylinder with brake fluid before starting.

 

[Alfajay]

I believe that other, later-model Alfas also used this switch/junction block. Mid 70's spiders have them mounted on the right hand fenderwell, sort of near the starter.

It's odd that with all the parts available for 105 cars, no one offers new or rebuilt rear pressure-limiting valves, or this differential pressure sensor. (Yes, I know that there are aftermarket sources for the rear pressure-limiting valves). You'd think that ATE would have sold these parts to a number of car manufacturers, and that replacement parts would still be made. But, I guess not.

To ask a naive question, why not just eliminate the thing? I don't see that it performs all that vital a function: I'd like to think that if anyone on the BB lost half of their brakes, that they wouldn't need an "idiot" light to tell them!

A simple fix would be to install a couple of unions to tie the existing lines together. A more sophisticated fix would be to gut the housing, install some sort of a dam at its center, and re-install it. The concours judges aren't going to to ask you to cut a brake line to prove that the warning light really works!

 

[alfavirusnz]

We don`t have these on the Euro versions, so I`m guessing it can be eliminated but I`m a fan of keeping these cars reasonably original. If you retain it and there is corrosion in the bore that won`t go with a light hone you will need to get the unit resleeved-locally we get them done in stainless. The pistons are easy to make up in a lathe if you have access-again I would turn out of stainless rod, but I would first of all give them a rub in wet and dry to see if they come up better. Those seals don`t look particularly unusual. surely you guys have a brake specialist/remanufacturer like us that has an extensive range of seals-they are all made to a handful of diameters so it is the shape and depth that you need to match up. If stuck I can provide the details of a local firm that I deal with. We`ve been making do with and rebuilding things down here you guys wouldn`t even think was possible.

Richard J

`65 Giulia Ti, `69 GT Junior, `74 GTV 2000, `76 Alfetta GTV, `77 Alfetta GTV, `84 GTV6

 

[1750GT]

Jay...I'm not too keen on modifying a braking system component that to me seems to have a lot merit and function (notwithstanding the fact that it is a complex system by later standards). I'm very confident that the braking system was carefully thought out and purposefully designed by the automotive engineers at ALFA with a lot more experience than us. Also, I don't believe that a warning light should be termed an "idiot light" either. As Osso explained, a loss of fluid on side (one half of the system) will cause this valve to shut the flow through it thereby preventing a total loss of fluid from the reservoir. If you simply introduce a dam in the unit you could potentially lose all of the fluid....not a scenario that I'd want to be caught in. Lastly, don't underestimate the liability situation that one might be trapped in should a "modified" vehicle be involved in a traffic accident.....or god forbid a traffic fatality! That said, thanks for the suggestion anyway.

 

[1750GT]

Richard, yes the bore itself should hone out nicely, it's mainly the seals and the pressure switches that I'll be needing. One seal looks OK physically but it is almost 40 years old and probably well past it's expected life. I will continue my search locally (I've really only just started). The warning switch has part number 0343102010 and is BOSCH unit used on same period Porsches (seems to be available in Germany). The other two sensors are ATE units that may or may not be functioning (I haven't tested these yet) but if they are available NOS I'd like to get them for spares. In the end I may very well come back and ask you for the name of the shop you deal with.

Thanks.

 

[daveydog]

I know that when I was rebuilding all four brake calipers on my '74 that there was guite a lot of goop in each of them. Kind of a jelly-like substance, but blackish dirty,well, goop!
Once everything was all cleaned out and with new seals in the bores I was feeling kind of good inside that I'd "done another good brake job" but now I see I've missed a rather important part of the brake circuit. I wouldn't take that dual circuit valve out either. It's there for a purpose and somewhere on this planet (and if you do find one let us all know will you? ha ha ha ), there is a supplier of those seals.
Also, I think using heat on any brake part not near the calipers is a risky technique to remove the pistons. My money would go on using compressed air and a fluffy rag to catch the projectiles. And I don't even have a compressor, but some actions require the use of a mechanic's shop, even if it's just for the air...

 

[1750GT]

Daveydog..I do have an air compressor and tried the air method at first as well...but to no avail (probably the piston area is too small and does not generate a force large enough to overcome the friction caused by some of the corrosion and crud inside). The heat I applied was via a propane torch and not an acetylene torch and so I was not concerned about damaging the housing by overheating. I really had to slam the unit down hard for about 15 minutes and with repeated heating cycles before the pistons finally moved out. Now had this failed I would have tried to use the compressed grease into the cavity approach which I recall someone on this BB suggested using instead of air.

 

[papajam]

...a loss of fluid on side (one half of the system) will cause this valve to shut the flow through it thereby preventing a total loss of fluid from the reservoir.

This is not correct.
Please read this thread for an explanation on how the brake pressure differential valve works.
If still not convinced that the BPDV does not shut off flow, think about this question. If the valve shuts off fluid flow in the event of a pressure loss, how is it possible to bleed the brakes?

 

[[email protected]]

I once had the brake-balance device on my Peugeot 504 wagon fail. I tried bypassing it but got instant rear lock up. A family friend who built hydraulic agricultural equipment fixed me up with a simple "o" ring of the correct dimensions. He said it was as good as the square cut seal it replaced. He lso said, if he had no ring the right size, it would be no problem to cut a new groove for a seal of an available size. I was skeptical, but I never replaced that "o" ring for the next several years I drove the car all over the western states. I'll bet any good hydraulics technician could redo one of these goofy devices on 69 GTVs. I did not even know I had one until now, so I will also have to decide how to go. Repair or eliminate? I look forward to further feed back.

 

[1750GT]

Thanks for the clarification Jim. BTW, I took measurements of the piston (which are in metric mm)...perhaps someone can assist to find a "lip seal " from some other application that is compatible with the groove configuration of the ATE piston.

View attachment ate valve piston.pdf

 

[Alfajay]

1750GT had written the stuff in quotes:

"I don't believe that a warning light should be termed an "idiot light" either."

Well, OK, that is an emotionally-charged term. But, how would you characterize someone who needs a light to figure out that they've lost half of their braking system?

"As Osso explained, a loss of fluid on side (one half of the system) will cause this valve to shut the flow through it thereby preventing a total loss of fluid from the reservoir. If you simply introduce a dam in the unit you could potentially lose all of the fluid....not a scenario that I'd want to be caught in."

Two points: 1) Papajam tells us that the BPDV does not shut off flow. 2) most master cylinder reservoirs have a warning light that indicates when the fluid level has dropped. Now that function I agree is critical - you aren't going to know that the brake system has begun to leak by the "seat of your pants".

"Lastly, don't underestimate the liability situation that one might be trapped in should a "modified" vehicle be involved in a traffic accident.....or god forbid a traffic fatality!"

You know, that is a very good point. Still, I worry that if someone gets injured by my 40 year old car, I'm going to get crucified even if it is 100% original.