Possible solution for PM accumulator

[gofstbuick]

I have noticed that the Tevis ABS (2,3 and 4) systems use an nitrogen bladder accumulator (pressure range is 2000 to 2600psi). Our thread pitch on Powermaster is M12x1.5. The thread pitch on a Tevis ABS accumulator is M14x1.5. There is no metric male to metric female adapter (already checked). Has anyone tried opening up the accumulator hole (on the master cylinder) and changing thread pitch to M14x1.5 and installing a Tevis accumulator (in place of the powermaster accumulator)?

 

[acoen]

Do you have any information on supplier or manufactuer for the accumulator. Sounds like they were used on many different cars. It would be interesting if Teves had an accumulator that matched our car's specs. Do they look the same, I always thought the accumulators were made by Bosch.

 

[Mac in SD]

Good work, gofstbuick. There's got to be a solution here somewhere.

 

[gofstbuick]

Do you have any information on supplier or manufactuer for the accumulator. Sounds like they were used on many different cars. It would be interesting if Teves had an accumulator that matched our car's specs. Do they look the same, I always thought the accumulators were made by Bosch.

The supplier would probably GM, since the Tevis ABS system is licensed to manufacturers (actually all Big 3 automakers, and GM subsidiaries like Saab) to use this type of ABS system. The Corvette uses a different system. Someone who does brakes for a living, would have to drill and rethread a PM master cylinder body and install a Tevis style accumulator. The thread pitch is M14x1.5. I have a set of brake gauges to test the pressures, but we need someone to loan a accumulator from a wrecking yard and a bad PM unit to drill. The bores of the PM mastercylinder are anodized, so there can be no pits in the bore. Tevis was used on 1985-1999 GM vehicles. Powermaster is Tevis version3.

 

[GNVYUS 1]

Whats the price of that accumulator?

It's possible someone could make that adaptor piece, hell my neighbor is a machinist and another friend owns a CNC company.

 

[Race Jace]

what is the cost of these accumulators? i could possably make an adapter.

 

[acoen]

I did a quick search on the web the other night, it looks like the Teves ABS system was used on several different makes and models.....Looks like we have a good chance to get one of these to work.

 

[V6POWER]

I believe the pressure range on our accumulators is 200-700 psi. Since the Tevis is 2,000-2,600 it would be out of our range. Please correct me if I am wrong.

 

[gofstbuick]

what is the cost of these accumulators? i could possably make an adapter.

That would be great (and we can talk at the Nationals), but I don't know about an adapter. I checked with all the industrial hose and fitting shops around town and nothing. Plus there is a shoulder (on the MC body) and o-ring to contend with. I suspect the easiest method would be to tap the existing hole to M14x1.5. Since Tevis is manufactured by one manufacturer (like Bosch) I'd be willing to bet they made very little changes to tooling to change thread pitch. I now need to investigate the price of a Tevis accumulator. Will keep you posted.

 

[Race Jace]

yes I think the pressure difference is going to cause some problems.

you can't hand machine your existing master. although is sounds easy on the surface the o-ring seals against a bore with a special lead taper and radius leading to the bore. This "port" (we call it) has to have a 16RMS finish for the oring to seal correctly. this can't be done with a hand drill. the threads are simple but the port is not. an adapter would be made with a male m12 with o-ring and a female m14 with port.

this would work if it weren't for the pressure operating problem.

there were some dodge mini vans that used the balls. Is there anyone out there that knows about these?

this is the criteria that we need to look for in finding a suitable alternative. In order of priority.
availability
pressure compatability
price
mating compatability ( I can make an adapter to fix this but it would be nice to just have one with the right thread/port)

 

[gofstbuick]

I believe the pressure range on our accumulators is 200-700 psi. Since the Tevis is 2,000-2,600 it would be out of our range. Please correct me if I am wrong.

I just confirmed that myself, but if you apply pressure to the diaphram, aren't you just looking for a response in return? The pressure switch controls pressure. It just shut the PM motor off when a specific pressure is achieved. There is still 300psi of pressure on the nitrogen side, so what happens when you apply 735psi agains that diaphram. It probably moves (the diaphram) and once it drops below working pressure the pressure switch signals the motor on again.

 

[gofstbuick]

yes I think the pressure difference is going to cause some problems.

you can't hand machine your existing master. although is sounds easy on the surface the o-ring seals against a bore with a special lead taper and radius leading to the bore. This "port" (we call it) has to have a 16RMS finish for the oring to seal correctly. this can't be done with a hand drill. the threads are simple but the port is not. an adapter would be made with a male m12 with o-ring and a female m14 with port.

this would work if it weren't for the pressure operating problem.

there were some dodge mini vans that used the balls. Is there anyone out there that knows about these?

this is the criteria that we need to look for in finding a suitable alternative. In order of priority.
availability
pressure compatability
price
mating compatability ( I can make an adapter to fix this but it would be nice to just have one with the right thread/port)

Is it possible that the taper for the o-ring is the same size as the GN accumulator? Remember that the threads are sunk in deeper and there is a larger bore that the accumulator body rest against the MC body.

 

[gofstbuick]

I have a call to Continental Teves NA (for confirmation), and I also spoke with a Teves certified instructor. According to the instructor, an accumulator ball is an accumulator ball. It has a diaphram and when pressure is applied, it reacts. The pressure switch controls motor on and off. Remember that an ABS system is required to pulse the brake system many times (during a panic situation), but on Powermaster, the operator will hammer the brakes and just needs additional assistance (for force). Therefore, the operating pressures for Teves ABS requires additional working pressures to allow multilple pulses once ABS is engaged. Minimum pressures on Teves is 1500psi, which equates to 1100 psi of pressure for a working range (before a code will set) and can probably still pulse the brakes below that range (1500psi and below). At 200-735psi the Teves ball will probably still give the braking system it's standard 2-3 brake pedal pushes, before turning the motor on (that is the basic PM spec).

 

[turbofish38]

I actually went down to the boneyard and looked at the difference between the two. A lot of work to get that Teves to bolt on IMO. One thing on the Teves system is there is a metal tube about one inch long running up into the accumulator where the PM1 doesn't. If the PSI doesn't make a difference than here is how I would do it. Machine the adapter so it has the PM1 style booster end with the other end having the Teves setup with the tube. I'm thinking the whole adapter should be in the 1 to 1.5" range for overall length.

Not to be a smart a$$ but if this does work than what are you going to do if you need some other discontinued part like the rebuild kit? And someday the those expensive pressure switches will be discontinued too? Seems like a lost cause sometimes when you start throwing money at something that always needs to be fixed.

 

[gofstbuick]

Is the tube required to be attached to the accumulator? All I'm interested in is the accumulator. Though I cannot see first hand like you (haven't looked at on in the bone yard yet), it looks like the accumulator ball removes from the pump body or the master cylinder body of the Teves system.

Yes, some day some of the parts may be discontinued (and are already). But this will give some of us an option, if we want to retain a stock appearance.

 

[GNVYUS 1]

I didn't want to volunteer Race Jace, but since he did himself that works for me.

I bet you Caspers could work out a pressure switch if it came to it. Hell the guy came up with a better cam sensor cap and thats way more involved then the brake pressure switch.

If this works out and the adaptor piece and acc balls can be reasonably priced, it comes down to the motors, and the last I heard, the guy who had the tooling for them was not very kind to a GN'er with a problem he had with his motor. :frown:

 

[turbofish38]

I beleive the only purpose of the tube was to channel or direct the fluid into the accumulator. I think it would be a vital part so it should be part of the adapter. Right now if I had the time I would be more than happy to donate a complete used Teves system to Jason so he could have the part to look at and to get a better feel as to what he is looking at. My schedule is a little screwed up so it would be at least another month before I can get to the boneyard to pull one off.

I was playing around one day and found this link for an accumulator the Homies use on lowriders. The company tells me it isn't compatable with DOT brake fluid. I wonder if someone might be able to find the company that manufactures these. They would have the tooling in place,all they would have to do is make it to the PM1 specs. http://www.catalog.prohopper.com/product_info.php?cPath=1&products_id=34

 

[TurboKen]

I remember looking at the accumulators a while back. The late 80's BMW's had them too, but it was much larger than ours. What I did learn is they are made in germany, and if I remember correctly, from a company called ATE, aka Teves, maybe we should start there

Kennyg

 

[tbirdv6]

I've had a few Thunderbird Supercoupes that braking system (89-95)
& uswd an accumulator like ours -but don't know the thread size
FRED

 

[Ormand]

I don't think they can be used unless the pressure range is right, and the volume. The pressure in the accumulator when it is "empty" should be about a few hundred psi. Then, when it is turned on, the pump will pump in fluid until the pressure reaches 675, more or less. Then the switch shuts off the pump. In use, when the pressure drops to about 500, the pump comes on and repressurizes. The volume of fluid between the two set points on the pressure switch is good for a few stops, maybe ten if the PM is in good shape and all the brake hoses are new. If the volume is greater than stock, then the pump will run too long, and it will soon be toast. If the volume is LESS than stock, the pump will cycle a lot, and you may not have enough reserve to stop the car if the pump or the switch fails. (That will pucker you up, pretty quick!) If the empty pressure in the accumulator is more than 675, the pump won't be able to pump any fluid into the accumulator before the switch shuts it off. So, as I see it, the accumulator has to be pretty close to the stock one in both size and initial pressure.
But there are plenty of accumulator manufacturers. Just look here:Accumulator Vendors Should be possible to find one that's the right size, shape, and pressure, without doing any major machining.