WABCO Accumulator

[heygibb]

After failing both ROJ accumulator tests, I installed a new WABCO STC 2784 accumulator in my ’90 coupe. Threading was exact fit. Only mod was to shim up cross brace w/ a couple of large washers at each attachment lug. W/ old accum, I got zero pedal pushes before pump engaged. Now I get 5-6 pedal pushes after system is pressurized. Initial pressurization is ~21 seconds. The fluid level in the reservoir drops 3/8” during pressurization.

I purchased from supplier in England on eBay. I received it in 2 days. Cost was $159.99, delivered.  I contacted MeritorWABCO to verify warranty. It’s good to go. I've had no problems in 3 weeks of use.

 

 

 

[DAVES89]

good for you! Glad guys are looking elsewhere for parts. Spinning Wheels is a good supplier but I have suspected for some time that they wait until they have a number of orders from guys like us and then order in a shipment. Good way to maximize profits and minimize inventory.

Personally I like the stock size, so have built an inventory of used balls. However there will be a day I will need to buy a new one...

[Ronnie]

Thanks for posting this information on the Wabco. I see that on eBay there is a vendor that is in Nashville that is selling the them. It's good to know there is another vendor other than Spinning Wheels that sells an accumulator that works on the Reatta.

[heygibb]

good for you! Glad guys are looking elsewhere for parts. Spinning Wheels is a good supplier but I have suspected for some time that they wait until they have a number of orders from guys like us and then order in a shipment. Good way to maximize profits and minimize inventory.

Personally I like the stock size, so have built an inventory of used balls. However there will be a day I will need to buy a new one...

 

One of the reasons I went WABCO was my perceived difficulty in buying from Spinning Wheels. I didn't quite like what I read about the Hydac either, for some reason. Isn't that the brand they sell or do they re-sell used balls?

The flajunkie thread at AACA had the info I used to go this route. I wanted new, and this version seems to be readily available. I don't know if linking to that forum is acceptible so I won't, but I posted a similar thread there that has the link.

 

re the stock size...this version was close enough for me to feel comfortable w/ it. The shimming of the cross brace was simple enough. The larger volume of the ball is a consideration, I suppose, but as long as the pump performs w/out overworking, I think I'll be all right...knock on wood. If my pump wears out, I'll post about it.

[Ronnie]

 

... Isn't that the brand they sell or do they re-sell used balls?

The flajunkie thread at AACA had the info I used to go this route. I wanted new, and this version seems to be readily available. I don't know if linking to that forum is acceptible so I won't, but I posted a similar thread there that has the link....

 

Linking to the AACA forum is fine. I consider Reatta owners to be in one big community and that forum is a huge part of it. I read every post on the AACA forum but I no longer post there.

 

I started ROJ to be an extension of that forum in order to make valuable information that was posted on that forum easy to find. Helping people find the information they need is my way of giving back for all the help I've received over the years. 

 

Some Reatta owners post in this forum, some Reatta owners post in that forum, and some post in both places. ROJ was never intended to be in competition with that forum.  I consider us all to be one big happy family no matter where you choose to post. I :)

[heygibb]

Thanks for clearing that up. I always received your site as a depository of the info revealed there, in a way, but organized. You've collected lots of extremely helpful procedures and posted them in a way that is easy to access. I, for one, have saved thousands using both forums.

[Ronnie]

I'm happy that you find it useful.

[2seater]

Does the Wabco list what the gas pre-charge is? The rated pressure and fluid capacity are the same as the Hydac, or very close, but the level of charge is of interest. It sounds like it is certainly in the ballpark but I am curious as it has a direct bearing on the reserve capacity.

[heygibb]

Does 80 BAR sound about right? That number on the ball, ending w/ /80 could be an indicator. The "200 BAR" immediately following it would be the max pressure rating. I have no official specs re this though. Re reserve capacity, are you referring to the need for the pump to keep it pressurized? After starting pump w/ key on, engine off, I consistently get to the 6th pedal push before pump restarts.

 

The info could probably be had here. There is an email link for technical help. This model is STC 2784.

http://www.meritorwabco.com/Contact-Information

[Ronnie]

When I do a search for the  STC 2784 a lot of the photos of them show a female fitting on the bottom instead of a make fitting like the Reatta accumulator. Is the female fitting a removable adapter OR maybe a cover for the male threads?

[heygibb]

Ronnie,

It's a protective cover for the male threads. If you have one, post a pic of the female threads. I haven't seen that.

 

[2seater]

Does 80 BAR sound about right? That number on the ball, ending w/ /80 could be an indicator. The "200 BAR" immediately following it would be the max pressure rating. I have no official specs re this though. Re reserve capacity, are you referring to the need for the pump to keep it pressurized? After starting pump w/ key on, engine off, I consistently get to the 6th pedal push before pump restarts.

 

The info could probably be had here. There is an email link for technical help. This model is STC 2784.

http://www.meritorwabco.com/Contact-Information

 

Yes, 80 bar, or 1,176 psi sounds like it could be. That is a fair amount greater than the Hydac sticker pressure of 1000psi, and could be of some benefit. What matters is how much fluid is contained in the ball in the 2000-2600psi range and it sounds like it is working well. I am almost tempted to buy one just to check the capacities compared to others I have tested. The 200 bar does sound right, just shy of 3000psi, about the same as all other compatible accumulators. It is a good find.

[heygibb]

re your Hydac number. Since it's precharge pressure is lower, that would explain why those using it have fewer pedal pushes after pump is off, no?  From what I have read, seems like 3 or so is the mean.

I'll keep an eye out for your bench test, if you do one. Your info is appreciated.

[2seater]

re your Hydac number. Since it's precharge pressure is lower, that would explain why those using it have fewer pedal pushes after pump is off, no?  From what I have read, seems like 3 or so is the mean.

I'll keep an eye out for your bench test, if you do one. Your info is appreciated.

 

The number of pumps seems to be somewhat flexible, and since all of the data we have is from different installations, it is difficult to make a hard judgement. I did a series on my own car with a selection of accumulators to better judge the comparative merits of each one and would be the only real way to judge if one is better than the other. A bench test does tell a story but can be duplicated pretty accurately with a pressure gauge on the car. I do think that somewhat higher pre-charge may be of benefit if accurate.

[Captmike]

After failing both ROJ accumulator tests, I installed a new WABCO STC 2784 accumulator in my ’90 coupe. Threading was exact fit. Only mod was to shim up cross brace w/ a couple of large washers at each attachment lug. W/ old accum, I got zero pedal pushes before pump engaged. Now I get 5-6 pedal pushes after system is pressurized. Initial pressurization is ~21 seconds. The fluid level in the reservoir drops 3/8” during pressurization.

I purchased from supplier in England on eBay. I received it in 2 days. Cost was $159.99, delivered.  I contacted MeritorWABCO to verify warranty. It’s good to go. I've had no problems in 3 weeks of use.

 

 

I just ordered one wabco. In thursday.....hope it does trick. 

 

CC@AACA forum

[Ronnie]

 

The number of pumps seems to be somewhat flexible, and since all of the data we have is from different installations, it is difficult to make a hard judgement. I did a series on my own car with a selection of accumulators to better judge the comparative merits of each one and would be the only real way to judge if one is better than the other. A bench test does tell a story but can be duplicated pretty accurately with a pressure gauge on the car. I do think that somewhat higher pre-charge may be of benefit if accurate.

 

I know we've considered the number of pumps before the pump starts to be the benchmark of the accumulator condition but something Jim Finn said on the other forum seems to make a lot of sense. I don't want to quote another forum here but he basically said he though the number of pedal pumps before the red warning light comes on is what is important. I tend to agree because when the pressure in the system drops low enough that the red warning light comes on it means you have lost enough pressure that the system is no longer safe. Plus, you also lose the ABS feature of the Teves system at the same time. Therefore I have added the following to the accumulator testing instructions here on ROJ. I would like us have a good discussion here about this method of testing an accumulator. I wish Jim was on this forum to join the discussion. What do you guys think about this way of testing the accumulator ball?

 

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Test number 1

The purpose of this test is to see how many pumps of the brake pedal it takes to get the red brake warning light to come on. The higher the number the better. A new accumulator will be about 7 pumps and a shot accumulator would be 1 pump.

1. Turn on the key (don't start the engine).
   
2. Wait for the red and yellow brake warning lights to go out and a few seconds later you will hear the pump stop running.
   
3. Rapidly pump the brake pedal about 4 times while watching to see if the red brake warning light comes on.  If it does, wait for the pump to build up pressure again. The light will go out and the pump will stop.
   
4. Then pump the brake pedal 3 times to see if the red light comes on.
   

[DAVES89]

Jim is far and away the most knowledagble guy in regards to Reattas. He has owned them almost since they were offered and has been parting them out and selling parts for years.

Your additional test looks good to me.

[heygibb]

 

 

------------------------------------------------------

Test number 1

The purpose of this test is to see how many pumps of the brake pedal it takes to get the red brake warning light to come on. The higher the number the better. A new accumulator will be about 7 pumps and a shot accumulator would be 1 pump.

1. Turn on the key (don't start the engine).
   
2. Wait for the red and yellow brake warning lights to go out and a few seconds later you will hear the pump stop running.
   
3. Rapidly pump the brake pedal about 4 times while watching to see if the red brake warning light comes on.  If it does, wait for the pump to build up pressure again. The light will go out and the pump will stop.
   
4. Then pump the brake pedal 3 times to see if the red light comes on.
   

 

I just saw this post, so I did the procedure. I pumped 19 times, after original pressurization, before red brake light came on. After waiting for pump to re-pressurize, I pumped another 14 times before red brake light came on. On both occasions, the amber ABS light came on a second or two prior to red brake light. My pumping was aggressive and consistent. That is w/ the WABCO accumulator I installed 6-7 weeks ago.

[Ronnie]

Fourteen pumps is good. I get about 10-12 before the warning lights come on with my ACDelco accumulator that was installed about 7 years ago.

[heygibb]

Good to know. I expect mine to last many years. I think I'm done w/ any major fixes for awhile...knock on wood...so, back to driving more and tinkering less.