ABS codes

[brantgab]

I'm getting codes 21 (main valve) & 12 (EBCM) from the ALDL. I'm quite certain that the accumulator is shot. Would this be what is causing the 21 code? Is there any way to test the EBCM to make sure it is working properly?

[Guest Mc_Reatta]

Not really. Just need to be sure it is getting power. Relay and fuse in the circuits.

What are your symptoms?

What is going on with the red and yellow lights?

Have you taken the brake tests here, and what were the results.

http://reatta.net/brakes/brakes_troubleshooting.html

[brantgab]

Under normal braking conditions everything works fine. The yellow ABS light comes on initially but goes out as I continue braking. If I get on the brakes hard, the pedal becomes really stiff and I have to stand on it to slow down.

test results:

test 1 - yellow 1, red 4

test 2 - 1 pump

test 3 - red never came on, yellow off in 2 sec

test 4 - pump off in 2 sec

test 5 - I stopped at 100 pumps - never came back on

test 6 - no change

test 7 - feel tap and hear thump

Edited May 23, 2014 by brantgab (see edit history)

[Guest Mc_Reatta]

Yell, the good news is test 7 tests the main valve, and it passed that test.

The other answers have me thinking the main issue is a flaky pressure switch. The first test is main indicator of the accumulator state, and 4 pumps to red isn't horrible, but yellow light should not be on.

I recommend you pull the electrical connector off the pressure switch and look at both ends to see if you have the least bit of moisture inside. That is a good indicator the the switch is bad.

Here's a link to Ronnie's write up on the switch replacement showing where it is located etc: http://reattaowner.com/roj/component/content/article/84-suspension-a-brakes/brakes-electrical/163-abs-pressure-switch-replacement

[brantgab]

I checked the pressure switch connector and there is no moisture present

[Guest Mc_Reatta]

Some of the test results don't seem to make sense and conflict with other results. I still feel that the pressure switch may be the cause, but can't rule out the EBCM or other causes. Before I would recommend replacing anything, I think you should flush and bleed the brakes if you haven't done it recently.

Here's a link to ROJ on how it's done:

http://reattaowner.com/roj/component/content/article/64-suspension-a-brakes/brakes-mechanical/167-how-to-flush-bleed-brakes

You can browse the other brake procedures for the great information accumulated there.

Once you have accomplished the flush, retake the brake tests and let's compare the results.

[brantgab]

I actually flushed the brake system last week. What parts of the test do you find conflicting and why?

[Guest Mc_Reatta]

I actually flushed the brake system last week. What parts of the test do you find conflicting and why?

Test 2 conflicts with 1. 4 pumps vs 1 pump. Should take more pumps till hard pedal than red light coming on.

Test 3, if pedal was hard, system should be depressurized and your red light should come on immediately. Your red light never came on and pump only ran 2 secs.

Test 5, pump never came on. Seems to indicate you can't depressurize the system by stepping on the pedal. This could be a problem with the main valve, but it passes test 7.

Can't figure out if the valve isn't working, or the pressure switch isn't responding properly if it is.

If you have a DVM, measure the resistance of the main valve with connector removed, and measure the resistance the meter shows with the two probes shorted together. Valve has a very low resistance and need to see how close the meter is zeroed out to keep from getting an erroneous reading.

[brantgab]

I think I may be mistaken on test 5. When performing the test I never heard the pump come on the way it does when turning the ignition on; However, I did hear a different noise every time I pressed the pedal. Thinking back, when I flushed the brakes I was able to keep the pedal pressed down and the fluid kept pumping out the bleeder for as long as I kept the pedal down. I think the correct answer to test 5 might be every time. I am away from home for a few days and can't do any further testing until I get back.

[Guest Mc_Reatta]

Did reservoir run dry before or while you you did brake flush?

Different sound of pump may be due to some air causing cavitation in the pump.

Did you do any brake work or have other brake problems prior to these current issues coming about?

[brantgab]

I did not allow the reservoir to run dry at any time while flushing and have performed no other brake work. I just bought the car recently and this problem existed when I bought it.

[Guest Mc_Reatta]

OK, guess we'll wait till you can get your ears back on the pump. Maybe you can get an assistant to help out too.

[padgett]

Can't really trust the code, more how is it acting and what lights are on. Do you have power brakes ?

[brantgab]

I got back today and measured the resistance of the main valve at 4.5 ohms. I retook the test and got similar results:

1) both lights on with 1 pump

2) brakes are hard on 1st pump

3) red light stays off, never comes on to begin with; yellow light off in 2 seconds.

4) pump off in 2 seconds

5) the pump runs every time I press down the pedal. ***

6) no difference in fluid level

7) feel tap and hear thump

*** When I first took the test I didn't think the pump came on at all in test 5. I mentioned that I would hear a sound different to the sound of the pump. What is actually happening is that the pump stops running so quickly that the sound of it is being drowned out by the sound of the fuel pump running. The sound I am hearing every time I press the pedal in test 5 is in fact the pump.

[brantgab]

padgett,

I do have power brakes, but if I get on them too hard the pedal gets real stiff and braking is difficult.

[Guest Mc_Reatta]

It sure seems to me the pump is not building full pressure. The first note in the analysis says this will throw all the results off, which is what I see here. Accumulator is probably bad as well, but results that would prove this one way or the other aren't present.

The only test that looks good is the one for the main valve, test 7.

Since you get some breaking at first but it goes away withing one pedal push, my recommendation would be to replace the pressure switch and see if that cures most of the symptoms. It seems your pump runs and can build some pressure so I'm thinking the pressure switch is turning it off well before it can reach proper pressure level.

The only thing I can think of to test this out would be to force the pump to run and see what happens. Rig a jumper to short the switch output to the pump or another way to get 12 volts to the pump. Run the pump for at least one full minute. Disconnect the jumper and retake test 1. Check fluid level and then run pump again for at least one minute. Recheck fluid level (test 6) and then rerun test 2.

Let's see if this makes any difference in the results. At least it should prove the pump is capable of running for more than two seconds, and the switch is shutting it off and not something wrong with the pump itself.

Throwing parts at a Teves gets expensive real fast. You can get tested used pumps and switches from the vendors here, and new or rebuilt parts can be had from ROJ's store and FLAPS at higher cost.

Edited May 29, 2014 by Mc_Reatta (see edit history)

[brantgab]

Well, I was able to run the pump for a minute to charge the system, but the test results were all the same. Now I am really at a loss.

[Guest Mc_Reatta]

That's not what I was hoping to hear. It does show the pump is capable of running but we still don't know if its building the necessary pressure to charge the system.

I searched for previous posts on making a pressure gauge to test the system, but the discussion feel apart with no real practical solution. The dealers had a test gauge available, but I know of no commonly available way to find one.

A gauge is easy enough to find (Amazon, Northern Tool) for about $20 but how to connect it to the Teves is an unknown.

Here's a possibility that Amazon lists:

http://www.amazon.com/SSBC-A1704-Brake-Pressure-Gauge/dp/B003VYVFSS/ref=pd_sxp_grid_pt_0_0

One of those metric adapters (7mmx1.0 or 8mmx1.25) may screw into the accumulator port. Anyone know for sure?

At this point I'm not comfortable to identify one part I'd say to replace. If you're not building pressure why does the pressure switch shut off the pump and red light? If you're building pressure why don't you get more than a spurt of breaking at the wheels.

If you can verify the operating pressures, we can probably zero in on one component, but it might turn out to be the MC body itself, and not a pump, switch or accumulator.

My personal choice if I had the funds would be to seek a complete used or rebuilt working Teves unit and replace the complete unit. Then keep the old one as a parts donor for the future.

[brantgab]

I was able to locate a pressure gauge and adapter on ebay, part #'s J 35604 & J 35604-88.

There are others available there. Should have them in a few days and I'll see what kind of readings I get.

[brantgab]

I received my pressure gauge today and ran some more tests. Here are my observations:

I first ran 12v directly to the pump and the pressure reached 3000 psi in 4-5 seconds.

1 press on the pedal and the pressure dropped all the way to 300 psi.

2 presses and the system was totally depressurized.

I turned the ignition to the on position and the pump kicked off at about 2750 psi.

It took about 4-5 seconds to reach that pressure.

From there the pressure slowly dissipated:

2500 psi in 15 seconds

2300 psi in 1 minute

2000 psi in 3 minutes

The pressure continued to slowly dissipate until it dropped to about 1850 psi where it held.

Again, 1 press on the pedal dropped it to 300 psi and 2 presses totally depressurized it.

I measured the difference in fluid level between pressurized and depressurized and there is only about 1/16" difference.

It seems to me that the pump is working fine, although it seems to get up to pressure very rapidly.

The pressure switch seems to work as well, shutting the pump off where it is supposed to. I couldn't test at what psi the pressure switch kicks the pump on because the system depressurizes so rapidly. My earlier tests showed the pump engaging with every press of the pedal, so I'm thinking that the switch is fine.

I'm thinking that the problem is with the accumulator; It seems as though there is no nitrogen in the bladder, which is why there is little difference in fluid levels. That would also seem to explain why the system pressurizes so quickly.

[Guest Mc_Reatta]

I concur. Accumulator is totally shot.

Don't remember anyone posting how long the system pressure holds after pump shut off before, so not sure if your leakage figures are normal or not. If I remember correctly, red light goes off around 2000psi, and switch should shut pump off around 2500psi which is what it is doing. Forget exactly when switch turns pump back on but it's around 1500 t0 1750psi, and if it gets down under that, red light comes back on.

So an accumulator should improve performance significantly and allow further investigation of issues of the internal MC seals, and brake lines and calipers if needed.

[Ronnie]

I received my pressure gauge today and ran some more tests. Here are my observations:

I first ran 12v directly to the pump and the pressure reached 3000 psi in 4-5 seconds.

1 press on the pedal and the pressure dropped all the way to 300 psi.

2 presses and the system was totally depressurized.

*A logical reason for the quick drop in pressure would be because the rear brake lines are full of air that easily compresses causing the fast pressure drop when you press the brake pedal and dump the pressurized fluid into them. You should bleed the brakes, especially the rear brakes, using the instructions on found on my website. Follow the instructions exactly as written.

I turned the ignition to the on position and the pump kicked off at about 2750 psi.

It took about 4-5 seconds to reach that pressure.

That sound normal after the system had already been pressurized once.

From there the pressure slowly dissipated:

2500 psi in 15 seconds

2300 psi in 1 minute

2000 psi in 3 minutes

The pressure continued to slowly dissipate until it dropped to about 1850 psi where it held.

Again, 1 press on the pedal dropped it to 300 psi and 2 presses totally depressurized it.

A slow drop in pressure should be normal over a period of time but if you had the key on the pump should have came on at some point to build pressure up again. If if doesn't the pressure switch could be bad.

I measured the difference in fluid level between pressurized and depressurized and there is only about 1/16" difference.

Normally that would mean you have a bad accumulator or the pump is not running.

It seems to me that the pump is working fine, although it seems to get up to pressure very rapidly.

The pressure switch seems to work as well, shutting the pump off where it is supposed to. I couldn't test at what psi the pressure switch kicks the pump on because the system depressurizes so rapidly. My earlier tests showed the pump engaging with every press of the pedal, so I'm thinking that the switch is fine.

You really need to know the pressure where the pressure switch starts the pump again.

I'm thinking that the problem is with the accumulator; It seems as though there is no nitrogen in the bladder, which is why there is little difference in fluid levels. That would also seem to explain why the system pressurizes so quickly.

I think you do have a bad accumulator but I don't think that is your only problem. I believe you still have air in the rear brakes.

Accumulators and other parts you need are in The Reatta Store.

[brantgab]

Thanks for the comments. I flushed the brake lines a couple of weeks ago - there is no air in the system. Didn't think to leave the ignition on and check pressure at which the pump comes back on. I'll rerun the tests when I replace the accumulator, and if anything seems out of line I'll hook the gauge back up. Thanks again.