2004 Spongy brakes after several bleedings

[boppa7]

Last week my wife complained that the brakes don't seem as strong as they used to on her CRV. While switching from snow tires back to summer tires on the weekend I decided to try the brakes for myself. They were bad... very soft and the pedal would travel to the floor while the vehicle was running. I almost couldn't get the ABS to engage. So my easter weekend was spent trying to get the brakes back into shape.

Here's a recap of what I've found, fixed and continue to have problems with...

First there is the bleeder screw on the right front caliper that was leaking fluid around the threads when I would open the bleeder. It wasn't a lot of fluid but enough for me to buy a new bleeder screw and install it. No more leaking around the threads.

Next is the fluid itself. The bottom of the master cylinder had some really ugly looking black gunk in it. I decided to replace the fluid and when sucking the fluid from the MC I could only get down so far with the end of the hose. So when I sucked the fluid down to the "MIN" mark there was still some black fluid at the bottom. Seems to me that the only ways to get it out would be to bleed it through the lines or remove the MC. I chose to bleed it through as I have never removed/installed an MC before. Is there another option? Should I remove the MC?

When replacing the fluid I started on the LF then moved through RF, RR and LR as outlined in the bleeding section service manual. I assume that bleeding and fluid replacement should follow the same pattern.

The LF seemed to have endless air bubbles as did the RR. The RR also had a lot of gunk getting pushed out.

After satisfying myself that the fluid had been flushed using a full litre/quart of new dot 3 Penzoil fluid I decided to try them out.

With the vehicle off I pumped several times and the pedal was high and firm. I then held the pedal down and started the car only to feel the pedal travel right to the floor. It was still very soft. I tried pumping the pedal with the car on and again it would travel to the floor.

So I'm now thinking about three possible causes.

1. I didn't get all of the bad fluid out of the lines when doing the flush/fill. Should it take more than one bottle of fluid for a flush/fill? Should I change the order of the wheels?

2. The brake booster is faulty. In my Haynes manual it suggests two tests for the booster. First press the pedal and start the car... the pedal should go down slightly. Mine goes down all the way. Second is to start the engine and after two minutes, stop it and pump the brakes to confirm that they get firmer and higher with each pump. This worked as expected. Could it really be the booster?

3. The ABS system has air in it. Again from the Haynes book I read "On models equipped with ABS it is possible for air to become trapped in the anti-lock brake system hydrolic control unit, so, if the pedal continues to feel spongy after repeated bleedings or the BRAKE or ANTI-LOCK light stays on, have the vehicle towed to a dealer service department or other qualified shop to be bled with the aid of a scan tool". From what I've read on these forums I should be able to address this by activating the ABS from a few hard stops. Is that correct or should I be towing the car to the dealer for the scan tool treatment?

If there are any suggestions or ideas I would be grateful.

Jason

[mike99992000]

Hi,

I'm not an expert on cars, but I do have a lot of experience with motorcycles. The brake fluid hoses may have expanded, and that usually contributes to spongy brakes on motorcycles, it's a quick fix, you change stock brake hoses to steel braided hoses. Not sure if you can do that in cars though.

[Honda Tech]

So I'm now thinking about three possible causes.

4th possible cause - master cylinder.

FWIW, a faulty Brake Power Booster would not cause a brake condition of:

"very soft and the pedal would travel to the floor while the vehicle was running"

Cycling the ABS solenoids while bleeding the brakes is more of a GM thing, rather than a Honda thing.

That said, I don't know that I would want to be driving a vehicle around on public roads trying to trigger ABS events in a vehicle that has sub-standard brake operation to begin with.

If one is reduced to guessing at a diagnosis on a critical safety system on a motor vehicle, perhaps the best course would be to suck it up and seek professional assistance first hand, rather than over the internet?

[thud105]

After satisfying myself that the fluid had been flushed using a full litre/quart of new dot 3 Penzoil fluid I decided to try them out.

Jason

First off, welcome to the forum. I noticed you used Penzoil brake fluid, you want to stick with genuine Honda DOT 3; Honda is particular about their fluids (transmission, differential, etc.)

I've had a master cylinder go on my CR-V and another vehicle, the symptoms were almost exactly as you describe. So I think it's a lock your MC needs to be replaced, that's my "over the internet" guess anyways Good luck.

[boppa7]

I'm not an expert on cars, but I do have a lot of experience with motorcycles. The brake fluid hoses may have expanded, and that usually contributes to spongy brakes on motorcycles, it's a quick fix, you change stock brake hoses to steel braided hoses. Not sure if you can do that in cars though.

While I agree that steel hoses may help, I'm reluctant to spend the money given that the hoses I have seem to be in good shape. But thanks for the idea.

If one is reduced to guessing at a diagnosis on a critical safety system on a motor vehicle, perhaps the best course would be to suck it up and seek professional assistance first hand, rather than over the internet?

But does it not make sense to spend a little time and money on the DIY route first? I've been doing brake work on my trucks and cars for many years with great success and the internet advice I've received over that time has been pretty damn good ;-) The vehicle is presently sitting on jack stands in the garage and will stay there until I'm satisfied that it is safe to drive... or it will get towed to a service bay for professional treatment. In the meantime, thanks for replying and trying to help.

I noticed you used Penzoil brake fluid, you want to stick with genuine Honda DOT 3; Honda is particular about their fluids (transmission, differential, etc.)

I actually did research this quite a bit and my conclusion was that dot 3 is dot 3 so the Honda brand is not critical. For ATF and Differential fluids however I use the (expensive) Honda products.

I've had a master cylinder go on my CR-V and another vehicle, the symptoms were almost exactly as you describe. So I think it's a lock your MC needs to be replaced.

Thanks... can't believe I didn't consider that. Is there any way to test the MC directly before replacing it?

[motoguy128]

Is there any way to test the MC directly before replacing it?

I blieve the simpliest way is witheh engine off and in park, you should be able to press on the brake and hold it there without it sinking to the floor. You may have ot pump it a couple times, but after that it should remain firm. If it goes to the floor, you either have a leak somewhere, or the master cylinder is bypassing fluid.

Remember, the master cylinder is generating pressure in the lines. If it's not maintaining pressure when pressed, then it's either pushing out fluid somewhere, or fluid is going past the master cylinder.

One way I sued to get the last few micro bubbles out of the brakes lines in my motorcycles was to squeeze the brake levler and clamp it in place lightly with a hose clamp over night. The bubbles would rise to the master cylinder (the high point in the system) and you could bleed them at that point. I think the pourpose of squeezign the lever was to push the pistons all the way out, whcih would allow some trapped air bubbles to more easily escape the calipers.


It think you might be able to rebuild the master cylinder rather than replace it. I thouhgt the pistons had rings or seals on them that wear over time.

[boppa7]

I blieve the simpliest way is witheh engine off and in park, you should be able to press on the brake and hold it there without it sinking to the floor. You may have ot pump it a couple times, but after that it should remain firm. If it goes to the floor, you either have a leak somewhere, or the master cylinder is bypassing fluid.

Remember, the master cylinder is generating pressure in the lines. If it's not maintaining pressure when pressed, then it's either pushing out fluid somewhere, or fluid is going past the master cylinder.

Hmmm... this is puzzling me. When the engine was off I could pump the brakes and get a very firm pedal. I'm a big guy and I was putting some pretty good pressure on the pedal and it didn't move. I'll confirm again tonight but if firmness with the engine off is a test of the MC then I'm thinking the MC may be ok.

My problem is that as soon as the engine is started, the pedal travels completely to the floor without a lot of effort. What components affect brake pressure while the engine is on? The booster? The ABS system?

[thud105]

Hmmm... this is puzzling me. When the engine was off I could pump the brakes and get a very firm pedal. I'm a big guy and I was putting some pretty good pressure on the pedal and it didn't move. I'll confirm again tonight but if firmness with the engine off is a test of the MC then I'm thinking the MC may be ok.

My problem is that as soon as the engine is started, the pedal travels completely to the floor without a lot of effort. What components affect brake pressure while the engine is on? The booster? The ABS system?

When the engine is off there is no vacuum going to the power booster, the pedal will be much harder to press. I'd think the engine would have to be on for an accurate test.

[Honda Tech]

I have never removed/installed an MC before.

I've been doing brake work on my trucks and cars for many years with great success

If you choose to replace the master cylinder yourself, will you:

1. purchase, rent or borrow the tool for measuring the pushrod adjustment between the brake booster and master cylinder?
2. study the situation and fabricate your own tool?
3. just bolt the new master cylinder up and not worry about the adjustment?

[boppa7]

If you choose to replace the master cylinder yourself, will you:

1. purchase, rent or borrow the tool for measuring the pushrod adjustment between the brake booster and master cylinder?
2. study the situation and fabricate your own tool?
3. just bolt the new master cylinder up and not worry about the adjustment?

More great advice from the internet. Thanks Honda Tech ;-)

I think I'll take option number 2. I've managed to find a pretty interesting approach to the adjustment that doesn't require buying a special, single purpose tool for >$100. http://www.tegger.com/hondafaq/maste...djustment.html. Is this what you had in mind regarding fabrication of a tool or are there other approaches you know about?

That site also contains a pretty good description of how MC's fail and my situation seems to fit the bill. Based on what I've read, it seems my bleeding may be the culprit in that I was sending the pedal right to the floor during bleeding which aligns with reason 3 on this page.

I'm ordering a new MC tomorrow and will report back once I get started.