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2004 SRX V8
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147 Posts
Discussion Starter · #1 ·
Ok, I am getting close with my used SRX. I have done a lot of work on it and it is driving very well. One irritating problems remains. The braking is weak. The brake pedal feels soft, goes pretty far towards the floor, and requires more pressure than I think it should to stop the car. So far, I have replaced these parts:
1. front rotors
2. front calipers (leaking bleeder screws)
3. front pads
4. rear rotors
5. rear pads

The brakes were bleed and now feel almost exactly the same as they did before all the new parts. I see no brake fluid leaks. Only thing I can think of is either the brake booster or master cylinder. Any thoughts?
 

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11 CTS-V Sedan, 07 Corvette Convertible
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237 Posts
Could try replacing the brake fluid, it could be contaminated with water especially since you had leaking bleeders. Use the bleeder tool to suck out all the fluid out of the reservior, and then add new brake fluid. Then bleed each line until it looks new and add more fluid.
 

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2008 SRX AWD V-6
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177 Posts
You might consider checking the flex lines going to the pistons. Several TBSS owners were switching to stainless braided lines to
help with a spongy brake pedal. I've noticed the excessive pedal travel on my '08 SRX too, and plan to address it when I resurface the rotors and replace the pads.
 

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2004 SRX V8
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147 Posts
Discussion Starter · #4 ·
I did replace the brake fluid. Sucked out the old fluid from the reservoir, then bled from the passenger rear working my way to the driver front.

How would replacing the flex brake line to the caliper help with spongy brakes? Very curious about this.
 

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2008 SRX AWD V-6
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177 Posts
I'll confess that I haven't had my SRX long enough to even pull a wheel. So I don't know if they are using the rubberized flex lines that were OE on the Trailblazer SS's or not.
Several SS owners installed custom made SS braided lines and insisted that
it addressed the spongy pedal issue.
This was one of he mods I had intended to do before I lost my truck in a flood in March.
 

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2010 CTS AWD Wagon 2010 BMW X5 35D 2008 GL320
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2,623 Posts
I would think you have air in there hiding on you, do another bleed and follow the book to make sure the ABS unit gets done right.

SS lines are nice but will not fix a pedal that is going to the floor as you can't have that much flex in the rubber lines, go for air first.
 

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2004 SRX V6 RW
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76 Posts
I'll second what conedoctor said, you have air in the brake system. " The brake pedal feels soft, goes pretty far towards the floor".
Those are classic symtoms of air in the brake system.
 

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2008 SRX AWD V-6
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177 Posts
I guess I missed the part where he said the pedal "went to the floor".
I consider a brake pedal to be spongy if it drops more than an inch and a half.
On the trailblazers, that would have been on spec providing you are running ceramic pads.
The guys who switched to the braided lines didn't want even the 1.5 inches of pedal play.
 

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2010 CTS AWD Wagon 2010 BMW X5 35D 2008 GL320
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2,623 Posts
Lets assume the pedal assembley is not worn and adjusted correcty.

Lets not blurr pedal movement and feel, the brakes also adjust themselves as the pads wear and for the life of me I can't understand why ceramic pads would change how far the pedal moves?

Initial torque of a pad may change how the brakes "feel" but should not change anything else in the movement.
 

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2008 SRX AWD V-6
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177 Posts
Last shot at this. When I do my brakes I will be using ceramic pads. Those of you who wish to use stock pads fell free to do so.
Ceramic pads actually provide greater stopping power as they heat up which is why those of us who favor them, use them.
When one takes into consideration that there are 4 flex hoses in the system each can and does contribute to brake pedal travel
as the brakes are applied. Stainless steel braided lines help to alleviate this issue.
 

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11 CTS-V Sedan, 07 Corvette Convertible
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237 Posts
Flexible lines are made of a rubbery compound to allow them to move around and connect to the wheel's brake assembly which move around due to steering and suspension travel. If the lines get worn the diameter of the line can expand when pressure is applied to the brakes (and the brake fluid). This increase in volume can cause increased pedal travel (in order to supply the same amount of pressure to the brake pads) and a spongy feel to the brakes. Air (and water) in the brake fluid causes simlar problems because the pedal pressure is compressing the air (or water) and not compressing the caliper pistons. Brake fluid is a non-compressible fluid, meaning that when it is compressed (or pressurized) it does not change density or volume. Air and water are both compressible. Air much more so, so even a small amount of air can cause big problems (and if enough air is present in the system will cause the brakes to not work at all), while water will cause a spongyness similar to bad flexible lines.
 

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2010 CTS AWD Wagon 2010 BMW X5 35D 2008 GL320
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Stock pads are lame, hands down but they should still work fine.

Ceramic pads provide better stopping power than maybe stock pads but they do not brake as well as many performance compunds, they do not dust as much but I found they would fade faster.

The flex hoses are like 12" long and yes they will flex but not much, the rubber on the outside is just to protect the hose, it will have an extruded tube with braided re enforcment then covered in rubber or maybe EPDM. We are talking a bit of flex here guys not huge amounts, in the morning I will go take one of our hosed up to 10,000psi and see if it expands much just for fun but I don't think it will.

Water will compress about 1/2% per 1000psi, not huge. Now if it is full of water it will boil lower but I doubt it is the problem.

I would do this.

Flush and bleed with new unopened fluid, bleed the master cylinder also as air can get stuck in there.
If it does not work test the pressure at the master cylinder and make sure you are getting correct pressure.
 

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2004 SRX V8
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147 Posts
Discussion Starter · #14 ·
Stock pads are lame, hands down but they should still work fine.

Ceramic pads provide better stopping power than maybe stock pads but they do not brake as well as many performance compunds, they do not dust as much but I found they would fade faster.

The flex hoses are like 12" long and yes they will flex but not much, the rubber on the outside is just to protect the hose, it will have an extruded tube with braided re enforcment then covered in rubber or maybe EPDM. We are talking a bit of flex here guys not huge amounts, in the morning I will go take one of our hosed up to 10,000psi and see if it expands much just for fun but I don't think it will.

Water will compress about 1/2% per 1000psi, not huge. Now if it is full of water it will boil lower but I doubt it is the problem.

I would do this.

Flush and bleed with new unopened fluid, bleed the master cylinder also as air can get stuck in there.
If it does not work test the pressure at the master cylinder and make sure you are getting correct pressure.
I'll start with a flush and bleed. Hopefully the second time will be the charm. I'll try to do it tomorrow. The new pads are ceramic (Napa). The thing I find strange about this is that with all the changes I made, Pads, rotors, front calipers, flush, and bleed, the brakes feel exactly the same as they did before. The car stops, but you have to use way more pressure than you should. Even my wife, who doesn't notice anything, feels the brakes are weak and require too much pressure. Maybe there is some air still in the system.
 

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2010 CTS AWD Wagon 2010 BMW X5 35D 2008 GL320
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High effort may be as you said a booster or master cylinder issue just not as common, may also be the check valve on the booster so your not holding vaccuum.
 

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2010 CTS AWD Wagon 2010 BMW X5 35D 2008 GL320
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I chased a brake problem on my Talon for years and could not fix it to save my life, one corner they would work the next nothing then half way throught he brake application they would work, drove me nuts.

I changed everything and I mean everything and they still sucked so I feel your pain. I ended up bending the brake pedal arm end the end of a long straight trying to slow down enough to make the corner, front brakes caught fire and I went throught the corner sideways. So anyways I hate when brakes don't work.

I enjoyed the Hawk ceramic pads on our A6 but when I did get it out on the road course they really started to fade early but I think I was asking too much from them, they were great on the street.
 

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2004 SRX V8
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147 Posts
Discussion Starter · #17 ·
Well, first off, thanks to everyone for comments and suggestions. I need all the help I can get :yup:. I bleed the system this morning. I had my wife help this time instead of doing a one man bleed. I also followed the pattern listed in the shop manual, right rear, left front, left rear, then right front. I got no air out of three sides. The front right gave me a couple bubbles and that was it.

I test drove the car and the brakes may feel just a little better. Still not right since I may just want it to feel better.

A question for all of you. When the car is running and I press the brake pedal, I hear a "woosh" sound coming from behind the brake pedal. Is this normal for the SRX? I don't get this sound from any of my other cars.
 

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05 srx awd v6 (gone), '07 GXP, 2010 li'l red wagon 3.6
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The vacuum booster is a dual diaphragm design. Could one have failed?
 

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Base 2007 Escalade EXT, 04 Cadillac SRX V8
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271 Posts
Josh12, I got the same symptoms with a spongy pedal and the "woosh" sound. Braking power is not good at all. Please let us know what you find out. The other day when I started the car and applied pressure to the pedal after the car had been sitting for a long while, the brakepedal went all the way to the floor and gave lots of that "woosh" sound. I have enough fluid in the reservoir. Any suggestions from out there?
 

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2004 SRX V8
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Discussion Starter · #20 ·
Well, some interesting news (listen up JD2004). I decided to do a "brake booster" test as listed in the shop manual. The brakes failed the vacuum booster test but what the brakes did was not listed with a solution. This test requires you to start the car with the brake pedal depressed. If the pedal sinks "slightly", the vacuum booster is working. My pedal sank pretty close to the floor.

I decided to check the "check valve" on the brake booster vacuum hose. I grabbed the vacuum hose to check if there were any holes in it. Well guess what, it wasn't connect to the engine. I pulled on the hose and before I knew it, I had the end of hose in my hand.

The hose connects to the back of the engine on the manifold. I couldn't see back there so I just felt around till I found what seemed to be a protrusion with a hole in the center. The hose fits on this but there is no clamp to hold it on. I just pushed in on as tight as possible, started the car and drove around the block. The brakes seemed perfect. I am taking it now for a 40 mile round trip drive and will update you on how it is.
 
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