Last saturday when driving normally, my pedal felt a little bit squishy....thinking I popped a brake line (felt this feeling before in another car) I immediately pulled into my driveway and checked under the car. No leaks. I then checked the brake fluid reservoir and it was still full.

So I brought the car back to the guy i bought it from he said he'll bleed the brakes and it should be good. While driving it back from him I noticed the problem hasn't been solved. Basically what's happening is sometimes when I step on the pedal the brakes react normally, other times the pedal drops about 50-75% (Squishy) with no reaction and then I have to pump them again to fully come to a stop.

One thing I did notice today when driving it back from the dealer was when I would let the pedal travel farther than the 50-70% mark the seatbelts would tighten (safety feature?). The car was recently in the dealer for an oil change and an inspection (After i bought it to make sure everything was good) and outside of dirty filters he said the brake and power steering fluid was cruddy. Could the dirty fluid be the culprit behind this?

A few posts below yours, please see Bicsintegra "Forum to the rescue"
How were your brakes bled? If air is trapped in the ABS valving, the old method of pumping brakes to bleed may be ineffective.

Old fluid that has accumulated moisture can boil off at a lower temperature. This could cause the sensation you are experiencing.
This can occur when brakes are hot & fluid is contaminated, but I cannot be sure this is happening in your case. I would inspect the brake lines carefully, you could have one that is expanding (swelling) when things heat up.
Does this only occur while brakes or hot, or under heavy usage?

Sounds like a goofy brake booster to me. Here's how you can test it:
- Sit in the car with the engine turned off.
- Push the brake pedal fully and release fully.
- Repeat.
Does it get progressively firmer?

EdBwoy wrote:Sounds like a goofy brake booster to me. Here's how you can test it:
- Sit in the car with the engine turned off.
- Push the brake pedal fully and release fully.
- Repeat.
Does it get progressively firmer?

If it does?
Is it supposed to?

steve_c wrote:A few posts below yours, please see Bicsintegra "Forum to the rescue"
How were your brakes bled? If air is trapped in the ABS valving, the old method of pumping brakes to bleed may be ineffective.

Old fluid that has accumulated moisture can boil off at a lower temperature. This could cause the sensation you are experiencing.
This can occur when brakes are hot & fluid is contaminated, but I cannot be sure this is happening in your case. I would inspect the brake lines carefully, you could have one that is expanding (swelling) when things heat up.
Does this only occur while brakes or hot, or under heavy usage?

I'm assuming it was bled the regular way....something interesting happened today when driving to work. The weather was relatively cool mid 50s low 60s and the brake was actually acting normal for like 10 mins then it started again

EdBwoy wrote:Sounds like a goofy brake booster to me. Here's how you can test it:
- Sit in the car with the engine turned off.
- Push the brake pedal fully and release fully.
- Repeat.
Does it get progressively firmer?

Did this and the brake pedal doesn't actually hold at all it just slowly goes down to the floor regardless of pumps

bgreen wrote:

EdBwoy wrote:Sounds like a goofy brake booster to me. Here's how you can test it:
- Sit in the car with the engine turned off.
- Push the brake pedal fully and release fully.
- Repeat.
Does it get progressively firmer?

Did this and the brake pedal doesn't actually hold at all it just slowly goes down to the floor regardless of pumps

Actually it does get firmer and firmer as I repeat presses but once again if I hold pressure on brake pedal it eventually just lowers

Look at your master cylinder. What color is the brake fluid? It should be clear to a tint of yellow at most.
You said someone told you the brake fluid was cruddy looking. If it was bled properly, it should look clear & not dark.

From the test you performed, the results tell me you might have a spongy brake condition, and a PROPER brake fluid flush & bleed is where I would start if it were my car. A leaking seal within the master cylinder could cause the condition also, but usually you would see fluid dripping from behind the booster (check the inside of your floorboard where the brake rod attaches to the booster) or from the bottom of the booster itself (in the eng. compt.). You did mention there were no signs of leaks however.

What color is your fluid?

My fluid looking from the top with the cap off looks yellowish, but when you look at the whole reservoir from the side it is a dark bronzeish im going to go with the full on flush when I bring the car in for its airbag recall...and hopefully that solves it.

you most likely have air in the line or moisture, trust me bleed the brakes with a pump and completely flush the system it is the only way to get it done right.

bicsintegra wrote:you most likely have air in the line or moisture, trust me bleed the brakes with a pump and completely flush the system it is the only way to get it done right.

After talking to a guy from the stealership since the brakes weren't pressure bled by the seller, even if he did a legit bleed it wouldn't of been effective. Gonna pony up the money for the a brake flush next week

How much is the stealership charging for a flush?

bgreen wrote:

bicsintegra wrote:you most likely have air in the line or moisture, trust me bleed the brakes with a pump and completely flush the system it is the only way to get it done right.

After talking to a guy from the stealership since the brakes weren't pressure bled by the seller, even if he did a legit bleed it wouldn't of been effective. Gonna pony up the money for the a brake flush next week

the pump is about 60 dollars you can do it by yourself and it takes maybe 20 minutes when the car is lifted and the wheels are off. the stealership will charge atleast 90 dollars.

Wow.....I'm amazed at the lack of understanding how brake systems work. Your brakes didn't need bleeding. It's a sealed system. Although, they likely do now that someone opened the system. Bleeding is to get air bubbles out. Except that if you have no leaks there is no way for air to get in. That should have been ruled out immediately. Your symptoms point to a faulty master cylinder. Although on these cars it could just as likely be something electronic. Start with the master cylinder.

just did both front and rear pads on my 2009 M35x.
I had bought the full BrakeMotive kit like so many others a while ago. Only the pads needed replacement so I'll keep the new rotors for another day and probably paint them when I can. I've been doing brakes for years on many different cars. This was my first brake job on this car. Couldn't be easier. I started with the great info How To brake replacement provided by Ilya. Since I was only doing the pads it made the job even easier. Of course I started with the pass rear which is farthest from the MC. Loosening both 14 mm bolts and only removing the top bolt allow the caliper to swing DOWN w/o any strain on the brake hose. Simple pad replacement, clean, grease etc. I had a Motive product brake bleeder I used for years with all my SAABs. I bought a Ford 3 tab adapter to adapt the bleeder to Infiniti. (good investment as my daughter has a Q50). I just fill the MC reservoir with fluid, attach the Bleeder and pump it up to 10psi. (avoids cleanup of fluid in the bleeder bottle). I then go back to the wheel and bleed (rear is 8mm) until flushed and clear fluid. I always flush BEFORE I push the piston back. I then remove the bleeder so that when I push the piston back I'm not working against the pressure. I then go to the driver rear and do the same process.
The front is a similar process except I removed the bottom 14mm bolt and swing the caliper up to accommodate the hose limitation. The bleeder is 10mm instead of 8mm on the rear.
My intent in writing this is to encourage those who haven't done brakes before to give it a try. Its really very straight forward. Simple way to save money (dealer is typically around $300 per axle by the time you add everything up. They do turn the rotors but if my brake pedal doesn't modulate(warped rotor indication) when I press it, I leave the rotors alone. Turning the rotors unnecessarily just removes more mass from them thus they'll be more susceptible to warping in the future. Even if you buy pads from the dealer you're saving an easy $200 plus per axle.
Took me about 45 minutes per axle by the time I got all my tools/equipment ready.
I then follow the pad brake-in process that others have provided.
Hope this helps.

Came upon this as I was looking for the name of the bleeder kit people were using.
I have always had success with the old school manual bleed, but with about 6 cars to bleed by the end of the year. I need a pedal pushing partner that won't get tired or bored.

Anyway, Bgreen was there any solution to your issue?

I use this one - it works great:

https://www.amazon.com/gp/product/B009X ... UTF8&psc=1

EdBwoy wrote: ↑

Fri Sep 08, 2017 8:12 am

Came upon this as I was looking for the name of the bleeder kit people were using.
I have always had success with the old school manual bleed, but with about 6 cars to bleed by the end of the year. I need a pedal pushing partner that won't get tired or bored.

Bleeders are broken down into 2 camps, vacuum & pressure.
I use a vacuum bleeder (see link below). An air compressor is required to use it, it is not a manual pump system.
I have been told on certain applications, a vacuum bleeder is not as effective as a pressure bleeder because certain ABS systems incorporate check valves that make vacuum bleeders ineffective.
I have not run across this as of yet, so I cannot say if it is true or not.
I can say folks who use either system are happy with what they went with, as I am.
The unit Kmiles linked to seems like a great inexpensive vacuum bleeder.
The MityVac unit I use was much more expensive. They come in a few kits, varying by accessories offered. The flow control switch (the black upside down U shaped trigger that is bolted to the handle) is a variable flow control, so you can vary the amount of vacuum applied. It stays in the position you put it at, so it is hands free as you work the bleeder screw.
The unit is extremely well built.

https://www.amazon.com/Mityvac-MV6835-V ... 06XRAHTYV9

I don't know if OP ever got this fixed but it sounds more like a master cyllinder issue to me.

I have the Motive pressure bleeder, but I have yet to use it. I hate dealing with brake fluid and my local oil change place does a flush of the whole system for $60, so I just pay to have it done. I'm lazy.

The OP said in the end it was the master cylinder. Clearly, we have a good chunk of knowledge on this forum.

Thanks to everybody who takes their time to contribute and help other members.
For posterity, I like to come back and update threads when I get a chance, so I will update the title.

Yes. EdBwoy is correct. Thanks for updating this thread.