Maybe someone can help me out here.........

I have a 2003 coupe with almost 200,000 miles on it. I keep having an issue with the brakes locking up? It happened last year and I had all new rears done along with cross drilled rotors. Happened again and my mechanic replaced everything under warranty but now it is the front locking up???? I don’t know if this is maybe an ABS issue? Car shakes terribly over about 70 and can smell brakes burning. Getting very frustrated here because just want to figure this out. My mechanic just dropped the motor last week to fix oil leak (rear main seal) so just trying to keep her running here in best shape possible

Any ideas here would be greatly appreciated

 

Sticking calipers maybe? Did your mechanic check them?

 

Yeah if it's cooking the brakes with the pedal released it's probably a jammed up / gunked up caliper slide pin. A proper brake job includes cleaning/lube the slide pins.

 

The rear calipers were just replaced under warranty when he fixed the oil leak because they were sticking (again) but now it is definitely the front and I don't think he checked them

Making me think something in ABS system is giving signal for them to randomly lock up? I am going to replace front calipers and rotors but just afraid new ones will get screwed up if problem is due to ABS

 

Since you are going through all this, you may want to do a system flush and put in new fluid. Brake fluid has the tendency to absorb moisture. Moisture is water that boils creating steam that expands rapidly and not allowing the system to operate as it should. Moisture also causes rust to form on the caliper cylinder wall, causing the caliper piston to stick.

 

It's a fairly simple system, ABS sensors on each tire, steering angle sensor on the spiral cable (steering wheel), yaw sensor under the center console, ABS relay next to the brake ABS valve block.

However the ABS system does NOT ENGAGE YOUR BRAKES, the only pressure on the brake pads comes FROM YOUR FOOT ON THE BRAKES.

The ABS motor just causes a rapid pulsing on the valve block to divert pressure off a wheel that it detects is not rotating. There is a corresponding light on the dash saying SLIP. If there is an error with the system you will get both VDC/SLIP lights on all the time and the ABS system will be disabled.

You will also feel it in the pedal when you brake, the best I can describe it on the G35 is a sort of "grinding feeling coming from the pedal".

If the ABS system is not triggered, no lights, no brake pedal grinding feeling then the ABS is NOT on.

What I think happened is you had a front rotor slide pin that has not been regularly maintained (every time the brakes are replaced you need to grease the slide pins), the pin has corroded and the caliper is sticking against the rotor, this generates a significant amount of heat and will quickly warp the rotor and ruin the brake pad. The calipers don't need to be replaced unless they are leaking fluid (rebuilding is generally better than replacing), the slide pin hole needs to be thoroughly cleaned and regreased, you probably also need front pads (have to replace them both, not just one corner) and you probably have a warped rotor that needs replaced as well.

Have a conversation with your mechanic about how he typically does a brake job, don't mention greasing the slide pins, if he doesn't tell you he greases the slide pin then he doesn't know how to properly do a brake job and you would need to find a reputable mechanic that knows what they're doing. There are a LOT of shady/bad mechanics out there that cut corners and/or just don't know how to PROPERLY do repair work on various systems. If this mechanic wasn't the last guy to service the front brakes then it's not his fault the slide pins failed.

Brembo front rebuild kit https://www.z1motorsports.com/front-...nt-p-5451.html

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Non-brembo front rebuild kit https://www.z1motorsports.com/front-...35-p-9185.html
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Brembo rear rebuild kit https://www.z1motorsports.com/rear-b...ar-p-5484.html

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Non-brembo rear rebuild kit https://www.z1motorsports.com/rear-b...35-p-9186.html

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That vendor also has the Nissan part numbers listed on the page in case you want to buy the stuff at your local Nissan / Infiniti

I strongly recommend rebuilding the brake master cylinder anytime you do the brakes, it's just a matter of time until that component fails as well.

Luxury sports cars aren't cheap to maintain if you are paying shop rates for a mechanic to service the vehicle. Rebuilding components is a lot cheaper (and better than cheap aftermarket) in the long run because they will typically last a lot longer.

 

I haven't been getting the slip light - that only happens from my crazy maneuvers when I push her limits (admittedly I drive like a nut)

I will take your advice - I know I need new rotors anyway so might as well do the re-builds

Let's hope for the best