Changed front brakes and sensors today on 2011 base Cayman and abs and psm failure appeared on dash along with check engine light. Drove it a bit hoping it would fix itself, however no go. This is a first of any brake job for me trying to learn to maintain the vehicle myself. Any ideas of potential pitfalls? Thanks in advance!

 

Well one pitfall is to do something that causes an ABS and PSM failure. The check engine light might not be due to a real engine problem just indicating there is something wrong.

Most likely you disturbed a wheel speed sensor. Disconnected it, or damaged the wiring, or I believe in newer cars the speed sensor somehow gets its signal from the wheel bearing but regardless something was disturbed or perhaps when you replaced the sensors you disconnected the wrong connector.

If you could read the error codes -- you need a special Porsche diagnostics computer for this or possibly a Durametric can obtain the codes -- you might learn which specific wheel speed sensor is bad/not functioning and save you some time.

Otherwise you will have to get the car up in the air and remove each wheel and carefully check the wiring and connectors for the sensors you replaced and what I assume will be other wiring/connectors for the wheel speed sensors.

Regarding other pitfalls...

One pitfall is to avoid doing half a brake job.

Did the brakes on my 2002 Boxster a couple of times. Changed pads, rotors, wear sensors. Replaced other brake hardware the factory manual called out to be replaced. I forget now what hardware exactly. Porsche offered a "kit" that contained all the replacement hardware. The kit covered the brakes on one axle.

Some owners skip replacing the rest of the hardware. In most cases, at least immediately after the brake job, there are no issues. But we do not always get a long term report.

I like to point out brakes are a safety critical system and it is not worth it to me to skimp or cut corners on the brakes. I don't throw pads/rotors made of unobtanium on the car, the factory hardware is quite adequate for my use of my car, but I do like to use genuine factory hardware. Now over the years both the pads and rotors differed slightly. This arises because Porsche sources brake hardware from at least two OE companies. Except for the slight cosmetic differences the hardware delivered the same braking performance and component life.

I do a wheel at a time. I leave the other side untouched to have it to refer to if when I am putting the brake hardware back together I run into a question of what gets installed where and how.

I use a torque wrench to ensure the caliper bolts are properly tightened. I use or don't use any lube based on what the factory manual calls for.

Before I start I use a can of aerosol brake cleaner to remove as much grime from the brake hardware as I can. While some of the parts get replaced and cleaning the old hardware is a waste of time, primarily I want to remove the grime from the pistons and their dust boots. Also, I use this time to clean the brake wear sensor connector even though I have not disconnected this yet.

I'm careful to when installing the new rotor to ensure the surface of the rotor that mates to the surface of the hub, that these surfaces are clean and smooth so the rotor and hub go together and the rotor spins true with no radial or axial run out. (I avoid over tightening the one or two small flat head screws that are only there to hold the rotor in placed when the wheel is removed. Also, I put a bit a tiny bit of high temperature grease on the threads. Makes it much easier to remove these screws 50K or more miles (my 996 Turbo front brakes lasted around 140K miles) later when it is time to do the brakes again.

The brake wear sensor connector is exposed to some pretty severe/harsh conditions so I am as gentle with these connectors as I can be. Routing the brake wear sensor wiring is very important and doing the brakes the first time it might be a good idea to snap some pics of how things look, how the wiring is routed.

When I get the wheel back on and snugged up -- use a torque wrench and tighten the lug bolts in a star pattern -- I spin the wheel if possible to make sure it turns ok and there are not any scary noises

As you go from wheel to wheel you will have to push the pistons away from the rotor. Be sure you check the brake reservoir fluid level and remove -- use a turkey baster -- some fluid to keep it from overflowing. Since I'm replacing the pads/rotors I just use a large screwdriver and pry against the rotor. It doesn't take much force and you have to apply it for a bit as the pistons slowly are forced against fluid pressure back into the caliper.

After all the brakes are done it is a good idea to bleed the brakes to remove the old fluid. This should be done ever 2 years and if the car is equipped with a manual transmission the clutch hydraulic system should be flushed/bled at the same time.

Do not skimp on this fluid flush/bleed. I let this go just 2.5 years with my Boxster and the fluid deteriorated enough clutch action and as a result transmission shifting action was affected. Braking appeared to be unaffected but I was amazed at how the clutch action and shifting action improved after the fluid flush/bleed.

I use factory brake fluid. I see no reason to use any exotic brake fluid and some require a flush of the brake (and clutch) hydraulic system before it can be used, and once used one can't go back to the original fluid.

After the brake job, the fluid flush and bleed a road test is called for. You want to be cautious and stay out of traffic just in case the brakes manifest any signs of a problem.

After you have some suitable level of confidence the brakes are ok then bed in the brakes. What I found was on a stretch of road where traffic permitted it to accelerate the car up to highway speed then apply the brakes hard, short of tire lock up, ABS activation, but you want to really slow the car down. Bring the speed down from say 65mph to 30mph. Release the brakes and as quickly as you can, as the car can, accelerate back up to 65mph then repeat the braking action. Do this speed up/brake thing one more time, for a total of 3 times. What I noticed was the brake bit better each time but the improvement fell off that even though the first time I did a 4th accelerate/brake action there was no noticeable improvement, so I never did more than 3 again.

Do not bring the car to a stop from speed with the brakes hot! Be sure to after the bed in process and the brake hardware is hot you drive the car long enough to give the brakes plenty of time to cool down.

Remember that after you wash the car to drive it and use the brakes enough to thoroughly dry them or they'll rust up something fierce. The risk from this is when you drive the car again if you use the brakes hard, bring the car to a stop, while the rust is removed it can lead to pad material being left on the rotor surface where the hot pads and rotor make contact. Afterwards when you brake and the area of the rotor that has the uneven material deposition comes under the pad the brakes will "pulse". (This actually happened to me with my VW Golf TDi.) The only cure is to resurface the rotors or replace the rotors.

The above is not a full coverage of a Porsche (or any car) brake job but I tried to highlight some areas/things to be careful about.