McLaren MP4-12C: DIY brake system overhaul

The McLaren MP4-12C is an amazing driver's vehicle. I've driven my 2012 all over California and loved every second. I've had it on track just a couple times, and it always impresses me. But I took it out for a few laps at Sonoma Raceway one day and I was getting very weird brake response. The brakes were not stopping with full power and were unsettling the car, dancing a bit left and right going into hard brake zones like Turn 7 and Turn 11. And if you've ever gone into Turn 11 at Sonoma at high speed, you know that the last thing you want is to feel unsure about the car's direction or stopping power. There's a pretty ominous wall in front of you as you approach at 120+ MPH.

I cut the day short at the track. Good thing, too. Taking off a wheel when I got home, I could see that the OEM brake rotors were more than a bit worn. More importantly, I could see that the pads had been wearing very unevenly... the top of the pad was thicker than the bottom, which meant the brake calipers were exerting uneven pressure. At least one of the caliper pistons was stuck or hindered.  It was time for a complete brake overhaul. I called the dealership: estimate was $18,000. Holy cow. New brake calipers, new rotors, new pads, full system flush. I decided I could do it myself for well under $4000. The brake calipers were the most expensive part, so I contacted the manufacturer of the OEM calipers (AP Racing), and they said they could rebuild the calipers to factory spec for $160 each. I found that Girodisc makes rotors for the 12C for about $700 per wheel. Plus pads for a reasonable price.  Yup, I could do it all myself for under $4K.

First thing to do was to get the car up on my Quickjack. This required the rail extenders because the jack points are spread fairly wide along the wheelbase. The extender rails for the quick jack also add height to the jack itself (because they are stacked on top of the base rail), so the jack was now too tall to slide under the car.  So, to get the car high enough to slide the jacks under it, I drove it up onto 4 small blocks of 2x4 wood placed forward of each tire. Up she went another 1.5 inches and that allowed the QuickJack to slide under and place the rubber blocks at the proper jack points. I bought all my components but the first thing I needed to get done was to send the calipers to AC Racing via their US partner Essex Parts).

The MP4-12C brakes are pretty easy to work on. First step is to make sure you have turned OFF the electronic parking brake so that when you work on the rears, they won't be in park mode (more on this later). The parking brake automatically engages when you turn off the car. You have to go through steps so that the brake does not come on when you turn off the car. This is key, or you will will not be able to remove the rear rotors (unless you do what I did, which is to hack into the parking brake with a battery and a couple wire leads later.... not easy). 

To remove the brake pads, you simply tap out the two retaining pins using a center punch. They are held in place by the spring clip, so it's easier if you take pressure off them by pushing inward on that flat metal retainer with the down arrow stamped in.

Once you remove the pins, you can use a caliper spreaders (or a large set of pliers and a soft cloth) to spread the pads and compressing the caliper pistons back into the rotor.

You can then gently work out the brake pad wear sensor which is held into its slot with a small pressure clip. Just work it back and forth to remove without breaking it. These can be re-used or can also be replaced, as I chose to do in this case.

With the rotors free of the pads, you an how use the proper Torx bit to remove the rotors.

Then it was time to remove the caliper itself, which is held on by two large bolts into the spindle. You have to disconnect the brake line, so have a catch can for fluid loss.

I removed the front calipers and prepared them to send to AP racing for rebuild. I was about to move to the rear but figured I'd put on the shiny new rotors from Girodisc on the front first. They are slightly larger in diameter (more surface area for heat dissipation) and, depending on your car and application, generally come with a spacer and longer single bolts to accommodate the larger diameter. Already looking better! 

Now it was time to remove the rear rotors and calipers. Ah, but here is where I discovered my parking brake error. The parking brake was fully engaged. I had no way of removing the calipers if the parking brake is engaged.  S&%T. The only way to disengage the parking brake is by first turning the car on (car must be running, not just be in accessory mode). But wait: I have disconnected the front brake lines and there is no pressure in the brake system. Damn. Which means the car will not let me start the engine (brake pedal myst be applied to hit the start button.  No car start, no brake disengage. No good. Hmmm, I called myself a few choice names, most of which I deserved.  Then I started to do some Google searching and I learned that you can zap the rear parking brake piston from a battery to engage and disengage. 

So I removed the battery from another car and hooked it up to a couple wires I had with alligator clips at each end. On the backside of the parking brake caliper I found the small wiring harness that plugs in there. I removed that and saw two leads. Depending on how you hook up your negative and positive leads, the piston in the caliper will engage tighter or it will loosen up. I tested it by hooking the clips to the caliper leads, then hitting a quick tap on the battery terminal.  I heard the electric parking brake make a noise and it presumably moved. The rotor didn't seem to be any looser, so I assumed I may be causing it to tighten. I switched the leads and did a couple test taps again. The rotor appeared to free up a bit so I surmised that I had the correct "direction". I tapped a couple more times lightly and noted my ability to now turn the rotor a bit. I tapped some more an the parking brake fully retracted.  Yay! Crisis averted. Although this little detour added a couple hours and lots of stress and swearing to my brake job. I started to wonder if $18K wasn't such a bad deal?

With the parking brake pad removed I could now remove the rotors, pads and rear calipers (no need to remove the smaller parking brake caliper because it wasn't being rebuilt). I repeated the same process from the front and soon had all four new rotors installed. 

Now it was just a waiting game while I mailed the calipers to AP Racing and waited for them to return. It took a bit, but eventually they came back, beautifully refurbished and ready to go. This alone saved me $9K in not having to buy new calipers from McLaren. AP painted them black again. I had considered a color change but thought I'd keep it stock. I sourced my own decals elsewhere to finalize the look.

 

Now it was just time to bleed the brakes. I put on my PowerBleeder, drained the old fluid out of the master cylinder with a turkey baster, filled the master back up with Motul 600 brake fluid, and started bleeding away.  Easy stuff if you have a good 11mm box/open/line wrench and a bleeder hose and catch-container.

When it was all done, it felt pretty good! Once I started the car, the brakes came nicely up to pressure after a few brake pumps and I managed not to go flying out the back of the garage with no brakes. Happy car, happy owner.  Ready for adventures again!

McLaren MP4-12C: DIY fix of the dreaded "cloudy headlight"

As a reminder, I've had my McLaren MP4-12C for about 6 years now. It's a 2012 that I bought in 2014. It has about 55,000 miles on it now. 

If you own one or have been around a few 12Cs, you have likely seen or heard about one issue that has come up in a number of cars: the sealed headlights had a tendency to develop a condensation-like cloudiness on the inside of the plastic headlight covers. It's actually a kind of mold or bacteria that is not easily removed, so the typical fix is to replace the headlight.  Go to the dealership and a pair of new headlights will cost you several thousand dollars. Alternatively, you can generally find used  headlights on EBAY for about $500 -$800 each. Plus installation. My local dealership quoted me about $2400 to remove the headlights, recondition then, re-seal them, and re-install them. So, I decided to do it myself, and followed the repair advice of a number of members on the car forum MclarenLife.com. As it turned out, I did the whole job in a matter of hours over a day or two and with less than $10 of materials. I thought I would share it here in case it is helpful for anyone else.  

The first step is to get the car up a bit, so it is easier to get underneath the exterior panels to remove the bumper. So before we get to the fix, just a word about using my QuickJack BL-5000SLX on the McLaren. I've used my 5000SLX primarily for simple and easy access on my Cayman S and my Shelby GT350R. In both cases, it's a perfect fit. For the McLaren, the lift points are spread farther apart (front-back distance). So I needed to get the extenders from QuickJack.

By adding the SLX Frame Extension from Quickjack (https://www.quickjack.com/slx-frame-extensions/), the overall length of the lift rails is six inches greater, allowing the proper reach to the factory lift points (just barely!). The lift points are indicated underneath the car by colored circles.

But no good deed goes unpunished, and no purchase goes perfectly, either. Now that the lift is long enough, the added height of the adapter makes it impossible to slide the jack underneath the car. Mostly for the front, as the rear still has enough clearance. This photo below shows the new height (and length) of the lift with the extensions. I knew it would be close, as the website and docmumentation for the QuickJack is spot-on for their measurements, but I was hopeful I could slide this under.  As it turns out, I CAN do so, but then I have no room to insert the rubber blocks that go between the lift and the car's lift points.

So, I resorted to the simplest solution... drive the car onto a couple of "ramps" up front.  OK, maybe that is a grandiose label for a couple of 1"x6" blocks of wood, cut with a small angle on the leading edge.  In any case, by driving the car's front wheels up onto these block, the front end is now high enough to slide the jack underneath.  Add a couple of right-sized rubber lifting blocks that come with the Quickjack, and the car is up safely in minutes.

OK, so now that it was up, on to the somewhat laborious and intimidating job of tearing apart the headlights. There is no small about of trepidation associated with removing body parts off an exotic car, but in the end, it really isn't that much different than the old days when I was 17 and tearing apart my 1972 Datsun 510. Of course, back then, if it didn't go back together, who really cared?

Removing the front bumper consists of removing the fender liners and the plastic covers underneath the front splitter/skid plate. I found a number of helpful websites and YouTube videos, but in the end, there's a bit of hunting around for the next bolt to remove. Wish I had more photos for you, but my hands were kinda full and I was busy swearing at inanimate objects ;-). About 45 minutes later, I had the bumper off and laying peacefully on a tire.

There are a couple of headlight bolts that are hard to get to if you haven't pulled the fender liners off, but you can get to them. I hope you don't have chubby hands.

Headlights are off. Here is what they looked like. Note the milky condensation looking stuff that clouds the top third of the headlight. Yes, it would be great if you could just shove a Q-tip like swab in there to wipe it out, but it isn't just moisture. That stuff takes a lot of work to get off the plastic.

So here was the  weird part... it is now time to bake these babies at 200 degrees for about 10 minutes. In the oven. In your kitchen. Don't let your spouse or chef/foodie roommate catch you doing this. 

After time baking in the oven, the seal and rubber around the plastic becomes softer and pliable and you can then use a series of screwdrivers to (carefully!) work around the latch-tabs and the rubber to separate the headlight cover. This takes time, and time isn't your friend because the darn rubber sealant is hardening as it cools. I used a few more choice words at about this point, and questioned my own sanity.

But hey, it all came apart. Here are a few more close-ups of that mold.

At this point, I used a couple bottles of Meguiar's PlastX Plastic cleaner and polish and a pointed wheel polishing attachment on my high-speed drill.  I couldn't use my larger car buffer vert week because of the small areas being buffed. You have to get in those crevices, and this takes an hour or more for each headlight. After the first few passes with PlastX, I used a polishing compound to complete the refurbishment. When I was done, I baked it again to soften the rubber and reassembled the headlights, using black silicone sealant to augment the existing sealant material, which had taken a beating from my work.

Back together and looking pretty much as good as new!!

Of course, whenever you reassemble, there is ALWAYS that one extra part. Luckily, I knew exactly where it came from and it was only about a 10-minute detour to take the fnder liner back off and gee this little guy back where he belonged.

I managed to complete this all in maybe 4-5 hours total, not including couple trips to the store and a long explanation to my lovely wife as to why I was cooking car parts in the kitchen.

Back in business and rear for a little track day fun at Sonoma Raceway, but that's another story!