“A 2015 Mini Cooper. Engine bay might be a bit tight, but there’s no rust, so this job will be easy!” I told my naive self before agreeing to fix my friend’s engine mount. His dealer had quoted him a huge figure for the job and I couldn’t stand by and watch him part with all that cash, not when we could easily do it ourselves for cheap! But oh how wrong I was. The Mini now sits stranded in a garage in Washington D.C. because I screwed up royally.
Ever since the high-stakes Holy Grail Jeep Grand Cherokee trip I made back in December, I’ve been taking a break from wrenching and working on some personal goals (namely discovering cool cars in southeast Asia). But when my good friend Jeb asked for advice about a quote he got from his dealership, I dusted off the old wrench, and headed to D.C. where I had to go anyway to track down a separate story.
On the menu for the Mini was a new cabin air filter, replacement spark plugs, freshly-squeezed-from-the-bottle motor oil, clean brake fluid, and—the big one—a non-leaky engine mount.
I’d done a bit of googling, and learned that swapping the motor mount looked fairly trivial—we just had to remove one of the headlights, unbolt some trim, support the motor, and wiggle the old mount out, so I wasn’t even slightly worried. Which is why when yesterday ended like this, I was a bit bummed:
I say only “a bit” bummed, because I’ve been wrenching long enough to know that pretty much any wrenching job has the ability to turn into an NOAA-certified shitstorm in short order, but I was really hoping that my two-month wrenching hiatus would end in an easy victory.
At first, everything seemed to be going swimmingly. None of the car had any corrosion, so every bolt came out with ease, and despite the compact front-wheel drive, transverse engine layout, accessing various under-hood components wasn’t horribly difficult.
Jeb and I were on the fast-track to having big checks in our W columns when disaster struck. No matter what we did, one of the two bolts holding the engine mount to the body would not thread properly. What’s worse is that we didn’t realise how bad it was until we’d cranked the thing into the body, removed the bolt, and glanced at the copious metal shavings on the threads.
Normally, I start my bolts by hand to prevent this sort of thing, but there was a piece of difficult-to-remove plastic trim pushing against the side of the bolt. Jeb and I thought this was the source of the resistance to rotation, but it turns out, it was the dreaded phenomenon known as the cross-thread. Now, every time we insert the bolt—and we’ve tried this 100 times—it binds up. And looking inside, it’s clear that we’ve really screwed those threads up pretty badly.
This is a big deal, because the engine mount—which literally holds the 2.0-litre turbocharged motor to the car—is held to the body of the vehicle by only two 12-millimetre bolts. If the fastener shown in the top right of the photo above isn’t doing its job, the motor will flop all over the place, so this bolt absolutely has hold the motor mount in place. It’s critical to the operation of the car.
After over six hours of wrenching, Jeb and I had to give up and leave the car in his in-laws’ garage overnight, where it now sits without one of its motor mounts, and with a floor jack supporting the engine from below. Since last night, I have been tossing and turning, agonising about how I’m going to solve this issue.
There’s no way to get to the hole—which goes into the vehicle’s suspension strut tower—from the back side, which means if I wanted to insert the bolt or a thread chaser from the other direction to clean/align the threads or, worst case, install a nut and washer back there, I can’t.
What makes things more tricky is that there’s no room to drill the hole out and throw in a helicoil (a threaded insert that would provide new threads that are the same dimensions as the current ones, meaning I could use the factory bolt meant for that engine mount).
So really, I have only one hope of fixing the dastardly hole shown in the top left of the photo above: I have to use a thread restorer (essentially a tap), and pray that I can spin it into the hole, and fix what’s left of the threads to an extent that allows the bolted connection to reach the 74 lb-ft torque spec.
I have had success with a thread restorer kit before (I’ve also had terrible luck with one before, when I accidentally used one of the dies as a nut, and had to undo a bunch of work to get it back out—clearly, I make lots of mistakes while wrenching) and looking at the reviews of the one I plan to rent for free from AutoZone, I am relieved to know I’m not the only dumbass who leaning on this tool to solve a critical motor mount problem:
If this doesn’t work, I’m not really sure what I’m going to do. I can try to find a compact, right-angle drill to make a new hole, and then tap new threads and use a larger bolt (or I can use a helicoil), but I think the area that I’m working with its just too tight.
So there’s going to be a lot of pressure not to screw up this thread restoration operation.