Piston Slap: It's Not You, Drain Plug…it's Me?

Seth writes:

Dear Sajeev,

I have terrible luck with oil drain plugs. Of the last 4 oil changes I’ve done, only one has been successfully completed in a single day, because I can never get the drain plug loose.

The culprits in these comedies of errors are a 1999 Saab 9-3 and a 2006 Honda Pilot. The first time I came across the stuck plugs, the Saab was a recent acquisition, and the Pilot had had its last oil change done at a local mechanic’s shop down the road. Therefore, I assumed that an overzealous shop jock who got trigger happy with an air gun was to blame. In the process of getting the plugs out, I managed to mangle the Saab’s bad enough to require the purchase of a new one, and should have also bought a new plug for the Pilot, too (but didn’t). When I reinstalled them, I put them in fairly snugly, but with the mindset that I didn’t want to get myself into this mess again.

Fast forward to the next oil change, and the Saab’s plug came out easily. Too easily. In fact, the wrench wasn’t even necessary, which makes me think that I was too cautious when I installed it. The Pilot, on the other hand, is stuck solid and won’t budge.

Like anyone who’s had a few failed relationships, I’m starting to think that “it’s not them, it’s me.” So, what’s the secret to getting the plugs snug enough that they don’t work loose, but so that I can still get them off when the time for the next oil change comes?

A few bits of info you might find useful:

-I was recently defeated by an oxygen senor in the Pilot that I also couldn’t budge. After a month of wrenching on it with then engine hot, cold, and everywhere in between, as well as dousing it with multiple varieties of chemicals, I caved and had a shop change it. Therefore, the possibility exists that I’m just a weakling when it comes to these things.

Thanks,

Sajeev answers:

Is the oil change guy using air tools on your pan a valid concern? Granted they do have uber-leverage with the car in the air/underground work area and aren’t necessarily concerned about the next guy who might do the job on their back. The real concern is the condition of the threads on both the pan and the bolt. (And the condition of bolt’s washer/gasket thingie…)

For starters, new oil pan bolts are cheap insurance and readily available online or at a parts store. But–and I did this last night on a T-5 shift knob’s fussy threads–reconditioning threads is a great idea and free…once you buy the tools.

Using a thread chaser set (less aggressive cutting, more like cleaning) or a tap and die set (more aggressive cutting, be careful!) ensures your threads stay healthy and unstripped. Again, while that new oil pan bolt is cheap insurance, running a thread chaser on the pan can’t hurt.

My cars are old enough to need a tap and die set from your local Chinese tool import house. It’s paid for itself after 3 months, fixing radiator mounts, throttle body threads and two shift knobs. I also used it (gently!) like a thread chaser on a recently painted body part, freeing the metal threads of paint. I recommend these tools, practicing on a few throwaway parts before workin’ on your ride.

And no, I wouldn’t try this on seriously loaded/stressed parts like engine internals…research and listen to experts before you go crazy with a tap and die set.

BONUS! A Piston Slap Nugget of Wisdom:

Oh, about your oxygen sensor defeat: get a metal pipe (6+ inches long) from the hardware store and slide it over your wrench. This provides much of the leverage found in a breaker bar without paying for one. Wear gloves so the unfinished metal pipe won’t slice up your pretty hands: break the stuck bolt free, slide off the pipe and resume your normal wrenching to fully remove it.

[Image: Shutterstock user Ohms1999]

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.