Oil Pan Perfection

The symptom was clear: low oil pressure at all engine RPM’s. The modern small displacement alloy V-8 used a block-mounted oil pump making inspection easy, but clearances were within tolerance, not surprising for a medium-mileage engine with a history of regular oil and filter changes. What gives? The answer was surprisingly simple: a damaged oil pan. Dents are common in stamped-steel oil pans, and unless they generate cracks, are often harmless. In some cases, however, especially if the pickup is reinforced and hugs the pan interior, an even scrape can flatten the pan bottom enough to effectively close the pickup to oil flow. Even if oil pressure isn’t affected, aeration of the oil can result, leading to expensive failures at bearings or valve train. The simple solution is to pull the pan and pound it out. Like all hammer work, however, stone hands will make the problem worse, so a game plan is in order.

Inspect and then remove

Every tech knows that a pan drop can be a ten-minute breeze or a two cigarette knuckle-busting PITA, depending on the vehicle make and model. Start with a quick visual inspection. Does it leak? If the pan is cracked or the plug threads are stripped, you may be in for a new pan no matter what — but don’t order a new one just yet. First check for missing bolts. It’s better to know you need that oddball metric bolt now instead of at the end of the job when time pressure is a factor. If you’re removing engine mounts, which is common these days as cross members are tighter than ever, give them a look. If they’re cracked or broken, this is a good time for service. If the engine is slung securely, consider removing the bad mount along with the oil pan, then replacing it after the pan to buy extra maneuvering room when replacing pan bolts. With the pan off, check the pickup. This is why it pays to wait before ordering a new pan, because a dented pan can distort or damage the pickup. I replace any pickup that’s bent or distorted, even if it can be straightened on the bench. Why? They’re often brazed or silver soldered at the flange joint, which is a weak spot. Unless you prepared to do a little reinforcement brazing and inspect very carefully, swap in a new one along with the pan, as the oiling system isn’t a place to count pennies.

Ball-peen adjustment

If the pan is only lightly dented, it may be possible to pound out the dent, but common sense still needs to apply. If the interior is fully accessible, the best way is to use a sandbag for backup and hit the centre with a rubber mallet or wooden block and club hammer. Stretched sheet metal is thin and brittle, so the ideal fix is a single blow that restores the shape as much as possible. Don’t chase small creases with excessive hammer work. The metal is stretched, so get the floor off the pickup and stop while you’re ahead. Re-inspect for cracking and take a look at the flange. This is a good time to do a little tin bashing to bring down the extruded flanges typical of an over tightened pan. Ideally, use a wooden back up in a bench vise and a light hammer. Body hammers are ideal (planishing, not shrinking) and again, get it close but don’t spend hours chasing the perfect contour. Now wash out the pan thoroughly and replace as normal. I prefer to avoid silicones here, usually using “hi-tack” with a new gasket, held in place with strong thread through a few bolt holes in the corners. Finger tighten the pan bolts and then use long needle-nose pliers (I use long stainless surgical forceps, mainly because I got them cheap at a dollar store) to yank the threads. You don’t want them in the pan! I usually spritz the pan with a little rust paint just in case somebody peeks under there; that way it looks like someone’s worked on it.

New pans are often the best solution and are reasonably priced for popular applications, but if you have no choice but to bash your own, use as little brute force as possible, and keep your eyes open!