When an oil change mistake leads to complications for all involved

June 1, 2019

There was a local repair shop that had an oil change go wrong on a 2011 Kia Optima with a 2.4 L engine (Figure 1). The shop mechanic had an easy task of simply replacing the oil filter and removing and reinstalling a drain plug to drain and refill the engine with oil. The oil filter was installed properly and the correct oil type and quantity was put in the engine but the drain plug was never secured with a wrench and only hand tightened. Somewhere in the thought process the mechanic forgot to tighten the plug with a wrench and allowed the vehicle to go down the road with a loose drain plug.

Figure 1

Over time and enough road vibration, the drain plug worked its way loose and the oil started to drain from the engine. The driver of the vehicle did notice the oil light come on but proceeded to drive to get to a public destination off the roadway. Some drivers would just pull over, shut the engine off and call for roadside assistance but there are others that will not, and this sealed the fate of this vehicle. The vehicle was driven too far on oil starvation and the engine seized.

Back at the shop

The car was towed back to the shop that serviced it to find out what happened to the vehicle. The shop owner was not a happy camper because he discovered that the drain plug was missing and all the oil drained out leaving behind a seized engine. He confronted his mechanic to educate him about why it is so important to always go over your service repairs and that he would now be partially responsible on some labor involved without pay. Hopefully, this would condition his mechanic to be more aware down the road. To keep operating costs down and not go through insurance, the shop mechanic was instructed to pull the engine so it could be sent to an engine shop for repairs.

Once the engine arrived at the engine shop, they pulled the oil pan to discover a damaged crankshaft and bearings. Luckily the cylinder walls were not scored and most of the damage was lower end. The engine shop recommended a replacement crankshaft, main bearings, rod bearings and an oil pump. The repair shop decided to go ahead with the repairs that would be less costly than purchasing a used engine.

After about 2 weeks, the engine repairs were completed and the repair shop drove there to pick up the engine. Once the engine arrived back at the shop, the mechanic was eager to get the engine back into the vehicle and out of his life. After a full day to install the engine, it fired up and ran. It did not crank over instantly but it did run without any noises or signs of upper engine issues. As the vehicle ran in the bay, the Check Engine light came on, so the mechanic hooked up a scan tool to retrieve any codes to see if he left anything unplugged or not fully seated in the install process.

Whose mistake is it?

The code he pulled was a P0336 for "Crank Position Sensor Circuit Range Performance" (Figure 2). The vehicle never had this issue before so maybe something happened in the engine repair process. The engine was running so the crankshaft sensor had to be working or maybe it had a glitch in it that the ECM did not like because the wiring to the sensor seemed okay. The shop did not have a scope so they were just using old school tactics and a scan tool to figure this issue out. The shop decided to replace the crankshaft sensor with a new one and when this did not work they put blame on the engine shop thinking that they did not set up the valve timing properly.

Figure 2

The repair shop sent the entire vehicle back to the engine shop to have them resolve the issue. The timing chain and gears were checked and everything seemed in order. It was at this point I was called by the engine shop to get a second opinion.

The REAL cause

Figure 3

When I arrived at the shop I was given the whole story of events and I decided the best place to start was to hook up my 8-trace scope and look at the Crank and Cam sensors to make sense of it all. I placed my Yellow lead on the Crank Sensor, Red lead on the Intake Cam Sensor and my Green lead on the Exhaust Cam Sensor (Figure 3).

The signal patterns seemed fine with good signal amplitude and no dropouts (Figure 4) but I needed a good known pattern to compare it to. If you don’t have a good known car to hook up to its always a good idea to head to the Internet to see if you can tap into someone’s waveform library and one great place is IATN if you have a membership to access information. I logged onto their site and sure enough I was able to find a Crank to Intake Cam Correlation waveform (Figure 5). The pattern seemed similar to the vehicle I was working on and the Crank to Intake Cam correlation was identical indicating a non-timing gear issue but what caught my eye was the Crankshaft pattern.

Figure 4
Figure 5

When I zoomed into my Crank pattern (Figure 6) I counted 57 teeth between the synch gaps with an extra open gap but the good known pattern did not have this extra open gap and showed 58 teeth between the synch gaps. This indicated that there might be an issue with the crankshaft that was installed in the engine. I asked the engine shop if they had another crankshaft for this car in their huge inventory and they were able to produce one (Figure 7). You could see that this crankshaft definitely had 58 teeth between the synch gaps incorporated into the Crank trigger wheel but with no extra gap.  It was now a wait and see once they removed the oil pan for inspection.

Figure 6
Figure 7

Later in the week I drove back to the engine shop to see what they found. Apparently, someone had dropped the crankshaft they installed and caused damage to one of the teeth on the trigger wheel (Figure 8). I was totally taken back by how someone could drop a crankshaft and not take the time to inspect it thoroughly for any damage they might have caused. The trigger wheel was not a solid gear but rather a thin plate with teeth on its exterior edge. When the crankshaft was dropped it literally bent one tooth inward towards the crankshaft and the crankshaft sensor was unable to create a consistent magnetic field once it crossed its path. This created the extra gap in the crankshaft pattern that the ECM was unhappy with. The P0336 was more of a performance code than it was a circuit code and a scope would be the only option to use to actually see what was going on.

Figure 8

Once the second new crankshaft was installed, the vehicle was test driven by the engine repair shop to make sure there were no other issues with the vehicle. They wanted to make sure there was Check Engine light coming on because the last thing they needed was another comeback to bite into any profits that were left. They stood behind their work and the engine shop had to eat the labor to not only pull the engine but also to dissemble the engine to replace the crankshaft a second time. This vehicle was not a money maker for anyone involved and it only started out as a simple oil change. The only thing that came out of all of this was a valuable lesson to be learned. The vehicle was finally delivered to the repair shop and after their final inspection it was delivered back to its owner who was inconvenienced long enough without a vehicle. The owner did not request a loaner so that was a good thing but you really need to unravel how this happens in our industry.

We are in such a great rush to beat the clock and get these cars in and out for the demands put on us from our customers. Then mix this with the constant distractions in our lives or in the shop. I have seen many people working in bays actually plugged into headphones while working and it just amazes me how they can tune themselves out by doing so. I have always promoted the 5-Sense Diagnostics of Hearing, Feeling, Seeing, Smelling and Tasting while working on cars. I’m not promoting tasting but I can tell you over the 43 years working on cars I know what a few fluids taste like. It’s helped in a few cases.

The vital other four senses are so crucial when working on and diagnosing cars. Use your eyes to look at vehicles and components for anything that’s not right that should be brought to attention. Use your hearing to hone in on any noises that may not seem normal that can alert you to a problem. Use your nose to smell for anything unusual like antifreeze leaks, burnt components, batteries overcharging or even a gas leaks. Use your hands or body to feel for that miss in the engine or for the proper latching of a simple connector. The most important of all is staying focused on what you’re doing so your mind is connected to the vehicle so we don’t forget to do a simple task like making sure we tightened a drain plug. I am sure that this story will hit home with many readers out there and my only hopes is that we put our phones down in the shop and adhere to the old rules of yesteryear.

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