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Dealing with pattern failures that are anything but

Saturday, December 1, 2018 - 08:00
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An expansion valve took care of that one. As an aside, the owner had, on a previous day dropped by a dealer shop when she was in another town for a quick check of the A/C and they told her she’d need a $1500 evaporator case replacement to take care of the no-cooling issue because, in their words, “the actuators aren’t communicating.”  I’m not sure what pocket to put that in, but she was glad she had opted against letting them do that!

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Mysterious bearings

Another one of my colleagues drives an old Sentra that had developed a nasty noise, and after we determined by doing some tire-swapping that it was a bearing noise, we went out of our way to make sure we got the right bearing – these can be really tricky sometimes (can I get a witness?), and this one was no exception. I told the owner that we might wind up having to replace both bearings and he gave us his blessing. Using the Chassis Ear® we thought we had it pinpointed as the one on the left front, (swerving seemed to point to that bearing too), but when we broke it down I could have a good look at those shiny balls and race, I could tell that we had misfired on that – Mr. Murphy is alive and well, you see. But we were at the point of no return, so we installed that bearing and drove it again – no change.

The only difference between the noisy bearing and the non-noisy one was the color of the grease – there was no visible wear on the balls or the race.

With that, we attacked the other bearing, which still didn’t show any brinelling or wear as we had supposed, but we did notice that the grease in that bearing was discolored – instead of a healthy cream color it was kind of brown, and even though the balls and races looked good, replacing that bearing eliminated the noise. We had no smoking gun, but we had a solid fix.  That always bugs me, because I like visual verification of that kind of thing. Granted, you don’t always get that with transmission or ring and pinion gears, but with bearings you usually see something. This time, not so much.

The Altima – A perfect storm

This one came to us with the story that a guy at a shop in another town had replaced the transaxle, but that after only two hours of driving around, the transaxle had started slipping and then stopped pulling and now the guy who had changed the transaxle was telling them it needed a flywheel. So they brought the car to us with a used flywheel they wanted installed. How tough or annoying could this one be?

This bushing was never intended to contain a spinning torque converter snout – subsequently, when the flywheel failed while driving, that’s exactly what it did for probably 2 hours – and the results are plain to see.
This flywheel failed in such a way that the engine was able to spin the bolt circle very nicely – this was the perfect storm for the torque converter and its bushing, since the flywheel was stationary all this time – as was the converter

We worried that CVT out of there to find that, although we had unbolted the torque converter, it stayed attached to the engine when the CVT was removed. Furthermore, it didn’t want to come off – at all. But it was rattling around loose. After using a big prybar and a hammer and whatever else it took, I managed to get the torque converter on the floor.  It was at that point that I discovered a very serious issue.

The flywheel had broken smoothly enough that the engine was spinning the now-separate center of it. The outside of the flywheel and the torque converter were both sitting still while the engine was spinning to beat the band, and the pilot bushing those Nissans have in the back of the crankshaft had been whirling on the pilot of that converter until the pilot had become red hot and had swelled to the point that the pilot bushing came out of the crankshaft when we pried the converter out of there. This was surprisingly annoying, and that wasn’t all.

On the left is a good bushing in place (this was the 2004 engine). On the right is the cavity the destroyed bushing came out of when the flywheel was pried off. Note the cracked and overheated flywheel.

This was ultra-nasty, because all the information I found was that the bushing in question is not obtainable apart from buying a replacement crankshaft. Granted, with the right dimensions, a machine shop could have made us one on a lathe, but machine shops are hard to find these days.

As it was, this customer got lucky. It just so happened that I had a defunct 2004 Altima powerplant sitting in the engine shop that had been swapped out because it was knocking, and I got the bushing out of that one. It was an annoying process, but with a high-speed cutter, we made it happen. The bushing was a perfect fit, and with a replacement torque converter and the CVT back in place, the Altima was good to go.

Far left is the bushing in its boss – we used a high-speed cutter to surgically remove it. Middle is the bushing – far right is the bushing being driven into the rear of the crank on the Altima.

The customer asked if the previous tech had done anything wrong to cause this. My answer was that he hadn’t, and that was that.  I told them about a transmission we had replaced in a four-wheel drive Expedition that came back a month later with a busted flywheel it’s always annoying but sometimes it happens.

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