14 November 2009

Insert Tab A into Slot B

Has a more dreaded instruction ever been written?

The brakes on the SCTruck went soft and the brake light was illuminated. The pedal would slowly drop to the floor. My first guess was "bad master cylinder". Which translates into "Master Cylinder and power booster" because the fluid tends to leak past the master cylinder and into the power booster which eats a hole in the diaphram. Anyway the whole package is about $200.

But a close inspection of the area around the booster and inside the pedal turned up not a trace of brake fluid. Hmmm... That's odd. The pedal slowly dropping to the floor means the fluid is going somewhere. The puddle formed on the garage floor at the left front. I beckoned for help from the rest of the SCCrew and the SCQueen answered. "Step on the brake - I need to find the leak."

She did and I did. A fine stream shot from the hose down to the caliper. In most cars that's not a big deal. They all have standard ends. You go down to the local parts purveyor and buy a similar length hose for $10 and all is well. But Nissan has a funky end and special bolt that brings the fluid down the center of the bolt. Ugg, probably a dealer only part. Instead of $10 today, it will probably be $60 and 6 weeks.

But the local import-specialty parts purveyor said "I have it in the warehouse. Will be here after 9:30am tomorrow". Today the installation was attempted. Felt like it seated OK but fluid leaked out at the mating face. Hmmm, maybe it's upside down. Nope, Still leaks.

Lets take a close look at the parts. First lets look at Slot B. This shows the bolt hole and slot. If you look close at the slot, there is a small 45 or 60 degree ramp at the bottom of the slot, apparently to precisely position the hose fitting. That means the tab width and distance from the face to the tab are the critical dimensions. If it's too wide or the corner is too close to the mating face, it won't seat correctly.

So now lets compare Tab-A on the original part (top) to the replacement (bottom). It might be obvious to the eye the distance from the mating surface (left side of picture) to the bottom of the tab is different. Less obvious, the tab is wider on the new part. Measured with a caliper, the mating face-bottom tab distance was closer by 20 thousandths and the width is 10 thou over. That explains the failure to seat the mating surface which allowed the fluid to leak.

Now this is a problem I can correct in a few minutes with a file. But dang it, the part should be right! I shouldn't have to modify a part to make it work. Besides, if I do a bunch of filing on the part and run into a different problem, they won't take it back.

The SCQueen suggested I call the parts purveyor. I explained that the part they sold me wouldn't seat. It appears the tab is ground to shape and sloppily done in this case. The parts-purveyor wants to make it right and will have another hose Monday AM. But he confirmed my suspicion that they would not be able to take back any modified part. So the choice is to modify the part or wait until Monday for a new part which may or may not be closer to the original. The downside is that the truck will be down for the weekend. Fortunately the truck is normally the "spare car"* so it doesn't have to be fixed tonight. We may end up back at the $60/6week dealer only option.

* As one that maintains their own vehicle, a spare car is the penultimate luxury. A spare car means "I don't have to fix this tonight" or "I don't have to ride my bike to the parts purveyor". In the past I have done both - worked until the wee hours of the AM because I needed to drive it to work tomorrow, and ridden a bicycle to buy parts. A garage to work in is the ultimate luxury!

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