The pilot bearing froze, solid. The outer race held fast and the IO of the inner race was just starting to machine the input shaft of the transmission. The throw out bearing, clutch disk and pressure plate look great but, it's all getting replaced.
Turns out both motor mounts were bad, one was really dead. Added to the list. The alternator belt has always slipped just a bit when started on a cool morning. Turns out the mounting bolt hat stripped the treads from the mounting ear, looking for a longer bolt with a nut.
The crank seal had never been replaced, the cam belt had. The residual goo on the inside of the crank pulley was telling me that something might not be well inside the motor and upon the removal of the first rod cap the path to be taken was now set.
The machinist could not believe that this thing had not spun the rods. So for the cost of an $8 dollar part, I'm saving a fortune. Ish!
In reply to MrJoshua:
His car is busted and he's giving us the list of items that need fixing.
Yes, broken. But more like warn out. The motor did not vent a rod. So I only get to replace parts that ware out.
My take on this is the crank seal failed, the oil pressure forced the oil all over the front of my motor, at the rate of a quart every 7 to 800 miles starving the rod bearings just enough to just about be catastrophic.
So, if your Miata motor looks like it would be more at home in something British, change the rod bearings. When your are replacing the crank seal.
Before your lucky enough to have the pilot bearing seas.
Those front crank seals may look good at 60k, but by 120k they're leaking. Change them at the same time as the timing belt. Note that it's not a pressurized seal, so a loss of the front crank seal will not affect the oil pressure at the rod bearings.
I've never seen one dump a quart in 700 miles, though.
No way a quart/800 miles leak from the front seal killed the bearings. A car engine oil pump flows several gallons per minute. EDIT: Keith beat me to it with better data, but even if it were a pressurized seal (like the rear main), even with it gone entirely, assuming the sump never went dry, the bearing wouldn't care.
RedGT
Reader
6/6/16 2:50 p.m.
In reply to Keith Tanner:
Ooh, Ooh! Me!
I had a red '90 that would use that much out the front seal. Looked like an oil tanker underneath. By the time I dumped a can of ATP-205 in as a last ditch effort, it was letting out a steady drip at idle. (And that E36 M3 worked. Cut back to about a quart per 1500. Sold it that way and the car ran another year after that before the buyer finally replaced the front seal)
