The Answer for ALL engine failures??

[JohnnyT]

Posted on 6 club:

http://forum.mazda6club.com/index.php?showtopic=111995

Hey Watson, I've got it! What do you have Sir? I have THE reason for essentially all the engine failures. The key bit of info is the clutch pulsing. This ALSO explains why the BSD seems to have a longevity effect on the engine. Mazda has/had a problem with the thrust bearing clearances in their early series of 1.8 liter engines in the Miata as well. No BS in those motors, but the SAME type catastrophic engine failures resulting from excessive crankshaft end-play.

Ok, here's my theory and rationale:

The main cuplprit in the failures is the crankshaft thrust bearing. The thrust bearing is loaded heavily in the DISI turbo MZR from the BS angle-cut drive gears AND the HD clutch required to hold 280 lbft of torque against the AWD system and 3500 lb car. As such the thrust bearing wears, allowing excessive crankshaft end play and resulting side loads on the HEAVILY stressed connecting rods. A bit too much thrust bearing wear = too much side load on the con rod and Zoom, Zoom, BOOM, rod (pick one) and/or piston collapses from the off-center load and there you have it. Explains everything! Even why some new cars GO and some BLOW for no "apparent" reason.

I say EVERYONE concerned about their engine should check the crankshaft end-play per the FSM and see what they have. I don't have the reference right now, but it is a few thousandths of an inch. It COULD be another series of engines have the "incorrect" thrust bearing clearances at initial assembly.

ALL the failed engines to date can be checked for this clearance before the crankshaft is removed. I would wager that Mazda Japan already knows about this! The Miata crowd is very diverse and pursued their engine failures up through MNAO and got results. I should have checked mine when I had the pan off recently, but wasn't even thinking about it. I'll be checking it real soo though. It can be checked externally without removing the pan.

I also recommend jumpering the clutch switch so you can start the car WITHOUT pushing in the clutch. I have ALL my manual trans cars jumpered....

 

[mndsm]

Are you fucking serious? That's crankwalk! I know what that shit is, lost my DSM to it.

 

[JohnnyT]

I'm planning on getting the measurement for thrust clearance done at the dealer for my next oil change. I'd recommend everyone with an MS3/6 to do the same, just as a precaution. Definitely wouldn't hurt to print off some of the forum info. and bring it with. EVEN IF YOU HAVE A BONE STOCK CAR, DO THIS!!!

If you'd like to do it yourself:
Ok, I "found" the time to check my car last night and here's the how-to. Note, I assume that if you're doing this you have a clue, and a helper...

1) Lift front of car and remove main undertray, right front wheel and the plastic splash guard shielding the crankshaft pulley. See photo.

2) Using a short piece of wood( I used an 18" 1x2), gently, but firmly pry against the crankshaft bolt and the frame to push the crank fully to the rear (drivers side of car).

3) While holding gentle, but firm pressure against the crank bolt (with the wood pry bar), measure and record the distance from the crank pulley face to the timing cover machined surface near the center of the pulley. See photo. Mark the location of measurement on the pulley face for reference during any/all subsequent measurements. (My distance using the depth rod of the vernier caliper was 0.648"/16.42mm)

4) Remove pry bar and push in clutch pedal fully and hold. While holding clutch in, repeat measurement in step 3 using the reference mark to locate the caliper consistently. Record value. (My distance at this point was 0.660"/16.74mm) Subtract value recorded in step 3 from this value for the thrust clearance result. (My thrust clearance is 0.012"/0.32mm, pretty much the optimum value)