So is this issue grave...

[eidolon]

I cannot seem to find this issue occurring anyplace else in searches- The crankshaft in my 2001 C4 cab has quite a bit of horizontal play. I can see it move about a 16th of an inch inside the bell housing when pressing on the flywheel. This is causing a bit of a problem with my crank positioning sensor on deceleration (the engine dies when I step on the clutch). Decided to drop the tranny to check clutch and change my IMSB and RMS.

To much back and forth play in the crankshaft is giving me the creeps.... can that be repaired without a complete rebuild or engine replacement?

Edited December 9, 2011 by eidolon

[logray]

Did you remove the flywheel and try to move the crankshaft by hand to validate the play is in the crank and not the flywheel?

.0.0625" is a huge amount of play (21 times more than normal). I would be surprised if the engine is still running (it shouldn't be). I would validate those measurements with a good dial indicator on the crank before moving forward. And I wouldn't run the engine until you do so.

Normal radial play should be around .003" (less when there is oil pressure).

edit: the figures above are for radial play, for some reason I had this in my mind and misread the op's original post. What he is talking about is axial play (end play)... the issue is still very serious, end play carries different measurements and is controlled by the thrust shims as JFP notes below.

Edited December 11, 2011 by logray

[JFP in PA]

If the crank is moving that much along its axis, you have a thrust bearing issue, item #17 below:

If this bearing is failing, the engine has to come apart.

[logray]

And a complete engine teardown with new crankshaft and bearing carrier will set you back the cost of a replacement engine.

[eidolon]

I was afraid of this... I am just going to reassemble and drive it until completely fails, seeing how the prognosis is so dire for the engine anyway. Whats the worst that can happen? The engine fails. I am SOL anyway I slice it. The only good news here is that I know that my engine is failing so I have time to prepared for it eminent failure.

This will give me time to get my hands on a replacement engine to drop in.

You know what is really strange is, the engine is performing strong and there are no signs of anything in the oil (shavings from the failing bearing, etc.), This is incredibly bizarre.

[JFP in PA]

There is a very large difference: If you fix it now, the engine can be saved and go on for many years; if you don't, it could very quickly become a boat anchor requiring a much bigger expense to replace....

Edited December 9, 2011 by JFP in PA

[logray]

If the crank is really moving that much and the crankshaft journals are rubbing (wearing) on bare steel (once the top layer of bearing is worn through) the crankshaft is likely toast as no-one has oversize bearings or thrust washers. A used crankshaft might set you back $2-3k. If the damage is beyond the crankshaft in the bearing carrier, you are looking at another couple grand.

Complete engine tear down and rebuild (even without replacing bad parts) will set you back in the $14-18k range when done properly from a reputable source.

So... unless you are into rebuilding engines, you are likely better off sourcing a used engine. It looks like you have a line on one over on rennlist which sounds like an excellent buy from a reputable source.

Also, a few words on driving it until it blows up.

1.) It might be possible there could be collateral damage and the expense could be even greater replacing it after it blows up.

2.) Would you really want to be driving a time bomb knowing you might be stranded somewhere?

Edited December 9, 2011 by logray

[eidolon]

If the crank is really moving that much and the crankshaft journals are rubbing (wearing) on bare steel (once the top layer of bearing is worn through) the crankshaft is likely toast as no-one has oversize bearings or thrust washers. A used crankshaft might set you back $2-3k. If the damage is beyond the crankshaft in the bearing carrier, you are looking at another couple grand.

Complete engine tear down and rebuild (even without replacing bad parts) will set you back in the $14-18k range when done properly from a reputable source.

So... unless you are into rebuilding engines, you are likely better off sourcing a used engine. It looks like you have a line on one over on rennlist which sounds like an excellent buy from a reputable source.

Also, a few words on driving it until it blows up.

1.) It might be possible there could be collateral damage and the expense could be even greater replacing it after it blows up.

2.) Would you really want to be driving a time bomb knowing you might be stranded somewhere?

Yep, that the way I see it.... the engine is toast already, regardless if I try to rebuild it (which is more than just dropping in a replacement).

I think it will likely be ok until I drop in the new engine. I can't imagine it grenading itself any more than an IMSB failure.

[eidolon]

There is a very large difference: If you fix it now, the engine can be saved and go on for many years; if you don't, it could very quickly become a boat anchor requiring a much bigger expense to replace....

Thanks JFP, but it will be cheaper to drop in a replacement engine than to crack-open the block and rebuild.

[JFP in PA]

Your are correct; however, even with the bad thrust bearing issue, you currently have a viable core (read worth some serious money to an engine rebuilder); blow it up, you have nothing. I'd strongly think about getting a replacement while there is still some value to your current unit, which will help offset the replacement costs...........

[eidolon]

Your are correct; however, even with the bad thrust bearing issue, you currently have a viable core (read worth some serious money to an engine rebuilder); blow it up, you have nothing. I'd strongly think about getting a replacement while there is still some value to your current unit, which will help offset the replacement costs...........

Good point...

[wvicary]

Do you ride the clutch or keep your foot on the pedal while waiting at intersections? This will greatly reduce the operating life of the thrust brng.

[Q-Ship986]

Do you ride the clutch or keep your foot on the pedal while waiting at intersections? This will greatly reduce the operating life of the thrust brng.

I think you're thinking of the clutch release bearing, also known as the clutch throw-out bearing. The crankshaft 'thrust' bearing surface(s) diagnosed above as causing the play in the crank are different from the clutch release bearing that can deteriorate from holding down the clutch pedal too long. However, note that the parts shown above are for a GT3 M96 engine, a different case from the M96 variety in the OP's 2001 C4. FWIW. --Brian

[logray]

Hah good catch on the diagram! :)

Actually other errors too (which I edited to correct): I misread his original post and quoted radial play measurements when he reported problems with axial play... controlled by the thrust shims.

[wvicary]

If the operator keeps the clutch pedal pressed for long periods it will increase the wear on the crankshaft thrust brng.

[logray]

Indeed fellow North American! The thrust shims are not particularly happy with such vehicular operational behaviors!

http://forums.rennlist.com/rennforums/9089929-post13.html

[xmac]

Thanks logray. So is it part#24 "Thrust WASHER" or "Thrust Collar"? 99610112952

Amazing that an $11 part could be so critical. Doesit mean full engine teardown in this case?

[wvicary]

Complete tear down to replace thrust brngs.

[logray]

As mentioned, complete engine tear down. Yes, #24. Here are a few pictures of them.

from my engine...

from flat 6 innovations...