the car is idling about 800 rpm. when i depress the clutch, the rpm drops to about 400 rpm, and sometimes stalls. the engine was just fully rebuilt, but i'm wonding if this is a symptom of the throwout bearing being bad.i'd hate to pull the tranny after just installing the engine. i just need to know that's the issue before tearing it apart, or if it is something else.

 

What a situation. Is it straining when the idle drops? Weird. PLS come back and let us know what has happened.

 

Just to rule out something bad, do this check...

Engine running, idling in neutral.
Clutch engaged (that means pedal NOT pressed down).
Watch the front pulley closely as you disengage the clutch (press down the pedal).

Does the pulley move slightly away from the engine block? The force of the throw-out bearing against the clutch might move the crankshaft. That would indicate too much clearance at the thrust bearing of the crank.

 

interesting... the pully is moving slightly, about 0.010 Isn't that w/i acceptable limits(.004-.014)? or should it be completely solid when mounted? i just placed new thrust bearings in it, and visually inspected the crank for wear on the trust bearing surface. i wonder if the thrust bearings i got are bad (or the wrong size)?

 

i pulled the oil pan and mounted a travel indicator on the engine itself measuring against the flywheel. i tried against the crank pully bolt, but i was getting erronious readings from moving the engine on the rubber mounts. i measured .007 total movement no matter how hard i pryed. this is a static measurement of course. the pully movement i saw with the engine running is probably the entire engine moving slightly on the rubber mounts when viewed beside the wheel well.
my next guess it that my TOB is seized causing the crank to be pressed against the thrust bearings while dragging the rpm down.

 

Sounds like the end play is OK (0.007" is within the acceptable range). You got the range (.004-.014) from a reputable source?

That leaves the throw-out bearing as the problem, unless you can find evidence of something rubbing where it isn't supposed to. What about flywheel rubbing against the end of the block? (I guess that would make ugly noises)

You pulled the oil pan? See anything suspicious around the thrust bearing? Not real sure what to look for; maybe evidence that the thrust bearing isn't getting proper oil flow??

 

the .004-.014 is from the chilton manual in crank play measurements. everything looks immaculate under the oil pan. I bought a clutch kit, i'll see if that has any effect. I'm going to play around the crank a little more before sealing it up and dropping the tranny. the only other idea is that possibly the (oiler) is clogged for the thrust bearings; if that's how they get oil. maybe pik-n-pull should be on my agenda for looking into oil flow details without dismantling mine.

 

See if there's something in the DIY section thread about on-line manuals. Those seem to be the "official" Helm book so if there's one for near your year it might be more detailed than a Chilton book.

Otherwise, I can't think of anything else to do inside your engine.

 

we never figured this one out. #4 crank bearing melted into the block; didn't spin, just melted. 1-3 are fine. i tossed the engine and built another. it's running fine now.

 

Thanks for coming back.