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2G Random crankwalk

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Connor Wilke

Probationary Member
28
2
Mar 15, 2019
Hinsdale, Illinois
The question I'm asking is about crankwalk, and yes I know ow there a other threads out there but nothing like what I'm experiencing. So what I'm asking is where to look for trouble shooting more.

With that being said, I have a 98 gst. The motor is freshly rebuilt and has only idled and never driven.

The current issue I'm having is with crankwalk. The motor was assembled in a clean and clear space, bearing measurements within spec and everything torqued correctly. No oil leaks or anything of the sort. Motor has great oil pressure at idle with (5w-30) oil. However the crankwalk I'm experiencing is confusing me because like the typical symptoms of pushing the clutch in and rpm drops but it's very random and no l consistency with the rpm drop to the point where I don't know how to replicate it, it has a mind of its own.
So the question I'm looking for is if this is something anyone else has experienced with (crankwalk) coming and going randomly. Would running a 10w-40 help with possibly getting more oil pressure to the thrusts to prevent it?
 
I'll be dropping the pan tonight
Take a pry bar and see if there is any movement of the crank, see if the balancer moves or the flywheel. be careful what youre prying off of
I'll be dropping pan tonight to do that actually. I have been doing oil changes hoping it was the break in oil contaminating everything but still keep coming out glittery and the stranger thing is that the oil will be glittery on one change and then the next oil change it comes out clear. So it almost keeps flip flopping with being glittery and not
 
dont need to pull the pan, try this first and see if there is any movement. plus remember its a freshly rebuilt motor so youll have some glitter and such with everything being broken in

so if you clutch in and the idle drops but the car feels fine i bet you have an air leak somewhere, like an exhaust leak or a vacuum leak. check balancer for movement then do a boost leak test. if all checks out then well go from there
 
so if you clutch in and the idle drops but the car feels fine i bet you have an air leak somewhere, like an exhaust leak or a vacuum leak. check balancer for movement then do a boost leak test. if all checks out then well go from there
Cars on Speed density though. That would have nothing to do with pressing clutch in I assumed. Like I know for 110% that I don't have a leak. Vacuum at idle was around -12 Vacuum with 280 cams. I forgot already but I believe endless
Play need to be with .002-.005???
 
im on speed density myself, you can still experience it. it means its after your map sensor. ( injectors to head, intake manifold gasket, vacuum ports on back of intake, etc )

do a boost leak test, its always step zero.

i dont remember crank spec but go in and check it out, keep an eye it isnt the actual balancer moving aroundf but the actual crank
 
A couple things are at question here:

what is your crank endplay? You can test this with the engine off. Tap the crank bolt with a rubber deadblow to move the crankshaft towards the transmission. Affix a dial indicator to probe against the crank bolt and depress the clutch. Record the maximum value.
You can pry on the crankbut just remember any prying will move the motor against or towards the dial indicator, depending on pry direction, and cause false readings. If you don't have a dial indicator, use feeler gauges.

It's possible that you're not receiving enough oil flow and pressure across the thrust surface of the bearing that wants to press into the crank, even though everything could be in spec, measurement wise, where you checked. A partially clogged oil port or a malformed bearing surface could be directing oil away from that thrust surface. Your crank thrust surface, I assume, was checked as well as the width of the thrust bearing side-to-side. Endplay should be checked before or during assembly, definitely before you button up the pan. Misaligned top and bottom #3 shells will prevent proper lubrication to both.

How much is the drop? If it's random, your bearing is likely not grinding into the crank. Unfortunately, checking for #3 shell alignment is .. well, you can imagine. You could try to reseat them upside down, but see where your endplay is first.

Endplay max OE spec is .002 to .0071; death of the crank is regarded as above 0.009

For what it's worth, my 97 with a 6bolt had a random ~30 or 40 rpm drop that was basically only witnessable via link and a numerical value. when the engine came apart, the thrust width of the bearings were still 1.144", which is OE spec from the documentation I have available to me. Same as the ACL replacements. That engine had a few thousand kilometers on it by the time I chose to rebuild it cuz i need moar. Crank thrust surfaces, and all journal surfaces on the whole, looked great.
 
A couple things are at question here:

what is your crank endplay? You can test this with the engine off. Tap the crank bolt with a rubber deadblow to move the crankshaft towards the transmission. Affix a dial indicator to probe against the crank bolt and depress the clutch. Record the maximum value.
You can pry on the crankbut just remember any prying will move the motor against or towards the dial indicator, depending on pry direction, and cause false readings. If you don't have a dial indicator, use feeler gauges.

It's possible that you're not receiving enough oil flow and pressure across the thrust surface of the bearing that wants to press into the crank, even though everything could be in spec, measurement wise, where you checked. A partially clogged oil port or a malformed bearing surface could be directing oil away from that thrust surface. Your crank thrust surface, I assume, was checked as well as the width of the thrust bearing side-to-side. Endplay should be checked before or during assembly, definitely before you button up the pan. Misaligned top and bottom #3 shells will prevent proper lubrication to both.

How much is the drop? If it's random, your bearing is likely not grinding into the crank. Unfortunately, checking for #3 shell alignment is .. well, you can imagine. You could try to reseat them upside down, but see where your endplay is first.

Endplay max OE spec is .002 to .0071; death of the crank is regarded as above 0.009

So I actually don't have a dial indicator for the crank but the feeler gage idea is genius. I'll give that a try and hope to the dsm God's that the play isn't too bad. Now if and probably when I'm out of spec for the end play, I will more than likely have to drop the pan to see if the crank is damaged or if the bearing is just wearing down?
 
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You can't use a feeler gauge without dropping the pan. You keep inserting various gauge thicknessess between the bearing and crank thrust surfaces on the transmission side of the bearing when you pry the crank towards the trans, in either increasing or decreasing numbers, until you find the one that doesn't fit. Then you know your endplay is between the value that doesn't fit and the value that does.

Note that testing for endplay doesn't gaurantee that your bearing halves are not misaligned. It all depends on their saddle fitment. Some are so tight they can't move side to side, others are a little looser and need to be smacked laterally from the trans side. That's the surface that matters, not smacking it from the damper.
 
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The question I'm asking is about crankwalk, and yes I know ow there a other threads out there but nothing like what I'm experiencing. So what I'm asking is where to look for trouble shooting more.

With that being said, I have a 98 gst. The motor is freshly rebuilt and has only idled and never driven.

The current issue I'm having is with crankwalk. The motor was assembled in a clean and clear space, bearing measurements within spec and everything torqued correctly. No oil leaks or anything of the sort. Motor has great oil pressure at idle with (5w-30) oil. However the crankwalk I'm experiencing is confusing me because like the typical symptoms of pushing the clutch in and rpm drops but it's very random and no l consistency with the rpm drop to the point where I don't know how to replicate it, it has a mind of its own.
So the question I'm looking for is if this is something anyone else has experienced with (crankwalk) coming and going randomly. Would running a 10w-40 help with possibly getting more oil pressure to the thrusts to prevent it?
You never know until physically check the side to side play. You don't see the rpm drop symptom by crankwalk just right after the initial startup. If the crankshaft is really walking already, then obviously the cause is assembly error, the block side was already shot, you cranked too much w/ clutch pedal pressed in at the initial startup or started up dry etc etc.

Did you rebuild the engine by yourself? Why did you rebuild the engine?

Would running a 10w-40 help with possibly getting more oil pressure to the thrusts to prevent it?
see if the crank is damaged or if the bearing is just wearing down?
I don't want to discourage you but if the RPM drop is caused by crankwalk, it means you already have the crank and the bearings contacted metal to metal. Most likely the crank is already damaged. If that's the case, any bandaid won't work, rebuilding the engine properly would be the only way to fix.
 
You never know until physically check the side to side play. You don't see the rpm drop symptom by crankwalk just right after the initial startup. If the crankshaft is really walking already, then obviously the cause is assembly error, the block side was already shot, you cranked too much w/ clutch pedal pressed in at the initial startup or started up dry etc etc.

Did you rebuild the engine by yourself? Why did you rebuild the engine?



I don't want to discourage you but if the RPM drop is caused by crankwalk, it means you already have the crank and the bearings contacted metal to metal. Most likely the crank is already damaged. If that's the case, any bandaid won't work, rebuilding the engine properly would be the only way to fix.
Motor has always been built by me and rebuild was done because I melted pistons with bad fuel from gas station previously. Car run on e85 only and turned out the pump gave me 88 unleaded after talking with the tenant.

Ive built about 12 motors or more. So before i started the car and had it run for the first time I prime the oil pump with engine assembly grease and also removed spark plug wires and fuel injectors. Then crank motor over to prime oil and make sure it gets to the head. I also have clutch wire mod so I never have to press clutch in to try and help prevent the potential of crankwalk on start ups.

I took a video on my iPhone that showed the tiniest of movement when pressing clutch in, and when i say tiniest (i mean so small i had to watch the video about 5 time and decided to just pull it. so I'll be taking the motor out again in the next few day to see how bad the damage actually is.
 
I took a video on my iPhone that showed the tiniest of movement when pressing clutch in, and when i say tiniest (i mean so small i had to watch the video about 5 time and decided to just pull it. so I'll be taking the motor out again in the next few day to see how bad the damage actually is.
If the end play is within the spec, you can barely recognize it visually, even by eyes directly. So if you can see some movement in the video even tiny, most likely it is occurring. Sorry but yes you would probably need to drop the engine to rebuild. The sooner, the better. Hope the crank survives.
But just replacing the bearings or/and the crank may cause the same sooner or later. You have to figure out the cause and rebuild properly.

I actually don't have a dial indicator for the crank but the feeler gage idea is genius.
Ive built about 12 motors or more.
I recommend to get a dial indicator. It would help you to build the engine more precisely. It's not only for the crank end play.
 
I had a fairly random 30-50rpm drop with the clutch on a factory heavy flywheel and Stage 1 Exedy clutch (so, not a LOT of clamping force) and my endplay was just measured by the shop as ~0.0052 and the clutch was already put through thousands of kilometers before I got the car . That was without the clutch switch disabled as well.
The #3 bearings had some dry start appearance but still measured out 1.144" and the crank thrust was smooth.

Not saying you have no issue here but it's not as simple as blaming crankwalk. Check your endplay with a dial indicator, they're pretty cheap and useful for measuring all sorts of things, even your feeler gauges :p
 
It is pretty easy to check by using a magnetic base dial indicator from Harbor Freight and mounting it up front, zero it and have someone press on the clutch while you observe the dial. It should not move more than spec and always come back to zero when done.
It's a quick, easy, cheap test is all I am implying.
 
It is as easy and cheap as Marty says, you don't need a degree to do it.. but don't do what I did and mount the indicator to the subframe and then pry the crank with a bar.
That's a sure fire 1 way road to Dumbassville.

I shouldn't be spreading info about my dummery but I'm also not asking people to trust me with their lives here. I'm only human. But I'm working on that.
 
Mistakes teach us lessons. You made me smile! ROFL
 
I'll be taking the motor out again in the next few day to see how bad the damage actually is.
Your decision is right that you will inspect visually. From the above facts that you mentioned and apart if this is really at the beginning of crankwalk or not, the only way to completely get rid of your anxiety of crankwalk would be by disassembling and visually/physically inspect.
I don't usually recommend to drop the oil pan and remove the main or rod cap if possible, since it would slightly affect the crush height if it's after getting some heat cycle. But I think it would be better than running the risk of losing crank and block, or living in fear of crankwalk with a new engine.

Actually there is not much point to check the end play by a dial indicator right now. Because that would show you only how much end play you have for now. In your case, that can not get rid of your anxiety of crankwalk even if the end play is within the spec, as you are not sure how much end play you exactly had before the initial startup since you didn't measure it by a dial indicator. So you won't be able to know for sure if that amount of end play you see would be with or without wear. (But anyways you should get a dial indicator if you build engines and check the end play after reassembling)

The point is, the engine is new and it has only some idle time after the initial startup as you mentioned. It's not after driving 100,000 miles. So it shouldn't have any apparent wear.
In case if this is really at the very beginning of crankwalk, there may still be a chance to save the crank, but if you would check the end play now and if it would show the end play is ok and if you decide to keep running the engine by believing it, you may possibly finish the crank. I am sure that's the case you want to avoid most.

If there is sign of crankwalk, damage/wear on bearings, then something is not right. You have to inspect everything. And find and fix the cause, and rebuild properly.

Mercifully if there is no sign of crankwalk, no damage/no wear on bearings, then that's a good news. You would lose you time to inspect but you would get peace of mind instead. You should note how much end play you have for the future reference and put back everything properly and go on.
 
rpm drop is not necessarily a sign of crank walk. the engine still has a slight load on it when in neutral, you cant just spin the input shaft like a skateboard wheel when its in neutral. cold idle on these cars isnt the best test for a solid idle

id suggest cutting open the oil filter first before pulling the motor, pulling the pan to actually inspect and measure the walk.

I mean its never a bad idea to check everything before it contaminates everything as it goes bad but it doesnt seem to that point yet

also you say motor was just rebuilt, did you put a new oil pump on and have the block hot tanked to clean out any prior debris?
 
I'm terrible at reading the bearings understanding what they mean.
All I know is bearings look not great obviously but crank is in perfect condition still. Thrust bearing isn't even eaten up too bad

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How much mileage was on that since rebuild and what bearings are those? To me, the bearings' appearance looks like the engine was assembled in a sand pit.
Are we looking at the transmission side of that bearing or the front of the engine side?

You wouldn't be able to tell 3 thousandths of an inch off a bearing thrust face thickness by looking at it, but that's all it takes to go from high side of spec to trashed.
 
Yeah them two main bearings look pretty bad for an engine that was just “rebuilt”.

Judging by the picture you can definitely catch your fingernails on them??

-Daniel
 
I'm terrible at reading the bearings understanding what they mean.
All I know is bearings look not great obviously but crank is in perfect condition still. Thrust bearing isn't even eaten up too bad

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Is the engine out of the car?
 
Alright happy Saturday everyone

What I have done is very unconventional and slipped a new set of bearings. Upon doing so I double checked all bearing clearances again after installing a brand new set of ARP main studs and the mains have exactly .0002in on all bearings. Then finally bought a dial indicator and got right around .0065in of end play.
(When assembling the motor last time I believe the end play was wayyy more than what I'm getting now. I think the crank moved a bunch. Now everything is tighter and within spec and confirmed multiple times to cover my ass)

With that being im going to take the risk on my own and attempt to start the car again tomorrow morning because I'm at the f*** it stage and already building new block on the side.
 
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