Vibrates when free reving and in gear. Why?
05-31-09, 08:19 PM
#1
Vibrates when free reving and in gear. Why?
Ok guys I have multiple Fc's so i dont want to get this mixed up with my s5 that has issues.
This car is an S4 (NA coupe) that was rebuilt by a guy named Phil in Roanoake Rapids, NC. After about 100 miles on the fresh rebuild the var vibes pretty badly. The original owner takes the flywheel out and has it resurfaced and reinstalled. To me it feels like it is the flywheel but if that was the case it would have done that as soon as the guy was driving it after the rebuild, not later.
I took the tranny out and inspected the clutch and the flyhweel and the pressure plate had mismatched bolts going into it. I had to find a 13mm socket to get two of them off. The rest were 14 mm's. He also had a washer on one of the bolts that did not belong there.
The car vibes pretty badly until you are in about fourth or fifth and you cant really feel it.
I feel it may not be the flywheel at all. What could it be in the motor internally that could make it vibe like that, when it was fine directly after the rebuild? The car also does the same thing when it is not in gear.
This car is an S4 (NA coupe) that was rebuilt by a guy named Phil in Roanoake Rapids, NC. After about 100 miles on the fresh rebuild the var vibes pretty badly. The original owner takes the flywheel out and has it resurfaced and reinstalled. To me it feels like it is the flywheel but if that was the case it would have done that as soon as the guy was driving it after the rebuild, not later.
I took the tranny out and inspected the clutch and the flyhweel and the pressure plate had mismatched bolts going into it. I had to find a 13mm socket to get two of them off. The rest were 14 mm's. He also had a washer on one of the bolts that did not belong there.
The car vibes pretty badly until you are in about fourth or fifth and you cant really feel it.
I feel it may not be the flywheel at all. What could it be in the motor internally that could make it vibe like that, when it was fine directly after the rebuild? The car also does the same thing when it is not in gear.
05-31-09, 08:45 PM
#2
the front stack of bushings/needle bearings could be boned. I had a similar problem with my previous engine, previous owner of said engine must of done some work to it since the main pulley bolt had bent the internal key and had let the entire stack of bushings/bearings slip and cause vibrations at all rpms.
06-01-09, 11:48 AM
#6
If it's using the stock fan, any idea how old the water pump is? A bad water pump bearing will throw the fan out of balance and cause mid to high rpm vibration. If you want to do a quick test for it, unbolt the fan and free-rev the engine in the driveway. The vibration should go away. Just don't forget the car will overheat if you let it run for too long.
06-01-09, 12:44 PM
#7
I dont feel like it is the fan. It feels futher back in the engine. I have a feeling it is the motor mount gone bad. I will have to go check.
When it first starts it is rough and stays rough. When I free rev it the engine smooths out as it revs faster. Funny thing is though when in fifth gear on the highway I can tell the probem is still there but it doesnt vibrate as bad, like something is holding down tighter because of the taller gear?
Sounds weird. I wonder if it is the Torrington bearing. But I heard if it was that then it would vibe the same all the way through the rev range.
When it first starts it is rough and stays rough. When I free rev it the engine smooths out as it revs faster. Funny thing is though when in fifth gear on the highway I can tell the probem is still there but it doesnt vibrate as bad, like something is holding down tighter because of the taller gear?
Sounds weird. I wonder if it is the Torrington bearing. But I heard if it was that then it would vibe the same all the way through the rev range.
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06-01-09, 01:12 PM
#9
engine has a few hundred miles on it. The car did not vibrate directly after the rebuild. The builder told the original owner to get on it every now and then and red line it to break it in and he did it and then the vibrating started happening. If it was the torrington bearing it would have been vibrating right after the rebuild. Not 100 or 200 miles later.
06-01-09, 09:51 PM
#11
with the tranny out I got underneath the car and jerked the engine around and inspected the mounts and they appear to be in great shape.
The flywheel bolt hole for the pp seem to have some stripped bolt holes but it had all bolts in it but some were of the wrong size. The raised part of the flyweel (steps if you will) seems to have been ground, not much but still enough to be shiny and obvious. I dont know why they did this when they resurface the flywheel.
I also checked the fan and everything else and it all looks to be in working order.
I am going to change the flywheel with my stock s4 and see what it does.
The flywheel bolt hole for the pp seem to have some stripped bolt holes but it had all bolts in it but some were of the wrong size. The raised part of the flyweel (steps if you will) seems to have been ground, not much but still enough to be shiny and obvious. I dont know why they did this when they resurface the flywheel.
I also checked the fan and everything else and it all looks to be in working order.
I am going to change the flywheel with my stock s4 and see what it does.
06-02-09, 02:31 PM
#12
if this turns out to to be the torringotn bearing what am I likely to have to fix?
Would I just pull off the front cover and replace or would I have to tear down the entire engine, and if I do what gaskets would I need to replace considering the engine has been recently rebuilt.
Also if the torrington bearing did **** up would it not have happened immediately on startup or after some driving as is the case on this motor?
Would I just pull off the front cover and replace or would I have to tear down the entire engine, and if I do what gaskets would I need to replace considering the engine has been recently rebuilt.
Also if the torrington bearing did **** up would it not have happened immediately on startup or after some driving as is the case on this motor?
06-02-09, 02:49 PM
#13
Ok hold up. The tranny seems to whine like hell as well, but there is a sweet spot when you let of the gas when it stops. The guy that builds the motors does a great job from what I hear but he has his buddy do the install and the guy must be a total idiot as all kinds of **** was left unplugged, or wrong bolt sizes and ****.
I am thinking this fool stuffed the tranny in there and fucked up the pilot bearing really nice and good. This would also make that wobble as it feels it is coming from the back of the motor and not the front, and would account for that whine.
I am thinking this fool stuffed the tranny in there and fucked up the pilot bearing really nice and good. This would also make that wobble as it feels it is coming from the back of the motor and not the front, and would account for that whine.
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