Help needed - Vibration from the engine ? - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 24 Old 09-20-2019, 07:52 AM Thread Starter
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Help needed - Vibration from the engine ?

Hi, here's a recap.

Stock long block 5.0 from 1994. Was running on the highway and all the sudden, bad vibration appears. Towed car home and balancer bolt broke and balancer too. No visual damage to crankshaft itself. Bought another balancer from ATP and ran since. Few hundred miles later, medium vibration appears so I've replaced again balancer for a Powerbond. Vibrations seems cut in half but still present. Now started some tests.

Transmission removed and engine supported with a frame that used transmission mount on stock crossmember.

With Powerbond balancer (50oz) and Fidanza flywheel (50oz) and no clutch, vibration at approx 1200 and between 2200 to 2800 RPM. I can feel it seated. Bought another stock replacement flywheel (50oz) and issue remains. Verified all spark plugs, wires, no arcing and engine mount seem perfect. With or without engine strap and still present, no change. Found nothing in the oil too. It is possible main bearing have something that cause vibration? When I use force to move up/down the balancer, I can feel a very small bit of moving. Thanks

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post #2 of 24 Old 09-20-2019, 09:07 AM
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Did you cut the filter open when you changed oil?

If there is free play on the fwd end of the crank and some bad vibrations then there may be deeper issues.


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post #3 of 24 Old 09-20-2019, 09:30 AM Thread Starter
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Quote:
Originally Posted by 96pushrod View Post
Did you cut the filter open when you changed oil?

If there is free play on the fwd end of the crank and some bad vibrations then there may be deeper issues.
I should but didnt. What kind of deeper issues you are thinking of?
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post #4 of 24 Old 09-20-2019, 09:42 AM
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The next thing to investigate IMO is the rods. Run a compression test and see if one hole is way down on compression. If the rod is bent that will be the hole. I have seen stock 5.0s bend rods but it has usually been from nitrous.
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post #5 of 24 Old 09-20-2019, 11:03 AM
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Nose of the crank may be bent.

ks


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post #6 of 24 Old 09-20-2019, 11:21 AM Thread Starter
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Quote:
Originally Posted by KEVIN$ View Post
Nose of the crank may be bent.

ks
How could we measure or verify this with the engine assembled ?
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post #7 of 24 Old 09-20-2019, 11:23 AM Thread Starter
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Quote:
Originally Posted by AL P View Post
The next thing to investigate IMO is the rods. Run a compression test and see if one hole is way down on compression. If the rod is bent that will be the hole. I have seen stock 5.0s bend rods but it has usually been from nitrous.
Might be an idea. Just to understand, how a bent rod would affect the compression test result?
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post #8 of 24 Old 09-20-2019, 11:26 AM
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Might be an idea. Just to understand, how a bent rod would affect the compression test result?
If the rod bends the piston will not come up to top dead center in that hole.
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post #9 of 24 Old 09-20-2019, 12:33 PM
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Quote:
Originally Posted by bigger_is_better View Post
How could we measure or verify this with the engine assembled ?
You would need a dial indicator mounted on the engine some place then rotate the crank by hand to see if there is a wobble. All of this done with the H-balancer removed.

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post #10 of 24 Old 09-20-2019, 01:24 PM Thread Starter
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Quote:
Originally Posted by KEVIN$ View Post
You would need a dial indicator mounted on the engine some place then rotate the crank by hand to see if there is a wobble. All of this done with the H-balancer removed.

k
You're right. If my minds are good, crank is sitting flush with timing cover so when removing oil pan, I will be able to do it.

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post #11 of 24 Old 09-20-2019, 01:25 PM Thread Starter
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Quote:
Originally Posted by AL P View Post
If the rod bends the piston will not come up to top dead center in that hole.
I havent feel drop in performance but makes sense to me, thanks.
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post #12 of 24 Old 09-21-2019, 03:25 PM
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There is a possibility of a "compression imbalance" but I would really think the crank snout got bent when the first balancer blew.

First off, it seems like you would be able to see that at the balancer when checking timing, but if not, perhaps use 6" stud (with nut) to mount the balancer so that most of the stud extends out past the balancer and you would get a much more visual "read" on whether the snout is straight when the motor is spinning. If it is, the stud would spin perfectly with no wobble, if it off at all I would think it would be really obvious with the stud sticking out. I know it's a crazy idea, I'm just trying to help!
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post #13 of 24 Old 09-24-2019, 05:00 PM Thread Starter
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Will give a try for what suggested this weekend.
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post #14 of 24 Old 10-08-2019, 09:59 AM Thread Starter
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Havent chance of working that much on it. I removed the engine from the car and did some basic check.

Runout of Crank flange: 0,0041.


Leakdown test (cold engine

P-Rear-D
90 --- 92
90 --- 86
91 --- 82
90 --- 80
----F----

Not sure why on driver side, it doesnt seal like passenger one?

Will remove oil pan next to check crank itself.
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post #15 of 24 Old 10-08-2019, 11:18 AM
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Quote:
Originally Posted by bigger_is_better View Post
Havent chance of working that much on it. I removed the engine from the car and did some basic check.

Runout of Crank flange: 0,0041.
This seems like a lot if this is the crankshaft snout where the balancer mounts... I would think it would be .001 or less... Maybe someone else will chime in..

ks


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post #16 of 24 Old 10-08-2019, 01:19 PM Thread Starter
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Quote:
Originally Posted by KEVIN$ View Post
This seems like a lot if this is the crankshaft snout where the balancer mounts... I would think it would be .001 or less... Maybe someone else will chime in..

ks
Rear one, where flywheel is mount.
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post #17 of 24 Old 10-09-2019, 10:13 AM Thread Starter
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Did some measurement today. Crankshaft runout on main #1. 0,00085

Some pictures of the bearing are coming. What you think guys?
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post #18 of 24 Old 10-09-2019, 10:15 AM Thread Starter
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Use this link for pictures.

http://s76.photobucket.com/user/mart...brary/Bearings

Thanks
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post #19 of 24 Old 10-09-2019, 10:39 AM
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Thats 8 and a half ten thousandths, correct? .00085. Thats nothing, thats remarkably good. What does the crank snout measure? Bearings are reminiscent of a 25 year old bearing. Little more than 3/4 wipe pattern, crap run through the oil in the last few decades. Nothing shocking. Unless the main bearing clearance is very wide, over .004, main bearings just sit there and go along for the ride.

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post #20 of 24 Old 10-09-2019, 11:04 AM
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Yea, measure the snout/shaft that the balancer slides onto at the very end of the crank where the bolt screws into.

ks


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post #21 of 24 Old 10-09-2019, 01:17 PM Thread Starter
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Not quite satisfied of result because my crankshaft end is scored because of when balancer slipped out because of the bolt.

I have 0,0004 but will try to move in the taper zone, at the beginning of the bolt thread.
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post #22 of 24 Old 10-09-2019, 01:33 PM
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Quote:
Originally Posted by bigger_is_better View Post
Not quite satisfied of result because my crankshaft end is scored because of when balancer slipped out because of the bolt.

I have 0,0004 but will try to move in the taper zone, at the beginning of the bolt thread.
If that value is in the ballpark of what you find again then the snout isn't bent...Good!

ks


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post #23 of 24 Old 10-09-2019, 10:49 PM Thread Starter
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Quote:
Originally Posted by KEVIN$ View Post
If that value is in the ballpark of what you find again then the snout isn't bent...Good!

ks
We will know tommorrow. If it's not bent, I have no clue what is the cause of the vibration I'm looking for.
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post #24 of 24 Old 10-10-2019, 03:20 PM Thread Starter
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0,0014 at several places on the snout. What you guys suggest?


Thanks
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