Vibration: L18: Annoying: Clutch / Pressure Plate / Flywheel?

[Cardinal Grammeter]

Engine runs fine but has a vibration proportional to rpm.

 

Just off idle, I get vibration of the front bumper, defroster discharge vents, other dash parts, and you can feel it 24/7 in the steering wheel - but not through the gas pedal.

 

New alternator and water pump, but they wouldn't have the mass for this imbalance which is significant.

 

I'm hoping it's the clutch which means it will get fixed when the clutch wears out, however I'm not sure,  Seems to make no difference if the clutch is in or out when in neutral. 

[flatcat19]

Can you feel the vibration at idle?

[KoHeartsGPA]

Did it do it BEFORE you replaced a certain moving part?

[datzenmike]

Is this sitting still? or driving?

 

If sitting still....

 

Inspect the exhaust system completely to see if the pipe is rubbing the body or frame anywhere. Is it clamped solidly to a hanger or is it properly isolated with rubber?

 

Are the plastic fan blades damaged from hitting the rad or the shroud?

 

Get a 2x4 and pry up on both sides of the engine while looking at the engine mounts. Are they split or do they come apart? Is the engine supported away and isolated from the frame? Are the mounting bolts tight? Are the bolts between mount brackets and the block there and tight? Is oil pan sitting on or touching the cross brace under it?

 

Inspect the 4 speed rubber mount for loose bolts or broken rubber. Is the shifter rubbing the tunnel of the cab? Is any part of the transmission rubbing the cab? or frame, or torsion bars, or exhaust?

 

Is air filter rubbing underside of the hood. Raise the hood and try it... gone?

[flatcat19]

Don't worry, guys.

 

A new thread will be started with results tomorrow.

[Cardinal Grammeter]

Feel at idle:  yes - putting hand on valve cover makes it very clear.

 

Haven't changed anything except new WP - new ALT was installed by someone else.  But these small items would not generate enough impalance to shake the entire engine.

 

Don't know about the mounts - could definitely be them.  I would not know what to expect if they "went solid."  I do know a childhood experiment where I bolted a 2.5hp horizontal B&S onto a small frame to drive a pump - it turned into a vibrating jitterbug and could have been used for a soil tamper. 

 

Exhaust, fan, air cleaner, and shifter are clear of everything.  But if they were touching, that is just a rattle.  You put you hand on the valve cover and you say, Wow, where is that coming from?

 

Yes, does it parked in neutral.  And you can feel it when driving too.  When you buzz the engine up around 5000 rpm, you don't notice it since the frequency is so high.

 

I have an antique vibrating wire vibration frequency measurer which would tell me if it is 1 per revolution or more - however, I don't know where it is exactly.

 

I'm assuming Datsun engines are internally balanced?  I don't know if the monkeys that owned this previously did their banana magic inside the bell housing.   And there is no balance shaft that could have been mis-phased.

 

I had a BBC 427 2-bolt main w/cast crank and big heavy pistons.  I put the 425hp pistons in it which were very light.  Got the crank rebalanced and the shop was scared because of the amount of metal they would have had to remove from the crank - so they simply didn't do it.  Got it back and wow, that gave vibration a whole new meaning.  I was really pissed - had to pull the engine again and they finished up the job.  They should have done it for free since they completely bone headed it. 

 

This vibration is not totally unlike the way out of balance crank - which makes me think of clutch or more specifically, the pressure plate.  Even if the flywheel was wobbling, I don't think that would be a rotating imbalance since the CG would still be on the axis.

 

If it was the clutch disc, you wouldn't notice it parked in neutral - but you would notice it in gear.  So it's not the disc.

________________________

 

TO DO NEXT:  Check the mounts.

[flatcat19]

Recheck the alternator installation. Make sure it is tight and inline with your other pulleys.

 

 

And stop rambling. Stay on topic.

[flatcat19]

Let me back up...is this new or on-going?

[HOGIE]

Installed new alternator, *edit "by someone else"

 

 

 

Check the clearance between alternator and steering pitman arm grease cap.

[datzenmike]

I doubt the alternator but if you want take the belt off and start the engine. If that fixes it then it's the alternator or the water pump.
 

If it was the clutch disc, you wouldn't notice it parked in neutral - but you would notice it in gear.  So it's not the disc.

 

In gear or out of gear wouldn't matter. Clutch in or out would. 

 

Neutral, clutch engaged it's spinning with the flywheel.

Neutral, clutch disengages it is not spinning.... or should not be spinning unless damaged.

 

 

Your idea of vibration may be more sensitive than most. Not saying there's no vibration, but all engines 'vibrate' to some degree... and loose things do rattle. Engine rubber mounts don't 'go solid' but they can fail and metal touches metal. The engine and transmission are (and should be) rubber isolated by their mounts. The exhaust system is bolted to the engine but also supported by the body. Make sure the pipes and muffler are not touching the body/frame/differential or suspension.

[flatcat19]

Datsun, vibrating. Sounds pretty normal to me.

 

Been driving mine for the last two weeks...yeah, it shakes.

[KoHeartsGPA]

Datsun, vibrating. Sounds pretty normal to me.

Been driving mine for the last two weeks...yeah, it shakes.

I agree....I'm wondering at what degree this "shaking" is happening, this guy seems to be used to V8 and 4 cylinder engines aren't as well balanced as V8s....uhh....how about a vid of this thing?.....make a YouTube account, make vid with your phone....upload to your YouTube and post link here so we can see, please....

 

We want to help you, help us help you :)

[Stoffregen Motorsports]

"Normal" vibrations can be tuned out to an extent, especially if it's a poorly tuned carb and ignition or bad plugs or wires.

 

My vote is for motor mounts. Most times, guys look under the hood and say "yep, it has motor mounts" and that's as far as they go. If they've never been replaced, these are 40 years old now

[Cardinal Grammeter]

I had a BMW 1600 and that was atypically smooth - like an electric motor smooth.  The 2002 was unremarkable but clearly not smooth at all.  My 510 & B210 were nothing unusual.  I've had engines with race cams and they shake all over the place - I don't call that a vibration.

 

If I stand on the side by the fender and hold my hand on the side of the valve cover at the front, the vibration is clearly greater than if I hold my hand on the side of the valve cover at the rear.

 

The L18 is "buzzing" just about everything on the truck.  Bumper against the fascia, exhaust, few different dash buzzes and most annoyingly is you can feel it clearly through the steering wheel which is a real bad sign because that means the vibration is in the frame - the motor mounts should not allow that to happen.

 

I'm wondering if the motor mounts could have petrified and turned to solid blocks?  All the tie rod end cups have long since petrified and fell off - there isn't a one left on this truck.

 

The motor mounts appear to be simple blocks of rubber about an inch thick with steel brackets bonded to their faces,  so I'm guessing there is no metal to metal contact.  But they could be complex internally if they are designed not to separate if the rubber fails.

 

The flywheel and pressure plate always turn with the crank but the disc can be stopped when the clutch is in.  This makes no difference.

 

There is no crank harmonic balancer so that is a non-issue.

[KoHeartsGPA]

Again...video please...

[datzenmike]

Pull the spark plugs and look at them.

[flatcat19]

Pondering ain't gonna make the vibration go away.

 

 

Do work.

[Cardinal Grammeter]

I checked the front motor mounts - they are nice and soft.

 

However, I found a possible source:

 

Front Muffler clamp is directly bolted to the frame cantilever exhaust hanger - no rubber.   (no isolator #11 & #12)

 

I'll be addressing that later on today....  EDIT:  sway bar link bushings should work...

 

[Stoffregen Motorsports]

However, I found a possible source:

 

Front Muffler clamp is directly bolted to the frame cantilever exhaust hanger - no rubber.   (no isolator #11 & #12)

 

I was going to suggest having a look at the exhaust to see if it was hitting somewhere, but a solid mounted exhaust could certainly be the culprit.

[datzenmike]

This was suggested on the 4th post.

 

Is this sitting still? or driving?

 

If sitting still....

 

Inspect the exhaust system completely to see if the pipe is rubbing the body or frame anywhere. Is it clamped solidly to a hanger or is it properly isolated with rubber?

 

Are the plastic fan blades damaged from hitting the rad or the shroud?

 

Get a 2x4 and pry up on both sides of the engine while looking at the engine mounts. Are they split or do they come apart? Is the engine supported away and isolated from the frame? Are the mounting bolts tight? Are the bolts between mount brackets and the block there and tight? Is oil pan sitting on or touching the cross brace under it?

 

Inspect the 4 speed rubber mount for loose bolts or broken rubber. Is the shifter rubbing the tunnel of the cab? Is any part of the transmission rubbing the cab? or frame, or torsion bars, or exhaust?

 

Is air filter rubbing underside of the hood. Raise the hood and try it... gone?

[Cardinal Grammeter]

My Bad datzenmike!   I remember reading the first sentence but failed to read the second.

 

There will be some delays fixing here - have the wonders of a rogue April snow storm - actually two of them.

 

I still want to find my wire vibration frequency measurer to see if its 1 or 2 per rev.  Where 1 per rev is a rotating mass unbalance and 2 per rev is power stroke related.

[datzenmike]

Pull the spark plugs and look at them.

 

This will give you a 'look' into engine operation. A duff cylinder, blown head gasket or bad valve can cause a very jittery engine.

[Cardinal Grammeter]

I don't mind an engine that shakes, it's just when its a dead cylinder/burnt valve issue, that is another matter.  That will hammer out the key in the crank snout.

 

And I'm not going to talk about the weird 3rd gear, low frequency "oscillation" I can feel in the shifter (!)  It shifts OK and doesn't jump out of gear - so I'll leave it at that.

[datzenmike]

I don't mind an engine that shakes, it's just when its a dead cylinder/burnt valve issue, that is another matter.  That will hammer out the key in the crank snout.

 

 

 

 

There are three. For all the blown head gaskets, burnt or bent valves I have never seen this. All the broken keys I have seen were from installing them wrong and tightening the crank bolt down (120 ft lbs)

[Cardinal Grammeter]

RE:  Hammered keyways:

 

Never meant to imply Datsuns would do this.  But I have seen it happen:  My dad had a 1960 390 Cadillac that had a burnt valve and it hammered the balancer until it was loose and wobbling on the front of the crank.

 

The Suzuki G10 1.0 3-cyl (Sprint/Metro) will hammer out the crank keyway.  Problem is the G10's just wont't die - they keep chugging and chugging...   It's a known issue on geometroforum and teamswift forums.

 

For giggles:  While not a keyway, but actually a lot worse, Vipers with superchargers on them have been known to break the snout off the front of the crank.  OUCH!

 

I sandwiched in some old sway bar link or shock mount bushings and it killed at least 50% of the vibration.  While the vibration is still present, it's now within acceptable levels and easily un-noticeable.

 

So  SOLVED.