Jump to content

1965 M20E Vibration


Recommended Posts

I have a 65 M20E with the IO-360.  I’ve owned the plane since 2015 and have put approx 450 hours on it.  This is the first Mooney I have owned and the first IO-360 I’ve owned as well.   The engine has approx 900 SMOH and runs great.   However, I’ve had to have the top cowl repaired three times for a crack just above the spinner and I’ve replaced two LED landing lights do to cracking.  Additionally, I’ve had to have one of my Aspens replaced as well (although not sure that was vibration related.)
My first thought was prop balance.  I had that done and found it wasn’t very far out of balance at all.  My IA suggested that the cowl may be rubbing and transferring engine vibration.  He found the top cowl was touching on one spot and the lower cowling was making contact in several places.  He modified the cowling and its much better at lower RPMs but at 2200 to 2500 RPM, there is a definite “buzz” in the floor of the cockpit and vibration of the plastic interior side panel.  We have inspected the engine mounts and found they are a little warn but the engine isn’t sagging much if at all.  However, I do hear a bit of a bang on shut down or when I first start it as if the engine has a bit of play on the mounts.  
Has anyone else encountered this?  
Your thoughts and insight are appreciated in advance.  

Bart Chilcott 
N706WC
1965 M20E 
Serial #647

Sent from my iPhone

Link to comment
Share on other sites

1 hour ago, Whiskey Charlie said:

I have a 65 M20E with the IO-360.  I’ve owned the plane since 2015 and have put approx 450 hours on it.  This is the first Mooney I have owned and the first IO-360 I’ve owned as well.   The engine has approx 900 SMOH and runs great.   However, I’ve had to have the top cowl repaired three times for a crack just above the spinner and I’ve replaced two LED landing lights do to cracking.  Additionally, I’ve had to have one of my Aspens replaced as well (although not sure that was vibration related.)
My first thought was prop balance.  I had that done and found it wasn’t very far out of balance at all.  My IA suggested that the cowl may be rubbing and transferring engine vibration.  He found the top cowl was touching on one spot and the lower cowling was making contact in several places.  He modified the cowling and its much better at lower RPMs but at 2200 to 2500 RPM, there is a definite “buzz” in the floor of the cockpit and vibration of the plastic interior side panel.  We have inspected the engine mounts and found they are a little warn but the engine isn’t sagging much if at all.  However, I do hear a bit of a bang on shut down or when I first start it as if the engine has a bit of play on the mounts.  
Has anyone else encountered this?  
Your thoughts and insight are appreciated in advance.  

Bart Chilcott 
N706WC
1965 M20E 
Serial #647

Sent from my iPhone

Look for broken engine mount tubes at the right lower engine mount cup and the right lower fitting at the firewall.

There is an AD and 2 SB’s on the engine mount. https://cdn2.hubspot.net/hubfs/4147179/technical_documents/service_bulletins/sbm20-192a-1.pdf

https://cdn2.hubspot.net/hubfs/4147179/technical_documents/service_bulletins/sbm20-175-1.pdf
 

Clarence

Link to comment
Share on other sites

22 minutes ago, M20Doc said:

Look for broken engine mount tubes at the right lower engine mount cup and the right lower fitting at the firewall.

There is an AD and 2 SB’s on the engine mount. https://cdn2.hubspot.net/hubfs/4147179/technical_documents/service_bulletins/sbm20-192a-1.pdf

https://cdn2.hubspot.net/hubfs/4147179/technical_documents/service_bulletins/sbm20-175-1.pdf
 

Clarence

Thank you Clarence!  I’ll check that out!! 

Link to comment
Share on other sites

My C’s O360 found interesting ways to increase vibration...

enough that air bubbles appeared in the compass because the vibration was so much...

Some days... the prop was nicely aligned in the cowl... and one day it was nearly touching the bottom cowl from sag... then the next day it was nicely aligned again...?

Knowing planes don’t usually fix themselves.... I found the motor mount had been liberated from the two ears that connect the mount to a block of aluminum on the firewall... 

Sometimes the mount was nicely sitting on the aluminum block... and sometimes it had fallen off the front of the block...

Sooo... find out what is making it vibrate...

Ordinary stuff like static balancing of the prop can help... dynamic balancing of the prop can fine tune things...

Making sure the engine mount is firmly connected through the firewall is a great idea... :)

A good tug on the prop will show an interesting response if something isn’t the way it’s supposed to be... use caution... tugging on the prop has a lot of bad things that can happen...

PP thoughts only, not a mechanic or prop guy...

Best regards,

-a-

  • Like 2
Link to comment
Share on other sites

Although you said the rubber mounts are good! How old are they?  Like gear pucks, they get hard and don’t do much.  Recently changed mine with a top overhaul and it makes a big difference in transmitted vibration...or lack of.  Also, what prop do you have?  I have a red arc at 2000 to 2350?  Does not explain vib at 2350-2500...but below that..

  • Like 1
Link to comment
Share on other sites

  • 4 months later...
On 3/6/2020 at 7:45 AM, takair said:

Although you said the rubber mounts are good! How old are they?  Like gear pucks, they get hard and don’t do much.  Recently changed mine with a top overhaul and it makes a big difference in transmitted vibration...or lack of.  Also, what prop do you have?  I have a red arc at 2000 to 2350?  Does not explain vib at 2350-2500...but below that..

Hi Takair, the mounts are 20 years old.  Running a two bladed Hartzel. I went ahead and purchased new Lord mounts and will be installing them in the next few weeks. I’ll be posting my findings after install.  

Link to comment
Share on other sites

1 hour ago, Whiskey Charlie said:

Hi Takair, the mounts are 20 years old.  Running a two bladed Hartzel. I went ahead and purchased new Lord mounts and will be installing them in the next few weeks. I’ll be posting my findings after install.  

Make sure the correct torque is used when you tighten them in, Don't just guess at the torque with a "calibrated " elbow. 

  • Like 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.