Slight burning rubber smell

[Jim Peace]

Noticed recently that during approaches just after putting my manual gear down that there is a smell of burning rubber, not electrical.  Does not happen during takeoff or cruise or descent.  After landing and taxi in it is gone.  Happened after the last few legs.  

Had a MSC open the cowling to take a look and check for anything obviously wrong to include hoses, etc.  Nothing found.

The rubber boots around the rudder pedals and the ones above the nose gear well were new in March and are still properly placed..  

This did start happening after a MSC oil change but there is nothing that has been different from the last time they changed it.  They do great work.

Anyone have this before?

1964 M20C Johnson bar.....

[Shadrach]

Corrosion-X has kind of a funky "hot rubber" smell. was the plane treated recently?

[takair]

I had a Klixon landing light switch that was overheating and would make an unusual smell...not typical electrical.  Reach under (don't use your ring finger) and see if the switch is getting warm.  You may not notice on takeoff due to more air.  Kind of a long shot, but easy to check.

[takair]

Could also be your alternator/generator belt.  Check the tension/condition.

[Jim Peace]

Thank you for the last three comments

Had an ACF 50 treatment earlier this year.  

I fly with a parmethius plus landing light on full time.  Been doing it for the last 50+ hours no issues.

I installed the Alternator STC last March.  Belt looks just like day one.

[ArtVandelay]

Does the inside of the exhaust pipe look clean? The problem is the act of lowering the gear could just be disturbing the air flow and that's why you smell it then. Check the muffler supports as well, is the muffler touching anything it's not suppose to?

[Jim Peace]

The exhaust pipe is only about 50 hours since new......all is well with it and other exhaust components.....

[Jim Peace]

Update:  the plane was just flown by an experienced instructor.  He just had the same smell in the cockpit and both landing gear lights (red gear unsafe/green gear down) were determined to be inop during the let down process.  As well as some smoke in the cockpit........

Getting closer to a diagnosis........MSC mx is already notified.

I am not near any of my books.  Does anyone know of a component that is common to both of those lights.....

[carusoam]

Visual smoke in the cockpit? Noticeable aroma of smoke?

Often the lights get accidently turned dark by an over adjustment of their irises. Open the iris with a twist, let the light through.  Test the lights by pushing them in. Really cool devices in the 60’s...

There is one switch. Johnson bar in vs JBar out. Stick your finger up the hole to feel the switch.  

If the electric supply to the switch were lost, like a broken wire or it grounding, that may give the result you are describing.  What CB would it be attached to?  I would have to look that up...it should be popping a CB before smoking...

Are you familiar with the irises and the switch? 

These details are enough to identify the issues with the switch and the gear lights. Test them while on the ground. 

This is from memory of a 65C.

best regards,

-a-

 

Edited October 12, 2015 by carusoam

[N201MKTurbo]

The gear light circuit is simple for the C, it goes from the lights to the switch in the latch. The strange thing is that it only does it right after you put the gear down, not the whole time the gear is down. The gear warning also uses the switch on the throttle cable, it could be related to that.

Edited October 12, 2015 by N201MKTurbo

[Jim Peace]

Thanks all.....and yes the irises were open.......

[carl]

 

The gear light circuit is simple for the C, it goes from the lights to the switch in the latch. The strange thing is that it only does it right after you put the gear down, not the whole time the gear is down. The gear warning also uses the switch on the throttle cable, it could be related to that.

N201MKTurbo, 

Is that Bob Hoover's mustang in your avatar?

carl

[N201MKTurbo]

Yes, I fixed the alternator about six months ago. It was cool working on a Mustang.

[carl]

 very awesome 

 

[Jim Peace]

Limit switch under the gear latch suspected to be the problem/cause of short. New part should be in tomorrow. 

[Jim Peace]

Update:  gear warning horn toasted itself.....that was the cause of the smell and the reason why it happened in the approach phase. 

[Shadrach]

Let us know what it costs...Of all the things that could cause burning smells in the cockpit, you got off easy!  Was the horn still working?

[carusoam]

The sonalert that sounds when you pull the throttle out with the gear still up?

Is yours mounted in the ceiling?

Thanks for the update, Jim.

Best regards,

-a-

 

[Jim Peace]

I believe it is located behind the panel. Here is a picture. 

[Jim Peace]

Let us know what it costs...Of all the things that could cause burning smells in the cockpit, you got off easy!  Was the horn still working?

not sure if it was still working. I am a 1000 miles away from it. I understand that there will be an attempt to repair it or replace it. Mooney says it could be over a week to get one from them. Also installing a new limit switch supplied from mooney. 

 

Of course this is all happening less than two weeks of me flying a trans con in it. 

[Marauder]

The sonalert that sounds when you pull the throttle out with the gear still up?

Is yours mounted in the ceiling?

Thanks for the update, Jim.

Best regards,

-a-

 

The picture he is showing is the old gear warning horn before they went to the Sonalerts we have.

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[Mooneymite]

Update:  gear warning horn toasted itself.....that was the cause of the smell and the reason why it happened in the approach phase. 

Perfect example of why Mooneyspace is such a great resource.

Whodathunk?

Thanks for sharing.

Edited October 23, 2015 by Mooneymite

[Jim Peace]

 

The picture he is showing is the old gear warning horn before they went to the Sonalerts we have.

 

 

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is the sonalert an option for a 64c? Where can I get one?

[Marauder]

is the sonalert an option for a 64c? Where can I get one?

I'm not too familiar with the 60 series planes. Hopefully someone who has dealt with this horn can comment. The one on my plane is a 628 series.

http://www.mallory-sonalert.com/AVBySeries.aspx

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[Jim Peace]

Let us know what it costs...

It was all labor thanks to having to be a contortionist to get at the horn.  

600 dollars includes the 40 dollars in parts.......done at a MSC......