Engine Breather Tube Routing

Ask Questions and Offer Advice Related to the Cessna 120 & 140 Type

Moderators: 6643, 6183, V529

Forum rules
You must be a member of the Cessna 120-140 Association in order to post new topics, reply to existing topics, or search for information on this forum. Use the "Join" link in the red menu bar.
User avatar
7757
Posts: 16
Joined: Tue May 01, 2018 7:00 am
Location: Missouri
Name: Chris B
Aircraft Type: 1946 C140
Occupation-Interests:
Contact:

Engine Breather Tube Routing

Post by 7757 »

What is the proper path for routing the engine breather tube? Mine currently goes inboard of the filler neck for the oil tank and then goes down to a bracket next to the gascolator. My mechanic and I are thinking that isn't right...

-- Chris B.
Attachments
Breather Tube 3.jpg
Breather Tube 3.jpg (473.63 KiB) Viewed 5390 times
Breather Tube 2.jpg
Breather Tube 2.jpg (468.74 KiB) Viewed 5390 times
Breather Tube 1.jpg
Breather Tube 1.jpg (473.76 KiB) Viewed 5390 times
Chris B.
1946 C140
V529
Posts: 552
Joined: Tue May 01, 2018 7:00 am
Location: Michigan
Name: Victor G
Aircraft Type: C-120
Occupation-Interests: Work on airplanes till the cows come home..........they're still out.
Contact:

Re: Engine Breather Tube Routing

Post by V529 »

You and your technician are thinking correctly. That routing is not correct.

As I recall the breather tube should end up close to the outboard co-pilot side corner of the bottom cowling opening.

So outboard and/or below the filler neck.
User avatar
7757
Posts: 16
Joined: Tue May 01, 2018 7:00 am
Location: Missouri
Name: Chris B
Aircraft Type: 1946 C140
Occupation-Interests:
Contact:

Re: Engine Breather Tube Routing

Post by 7757 »

Does anyone have photos of how their breather tube is routed? If you can include shots of the brackets and where they attach, it would be greatly appreciated. Thanks.
Chris B.
1946 C140
User avatar
6643
Posts: 2326
Joined: Tue May 01, 2018 7:00 am
Location: KLCI
Name: John C
Aircraft Type: 1946 C140/C90
Occupation-Interests: A&P, semi-retired
Contact:

Re: Engine Breather Tube Routing

Post by 6643 »

When these planes were certified it was common practice to run the vent line straight down and aft from the fitting. This tends to encourage oil vapors to make their way out the tube along with the blow-by. Over the years many have been rerouted along the top of the engine then down along the firewall. I'm attaching a service bulletin that shows the modification on Ercoupes. My (Cessna) has a double adel clamp on the engine mount and a standoff on the firewall with a single adel near where it exits below the firewall. Be sure to drill a hole in the tube six inches or so above the bottom of the firewall to allow breathing in case the end of the tube freezes up.

The tubing comes in two pieces and there are two 3" pieces of rubber hose with clamps connecting one tube to the fitting on the engine and the first tube to the second. The second tube has a single bend where it exits the cowl and the joint is about even with the cylinders. An MS35489-17 grommet is used where the tube passes through the rear baffle.
Attachments
FOR_SB108.pdf
(455.37 KiB) Downloaded 564 times
V529
Posts: 552
Joined: Tue May 01, 2018 7:00 am
Location: Michigan
Name: Victor G
Aircraft Type: C-120
Occupation-Interests: Work on airplanes till the cows come home..........they're still out.
Contact:

Re: Engine Breather Tube Routing

Post by V529 »

Here is a picture of the breather tube "over the top" on a 120, if you choose to go this route.

At the very least, your breather tube on the 'stock install' goes outboard of the oil tank. You're almost a good 4 inches too high in placement.
DSCF1114.JPG
DSCF1114.JPG (309.04 KiB) Viewed 5284 times
V529
Posts: 552
Joined: Tue May 01, 2018 7:00 am
Location: Michigan
Name: Victor G
Aircraft Type: C-120
Occupation-Interests: Work on airplanes till the cows come home..........they're still out.
Contact:

Re: Engine Breather Tube Routing

Post by V529 »

The above picture has the breather tube "insulated" with standard fuel/oil line aviation "fire sleeve". Considering that if you fly in cold temps, then you need to realize some water vapor exits the engine and could freeze in the very cold air above the cylinders during winter ops.

If the breather line is below the cylinders (as yours currently is) or behind the baffle, then the air is much warmer and no need to insulate.

Take a look at your last picture. Envision the tube, not routed by the filler neck, but about mid span to the outboard side of the oil tank, aimed directly at the engine mount brace that is visible in the background. (mounting to the lower copilot side of the firewall) Adel clamp the breather tube to that engine mount tube and you'll have a "stock install".
User avatar
6643
Posts: 2326
Joined: Tue May 01, 2018 7:00 am
Location: KLCI
Name: John C
Aircraft Type: 1946 C140/C90
Occupation-Interests: A&P, semi-retired
Contact:

Re: Engine Breather Tube Routing

Post by 6643 »

Where did that engine come from? I worked for a shop a "few" years back that wanted to compete with the "Victor Black Max" engines and chose Ford blue... (Didn't last long, thank goodness!)
V529
Posts: 552
Joined: Tue May 01, 2018 7:00 am
Location: Michigan
Name: Victor G
Aircraft Type: C-120
Occupation-Interests: Work on airplanes till the cows come home..........they're still out.
Contact:

Re: Engine Breather Tube Routing

Post by V529 »

It's a "Victor Blue Max" special..........I paid a lot of money for that engine. ;)
User avatar
6643
Posts: 2326
Joined: Tue May 01, 2018 7:00 am
Location: KLCI
Name: John C
Aircraft Type: 1946 C140/C90
Occupation-Interests: A&P, semi-retired
Contact:

Re: Engine Breather Tube Routing

Post by 6643 »

ImaPoser.gif
ImaPoser.gif (1.26 KiB) Viewed 5279 times
(Rob: We need better Smilies!)
User avatar
6597
Posts: 331
Joined: Tue May 01, 2018 7:00 am
Location: Vancouver WA KVUO
Name: David Sbur
Aircraft Type: '46 140 0-200A
Occupation-Interests: Agriculture
Contact:

Re: Engine Breather Tube Routing

Post by 6597 »

Here's my 0-200 set up, right or wrong been that way for 25+ years...
Attachments
IMG_20190329_131548188.jpg
IMG_20190329_131548188.jpg (182.39 KiB) Viewed 5253 times
IMG_20190329_131426734_HDR.jpg
IMG_20190329_131426734_HDR.jpg (306.11 KiB) Viewed 5253 times
Post Reply

Who is online

Users browsing this forum: No registered users and 12 guests