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Brake Fluid PA18 -150

B

Bob Stern

Registered User
What is the reccomended brake fluid for a Cub? My left brake is very mushy and does not seem to work at all. I am hopingnitbis simple brake fluid issue. Although one mayvaskedvwhat caudsedvthe fluid levelto drop.

Thanks for your advice.


Sent from my SM-T560NU using SuperCub.Org mobile app
 
Touch a white paper towel to the fluid and see if it's red. If so, it's MIL-H-5606 hydraulic fluid. If not, you'll need to check the log books carefully for clues as to what it might be.

Don't get to worried. If you have any of the 'trapped' systems like Scott or North River, brake wear or the loss of two or three drops can decrease pressure. Just top it off and keep an eye on the pedal pressures.

Web
 
Early Cubs used auto brake fluid. I graduated to Dot 5 before it became prohibitively expensive. Almost all disc brake conversions use 5606.
 
Bob Stern said:
What is the reccomended brake fluid for a Cub? My left brake is very mushy and does not seem to work at all. I am hopingnitbis simple brake fluid issue. Although one mayvaskedvwhat caudsedvthe fluid levelto drop.

Thanks for your advice.


Sent from my SM-T560NU using SuperCub.Org mobile app
Click to expand...

Since you're asking, assuming you ID your airplane uses 5606 and put some on your shelf? Don't assume it'll work in other brake systems. That can be an expensive mistake.

Learn how to bleed your brakes. It sounds like that's what you need to do.
 
Steve Pierce said:
Only seen 5606 in any GA aircraft in the past 30 years.
Click to expand...

For sure Steve, though 5606 is probably misnamed as "brake fluid." Just like the master switch which should be re-named "battery disconnect" like it was in my SNJ. Maybe we can find some new fancy name like "deceleration device actuating fluid."

Ag Stearmans were largely converted to old fashioned automobile master cylinders with kits available from Dusters and Sprayers. Lot of them used auto brake fluid, but you needed to flush the lines and replace the wheel cylinders or mixing the fluid made jelly and blocked everything up. Saw it happen more than once. Red Line brake conversions have probably solved that issue by now - This ain't a Stearman site, but the problem is the same...well meaning, but under informed help mixing fluids. Glad the question was asked. Save some trouble and maybe even an -18...:oops::p:p
 
WhiskeyMike said:
For sure Steve, though 5606 is probably misnamed as "brake fluid." Just like the master switch which should be re-named "battery disconnect" like it was in my SNJ. Maybe we can find some new fancy name like "deceleration device actuating fluid."

Ag Stearmans were largely converted to old fashioned automobile master cylinders with kits available from Dusters and Sprayers. Lot of them used auto brake fluid, but you needed to flush the lines and replace the wheel cylinders or mixing the fluid made jelly and blocked everything up. Saw it happen more than once. Red Line brake conversions have probably solved that issue by now - This ain't a Stearman site, but the problem is the same...well meaning, but under informed help mixing fluids. Glad the question was asked. Save some trouble and maybe even an -18...:oops::p:p
Click to expand...

This is a good point. ID the fluid BEFORE you add. '5606 is petroleum based and systems like automotive masters are made for DOT 3 or 4 fluid which is not petroleum based. This means that the seals are different. Artificial rubber for '5606 and natural rubber for DOT 3/4

Web
 
I don’t know about using automotive break fluid in a plane but I do know that using the red aircraft brake fluid in a pickup can be a disaster. In a pinch I added red aviation brake fluid to my 60’s vintage Dodge one ton. It ruined the master cylinder, and all four wheel cylinders.
 
It will ruin early expander tubes on J3s too. Later tubes handle 5606. If you can afford it, Dot 5 is benign - doesn't attack anything. It is harder to bleed, since it can get agitated with little tiny air bubbles.

I could afford it when it was six bucks a quart, and stuck with it when it hit $30/qt. going back to 5606, due to expense and lack of availability. It does have a Mil Spec, just like 5606.
 
Just had an annual done and "something" (I think 5606) was spilled on one of the bushwheels. The fluid made the area on the tire gummy and doesn't want to wash off.
 
All Piper J4 used automotive brake fluid. Master cylinders were car wheel cylinders. I have had to change out an expander tube on my J4 but all of my spare expander tubes had run with 5606. Not a problem if you flush them out ( complete) with isopropyl alcohol. First squeeze out all the old fluid you can, then use a basting type siringe an fill the bladder full. Knead the bladder mixing the opposing fluids. Repeat a few times. Now your ready to switch fluid types.

Glenn
 
JWE said:
Just had an annual done and "something" (I think 5606) was spilled on one of the bushwheels. The fluid made the area on the tire gummy and doesn't want to wash off.
Click to expand...

Most likely Dot3 brake fluid. It destroys paint and some rubber.

Glenn
 
JWE said:
Just had an annual done and "something" (I think 5606) was spilled on one of the bushwheels. The fluid made the area on the tire gummy and doesn't want to wash off.
Click to expand...
Soap and water will fix it up. Dawn dish soap works. I hosed 5606 onto my 35s more than once this past year. Wash and rinse.
 
We buy Shell Aero 4 fluid which is red 5606. Our local Shell Oil distrib. has it 6--1 gallon cans to a case. Not very expensive but costs more than other highly refined hydraulic fluids which we buy in 5 gallon buckets.
 
I have had the same experience as Stewart, wash 5606 off Bushwheels with soap and water as fast as possible.
 
Steve Pierce said:
Only seen 5606 in any GA aircraft in the past 30 years.
Click to expand...
The light sports at work came from the factory with auto brake fluid, we change it out to 5606, the brand new ones still come with auto brake fluid...I think we have 9 or so sitting on the ramp waiting for buyers...
 
astjp2 said:
The light sports at work came from the factory with auto brake fluid, we change it out to 5606, the brand new ones still come with auto brake fluid...I think we have 9 or so sitting on the ramp waiting for buyers...
Click to expand...
What Light Sport?

Only thing I in aviation I have worked on with other than 5606 was the Curtis P40 Warhawk with a vegetable based hydraulic fluid and the Hamilton Metal Plane with automotive fluid and automotive master cylinders that went bad because someone put 5606 in them.
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