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ROUGH ENGINE - POOL OF BRAKE FLUID

ELEDSALL

Member
My latest attempt to run mogas in my Superior O-360 was not good. I had good luck running it until the temps warmed up and then problems. I suspected that my rough idle was due to mogas so I drained one tank and replaced the gas with 100LL. No problems in the flight around the patch. After landing, I switched to the mogas tank to see if it was indeed the problem. Sure enough, before I could return to the hangar my engine was barely running; coughing and loopy idling. Super I thought; no engine problem just mogas.

After I limped back to the hangar, I felt my right brake go soft. After shutting down, I noticed an ever larger pool of brake fluid forming around the right tire. I rolled the bird back in the hangar and within a few minutes, I had a pool around the left tire. I thought that the vibration might be enough to brake the al tubing that runs down the gear leg. I ordered braided lines and installed them this a.m. As I went to reverse pump/bleed the brakes, fluid immediately started running out of the brake caliper. I had not found any breaks in the al tubing so I was already questioning my analysis.... now I am baffled. Ideas please.
 
choices

One of the upsides to your experience is getting good braided lines right away. I have been suspicious of the solid lines on any RV.
When I look at my total investment in my plane, insurance, training and so forth... I voted against mo-gas. When all is said and done, not having any stinky residue around... a known, clean highly refined gas makes me happy.
When it comes to oil changes and fuel... I just chalk it up to the cost of aviation. And your engine will go back to smooth.... I hope.
 
In all probability its leaking from the O-ring on the caliper piston. Take it off for a look see.
 
In all probability its leaking from the O-ring on the caliper piston. Take it off for a look see.

As far as using mo-gas: I built my RV-10 with that in mind and made sure I routed and insulated all the FWF lines against heat, and also used a blast shield around my engine mounted fuel pump. I was careful in my testing but eventually found that even on hot days, I had zero issues with the fuel vaporizing. I would still keep fuel separated in the tanks: Left tank mo-gas and right tank 100LL. I would take off and land on the 100LL and cruise on the mo-gas. The engine never stumbled or missed a beat and I save a lot of money!
 
ELEDSALL -

I suspect you have run into the issue of auto fuel that has been formulated for winter. The winter formula allows the fuel to vaporize easier in lower temperatures .... as long as winter temps are cold you are in good shape. However, it gets really dicey when using the winter formula fuel when it gets warmer in the Spring.

I have read that when the temperatures get warmer, the vapor lock issue can be mitigated significantly by adding 30% of 100 LL to the winter fuel blend.
 
Thanks everybody for your thoughts and comments. Is it possible that the engine vibration caused both brake calipers to leak?
 
Murphy's Law.
Brake O-rings can go anytime. Same with over tightened brake line flares. Be thankful it happened at your home field.
 
Have you, or anyone, had the brakes apart? It is possible to re-install the piston backwards, so the O ring is very near the top rather than well down in the cylinder. After the pads wear just a bit, applying brakes can let the O ring come out of the cylinder, and leak fluid.
 
You didn't give any details about the auto fuel.

What octain did you try and did you test it for ethanol?
 
2 different issues.

Although your 2 issues happened about the same time, it is not likely that either of those are related in any way.
My latest attempt to run mogas in my Superior O-360 was not good.

I don't know anything about your history and "attempts" to run mogas.
It is quite simple to run mogas and it appears that I have company in fellow RV-10 pilot 9GT as well as many others. I run mogas 91E10 all year round and my experience is the same as 9GT's mentioned above.
However, careful attention was paid to fuel system installation and using mogas was not simply an "attempt" but a deliberate and carfully considered plan.

Mogas will do exactly what you describe if the fuel gets overheated, especially
during taxi when flow is minimal and nearly stagnant.
I see that you have a carbureted 0-360 and I would be surprised if you did not also have a "fuel cooker" gascolater mounted in the engine compartment.
Please tell us more about your installation and a little history with details on your "attempts" to use mogas
 
The way I figure is; If I can afford an airplane, I can afford the Avgas. When the day comes I can't, I'll go back to motorcycles and Mogas.
 
Is it possible that the engine vibration caused both brake calipers to leak?

Positively no.

Either a previous mechanic installed the pistons backwards, or (more likely) you overheated the calipers during your taxi tests to determine fuel performance, which bakes the factory-installed nitrile o-rings. When (not if) you remove the pistons to replace the o-rings, their condition will tell the tale.
 
No problems running 91+ no alcohol MoGas. Initially was a Lyclone O-360 with gascolator on the firewall. Changed the same Engine to Bendix fuel injection/IO-360, eliminated the gascolator and placed a cooling shroud around the fuel pump.
A fuel filter is now behind the firewall and water is sumped at the tank drains.

Never have had the first problem with either configuration in 350 hours.

A friend did have problems with winter blend left over on a very warm 90 degee day. It would run OK if he left his electric pump running. We think it likely was fuel vaporizing in the gascolator or a very small air leak in the fuel system
.
 
100+ hours on straight 91E10 here with almost zero problems. I say "almost" zero, because hot starts on the winter mix are sometimes interesting. I am planning to install the Airflow Performance purge valve to completely eliminate that issue, but as far as engine performance goes, zero problems.

No gascolator, no engine-driven fuel pump.
 
The way I figure is; If I can afford an airplane, I can afford the Avgas. When the day comes I can't, I'll go back to motorcycles and Mogas.

Infidel,
I second this, and could not agree more with you. Avgas factored in when I made the decision to purchase. When my life depends on it, I don't take chances with other fuels.
 
Infidel,
I second this, and could not agree more with you. Avgas factored in when I made the decision to purchase. When my life depends on it, I don't take chances with other fuels.

How you spend your money is up to you and is no one else's business.

Using mogas has never been about the money for me but the ability to use an alternative to 100LL. Let's face it, Tetraethyl lead (TEL) is a very nasty compound and in a low compression engine does more harm than good.

Thousands of mogas STC's were issued and blessed by the FAA and successfully applied to a large variety of aircraft. I know the addition of ethanol has put an end to those STCs for certified aircraft. I am also aware that a number of ethanol related problems occurred when ethanol was first added to mogas.
All of those problems have been resolved and today, hundreds if not thousands of experimentals fly on mogas without any issues.
You'll find a great number of fuel related aircraft accident data involving the use of avgas (or the lack thereof) and very few accidents, if any, directly related to the use of mogas.
My life depends on it too.:)
 
I'll pitch in with Ernst on this one. After a decade of flying mogas almost exclusively, I can say I have had zero problems with it. I have had troubles with 100LL - my engine simply doesn't seem to like the stuff and has had troubles idling when using 100LL.

Yes, the economics of mogas are a contributor to why I can fly as much as I do; around here, a 30 gallon fillup of mogas costs about the same as only 20 gallons of 100LL. That's quite a large difference. The new aircraft we are building has been equipped specifically to allow on-going use of 91 octane mogas.

To each his or her own. To slam mogas because one has personally chosen to use 100LL is a reaction based on emotion rather than an analysis of facts.
 
I've got the Superior XP. It is supposed to like mogas but, it doesn't. In fact, I tried it a couple times and it just sputters and farts. That was using the winter blend. As others have posted, that's probably the issue.

I suspect it is mogas intolerant (lactaid???). I've just decided to stick with 100LL and not worry about it!

Jim
 
Same problem as OP

I've got the Superior XP. It is supposed to like mogas but, it doesn't. In fact, I tried it a couple times and it just sputters and farts.

This is the most widely encountered problem when using mogas and a misconception that results in people just giving up.

Most low compression engines, 8:1 or less and preferably fuel injected are perfectly happy running on mogas, 91 or better 93 E10 or straight.

It is the fuel system that needs the attention, more details than I want to get into it but generally speaking, if you boil the fuel before it gets to the injection controller or carburetor, the problem is with your fuel system. Do whatever you can to keep your fuel cool.
 
Add me to the list agreeing with Ernst. Over a decade running E-free premium mogas in a carb'd 160 HP -4. Exactly *one* problem: me. Winter blend still in the tanks a couple of months into summer, gascolator in the stock position on the bottom of the firewall, 20 minute flight followed by sitting on a ramp for 2 hours in 100+ degree temps. Removed the gascolator-fuel boiler, made sure I'm not running winter blend in summer heat, and no further problems.

The only reason I don't run E-gas is that the plane was built (not by me) in 1991, and has already has issues with tanks leaking. I don't trust the tank sealant to be E-proof, like current sealants.

With injection & no gascolator, or with EFI, there should be no issues whatsoever with mogas, as long as the engine is less than around 9-1 compression.

Charlie
 
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