Murphy's law

Just bought my RV12 a few months ago. Been taking lessons, with everything being fine. Roughly 160 hours total time on plane and engine (2013 model SLSA)

My annual came due, and I assisted the mechanic in the engine aspects of the annual (changing plugs, inspection of everything, cowling removal and reinstall.

Immediately after my annual, I noticed on pre-flight inspection that my coolant level was a little low. I marked it, and after my lesson, it was lower than my mark, and I found drippings on the ground after shutdown and wetness on the underside of my cowling.

A friend helped me pull the cowling, and we Thought we found the leak. Sitting in the plane, it would be the left front cylinder, the metal tube that comes out of the bottom of the head, the clamp for the rubber hose was placed way up at the bend on the metal tube, maybe an inch away from the bulge in the metal tube.

The mechanic found the leak, said it was not uncommon, and let me use his tool to place the clamp properly, just behind the bulge, and I also installed a regular hose clamp behind that clamp just for insurance.

Well, after the next lesson, everything seemed fine, but after getting out of the plane, I found a small puddle, and again found the underside of the cowling wet in the same area, so I'm guessing it's the same piece of tubing or clamps.

My guess is it only leaks after shutoff, when the heat soak causes higher pressures and pushes the coolant out. It's not overtaking the radiator cap spring, and the expansion tank is not blowing over, just dropping in level slightly (like a few tablespoons, maybe 1/4 cup).

I plan to replace the hose and clamps before flying again.

Murphy's law I tells ya. Everything was fine until I had the annual done.

I'm going to pull the cowling later today and maybe run the engine, warm it up, and shut it off to see if I can't see the leak in action.

Chrysopelea - I just realized when reviewing my post that you have a S-LSA ... so the posted remarks below can't be used on your RV-12 without factory approval ... but others with E-LSA 12's may find the info useful ,so I won't delete this post.

Not saying this is your problem but it is another area to keep a close eye on .... don't overlook the small hose running between the coolant bottle mounted on the firewall and the coolant tank. The hose at that location is an American size hose stretched to about twice its normal size to slip onto metric pipes. Don't remember the sizes off hand, but it is in the link to the Blog below. To resolve the issue I went to a foreign car parts place and purchased some metric fuel hose for that location.

I had used a tubing cutter to get smooth, square cut ends and installed the supplied hose at the beginning of the year ... by July it had already split and that was prior to firing up the engine. I noticed it when pouring coolant into the system for the first time. Upon further inspection, both ends were splitting. Here is a link to the details.
http://www.dogaviation.com/2016/07/coolant-added-to-engine-split-hose.html

I have read there are hose clamps that have springs in them that allow the clamp, once tightened, to expand and contract with the material it is clamped to. Have not seen them used, but have read about them here in the forums. Others may have first hand experience using them on the Rotax engine's coolant hoses.

Chrysopelea said:

My guess is it only leaks after shutoff, when the heat soak causes higher pressures and pushes the coolant out. It's not overtaking the radiator cap spring, and the expansion tank is not blowing over, just dropping in level slightly (like a few tablespoons, maybe 1/4 cup).

Click to expand...

The system pressure after shut down should never be any higher than it is during flight.
The pressure cap on the expansion tank is what regulates the system pressure and it will release coolant to the expansion tank anytime the pressure goes above the set value (17 PSI I think), regardless of whether the engine is running or not.

http://www.vansairforce.com/community/showthread.php?t=121396&highlight=coolant&page=2

I posted this in June. Hose to overflow bottle had leak develop - simply cut off offending end and reinstalled.

My mechanic is a Rotax trained mechanic.

Not sure if replacing a small hose is something I'm not allowed to do myself. I'd consider that "regular maintenance", which I believe I CAN do. I've read SLSA owners can do regular maintenance like greasing wheel bearings, changing plugs, and changing this hose is no more complex than changing plugs, it's just a water hose, BUT, I will check and make sure and if my mechanic needs to perform the deed, I will have him do it.

I Will check the metal elbow that comes out of the head, it could very well be leaking from there. My mechanic located the leak originally after the flight where I discovered it was leaking, and it looked like it was simply leaking from the hose end, plus, the clamp was misplaced WAY back behind the bulge in the metal elbow, in the bent portion, not directly behind the bulge where it's supposed to be positioned.
I moved the clamp into the proper position, and added a regular hose clamp behind it (not too tight, just enough to squish the tubing) for a little extra insurance.

Apparently it didn't work, or it's leaking from somewhere other than the hose/clamp that I've been discussing.

Here's the hose that's leaking I think, it's number 7 in the pic when you scroll down to "cooling system", and leaking at the head end of the hose, OR the elbow is leaking.

https://www.cps-parts.com/catalog/rtxpages/5yearrubber.php

FAR 43.3 says that a pilot can do (only) preventative maint. on an aircraft owned or operated by them (this is in the context of a certificated or S-LSA aircraft)

FAR 43 appendix A (paragraph C) lists what the FAA considers to qualify as preventative maintenance.

OK

So we understand the issues of WHO can or cant do the maintenance, so where's the leak coming from? Is the liner of the hose deteriorated, and leaking between the liner and the reinforcement?
OR ---what changed during the annual to create the leak that wasnt there before the annual?
Tom

It's leaking from the rubber tube where it connects to the elbow that comes out of the bottom of the head.

I titled the thread "Murphy's Law" because nothing happened during the annual that could have caused this.

I was present, and assisted the mechanic in removing and installing the cowling, and the plugs, and watched as he inspected and performed everything else on the engine aspects of the annual. He went "by the book".

The tube was not touched. IMO it just decided to start leaking at this weird, unfortunate time.

I removed my clamp, and inspected the tubing. It is still soft and supple, not hard or cracked.

It IS RTV'd to the engine mount, about mid-tube, I wonder if the engine shaking with the tubing kind of "hard mounted" to the engine mount might have caused the tube to fatigue?

I consulted with my mechanic, and he OK'd what I had done, and I'm going to check the system before flying again.

I'll also probably have the mechanic replace the tube sometime soon.

Today, I'm going to get one of those spring type clamps mentioned here that allow expansion and contraction, and probably switch it out for my automotive style clamp. This clamp, regardless of type, is aft of the OEM clamp.

The leakage seems to only happen upon shutdown, and total loss is a few tablespoons to 1/4 cup.

I can tell it's not leaking during flight because there is absolutely NO evidence of coolant anywhere but directly under the tube, nothing sprayed around inside the cowling. Easily cleaned up.

Also, someone mentioned the expansion tank "pressure cap". My expansion tank has an open hole in the top, simply a cap with a hole.

The system cap is like that of an automotive radiator cap, with a spring for overpressure (which dumps into the expansion tank) and a small spring for reverse direction (which draws from the expansion tank if needed).

I checked the cap, and the system was 100% full, total loss of fluid both times was minute.

My mechanic said this type of leak was not uncommon. If it even hints of leaking again, the tube and clamps will be replaced.

Chrysopelea said:

The system cap is like that of an automotive radiator cap, with a spring for overpressure (which dumps into the expansion tank) and a small spring for reverse direction (which draws from the expansion tank if needed).

I checked the cap, and the system was 100% full, total loss of fluid both times was minute.

My mechanic said this type of leak was not uncommon. If it even hints of leaking again, the tube and clamps will be replaced.

Click to expand...

I am using the nomenclature that Rotax uses.....

The expansion tank is the round metal tank on top of the engine that has the automotive type radiator cap on it.

The white plastic bottle is referred to as the overflow bottle.

Your comment about your mechanic ok'ing your work would probably not amuse the faa....... the only thing they care about is if the person doing the work is certified to do so, or is being directly (present at the time the work is done) supervised by someone that is.

rvbuilder2002 said:

I am using the nomenclature that Rotax uses.....

The expansion tank is the round metal tank on top of the engine that has the automotive type radiator cap on it.

The white plastic bottle is referred to as the overflow bottle.

Your comment about your mechanic ok'ing your work would probably not amuse the faa....... the only thing they care about is if the person doing the work is certified to do so, or is being directly (present at the time the work is done) supervised by someone that is.

Click to expand...

OK, I have misnamed the two tanks.


I'm having him do the repairs, so as to have the repair done by a Rotax authorized mechanic.

This way there's no question about anything.

Under the supervision?

Sounds like you are doing an excellent job of diagnosis, troubleshooting and communicating "under the supervision" of your mechanic. I applaud your diligence and honest effort! Fly safe and keep on learning, despite those trying to neuter your efforts.

Ran the plane up to temp today, idling at my hangar, and took it to my mechanic (a stone's throw away literally), and found the plane still leaking.

Upon closer inspection, he found the leak was actually from the TOP metal elbow on the head. The coolant was seeping down between the fins, and onto the lower tube, making it look JUST like it was leaking from the lower tube.

SO, now I've been told to drain the coolant, and bring the plane to him.

He said "a couple days" but so far my observations are that "day" means "week" lol.

He's a good mechanic though, and SO close, so now it's hurry up and wait, Again!

Glad the leak was found finally.

Upon further inspection, it looks like the leak was caused by an improperly placed clamp on the short 3" tube from the expansion tank to the elbow on top of the head.

I saw seepage, but it really looked like the leak was coming from the elbow/flange. When I wiggled the small 3 inch long hose, it popped off! The clamp had been installed on the wrong side of the bulge, basically it was only clamping tubing, and so finally the tubing slipped down and almost off.

A new piece of tubing was installed, and now I have to fill the cooling system, and run the plane up, check for anything funny, but I think the problem is licked!

Afterwards I did a CLOSE inspection of ALL the other hoses, and it seems that whoever built the engine was not too particular about clamp placement, as long as it was behind the bulge in the metal tubing.

IMO the clamp should be JUST behind the bulge, or maybe a couple millimeters behind it. I found the clamps were ranging from there, to an inch behind the bulge, no consistency.

Anyways, none of those other hoses are leaking so I left all alone, thanked my lucky stars that my leak was a simple, easy fix.

I'm off to refill my cooling system, run my plane up to confirm no leakage, and then wrestle the cowling back on hopefully without scratching my nice paint.

I hope Murphy stays away from me for a while now. I've got lessons to take!