Fuel Leak Behind Firewall

[Steven]

I"ve had a smell of fuel in my CTLS for months but not seeing evidence of a leak I dismissed it as engine odor or some other benign cause.  But suddenly it's suddenly gotten worse with blue fuel streaking the belly of the plane, leaking through drain holes.  So I removed the left front avionics panel and saw the leak immediately and I can reach in and touch it, but looks like it's tough to work on.  The leak is at a clamp over a short rubber hose very near to the "Y" fuel hose intersection from the tanks.  It looks like it's just a simple clamp with no screw or the screw is missing.  It's dripping at a rate of about 35 drops per minute, so rather significant.  Evidently still slow enough that most of the fuel vaporizes over time.  Until recently no fuel leaked from the belly of the plane.  It also explains discrepancies between the fuel computer and actual fuel levels.  Around 2 or 3 gallons per week.

 

How does one replace or tighten the hose clamp ?  It looks tough to get at.  Do the fuel tanks need to be drained first ?   Does the center radio panel needs to come out for better access ?  The rubber connecting hose is located under the left side of the transponder shelf.  Aviation mechanics are very reluctant to work on my CTLS because it's an unfamiliar plane and engine.  I will talk to the local mechanic on Monday.  Hopefully he can do the job, but I'm wondering how difficult it will be and whether he's willing to tackle it.  It would be very simple if the hose clamp were easy to access, but that's seemingly not so in this case, unless I'm mistaken.

 

This problem developed right after my 5 year rubber replacement, but I don't know if the hose and clamp in question were replaced.  It could be a coincidence.

[Madhatter]

I have recently noticed that the "Y" tube is considerably smaller than the hose that attaches to it. It required me to tighten the clamp to its minimum diameter. The hose however is a tight fit at the fuel filter end.

[CT4ME]

I had one at the same spot for awhile... after my rubber replacement, too.   It was just a bad fit bad clamp.  Very hard spot to get into.   But ya gotta do it.  It took a couple of tries, 'finally just replaced it again and got the clamp right.   I kinda freak when I think of the couple of flights I made before finding the leak.  Raw fuel dripping in the panel with all that electricity....

[Steven]

Thanks, I fault myself for not taking the smell of fuel more seriously.  There are lots of wires behind the panel and a spark could have easily ignited a fire.  I now realize that the leak has been going on for months without evidence on the ground because fuel vaporizes rather quickly.

 

If the local mechanic is unwilling to tackle it, then maybe I can somehow wrap and tighten a zip-tie or wire around the hose near the leak as a temporary fix to allow me to fly the plane 2 hours to the dealer.  Getting a new clamp on it is probably not something I can do.  I'm not a mechanic.

[Anticept]

Go to an auto parts store and get a hose clamp.

 

This type, called a fuel injector clamp, are the better type. They clamp more uniformly and not as much force is needed. They are a bit more of a pain to put on because you don't get a lot of clamp to work with, and they have a tighter tolerance (need to be sized correctly to work).

 

This type, called a hose clamp or worm drive clamp, works fine too. Easier to work with because you can use long tails to significantly losen and move around on the hose. You might have to use this one because it can also clamp down even if oversized.

 

Both can be put on without removing the hose. The hose will have the sizes written on it, but it can be measured with a ruler, or, more accurately, a caliper.

 

Don't fly with zip ties or wire, even for a short time. Neither are clamps and would do a terrible job, if anything at all.

[Roger Lee]

Fuel injection clamp #14 or clamp off the fuel lines on each side. Slide the hose off and apply an Oetiker clamp.  The metal tubes are a little smaller than the hose, but work just fine.

 

No matter which clamp you use if you need to pull the hose off just clamp each one off.

[Tom Baker]

I have never had a problem with a leak like that after I do a hose change, but I do use the 7.5mm hose instead of the 5/16" like some others use.

[Steven]

Thanks very much for the feedback on what type of clamps to use.  Now my question is about access to the fuel line .... how much of the front dashboard needs to be removed for sufficient access to replace the faulty clamp ?  It seems that just pulling the pilot side glass panel may not be enough.  Or is it ?  Or do all the panels have to come out and then the entire dashboard ?  I hope it's not that complicated because if it is, I may have to hire a specialized sports plane mechanic to travel to Lake Placid to fix my leak.  It's a small airport with limited services and just one mechanic.

[Anticept]

The avionics panel in the center is held on by four screws. It's easy to remove. That and the pilot side will give you all the room you need.

[Doug G.]

This may be obvious, but don't forget to disconnect the battery first.

[Anticept]

This may be obvious, but don't forget to disconnect the battery first.

i prefer to live dangerously. /s

[Roger Lee]

As they suggested it is easier to remove the pilot side panel and the center panel. Just makes life easier to get both hands in. Once in I don't think you are going to find it that tough to get it done.

[sandpiper]

Thinking about working in that area is worse than the actual task. Sure, it's tight and unpleasant - but doable.

 

Question. Is there a chance that all that fuel leaking over time could cause damage to the belly composite?? 

[Anticept]

Thinking about working in that area is worse than the actual task. Sure, it's tight and unpleasant - but doable.

 

Question. Is there a chance that all that fuel leaking over time could cause damage to the belly composite??

 

They did submersion tests of the core in ethanol fuel for 8 hours at the foam manufacturer. No degredation. The epoxy *may* have a slight sensitivity to it over a long period of time, but that is why it is painted.

[sandpiper]

They did submersion tests of the core in ethanol fuel for 8 hours at the foam manufacturer. No degredation. The epoxy *may* have a slight sensitivity to it over a long period of time, but that is why it is painted.

Good to know. Thanks.

[Tom Baker]

The avionics panel in the center is held on by four screws. It's easy to remove. That and the pilot side will give you all the room you need.

I almost never pull the avionics panel. I would pull the pilot side panel and the lower center switch panel. That will get you to where you need to be.

Also you can clamp the fuel lines between the door post and mushroom. That will save draining fuel if you want to remove the line and inspect it.

[Steven]

I got lucky .... found a retired mechanic, whom I knew, working in his hanger at the airport this afternoon.  He had it fixed in just 5 minutes.  I held the pilot side panel and wiring while he pulled the hose further over the "Y" coupling tube and then managed to get a second clamp over it.  He did caution me that it's a temporary fix.  There's no more dripping, but he didn't know how far the tube went into the hose, so the second clamp may not entirely overlay the tube.

 

Now I can at least fly it to the dealer to check it out and make a permanent repair.

 

Thanks for all the commentary and advice.  I really appreciated it.  Never again will I dismiss the smell of fuel as mere engine odor or another benign cause !  I was shocked to see how much it was dripping. Around 35 drops per minute. It was evaporating and didn't leave a puddle under the plane (through water drain holes under the belly), just a wet spot and even that appeared only recently as the leak got worse.

[Anticept]

I almost never pull the avionics panel. I would pull the pilot side panel and the lower center switch panel. That will get you to where you need to be.Also you can clamp the fuel lines between the door post and mushroom. That will save draining fuel if you want to remove the line and inspect it.

I usually pull the lower panel too, but since Steven said he's not a mechanic, I didn't advise it due to the amount of wiring around there that could be damaged. I know avionics are expensive, but they usually give a lot of wire loop for removal in our aircraft in avionics.

[Roger Lee]

If you slid the hose farther on the "Y" and added a clamp there then you won't be able to fix it any better. The "Y" has long arms so it goes more than enough into the hose. The "Y" has a small curved area that technically the clamp goes over, but if you install a clamp almost any where (not at the end of course, but up higher) and it is tightened down it will hold without any issues. There is no pressure here so getting blown off the tubing is not a worry.

 

What type of clamp was the first one? If you have any worries leave the second clamp and just replace the first. It sounds like the first one was not clamped tight enough.

[Steven]

I don't know what type of clamp the mechanic used, but he tightened it with a screwdriver.  He said the original clamp was broken and missing the screw.

[Roger Lee]

If you have a new clamp then your most likely fixed. No need to travel just to put on another clamp.

[Anticept]

If you slid the hose farther on the "Y" and added a clamp there then you won't be able to fix it any better. The "Y" has long arms so it goes more than enough into the hose. The "Y" has a small curved area that technically the clamp goes over, but if you install a clamp almost any where (not at the end of course, but up higher) and it is tightened down it will hold without any issues.

Correct me if I am wrong, but I am pretty sure you aren't supposed to clamp down on tube beads (the curved area). It should go just behind it further up the tube. The bead is to prevent the hose from being pulled off while clamped, by making the OD of the tube larger than the clamped area. Clamping down on beads would create an irregular clamping force and larger diameter of the clamped area, making it much easier to slide off.

 

This is, of course, is excluding ribbed and ridged tube fittings, which are meant to be clamped on