Fuel Leak

[Pavewlc]

Hello all,
Yesterday I discovered a very large blue streak down the belly of the aircraft starting at the hole directly under the fuel select valve. Pulled the inspection plate and sure enough the top of the T valve was wet with fuel.
Logs show it was rebuilt about 3-4 years ago and has been trouble free since. Is this a difficult (ie expensive) fix? All the components in and around the area including the valve look to be in great shape; no corrosion, bends, scrapes or the like. The valve is a little stiff, but always has been.
Any advice would be great. I want to have some kind of back ground info/knowlege before I walk over the ramp to see the A & P guys.

Cheers,
Lee

[Iceman07]

http://cessna170.org/phpBB2/viewtopic.php?t=3537

[Pavewlc]

Thanks for the link, raises a few more questions:

1) How do I determain which I have with just a visual check?
--Logs just show repaired, but it "looks" very new compared to what I think a 50+ year old valve should look like.

2) Fuel seems to seep from the top, is this perhaps an indication of something else?

3) This may be a silly question, but I assume all fuel will have to be drained from both tanks first.

Thanks again,
Lee

[Bruce Fenstermacher]

Thanks for the link, raises a few more questions:

1) How do I determain which I have with just a visual check?
--Logs just show repaired, but it "looks" very new compared to what I think a 50+ year old valve should look like.

Look at the body of the valve. If it looks like it was cast it is the older style. If it is machined square aluminum it's the newer style

2) Fuel seems to seep from the top, is this perhaps an indication of something else?

Probably not

3) This may be a silly question, but I assume all fuel will have to be drained from both tanks first.

Yes it will.

Thanks again,
Lee

Your welcome

[Pavewlc]

I wanted to close the loop on this for others when they do a search on the topic:

1) I had the cast valve, the O ring at the top where the fuel selector came in was leaking.

2) AP/AI was able to repair with valve in place. He also lubed the valve. I asked him about the lub just coming off due to fuel additives washing it away. This had been mentioned in the 120/140 web links. He said he had a newer version and it should last for a good while. Will contiue to monitor it.

3) Since the fuel tanks had to be drained I had them replace all three fuel quick drains; 1 on each wing tank and the 1 gasculator. We had an aircraft here a few weeks ago taxi out and whole guts from the gasculator drain droped on the ramp during run up....kinda scary. $50 in parts seemed like cheap insurance.

4) Total cost was $300. 4 Hours labor and $50 in parts. I'm happy and feel better. I don't mess with fuel leaks.

5) The links above worked great. The 140/120 web site has a great discussion about the valves and is worth the read. Their repairs were a little over my head/abilities but helped in understanding what was going on and let me talk with some confidence with my AP.

Cheers,
Lee

[rupertjl]

I found out Sunday that I have the same problem, older style valve, leaking from the top. I had removed it last year during the annual to lap the surfaces but I think we put the old material back in ( I know, shame on me). So I'll drain the fuel and pull out the valve and replace the packing...minus Home Depot, where do you get the packing or is there a rebuild kit?

[rupertjl]

I took mine apart with the A&P assistance (my father)... well he watched. I was expecting to find the packing material in the guts but there was an O-ring instead. Couldn't find any part numbers in the parts manual for an O-ring so we matched size and shape and ended up using a Parker O-Ring, P/N MS29513-011. Lubed up the tapered valve and put everything back together, leaked checked OK. The old O-ring didn't look bad, but it definitely was leaking out the top. No more, taxied it up to the pumps and refueled the 5 gallons that I lost transfering fuel from a 40 gal trash can to a 5 gallon gas container to the wings 8 times. From the time of the first 5 gallons to the trip back from the pumps l left the fuel selector on BOTH and when I tied it back up, still no leak. I'm going to buy a few O-rings and have on hand for the next time I need to disasseble and lube up. Maybe then I'll catch it with only 10 gallon of fuel in the tanks instead of 40...and those two bolts that hold the selector in place took me two hours to get the nuts started to tighten...talk about frustration!

Bruce, can you cross reference the O-ring part number with what you used, I would like to know if we picked the right one.

v/r,
Jud

[Bruce Fenstermacher]

Judd

Here is a discussion in which I as well as others list the o-ring part numbers and cross reference.
http://cessna170.org/phpBB2/viewtopic.p ... sc&start=0

Sorry but at the moment I can't remember whether you would have the old or new style selector. You will note the person posting last at that thread used an 0-ring in size smaller for the shaft of the old style.

[rupertjl]

Bruce,

Thanks for the link, I have the old style brass cast valve, but I only had one O-ring in the whole unit and it looks like I was one number off, you list MS29513-012 and I used a -011 and the updated Cessna manual has it as -10. So my next questions is, how bad did I screw up and should I replace the O-ring and my second questions is that I assume you have the new style valve (I'm sure of it after reading your post) and that's what all the other O-rings are for.

My A-model parts manual has part nubmers for the packing material but no mention of a an o-ring...I'm thinking someone did a little modification at some point...

[Bruce Fenstermacher]

From the another thread posted by Mike

I have the older forged style valve used on the 170A.
the original packing #0413020-4 crosses to a 38481 at
cessna parts. The 120-140 associattion has a cross reference listed
as ms29513-011 (.18 at Spruce).

Yes I have the newer style thus all the o-rings. Looks like you used the same o-ring as Mike and others from the 120/140 association have to replace the packing material that was originally installed.

If it's not leaking and fuel is flowing as it should be I wouldn't touch it.

[rupertjl]

Bruce,

Man, you're good at that search function or have a great memory...

How's that saying go??? I rather be lucky than good anyday...

[flat country pilot]

I found a puddle of fuel under the plane tonight and the belly is wet. I hate fuel leaks.

I assume it is the fuel selector valve, but I did not look yet.

What is the best access to the valve, inspection plate or through the floor?

How do I drain the fuel tanks? Of course they are both full because I filled them a few days ago after flying.

I think I can find a metal gas can. Would that be better than plastic or does it matter?

What long term effects does the fuel running down the inside of the plane have on the paint and aluminum?

How's that saying go??? I rather be lucky than good anyday...

Sometimes I am not lucky or good, therefore I need to be very careful with avgas.

Bill

[Bruce Fenstermacher]

Bill the fastest way to drain the tanks is to pull the full sumps in each of them. Then drain the remainder from the gasolator. You will not be able to drain the fuel from the lines and the valve so don't be under it when you crack on of the lines.

Of course you will need something to hold 40 gal of fuel. This can be very tedious and most likely you will get fuel all over yourself in the process.

I don't have a problem using plastic cans. You might consider syphoning the most of the fuel out the top of the tanks which might be more controllable.

It's been a will since I did mine but you will need to do all the work through the access holes in the bottom but look down through the top through the flap handle slot to see what you need to do.

[flat country pilot]

Thanks Bruce.

I can pour the fuel from the can to my bulk trailer, therefore I can hold the 40 gals.

I don't have a problem using plastic cans. You might consider syphoning the most of the fuel out the top of the tanks which might be more controllable.

I may be able to syphon directly into the tank on the trailer. That way I can ground the plane to the bulk fuel tank. If I syphon the fuel out the top and then drain the rest out the gasgolator, I assume I can avoid pulling the sumps.

you will need to do all the work through the access holes in the bottom

Do you mean remove the valve through the holes or rebuild it through the holes?

Bill

[Bruce Fenstermacher]

Bill

Your stretching my memory here but this is what I remember of the sequence.

Drain fuel.
Cuss a little as you drench your self with fuel.
Remove flap handle cover.
Look down inside to see what your up against.
Disconnect and remove fuel selector linkage.
Through bottom inspection holes remove the fuel lines.
Cuss a little.
Through flap handle slot remove attachment hardware with extensions and reaching down through flap handle slot.
Cuss some more.
Remove valve through any opening it will come out.
Rebuild valve (see older threads how to do this)
Replace by reversing sequence doulbing the amount of cussing.