On-Condition Coolant and oil hoses

[John Vance]

I’m considering a change in hose material for the coolant and oil lines at the next replacement.  Does anyone have experience with teflon or other hose material that would allow remaining changes to be done on-condition?  This would be for a 2010 CTLS (S-LSA), and would require an MRA.  I’ve heard that teflon tends to harden with age and can crack if used in an application where the hoses flexes.  My mechanic tells me that he has the ability to make the crimps for the fittings, but I have no experience with this and don’t know what tooling is required.  Is this worth considering or are there downsides that would negate any benefits?  Any recommendations on sources or material specs?  

[Madhatter]

I know of no teflon product that would be acceptable for this coolant application primarily due to the mechanical properties of teflon for this type of installation. Oil lines, yes, I intend to do this but you must be ELSA.

[John Vance]

3 hours ago, Madhatter said:

I know of no teflon product that would be acceptable for this coolant application primarily due to the mechanical properties of teflon for this type of installation. Oil lines, yes, I intend to do this but you must be ELSA.

I talked to Arian about this, and he’s open to approving an MRA, but of course the details need to be spelled out.  I’m just getting started looking into this. What is the issue with teflon for coolant lines?

[Roger Lee]

The problem with Teflon fuel or oil hose going on condition is how do you inspect under the fire sleeve. Take all the hoses off and out of the fire sleeve? Won't happen. Teflon hoses can be damage from clamps too. Most oil and coolant hoses don't have an issue in the middle. It's usually over fittings and clamps.

[Anticept]

I would say teflon hoses up in the wings, and in the avionics pod would be a perfect application, and down to the gascolator. After the gascolator, keep it rubber, it becomes dicey.

You're also going to find out HOW INSANELY EXPENSIVE teflon hoses are. It will take 15 years before it pays itself back.

The only issue I can see inside the pod is with the fuel strainer and its need to be installed and removed, that part should probably also remain rubber.

[Madhatter]

If I recall I paid around $700+ for all fuel lines all the way to the gascolator.  This included eliminating banjo fittings and converting to AN fittings including  carbs. I had the old stainless carb lines so it made sense to me.

[Tom Baker]

2 hours ago, Anticept said:

I would say teflon hoses up in the wings, and in the avionics pod would be a perfect application, and down to the gascolator. After the gascolator, keep it rubber, it becomes dicey.

You're also going to find out HOW INSANELY EXPENSIVE teflon hoses are. It will take 15 years before it pays itself back.

The only issue I can see inside the pod is with the fuel strainer and its need to be installed and removed, that part should probably also remain rubber.

I have been installing the fuel filter between the "T" and the "U" tube. I don't remove the hoses from the filter, I disconnect from the T and U. This makes it muche easier to service. This was shown as an alternate installation on the fuel filter exchange SB. The only down side it you have to clamp the lines instead of just shutting off the valve.

[Roger Lee]

I do the same as Tom. I move the fuel filter from down stream of the shut off valve to upstream of it. Much easier to service. The downstream ones are a major PITA to get out and check and this is why very few ever get looked at, but put it right behind the left panel and life is easy and so is the filter inspection.

[Anticept]

They're a PITA to get out because of the barbs. They shouldn't even be barbed; they should be beaded fittings if there's clamps being used; I will take just the tips of the sharp edges off with a file because installing and removing that filter damages the hose end, and I've had to replace relatively new hose because the end of it had rubber breaking away.

[Madhatter]

Great point. Change them to beaded. That's the issue with dealing with the manufacturer on the CT, there needs to be common sense.  You should not have to jump through hoops and then pay them for doing something so benign. 

[Anticept]

Sadly this is common everywhere with hose clamps on barbed fittings. Barbed fittings are barbed because they're self retaining and self sealing, and dont require a clamp if you use the correct hose size. Unfortunately, it's either not well known or people just ignore it, not realizing you're reducing the effectiveness of the joint.

For joints that need to be removed, beaded with clamp is superior.