Rotax 5 Year Rubber Replacement?

[akarmy]

So I was reading through this post on the Rotax-Owner blog. Wondering what some of the rest of you are doing in reguards to replacement of the hoses and other rubber parts on your 912 engines? I guess the gist of the article is that Rotax recommends the full replacement of all rubber parts every 5 years.

Rotax 5 year Rubber Replacement

[Dave S]

Hi Andy,

Your post on this subject has gone unanswered for quite a while and my 5 year schedule is coming up so I have been thinking about it and decided to re-open the thread.

My wild-elbow guess is that there are a whole lot of situations where these parts serve for many more than 5 years. I have also seen 30 year old certified aircraft with their original rubber hose connectors at the fuel tank...and they seemed a little hard/brittle to me.

Having said that, I am not entirely convinced that a scheduled replacement at 5 years is the only way of addressing reliability issues. Nor is it a guarantee.....

A set replacement schedule can certainly be viewed as a black and white answer to product liability issues; and, easiest to quantify/establish for that reason. That keeps the engine manufacturer in the clear.

I do not believe hoses should be used forever....they do degrade with time and can suffer chafing/swelling/cuts/scrapes/clamping damage etc. with time.....but the time can be anywhere from 10 minutes to 10+ years. A set schedule is no guarantee the hoses are OK before the schedule has expired...and no guarantee there will not be a failure after replacement. That is what annual condition inspections and minor inspections are for.

I do not accept that fuel hoses, coolant hoses and oil hoses will all become unserviceable/unsafe at exactly the same time and at precisely 5 years. They are made of different materials and exposed to different fluids and pressures.

I have replaced the fuel hoses from the fuel shutoff valve forward already....the removal and replacement of the fuel filter results in a certain amount of wear particularly with the clamping. Also went to smooth clamps (auto fuel injection type clamps) because I felt the screw clamps were not as kind to the outside of the hose.

I am expecting to replace the coolant hoses at or very near the 5 year interval and upgrade the clamps to constant pressure type rather than the screw type clamps. I have noticed that the Rotax spring clamps (which are a constant pressure type) used on the lines from and to the cylinder head have been a lot kinder to the hoses than the screw clamps on the radiator hoses which have a tendency to need adjustment from time to time...and you can only do so much of that.

Haven't decided yet on the oil hoses, except that the ends are currently clamped with the screw clamps; and, I will probably replace the oil hoses and clamps at the same time. I have noticed that the clamping, even with the screw clamps, seems to be less wearing on the oil hoses that it is on the coolant hoses.

A couple other things I should mention.

1) I routinely do annual fuel flow tests of the entire fuel system on an annual basis primarily to get an indication if there is any internal swelling or constriction in the system.

2) Hose replacement carries with it it's own set of reliability issues that have to be dealt with and monitored. a) it's a new part with no history of use while the old hoses were "road tested" when they were still working b) Opening up a system creates an opportunity for contamination. The repairman's diligence is the only control...but things can happen any where from a spider crawling into a fuel hose to something flaking off the inside at a connector. c) the fact that the fuel system goes from a 5/16" to a 1/4" hose; and has a T creates a natural place for junk to lodge. The Rotax recommendation for a thorough test run after hose replacement is critical to establishing reliability of the replaced hoses.

So.....I am not quite to the 5 year recommended schedule; however, some hoses have been replaced and others are expected to be replaced not too far down the road from the recommended schedule. In the end, these are Experimentals and it is the it is the mechanic's/repairman's discretion.

Sincerely,

Dave S
KF7 Trigear - Flying
912ULS Warp Drive

[cap01]

ive also been concerned about the damage that the worm clamps do to the hose . the rotax website mentions an oetiker hose clamp that looks interesting , ive seen them on cars but didnt know what they were . i may have to get some and play with them

[akarmy]

Well, resurrecting this old thread as I'm finally doing the hose replacement on my engine. First off, let me say… this sucks. Wow it's quite a bit of work to get everything off, getting access to all the clamps and locations, pulling parts off the engine etc. Secondly it's messy, as soon you are dumping coolant, oil, and fuel all over the place. (while trying to not be messy or unsafe) but it happens.

First a before picture



During…



New Rotax fuel pump (SB out to replace the old one, and it gets replaced for the 5 year as well)



New 17MM hoses being fit to the expansion tank. Notice those red handled pliers, they are special made to clamp those spring clamps on the water lines. Amazing tool that makes the job possible in limited access locations.



so far I have the water lines all replaced including those to the radiator and heater core. I've started on the oil lines, but these are harder to access, especially since I have a external thermostat that involves 4 extra connections to the lines. Finally I've removed the fuel lines FWF and am having those remade using AN fittings and teflon hoses with fire sleeve so at least the FWF fuel lines will now be lifetime and not need replaced again.

[DesertFox4]

Good info and photos Andy. Thanks. You should have piece of mind knowing everything is refreshed firewall forward.
Hope it all works and no leaks when finished.

Question: What is the price of the refresh kit with new fuel pump?

[akarmy]

The pump itself is 98 from CPS

The rest of the parts I cobbled together from literally all over. Lots from CPS, 17mm hose from the UK, fuel lines from TSFlightlines in SC.

That's one thing I wish was easier and more standard. Maybe John could offer a full kit to do the replacement based upon the FWF kit?

[DesertFox4]

Thanks Andy.
A complete kit would be nice so scavenging pieces and parts wouldn't take so long.

[Av8r3400]

A kit would be awesome. I'd buy one, maybe two.

[Danh]

So would a fuel injected 912 make this 5 year hose replacement even more work and money?

[akarmy]

Not sure, doubt it as even on most 912S's the on-engine fuel lines are teflon and don't need replaced. Just the feed lines from the Firewall to the pump.

Guess you would have to take a close look at the install docs and see what hoses there are on the IS engine.