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Silicone hoses - are they OK to use?


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Hi All,

 

I'd love to hear anyones experience and any feedback good or bad regarding silicone hoses used on Rotax 912ULS engine and whether if this is appropriate? I recently completed a Rotax 5 year rubber replacement on my engine and replaced the one inch stiff ribbed style hose with a silicone one inch heater hose. This silicone hose flex (refer to pictures) easily meets/exceeds the temperature and pressure requirements of this system and there are no kinks when hot or cold. 

 

I would love to hear anyones opinions/feedback on whether if this was a good idea or not.

 

Thanks in advance!

Andrew

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I've used Aeroflow branded hose for several years.  https://www.aeroflowperformance.com/silicone-hose

I pulled some hoses off while changing coolant several months ago. It looks and feels very good, as new.

This hose has the "woven" reinforcement in it.  

I think it compresses less than rubber over time.

 

Your install looks good OT!

I wouldn't mind having one of those thermostats.....

Hows the ceramic exhaust coating holding up?

 

Edited by Downunder
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Silicone rubber hose is superior in every respect over "natural" rubber hose, as regard both low and high temperatures, has higher pressure ratings, is more resistant to UV light, and stays supple for longer.

 

Probably the weakest point of your installation is the cable ties. Make sure the cable ties you use are UV-resistant, and able to cope with the Australian sun. The white nylon ties do not have the UV-resistance of the black nylon ties.

 

https://swiftsupplies.com.au/nylon-uv-resistant-cable-ties-range

Edited by onetrack
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26 minutes ago, onetrack said:

Silicone rubber hose is superior in every respect over "natural" rubber hose, as regard both low and high temperatures, has higher pressure ratings, is more resistant to UV light, and stays supple for longer.

 

Probably the weakest point of your installation is the cable ties. Make sure the cable ties you use are UV-resistant, and able to cope with the Australian sun. The white nylon ties do not have the UV-resistance of the black nylon ties.

 

https://swiftsupplies.com.au/nylon-uv-resistant-cable-ties-range

Agree....Get rid of the zip ties altogether and use some P clamps. It would make that look way more professional and last for years (and safer). If you get the correct size, they could also be shaped to fit the square section. Reuseable too.

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1 hour ago, onetrack said:

Silicone rubber hose is superior in every respect over "natural" rubber hose, as regard both low and high temperatures, has higher pressure ratings, is more resistant to UV light, and stays supple for longer.

Just as long as you keep oil, fuel and hydrocarbons away from it....

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Downunder - Yes, that's a good point. Quality silicone hose contains Fluorosilicone, not cheap fillers, and the Fluorosilcone provides good resistance to oils, fuels and most hydrocarbons.

 

However, Aeroflow don't state what their heater hose is specifically made from, merely stating that it's not recommended for fuel or oil transfer. Their heater hose has an inner lining of Nomex, an Aramid-type material.

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3 hours ago, M61A1 said:

Agree....Get rid of the zip ties altogether and use some P clamps. It would make that look way more professional and last for years (and safer). If you get the correct size, they could also be shaped to fit the square section. Reuseable too.

I'd be hesitant to drill holes to secure the P clamp without mfg approval personally......

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46 minutes ago, Downunder said:

I'd be hesitant to drill holes to secure the P clamp without mfg approval personally......

Use two clamps...One shaped to fit the square section and one in the size of the hose, attached to each other.. Common practice. Drilling holes never comes into it.

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19 hours ago, Downunder said:

I've used Aeroflow branded hose for several years.  https://www.aeroflowperformance.com/silicone-hose

I pulled some hoses off while changing coolant several months ago. It looks and feels very good, as new.

This hose has the "woven" reinforcement in it.  

I think it compresses less than rubber over time.

 

Your install looks good OT!

I wouldn't mind having one of those thermostats.....

Hows the ceramic exhaust coating holding up?

 

Hey thanks Downunder and that's great to hear. Yes the ceramic coating is holding well so far also thanks, it was well worth the $300 investment.

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11 hours ago, onetrack said:

Silicone rubber hose is superior in every respect over "natural" rubber hose, as regard both low and high temperatures, has higher pressure ratings, is more resistant to UV light, and stays supple for longer.

 

Probably the weakest point of your installation is the cable ties. Make sure the cable ties you use are UV-resistant, and able to cope with the Australian sun. The white nylon ties do not have the UV-resistance of the black nylon ties.

 

https://swiftsupplies.com.au/nylon-uv-resistant-cable-ties-range

Thanks Onetrack for your feedback and much appreciated mate, I generally replace all my zip ties annually so it's not a problem 🙂

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I would never use zip ties in this application. At least no longer than an emergency temporary when you are out in the Tanami Desert. Like 30 days maximum.

AND

 

if you do use black zip ties, make sure you buy the ones with the METAL TONGUE. 

 

I would suggest NOT use the types with the plastic tongue, about 1 in 10 has a defect in my experience.

 

-glen

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The farm supplies store where I lived previously only stocked Ty-rap - Thomas and Betts cable ties. They are the best, have rated load and excellent UV resistance (black). Two should be used interconnected to attach soft hoses to frame work. 

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I agree with the recommendation of the Thomas and Betts ties

Be aware :

The Bunnings black ones, "UV" are good for 3 months in the sun, no more and most are a lower temp plastic.

 

Most of the black ones, unless rated ,  with soften around 90 deg C - 110 deg C. and

 

You dont need UV rating inside the cowl unless there is high reflected UV from the  on ground tarmac all day .

 

The Nylon clear/milky types are usually good for 150 deg C but check rating and if they are not rated don't use them. Nylons vary from about 50 to 250 deg C glass temperature.

 

 

 

Edited by RFguy
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57 minutes ago, RFguy said:

I would never use zip ties in this application. At least no longer than an emergency temporary when you are out in the Tanami Desert. Like 30 days maximum.

AND

 

if you do use black zip ties, make sure you buy the ones with the METAL TONGUE. 

 

I would suggest NOT use the types with the plastic tongue, about 1 in 10 has a defect in my experience.

 

-glen

RF you must be purchasing from some cut rate store/brand. In all the many many years I have been using zip /cable ties I could count on one hand the defective ones. Not only is a defect uncommon, it is easy to ID the ones that dont work properly and replace with one that does.

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You can get high temp ones for supercharged manifolds They are a brown/red colour and laminated of different materials.  I just wouldn't use zip ties for this application especially with any serious pressure involved.  Also some mechanical way of holding the hose on against the pressure is necessary.   Where the engine mounts allow quite a bit of movement make sure there's plenty of extra length . Quality must vary with this stuff. I've seen a lot go hard  and brittle with alcohol. and a leaking oil or fuel line is a VERY big fire risk. Nev

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I wonder - does coughing up the extra $$$ for silicon hoses not come with a potential negative - that being, the temptation not to do, in part at least,  your 5 year rubber replacement .

I make a point, at this time, of doing additional cooling system maintenance & inspection, such as coolant flush & replacement, blow any foreign bodies out of the out the radiator, check  coolant pump leak, inspection of all metal spigots for corrosion,metal fatigue, etc etc. Over the years I have found shaped automotive cooling hoses that fit my application almost perfectly. They are relativly light weight and cheap - not sure that I could justify the expense of silicon.

I appreciate that in the gyro world there are long distances between engine & radiator and finding suitable hose may be difficult  however I am sure that the Gates catalogue shows long hoses without ribs (the ribbed stuff is heavy & stiff).

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2 hours ago, facthunter said:

Hoses that have a lowered pressure (suction) need a brass spring wound through their interior to stop them collapsing and blocking the flow, Nev

In the past, I would have agreed with you but it would seem that this is now not always necessary.

 

It may have something to do with most automotive cooling systems (including Rotax 9 range) having an expansion fluid recovery reservoir.

 

My hypothalamus is that, instead of the system going to  a high negative pressure when cooled (common in the old style cooling systems), it draws back the surplus coolant from the reservoir. If anything a small positive pressure results - hence the spurt of coolant when you open the cap after the engine cools to ambient.

 

My 912 has Gates Holden Gemini non reinforced automotive hoses on the radiator top/bottom. They are light weight (thin walled) very flexible and so far (5+ 5  years) no sign of collapse.

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It's usually done on the suck side of the water pump, for obvious reasons. . Overflow fluid can't return without negative pressure and a lot depends on whether you run a thermostat and where it is located.  By the way what's your hypothalamus got to do with it ?Nev

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31 minutes ago, facthunter said:

It's usually done on the suck side of the water pump, for obvious reasons. . Overflow fluid can't return without negative pressure and a lot depends on whether you run a thermostat and where it is located.  By the way what's your hypothalamus got to do with it ?Nev

I agree with the "can't return without negative pressure" however it is not to the same degree as the old style cooling systems, where you only filled to the top of the cooling tubes, leaving an expansion space in the top tank and sealing it with a one way pressure relief cap. The old system seemed to create much lower negative pressure with the tendency to collapse the lower radiator hose.

 

In my experience modern systems where you fill to the top of the radiator (leaving minimal air space) and put a litre or two in the expansion/overflow tank, the negative pressures are not so great. If you go out and slowly open the cap on a cooled/ambient temp automotive system, you will almost always get a small spurt of coolant as you do so - this suggest a residual high pressure. Not so unlike when you think about how the two way pressure radiator cap works in these systems.

 

🙃Supposed to be hypothesis - I find the combination of my appalling spelling and the Forums auto spell to be quite challenging.

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In my view with aircraft which can't rectify things in the air it's better to be cautious. Why risk it? If you are always getting some residual high pressure you must be getting some escape of high pressure gas, (porosity or gasket seepage) or the engine is above a temp where the coolant boils at Zero pressure differential.. Nev

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