Engine Silicone Hose Replacement?

[Q Xopa]

Hello all,

My Yanmar 4JH4 Workshop and Service manual states

"Replace rubberized hoses (fuel and water)every 2 years ir every 2000 hours, whichever comes first.)" P 4-4, 'JH4 Series Service Manual 2007', if anyone wants to look it up.

Ok thats the 'official' version. Im pretty sure this is not normally done be most.

I'm interested to hear others thoughts on this.

I am currently doing a refit including a new 4JH4 engine install.

Im looking at collecting cruising spares including hoses.

Is anyone using Silicone engine hoses? I know they are not cheap. Touted as all sorts if wonderfull by the sellers.

But I can say that on aircraft hoses rubber hoses have a 10 year replacement life.

But Silicone and teflon are not calender life limited. They are listed as regular inspection and replaced on an 'on condition' basis.

Anyone using or has some experience with these?

[Nicholson58]

Originally Posted by Q Xopa

Hello all,

My Yanmar 4JH4 Workshop and Service manual states

"Replace rubberized hoses (fuel and water)every 2 years ir every 2000 hours, whichever comes first.)" P 4-4, 'JH4 Series Service Manual 2007', if anyone wants to look it up.

Ok thats the 'official' version. Im pretty sure this is not normally done be most.

I'm interested to hear others thoughts on this.

I am currently doing a refit including a new 4JH4 engine install.

Im looking at collecting cruising spares including hoses.

Is anyone using Silicone engine hoses? I know they are not cheap. Touted as all sorts if wonderfull by the sellers.

But I can say that on aircraft hoses rubber hoses have a 10 year replacement life.

But Silicone and teflon are not calender life limited. They are listed as regular inspection and replaced on an 'on condition' basis.

Anyone using or has some experience with these?

I think it’s crazy that we use hoses that are done years before a good garden hose. The hoses on my car last years and it’s uncommon for one to fail. I take my goofy twisty hose bits to the NAPA and cruise the racks for radiator hoses with similar kinks. Just cut out the bits that fit. I figured this out when it was obvious that replacements for my 1984 Westerbeke did not exist.

[Sailmonkey]

Our engine has all silicone hoses. They’ve been on there since 2002, and show no signs of degradation.

There is one small exception. An oddly shaped hose between the water pump and a section of hard pipe is rubber. It’s been replaced once because it started weeping.

[a64pilot]

I’m in the middle of changing over to silicone water hoses myself.
Of course you can’t use them for fuel hoses.
Aircraft normal hoses are 5 yrs, except for the Teflon ones, which I don’t believe have a calendar life limit.
2 yrs is ridiculous, all but one of my water hoses on my Yanmar 4JHE are 32 yrs old as they have the factory paint on them, at 32 yrs old, they still work, do not leak, but are as hard as a rock and removing a component may result in a torn hose.

However the hose from the strainer to the water pump is the thick heavy hose rated for below waterline use, it’s new and I’m not replacing it with silicone, just the engine hoses them selves

[thinwater]

There are downsides to silicone hoses, part of the reason high-end cars and heavy duty trucks are not always fitted with them.

• Permeable to AF. It will go right through the walls.
• Poor oil resistance. For example, I've seen hoses ruined and fail explosively that were under the dip stick (I was involved in writing the recall notice). Oil in the coolant can also cause this. Really, ALL hoses on the engine need to be oil resistant.

Just sayin' you may want to read up on the down sides. Not everyone in the vehicle industry believes silicone is better, based on bad experiences.

[Sailmonkey]

Permeable to AF?

Is that antifreeze? As in ethylene glycol?

[thinwater]

Originally Posted by Sailmonkey

Permeable to AF?

Is that antifreeze? As in ethylene glycol?

Water, ethylene glycol, or polypropylene glycol.


Racers love them because they are tough, but they have problems for everyday cars and trucks, which is why they are not factory equipment. I've known companies and bus lines to switch, and then switch back.



----

Drawbacks of Silicone

Permeability to oil and fuel (a problem anywhere there are drips)


The molecular structure of silicone doesn’t play well with oil, fuel, and other oil-based products. We do not recommend using silicone hoses for any applications where they will come in contact with fuel or oil.
Permeability to water molecules (significant problem on vehicals, such as buses and line-haul trucks with high run time)


Silicone is watertight, but water vapor can escape very slowly through the walls of the hose. Think of a balloon that you blow up with air and leave on a table for a week. The air escapes very, very slowly through the walls of the balloon. There’s a similar effect with silicone, and if you have silicone hoses on a car that you use as a daily driver, you’ll find yourself having to replace water in the reservoir from time to time - not because you have a leak, but simply because the water is escaping through the walls of your hose. While silicone hoses are a must for racing applications, some people don’t like them in a daily driver.

[a64pilot]

I’ve run silicone hoses on a few vehicles, and have not noticed any permeability issues. If water were permeating thru then there would be white residue on the hoses, just like you see from a water drip.

However I have always used the 4 ply 80 PSI rated hose. There are many, many people that use silicone radiator hoses, there are thousands of kits and have been for years, perhaps they have a Buna-n layer or similar?

[Q Xopa]

Originally Posted by a64pilot

I’m in the middle of changing over to silicone water hoses myself.
Of course you can’t use them for fuel hoses.
Aircraft normal hoses are 5 yrs, except for the Teflon ones, which I don’t believe have a calendar life limit.
2 yrs is ridiculous, all but one of my water hoses on my Yanmar 4JHE are 32 yrs old as they have the factory paint on them, at 32 yrs old, they still work, do not leak, but are as hard as a rock and removing a component may result in a torn hose.

However the hose from the strainer to the water pump is the thick heavy hose rated for below waterline use, it’s new and I’m not replacing it with silicone, just the engine hoses them selves

Sailmonkey and A64,

Where did you get, which make, of Silicone hoses are you guys using?

And yes, agreed that 2 years is rediculous. I'd hazzard a guess that there are not many people that do replace their Yanmar hoses every 2 years, even quite dedicated owners. For that matter I was suprised to see it written and would dare say that most owners are probably not even aware it is recommended.

[Q Xopa]

Originally Posted by thinwater

There are downsides to silicone hoses, part of the reason high-end cars and heavy duty trucks are not always fitted with them.

• Permeable to AF. It will go right through the walls.
• Poor oil resistance. For example, I've seen hoses ruined and fail explosively that were under the dip stick (I was involved in writing the recall notice). Oil in the coolant can also cause this. Really, ALL hoses on the engine need to be oil resistant.

Just sayin' you may want to read up on the down sides. Not everyone in the vehicle industry believes silicone is better, based on bad experiences.

Interesting.

[a64pilot]

I buy mine on Amazon, usually in bulk lengths, however there are many special shapes, at least 90’s and 180’s etc.
Just ensure it’s four ply and rated at 80 PSI or higher and high temp., cause there are hoses that I believe are meant for engine induction systems that are much thinner, however they usually are of course big sizes too.

All the high temp silicone hoses I have seen no matter the color of the outside are red on the inside, however there are many hoses that are not red on the inside, and I believe they are not high temp.

Do you need a 4 ply hose rated for 300F and 80 PSI.? Maybe not, but I like having the stronger hose.

[Sailmonkey]

Originally Posted by Q Xopa

Sailmonkey and A64,

Where did you get, which make, of Silicone hoses are you guys using?

And yes, agreed that 2 years is rediculous. I'd hazzard a guess that there are not many people that do replace their Yanmar hoses every 2 years, even quite dedicated owners. For that matter I was suprised to see it written and would dare say that most owners are probably not even aware it is recommended.

Our engine was supplied with them from Phasor.

[Q Xopa]

Originally Posted by thinwater

Water, ethylene glycol, or polypropylene glycol.


Racers love them because they are tough, but they have problems for everyday cars and trucks, which is why they are not factory equipment. I've known companies and bus lines to switch, and then switch back.



----

Drawbacks of Silicone

Permeability to oil and fuel (a problem anywhere there are drips)


The molecular structure of silicone doesn’t play well with oil, fuel, and other oil-based products. We do not recommend using silicone hoses for any applications where they will come in contact with fuel or oil.
Permeability to water molecules (significant problem on vehicals, such as buses and line-haul trucks with high run time)


Silicone is watertight, but water vapor can escape very slowly through the walls of the hose. Think of a balloon that you blow up with air and leave on a table for a week. The air escapes very, very slowly through the walls of the balloon. There’s a similar effect with silicone, and if you have silicone hoses on a car that you use as a daily driver, you’ll find yourself having to replace water in the reservoir from time to time - not because you have a leak, but simply because the water is escaping through the walls of your hose. While silicone hoses are a must for racing applications, some people don’t like them in a daily driver.

I suspect cost is a reason OEMs dont use them.

Yes, no doubt this is true.

However 'oil resistant' rubber isnt totally 'oil proof' either. And as we know and Yanmar are nervous enough about rubber degrades.

I guess there's no perfect answer. So I suppose the best we can hope for is being informed of the pros and cons.

I havent sourced or priced silicone hoses but I hear price is a con.

[thinwater]

Originally Posted by Q Xopa

I suspect cost is a reason OEMs dont use them.

Yes, no doubt this is true.

However 'oil resistant' rubber isnt totally 'oil proof' either. And as we know and Yanmar are nervous enough about rubber degrades.

I guess there's no perfect answer. So I suppose the best we can hope for is being informed of the pros and cons.

I havent sourced or priced silicone hoses but I hear price is a con.

As I said, whole bus and truck lines have gone to silicone, and then gone back after experiencing problems. It is not cost. It is pluses and minuses. They work out best on trucks with impeccably maintenance, where AF is checked frequently and there are zero oil leaks. Hose connections, particularly in the larger sizes, are more prone to leaks, because the hose grows and shrinks.


I'm not sayin' they aren't good. I've speced them in chemical plants. But they are not always better and generally ONLY makes sense if there is a specific issue, like very high temperatures. In fact, standard hose failures nearly always trace back to installation errors, often with the clamps, chafe, or hose routing (too hot, sharp bend, or not supported).

[a64pilot]

Ever heard of Silicone brake fluid?
Well, it’s good stuff,but probably not for everyone, Silicone hoses are likely the same.
If your engine is oily, greasy and nasty, silicone hoses are not for you.