Silicone hoses. Yay or nay?

tquattro

Well-Known Member
Joined
Jun 18, 2008
Messages
1,089
Location
Transylvania
Car(s)
Audi A3 1.8T
This weekend I found two PCV breather hoses sliced(part no. 2 and 4 in the diagram) on my car. For now, I ghetto fixed them. Today I wanted to order all 3 OEM rubber hoses (part 2,4,5) but they are quite expensive at ~120GBP (~180$) for the set. So I went online to search for alternatives and found this: part no2, part no.4 and part no.5. This would cost me 80GBP(120$) and apparently are more resistant than OEM.
Also, I'm thinking to buy this set as a preventive measure: 5 PIECE BOOST KIT AUM AUQ

Are they as good as advertised or should I go with OEM?
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From my understanding, silicone is significantly more resilient and resistant to temperature. It is also much more resistant to abrasion. If they are cheaper than OEM, it's a no brainer. The only issue with silicone hoses is that it can require a better or stronger clamp due to the low compressibility of the silicone walls. This can be remedied by buying better or bigger clamps and tightening it down properly. Once silicone had tightened it tends to almost bond with your aluminium intercooler piping and such and so it clamps much better, but be warned that you may destroy your standard auto parts store $0.85 clamps if you try to tighten them down on silicone.

All of my pressure and boost hoses on my R are silicone.
 
Another concern is that with some plastic or composite fittings, you might clamp down on a silicone hose (to seal it) hard enough to crack the fitting. Something to think about if you have such fittings.
 
Also, make sure what you are using isn't reactive to silicone. Like...you shouldn't use silicone-based lube with silicone sex toys.

...

*cough*
 
^:lol:

Good things to know. Part no.1 from the diagram is plastic. I will order them today.
Thanks!
 
Spectre possibly knows more about this, but I seem to recall something about it not being a good idea to use silicone hoses where they would interact with engine oil. The breather pipe blows oil from time to time. From what I remember silicone hoses are good replacements for coolant hoses and vacuum hoses only. I could be wrong though.

At least on my car, I've been told not to go cheap-o on the PCV system (if you are handy you could make the hoses yourself), and instead always go OEM.
 
You can't use silicone for hoses liquid oil is flowing through all the time as real silicone isn't very oil resistant. Using it for PCV purposes can be hit or miss and depends on the system. If it does rot, it will rot from the inside out, so you'd have to inspect regularly. Some 'silicone' hoses intended for oil use are really Viton or some other substance that looks like silicone (or have a lining) but are fine with oil so check with your vendor.

On the other hand, it's perfectly fine for boost/intake and coolant hoses.
 
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Now I have second thoughts. Found this issue, with oil sweating through the walls. I searched for problems with the CreationsMotorsport's ones, they seem like a popular replacement on 1.8T(on UK Skoda/Seat/Audi/VW forums), I didn't found any issues...maybe they need a little trimming, but other than that no real complains.
Apparently the OEM ones aren't really that resistant either. The ones that failed on my car were very mushy, they had oily walls but no crud deposits. I don't know if they were ever replaced, but I think that due to the mileage of the car -230000km=>more oil/gas vapours will get in the PCV system- a new OEM set will not last for very long.
 
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To the myth busters out there: While I was tearing down the 4A-GE an old drag racer told me to avoid silicone around the engine since it had a good chance of fouling the sensors (O2, I think was the one he mentioned). Was there any merit to this? True in the early days of sensors? early days of silicone usage? true in the early days of an old wive's tale?
 
To the myth busters out there: While I was tearing down the 4A-GE an old drag racer told me to avoid silicone around the engine since it had a good chance of fouling the sensors (O2, I think was the one he mentioned). Was there any merit to this? True in the early days of sensors? early days of silicone usage? true in the early days of an old wive's tale?

True with early versions of RTV silicone, but most of them are okay now which is why the packages say 'oxygen sensor safe' or just 'sensor safe'.

Which is a different kind of silicone than the OP's hose query was about. :p
 
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I didn't found online people complaining about misting or sweating problems with the Creations motorsport's PCV breather hoses, so I ordered them, including that 5piece boost set.

Thanks to all for your input!
 
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You hoser.

 
Can you tell when silicone hoses are getting worn out like you can with rubber coolant hoses? Squeezing rubber coolant hoses and seeing if they're squishy was the tell tale sign that the hose needs to be replaced asap or endure getting stranded.
 
Can you tell when silicone hoses are getting worn out like you can with rubber coolant hoses? Squeezing rubber coolant hoses and seeing if they're squishy was the tell tale sign that the hose needs to be replaced asap or endure getting stranded.

Not usually, which is one reason (cost being another) why 'normal' cars don't have them. Silicone lasts a lot longer but has more abrupt failure modes.
 
I replaced the 3 PCV breather hoses, they were perfect fit. I found two more slices in the old ones, they were really crummy. The lower breather pipe had lots of deposits on it's walls.Next week I will replace all the boost hoses, I need to order one more boost hose pipe( this will be OEM - didn't find any silicone alternatives). The intercooler will also get a good cleaning, I suspect that it is quite oily inside.

Maybe I should have invested a bit more to fit a catch can, this is inside the part no. 11 from the diagram:
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