Silicone Radiator Hoses: Not for the Street

I noticed that there are more and more “manufacturers” of silicone radiator hoses. We can thank China for finally figuring out a silicone formula that is similar to Samco’s silicone turbo and radiator hoses. I say similar because I am pretty damn sure any silicone hose from China is inferior to Samco’s. If you look on eBay, there are about 15+ pages of shit brand silicone radiator hoses and probably 1 page of genuine Samco radiator hoses. Who knows how many of those “Samco” hoses are actually genuine? China is really hard at work these days with the counterfeit shit recently. More on counterfeits later.

I can remember several occasions when people would tell me something like, “Dude I was driving the other day and my car started to boil over! I added 4 quarts of water to it! Did I lose a head gasket? Where the hell did the water go?” I would ask them if they had silicone radiator hoses and of course they would. So I told them, add water regularly or stop your bitching and get some rubber hoses on the car. While silicone radiator hoses are great, because they are capable of carrying much higher temperature fluids (max 350°F/177°C) than a standard EPDM rubber radiator hose (max 257°F/125°C), they are really only ideal for race cars. Here’s a fun fact: silicone’s water permeation rate is 15 times greater than EPDM rubber. What does that mean to you? It means with the daily heat cycling of a street driven car, that you will lose water from your cooling system over time. According to a Gates Corporation report, “Testing by Gates engineers shows that a Class 8 truck, operating at a temperature of 210°F with a two shift per day driving cycle, would lose nearly five gallons of water each year if it was equipped with silicone hose.” FYI, Gates makes both rubber and silicone coolant hoses so hold off on the forum bullshit line of, “Well of course Gates made that report. They sell rubber hoses!” If you want to read some more on this, check out this PDF pamphlet from Gates Autralia.

Silicone hoses are porous. That’s why you do not use silicone for fuel and oil. It’s also why you shouldn’t use silicone radiator hoses on a street car…especially if you’re the kind of person that does not like to frequently check your fluid levels. I use silicone radiator hoses for race cars or occasionally driven cars that are regularly maintained, but on street cars I use standard EPDM rubber hoses. On top of that, I prefer factory hoses from the dealership rather than the aftermarket hoses that are never molded quite right.

There’s the tip of the day. Now if you already have silicone radiator hoses on your street car just make sure you check your water level regularly. If you don’t want to worry about losing an engine because you didn’t want to listen to me then get yourself some new factory rubber hoses and check the water level occasionally.

7 comments

  1. Thanks for the heads up had no clue about silicone hoses and permeability leading to coolant loss.already bought $85 kit was just waiting on the SS t clamps to arrive for install.gonna eat the $85 and go with rubber oem hoses now.

  2. Yes, I also thought that and I really need my rubber hose to blow off if my truck were to overheat. I am afraid the hose would be too strong.

  3. I put a set on an Evo X I rebuilt after a fire and for the longest time I could not figure out where a near-constant coolant smell was coming from. I pressure tested the system and saw a very very faint drop but could never find any leaks.

    Finally I put some UV coolant dye in the radiator and put a few hundred miles on it. When I lifted the hood and shined my UV light in there, all of the hoses had a fine dusting of dye coating the outside, almost like they were painted. I then realized I was slowly losing coolant through the hoses. Back to OEM for me.

  4. It’s all I had after a radiator swap and I’m losing water rapidly. Maybe a litre this week I was worried head gasket or radiator was shit, now I’ll swap back to oem. Thanks 🤙

  5. Thanks everybody for the info. For the last few days I’ve been doing research on silicone radiator hoses and was about to drop $160 to buy the. You guys really help me dodge the bullet on this one. I’ll have to figure out another way to dress up my engine bay and work on heat reduction. Thanks

  6. I used silicone hose to replace two 1” x 2’ rubber hoses on my class 8 semi. Outlasted the rubber by a factor of 10. Most class 8 rubber hoses are huge and yes I think that would be bad to use silicone in those cases, but to make a blanket statement silicone is not for semis or the street is asinine. Use what works best for the situation. Silicone has advantages in situations and I proved that in 1 million miles of real world testing!

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