Hoses, the arteries of every engine, they carry the vital fluids and gases for it’s operation. Whilst many after market accessories are added to the original equipment of the vehicle, hoses are often neglected. This is especially true when components are installed to increase performance. Raising bhp and torque increases pressures putting more demand on to the standard hoses that do not have upgrade ratings. Exhaust temperatures also increase, causing higher under bonnet temperatures.
If you are looking to replace hose sets, at first glance you will notice the price of the replacement items and wonder what am I getting for the extra cost, well its not just for the pretty colours. If you look at the price of an OEM replacement then there is a good chance the silicone option will be cheaper and in the long term a much better purchase, … why?.
With the temperature range stability, ozone resistance, longevity due to lifetime flexibility, thermal, and electrical insulation properties, silicon polymer hoses are a miracle of modern engineering material development.
Good quality Silicone is apparent from the richness of the colour. Some manufacturers use two different types of silicone; one for the exterior and one for the interior. If your hose was not specifically made for coolant or oil use, it usually means a lower quality material has been used, however, there are special linings that are used for coolant and oil applications. Fluorocarbon is one such lining that is impervious to petro chemical substances, but this needs a double curing process thus increasing costs.
The best silicone hoses on the market today are still hand made and the benefits are in the long life and performance of the product compared to its counterparts.
Using the correct hose for the application is critical, for example you do not want to use a silicon water grade hose for a turbo fitting. Silicone does have a much higher temperature yield than standard rubber materials; silicone wrapped with fiberglass will have an even higher temperature yield around 300-400ºC. much more than normal grades of commercial silicone wrapped with other materials. One of the benefits of good silicone under high temperature is its increased adhesion properties to metals. Although small, this will reduce the possibilities of pressure loss, e.g. in turbo fitments. Another consideration is that radiator hoses are cooled from the direct transfer of coolant, which allows the hoses to have a longer life. Direct transfer of compressed air coupled with “operating” temperatures will dramatically shorten the life span of radiator hoses forcing them to have seam cracks and stiffen to the point that clamps have very little clamping pressure on the hose. Radiator style hoses will also expand under load.
Another point to remember is that silicone has a different crush capability than rubber, as in, when using jubilee clips to fit the hose, there is less flexibility to crush the silicone to form a seal. So make sure you have the correct size hose and clips to fit it.
Here are a few examples of poor silicone replacement hose materials;
1, The hose has a different inside lining and also a poor quality wrap and dull finish. Also, if you look closely, the lining has started to deteriorate due to the polyester lining absorbing extra fuel and oils. The polyester lining will ultimately swell and cause the hose to expand and weaken.
2, This 3.5″ hose is new. Notice the material used throughout. Good silicone hoses should have a smooth finish and the “wrap” should be minimal. Special bends, such as 90 deg and are over 4″ diameter will always have 4-ply fiberglass to support the bend.
3, This is a brand new 4 ply (layer) hose that has never been installed. Notice the polyester fabric is coming away. Furthermore, the outside (black layer) and the inside (blue layer) are of different quality. Good quality silicone should have a deep colour and not a dull appearance. Many manufacturers use two different materials therefore reducing manufacturing costs and possible performance in the long term.
There are many good manufacturers out there who will supply your hose kits specific to your needs. We would recommend to do your research checking quality and prices armed with the knowledge from above and beware of the cheap imports available on Flea-bay.