Re: Hoses

[Mike Wattam <101714.1343@domain.elided>]

Due to coolant hose problems I carried out a detailed investigation of hose
failures in 1990-1 which included detailed research by UK commercial
research organisations.  This was as a result of failures with unreinforced
hoses.  A copy of the full report is still available for those who want. 
The highlights are;

UNREINFORCED HOSES
Unreinforced hoses may be prone to failure on the Stag because of the high
operating pressure of up to 20psi.

The unreinforced hoses do not like very hot water - up to 230C on the Stag.

At high temperature they can often 'balloon' and stay swollen after the
engine has cooled down.

The rubber compound used may not be very resistant to externa lcontaminants
including oil, solvents etc.

They are heat moulded to shape after manufacture as an extrusion, this
means that on the outside of bends the material can be very thin.

Their safe life in use may be only up to 3 years.


REINFORCED HOSES
Reinforced hoses have a netting substance between the inner layer and the
outer layer of rubber, and traces of this can be seen at the end of each
hose.  The inner layer is coolant-resistant, while the outer layer is
oil-resistant.  These are scientifically designed, specifically to
withstand the hostile environment of cars.

Older reinforced hoses, as stated had the string netting wound round the
outside then bonded in place with a rubber glue - or sometimes more liquid
rubber - very messy and inaccurate.  These were also prone to attack by
solvents, oil etc..

YOUR ACTION
Check your coolant hoses to see if they are the reinforced type.

If not, 
        is there any residual ballooning when cold
        and are they thin on the outside of bends

Change any coolant hoses known to be older than 5 years, as a matter of
course.  This includes heater hoses.

Mike Wattam
Triumph Stag Register