KEEPING COOL
Porsche introduced coolant pipes with Henn connections (as opposed to hose clamps) on the 997/987 generation of 911/Boxster. These have steel male ends formed on the hose with locking slots and an O-ring seal groove. The male end is retained in a female housing by a C-spring clip. The housings are typically either a moulded plastic part, a formed end on a thin alloy tube or machined in a casting. These connections are reliable, quick and easy to use. However, if exposed to harsh driving environments, they are susceptible to corrosion. On the 987/997 models, some of these connections are in a very exposed location in the front wheel arches (alongside the steering rack) and can corrode badly. Other connections under the car may also suffer, albeit to a lesser extent. In a car used all year in all weather, the most exposed connections may begin to fail as soon as six years after manufacture.
Initially, the tell-tale sign is damp around the exposed connections, which are easily checked visually. Henn connections continue to be used by Porsche today, but 981/991 and later models have very different pipe layouts where the connections are better protected from road spray.
The complete cooling pipe layout for 987/997 models is shown in Fig 19 on page 115. Numbers shown in the following text refer to the labelled parts in this diagram unless otherwise stated.
The cross tubes (1) are alloy with a female Henn on one end. The second end connects to a plastic ‘distributor tube’ (3) by way of a conventionally clamped short hose (12). The rear ends of the distributor tubes turn towards the centre of the car where a short hose (10) with Henn connections connects them to the main (alloy) supply and return pipes (2), which run along the centre tunnel. At the rear, these pipes connect to the power unit via more hoses (11) with Henn connections.
The front end assembly shown in Fig. 5 (below) is mounted on the front crossmember with the cross-tubes running in a ‘tunnel’ under the body (shared with the steering rack and anti-roll bar). Some owners have managed to replace the alloy tubes in-situ. Removal
