Your worst nightmare: popping a cooling pipe on the back straight of your local track at 6,500 RPM effectively emptying your cooling system and overheating your engine in seconds. Luckily, the Mezger-based 996 and 997 engines are extremely resilient. This doesn't mean that you shouldn't prevent this failure from occuring. Successful ownership experience with a Porsche Turbo, GT2 and GT3 begins with preparation.
'When' Not 'If'
Start preparing- there's no better time than now to take action. While you're beginning to budget and plan your repair, here are some factors to consider:
The coolant block housings are made from cast aluminum while the pipe that the hoses clamp-to are made from extruded aluminum. Porsche engineers know that cast and extrusions expand and contract differently so they secured the pipes into the cast with an epoxy designed to expand and contract as well. Due to the rapid temperature changes in the engine compartment(my theory) and other factors, the epoxy can work loose and leave you roadside(or trackside) with potential engine damage not to mention inconvenience and expense.
What They Look Like
Below is an image of a cooling pipe that has come loose. The epoxy(brown substance) is in some cases not strong enough to retain the pipe. Note the pink residue beneath: this is evidence of coolant leakage before the pipe actually popped out. In most cases, popping pipes can be prevented. Periodic inspection can catch this failure before it happens!
Welding: At first glance, replacing the pipes and welding them into the cast housings looks and sounds great. Who can argue with how good this looks?
Unfortunately, cast aluminum components are porous and don't react well to welding. The heat inflicted pores will increase in size and generally cause future leaks. We've seen some circumstances where welding the pipes works and doesn't leak. A good quality casting and a gifted welder can produce good results with the right amount of luck. After some time, however, they will most likely look like this:
Again- more pink residue is a sure sign of a leaking coolant. Even after a bulletproof weld, this cooling pipe can't stop seeping.
Pinning: Another solution is to 'pin' the pipes to prevent their loosening. Simply put, anchoring the pipes into their cast housings with a high grade epoxy that can expand and contract with the metal coupled with a bolt that secures the pipe is a viable, cost effective solution that wont' disrupt the metal and guarantee it's integrity. We prefer this method. Here's how it will look:
The following method will produce a long lasting solution:
A hole is drilled and tapped to fit a stainless button-head allen screw.
The screw's length is equal to the thickness of the material so that it does not impede flow.
We use thread sealant on the screw during installation to prevent leakage.
The inside of the pipe is cleaned and wire brushed to ensure no debris remains after modification.