Engine Design
Call Us: 1-949-646-7461

Coolant Pipe Failures

Coolant Pipe Failures on 996 & 997 Porsche Water Cooled Engines


This paper is not to prove that one repair over any other is superior, but to explain the cause and, hopefully, put the reader at ease once the repair is done.

The cause.  Simply put, extremely poor engineering. It does show the level of engineering that is compromised today in an effort to increase profits. We all know the results. It is often asked, what is the best way to repair these water assemblies?

The repairs require the engine to be removed from the car to easily get access to all of the parts that require attention. These are the two water exit elbows on the top of the cylinder liner housings, and the water pump housings itself. On the later engines, the elbows that are below the heat exchanger also require repair. These elbows fail due to the material they are made from, which is not the same as the other pipes.

So the repairs that seem to be well known are welding or this “pinning” solution. I have not seen any parts repaired by pinning, but I expect this to include some sort of threaded screw holding the two parts together.  I assume it is a stainless screw and the pipe is re-glued into the housing with some sort of epoxy marine applicable glue. To comment on this repair objectively requires some understanding of exactly what is done. As I have not seen this in person, I will refrain from finding any fault.

However, this is not a repair process that I would recommend. I cannot imagine any experienced mechanical engineer doing such a repair on any water piping. For years’ engine water out and water in pipes have all been made from aluminum tubing, typically around 062” wall thickness. These would have been welded to other aluminum parts such as cast elbows, water pump housings, etc. For quite some time, we modified or made water system parts from aluminum piping and bent water pipes before CNC bending was available. We welded pipes into water pump housings, cylinder blocks, heads and many other required solutions without having failures. As with any modification, it should be well thought out, performed with the correct equipment and well tested before being used.

In the past 30+ years being around any sort of performance engine, I have never seen water pipes “pinned”. My take on this is, this repair came about due to the inability to weld correctly or no welding equipment was available.

Our choice is to weld the fittings into the casting housing, as this is how we have done this sort of solution for years on other engines and sub assemblies. We have “repaired” many of these parts on our own customer’s engines and on parts sent for repair from other assemblers. We have welded every one and none to date, to my knowledge, have failed.

I have read the concern about welding thin water pipe assemblies to much thicker castings. Welding should be done with “Tig” welding equipment by an experienced welder. It doesn’t have to be done by any professional certified welder, as many of the best welders I have been around in racing are not certified. They have become great at what they do from experience.

I am sure many will tell me their pipes have been repaired by this “pinning” process and they are surviving just fine. This is not to say that this process is wrong or will fail in time, but rather how we would repair the parts. In the end, customers need to feel confident in the repair and the best way to ensure customer confidence is a customer’s understanding of the repair shop’s knowledge and experience.