That engine is so cool!

Bad pun, I know.

This weekend saw the culmination of the cooling system plumbing and thankfully not the start of my comedic career. The fan isn’t installed yet, but it’s a major step to have completed all of the coolant plumbing from radiator to engine to overflow tank – anything involving the liquid itself. It involved quite a bit of problem solving and also required completing various other parts of the build like the water pump housing replacement.

As I showed in previous posts, I started out with the kit-supplied straight tubes under the doors. These were wrapped in header wrap to reduce heat seepage into the driver compartment. Towards the front, I connected them to Spectre Magna-Kool flexible stainless hose (the shiny ribbed stuff). It’s not the cheapest stuff, but it’s super-easy to bend by hand, yet once you mount it with the hose clamps it’s in place very solidly.

Front Magna-Kool flexible coolant hose
Under door coolant pipes wrapped in header wrap

Moving rearward towards the engine, I again used the flexible hose to make connections to the inlet (passenger) and outlet (driver) connections on the engine. To make the turn, it was easier to get a pre-bent 90 degree stainless tube which I made sure to have lots of rough surface beneath the clamps.

Driver side engine to straight pipe connection

Next up was the coolant overflow tank. I decided to use one which had a visible coolant level (not pictured). After getting the coolant hose from Porsche ($32 – cheap!), I spent quite a while playing logic puzzles in Lowe’s brass fittings section. Porsche hose has a very specific shape which I had to cut down, but the question was where to do so and finding the proper hose and fittings to make the connection into the SAE-sized tank fittings. Here’s the result of that:

Adapting the overflow tank hose to the OEM hose

Another point about the coolant tank is that it’s only barely above the level of the topmost part of the rest of the system. This is actually not at all different from the way the setup is in an actual Porsche, though it took some measuring to get the right place to install the tank when account for coolant level, where the center section lines up and the height of the rear deck lid. The final place was here on the passenger side:

Adapter for not having transmission coolant lines
Coolant overflow tank

With this engine, I would need a very specific tank size and shape to be able to mount it on the rear bulkhead unfortunately (i.e. a place where it’s definitely the highest part in the system). To mount the tank, I made my own u-bolts.

U-bolt manufacturing

The last part of the system came as bit of surprise. The Porsche GT3 transmission is a bit unique and highly sought after because it has a mechanically (as opposed to electrically) driven transmission oil cooler. This oil cooler works by getting coolant from the engine through two lines that run over the top of the engine and pumping it through a heat exchanger on the side of the transmission. I guess that this method isn’t the best and so my gearbox shop removed the cooler and just plumbed the return into the supply. I can always add an external air cooler if I feel like it or have temperature issues.

So with that I didn’t need the lines running over the top of the engine and I had to plumb supply to return. Below is a picture of what I needed to connect: the 90 degree hose on the left pointing away from the opening on the right (without the hose on it).

Transmission coolant return and feed line connection

It’s a little harder than it looks, because literally each of the four ends of the two hoses has a different size! What I decided to do was to again play a little Lowe’s brass fittings puzzle and make my own adapter. As it turns out, one side was pretty much exactly the size of a 3/4″ thread (remember everything on this engine is metric), whereas the other side was smaller. To make a good connection, I ground down the fitting on the one side with a Dremel and just left a lip at the end:

Making a metric coolant adapter out of an SAE fitting

I then connected the pieces again using silicone gasket maker to really make sure the 3/4″ side is sealed:

Adapter for not having transmission coolant lines

Intake goes back on and voilá, I poured some water in to see if I could discover any obvious leaks.

First splashes of coolant water going in

It’s really no test of leaks when there’s no motion or pressure in the system, but it’s just neat to be able to put the first liquid into the engine. Milestone!

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