After investigating further, I was able to determine the true source of the odd coolant leak. I initially thought it was the lower radiator hose, so I replaced every single clamp with stainless t-bolt clamps. The leak still persisted. I eventually traced the leak to a region higher up – the bottom weep hole of the water pump. Thankfully, the increased visibility and accessibility from going single turbo enabled me to finally find the source. This is the same mystery leak I saw when the car was still in the stock, twin turbo configuration. With the undertray in place and all the clutter blocking any sort of reasonable access, my attempts at diagnosing the problem was greatly thwarted back then. (Albeit, the leak was less prominent at that time.)

I noticed that the leak would only occur during a cold-start and disappear once the car was fully warmed up. This is likely due to the seal inside the water pump expanding from the heat. Regardless, when the weep hole is leaking, it is a sure sign of a failing water pump.

As much as I wanted to lay down the wrench for a while and just drive the car, I knew the only way that could happen is if I postpone my “vacation”. There was no skirting around the issue, I took immediate action and obtained all the necessary parts for the water pump service by the week’s end.

Allow me to demonstrate the Grand Mighty approach to maintenance. If I’m forced to go through the effort of removing and replacing a part, I may as well upgrade it. So in addition to brand new gaskets and hardware (every fastener I needed to touch for this job was replaced), I elected to swap in a new RE-Medy water pump from MazMart. I got lucky when I called MazMart, because I needed the water pump quickly and they happened to only have 2 left in stock.

The first step was to remove the idler and water pump pulleys, remove the thermostat housing, and then remove the water pump. While a water pump service on a rotary may not be as involved as piston-engined counter parts, where the timing belt is interconnected with the pump, there is a catch… The water pump housing is sandwiched between the water pump and the front cover on studs. I don’t think there is a reliable way to remove JUST the water pump without compromising the water pump housing’s gasket. Maybe if the gasket remains in one piece and any movement is severely minimized, but there’s still no guarantee against disturbing the seal.


To be comprehensive, I moved forward with removing the water pump housing as well. And as anticipated, the paper gasket broke apart instantly and needed to be scraped off.


The RE-Medy water pump uses a brand new OEM core, but features a CNC’d impeller blade. This benefits from being more effective at moving water and is said to be void of cavitation up to 10,000 RPM.

Here is a comparison between the stock water pump (top) and the RE-Medy water pump (bottom).


And a closer look at the new impeller.


Replacing the water pump is overall a relatively straightforward job, and especially so with my setup because much of the clutter up-front was removed after going single turbo. The V-Mount also provided adequate workspace, but I did need to remove the studs holding on the water pump housing, because there wasn’t enough room to slide it fully off. However, I spread the work over 3 days. The most time-consuming part was cleaning everything.

I gradually sanded and basically polished all of the mating surfaces. There was slight pitting on the water pump housing to water pump’s surface, so I took the time to fill them in (darker colored areas in the picture below).


Once the parts were ready to go, I dressed all the mating surfaces with a light film of RTV for added security (in addition to new gaskets, of course), and buttoned it all back up.


I’m not quite finished, as you can see, because I’m waiting on a thermostat housing from Japan. I’m used to having parts shipped Next or 2nd Day when in the States, but the whole “overnight parts from Japan” thing isn’t quite as easy. Until then, I’ll have to wait and pick this back up later.

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