1988 Isuzu Trooper diesel conversion

After filling the radiator for the first time a few weeks ago, I immediately noticed a large coolant leak coming from somewhere near the alternator, under the A/C compressor (this was why I filled it with water initially!). I had other things to do and so let it be for a while. I was able to repair it today, or so it seems... it has not yet been pressurized, but it doesn't leak during filling like it used to.

I removed the A/C compressor and was able to spot the leak - coming from the water pipe connection at the block. These types of connections employ a metal pipe with an O-ring around the end, slipped into a machined area of the block (in this case, a bolt-on water neck) and secured with a bolt. I've seen similar designs used by Honda. In any case, this water pipe runs from the block, loops around the alternator and becomes the lower hose connection underneath. It is similar to the water pipe found on the 4-cyl. Isuzu Trooper gas engine in this regard.

I removed the two bolts, one at each end of the pipe, which secure it to the engine. I also removed the alternator heat shield which bolts to the pipe - one of the mounting tabs is visible in the photo. I could then pull the pipe out of the water neck. The alternator has to be removed to get the pipe out completely, but I was able to work with it pulled back and to the side. I cleaned the water neck surface with some emery paper and cleaned the pipe's O-ring groove with steel wool, replaced the O-ring (I used a spare O-ring that came with my Wix fuel filter for this project - the O-ring is meant to seal the sedimenter at the bottom of the filter) and re-assembled the water pipe. Common O-rings available at the local hardware store would probably have worked as well.

No leaks after an initial filling of the system; it remains to be seen whether it will hold under pressure, but I feel confident that it will.