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.

Finding an oil filter for the 4JB1-T engine was a bit of a hassle. Apparently, older versions of this engine used a filter identical to the one used on the Isuzu C223T, the diesel available in the Trooper in the USA. My engine, however, required a different filter with rather strange specifications. The center hole is 26mm wide, making it difficult to match.

I found a page which listed a few different part numbers (go to the 'workshop' link and select 'part numbers') but none of them crossed over to any North American manufacturers. A 4x4wire member then found this page, which again lists a few different options plus an OEM number. Here is the 4x4wire thread discussing this.

I called my nearest Isuzu industrial dealer and was able to order filters based on this number. Apparently, no other Isuzu filters in the USA will fit, and there are no known aftermarket crossover parts available, so this is the only filter that will work (save for parts ordered from overseas).

As an aside, it is not a dual-stage filter like the one I removed from the engine. This means I will need to change it more often than the dual-stage interval of 7500 miles, but that's fine with me. The only other problem is that they cost $20 each!

Due to the custom pressure hose breaking at the pump fitting (due to a hose defect), I needed to re-work the power steering system a bit. The complicated pressure hose routing described earlier was eliminated in favor of a much simpler design. Instead of running to a hardline connected to the steering sector, the hose now runs directly from the pump to the sector.

The connection at the pump is a stock Trooper part. This one came with my diesel engine, but it is identical to the fitting on the 4-cyl. gas engine pressure hose (except for the pin on the side of the diesel connector - this is not necessary and I considered cutting it off). The hydraulic shop cut the hardline off the fitting and brazed on a standard threaded flare connector. This creates an adaptor fitting which can be connected to the rubber pressure hose itself.

The steering sector fitting is another stock Isuzu part, this one having been cut off the old power steering return line, which ran from the reservior to the steering sector and threaded right in. The pressure and return ports are the same thread size, so the fitting was cut off from the old hose and again brazed to a standard fitting, creating an adaptor fitting at the other end.

The hose itself is a rubber pressure hose with identical fittings on each end which allow the two Isuzu adaptors to be threaded on. This way, if the hose ever fails or deteriorates, I can just have a new center section made and re-use the fittings.

The upper right photo shows (most of) the new hose. The upper left photo shows it installed, with another short section of hose added on at the sector end to account for my measuring mistake. Next time, I will be more careful and only need to buy one section of hose!