Isuzu 2AB1 diesel rebuild

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Tallystick
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Isuzu 2AB1 diesel rebuild

Post by Tallystick »

So the diesel that came with my Triton turned over, but not all the way I recently discovered. Almost a full rotation but it would seize, almost completing a full rotation. I tore down the motor, removing all the accessories, and just succeeded in removing the head. The bottom end turns freely, pistons and cylinder walls look good. It appears the problem was a bent valve.

Lessons learned so far:

Rusted seized fasteners are obnoxious, but not insurmountable. Heat cycling with a propane torch, tapping with a hammer, and PB blaster is an effective regimen for removing rusted seized fasteners. Parts for these old motors ARE available, but not easy to find suppliers. A few of the Isuzu industrial dealers are able to obtain the few specialized parts I need. The gaskets and fasteners are easily purchased or fabricated from generic stock. Even the saltwater pump impeller is an OTS Jabsco part :)

Rebuilding this motor has actually been one of the more enjoyable projects so far. Beats deck fairing that's for sure.
Tallystick
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Re: Isuzu 2AB1 diesel rebuild

Post by Tallystick »

No bent valves. Just rust from the cylinder head had fallen down and was blocking the valves from fully closing haha. The valve components polished up nicely, so I reassembled and the motor turns fully and smoothly. Waiting for a diesel compression tester to be delivered. I think there's a good chance she'll have compression.
Tallystick
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Re: Isuzu 2AB1 diesel rebuild

Post by Tallystick »

Well a few of the valves leaked, so I had them reseated at an engine machine shop. Good trick for testing valve sealing is to pour water into the manifold side of the head to see if any liquid leaks out of the valves. The owner thought the old little diesel motor is cool so he only charged $30 to reseat the valves AND to remove a bolt that had sheared off in the manifold. What a deal!

Waiting for my diesel compression tester to arrive, and then I'll be able to test compression. The headgasket for this motor is made from copper, so it should be reusable. Just needs to be cleaned up and have copper gasket sealer applied.

Also had the water pump casting explode while trying to press out the bearing. I was able to find a new water pump for $325! However, on ebay I found a water pump for $30 with identical casting, but with a different flange so I bought that one. I removed the flange from the new pump, but the shaft on the new pump is 1mm larger. So now I'll have to hone the old flange to expand the ID by 1mm to fit the new shaft, and then it will work. I found a hone that attaches to a hand-held drill at McMaster-Carr for $15 that will do the job, and ordered a digital micrometer off Ebay for $15 to measure the ID during the honing process.

Meanwhile I'm cleaning all the external engine parts, rust-proofing, and prepping for paint.

Ended up breaking the seawater pump pulley casting. I'll try to weld it back together with nickel welding rod, which should work. If my welding skills aren't up to the task, I'll have to track down a new pulley.
Triton106
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Re: Isuzu 2AB1 diesel rebuild

Post by Triton106 »

Great story! Any pictures you can share of the project? I love those engine rebuilding project pictures.
Ray D. Chang
Triton 106 in Berkeley, CA
Tallystick
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Re: Isuzu 2AB1 diesel rebuild

Post by Tallystick »

Sure, I'll post a few pics. I'll take more, but these are already on my camera.

Here is a photo of my new Isuzu C201 water pump with the Pisces flange machined and attached. The brake cylinder hone worked well for expanding the ID of the flange.
Pisces_C201WaterPump_small.JPG
This one is a photo of the cylinder head after cleaning, and seating the valves. I'm still trying to figure out what is supposed to attach to the coolant ports indicated by the red arrows. They are rusted up and I can't tell if there were fittings for coolant lines, or freeze plugs that belong there. Trying to track down some other Piseces diesel owners to get photos of their motors. I have the Pisces parts catalog and service manual, but there aren't any parts listed for those coolant ports in the water jacket.
Pisces27Head_small.jpg
I had a tough time finding 11mm bolts to replace the broken head bolt and the few that had corroded hex heads. Fortunately, the friendly manager at the local Autozone let me rifle through automotive head bolts until I found some GM head bolts with the same size, pitch and length.
Tallystick
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Re: Isuzu 2AB1 diesel rebuild

Post by Tallystick »

No compression. Took the head back off, poured kerosene in the cylinders and the head to test for leakage. Cylinders held the kerosene well. Some was still in the bores the next morning, so the rings should be good. All four valves in the head leaked kerosene. So much for the machine shops valve seating job.

So the head went back to the machine shop. Got the head back and the valves are better, but 3 of the 4 still leak although more slowly.

Went to Autozone, bought some valve lapping compound and borrowed their valve spring compressor . I spent a few hours lapping the valves by hand.

Now all the valves are sealed nicely, and no kerosene leaks after 15min or so. Head should be good to go.



Turns out I didn't look closely enough at the head diagram in the Pisces parts manual. The holes with the red arrows in the above pic are for freeze plugs.
Tallystick
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Re: Isuzu 2AB1 diesel rebuild

Post by Tallystick »

The old 2AB1 now has compression. Had low compression initially after reinstalling the head. I could hear pressure escaping past the rings into the crankcase. But the cylinders look pristine, so after a bit of research, determined the likely problem since the motor hasn't run in years, was that the rings were partially stuck in the ring landings, preventing the rings from fully sealing as the pistons moved.

So I used some chemical magic to free the rings. A combination of kerosene, and lucas racing oil poured down the injector holes, first soaking and then working the solutions into the cylinders by hand rotating the motor with the glow plugs out, and then with the compression tester adapter connected seems to have done the trick. The compression tester adapter has a valve that allows pressurized air/fluid to escape, but still allows significant pressure generation in the cylinder. I was able to get some nice brown oil spraying out of the tester adapter, which was presumably the gunk preventing the rings from expanding.

So now I have compression numbers a little below spec, but I was testing compression with the motor cold and rotating by hand, so I think it's likely hot compression with the motor turned by the starter will be above the service limit once I'm able to test that. I don't think the large compression increase was merely from oil helping to seal the rings, because the compression didn't increase much when I initially put oil in the cylinders, it went up steadily as I went through the above process a few times.
Paulus
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Re: Isuzu 2AB1 diesel rebuild

Post by Paulus »

Good going!
Tallystick
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Re: Isuzu 2AB1 diesel rebuild

Post by Tallystick »

Pisces 27 with most of the accessories installed. Almost ready to fire up the diesel. Had to do a variety of fun things like weld a stud to the block to repair the broken boss for the alternator tensioning bracket, fabricate a bracket for the heat exchanger, build a new exhaust riser, cut new aluminum end cap for the manifold and tap pipe threads, rebuild the mechanical lift pump, and more. Transmission and prop shaft are installed and aligned.
Pisces27_may2012.jpg
Tallystick
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Re: Isuzu 2AB1 diesel rebuild

Post by Tallystick »

Cranked the motor with the starter and compression is nicely above specs. Built a glow plug circuit last night. Gotta test that, and if the glow plugs are operational, almost time for first start.
Tallystick
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Re: Isuzu 2AB1 diesel rebuild

Post by Tallystick »

Diesel motor is now operational. Fires up nicely after letting the glow plugs heat up.
Ric in Richmond
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Re: Isuzu 2AB1 diesel rebuild

Post by Ric in Richmond »

Very nice! Cool little motor.



For any old copper gaskets or washers a neat trick is to anneal them by heating with a torch and allowing them to cool. The copper hardens and by heating and slow cooling it softens it.

Handy when you don't have a new washer and the old one is not sealing.
Ric Bergstrom

http://andiamoadventures.blogspot.com/

Archived old blog:

http://andiamo35.blogspot.com/

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Paulus
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Re: Isuzu 2AB1 diesel rebuild

Post by Paulus »

Are you going to paint it?
Tallystick
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Re: Isuzu 2AB1 diesel rebuild

Post by Tallystick »

Already is painted. Clear polysiloxane. Exhaust riser is painted with silver high temp paint, and is now wrapped in fiberglass thermal wrap. Fasteners are coated with a thin layer of marine anti-seize. After I run the motor enough to make sure nothing leaks, I'll degrease the motor and paint a 2nd coat of the clear PSX-700.
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