Well, I just completed the thermostat replacement… IT IS as much of an PITA as everyone said. Only in my case, it was complicated by lack of planning! I (foolishly) figured that I will just run over to a nice hardware store next to my town and match up the oring (SINGULAR) that I need… There were THREE things with this plan:

1. Hardware store didn’t have the size that I needed!
2. What you find at most hardware stores (and even the hydraulics stores!), are Buna-rubber orings. They are fine up to 200*F, but most car engines can often get up to 200-230*F! They will work fine at first, but eventually they will harden and will start to leak. That might take 5+ years to happen, so it will be OK for most people.
3. There are actually TWO different sizes of o-rings! The “small” (20mm ID) and the “large” (24mm ID). Technically, you only MUST remove the smaller one. BUT once I saw its condition (was hard as PLASTIC!), I decided to replace the lower/large one as well. Only at that point, I didn’t realize that they were two different sizes… That cost me one more day.





What I should have done, was to order from Honda/Isuzu:

Isuzu/Honda part numbers :
9-09561-225-0 Gasket, Water Pipe
9-09561-220-0 Gasket, Water Pipe replaced by 1-09623-130-0
8-97123-161-4 Thermostat

Info is from Isuzu Planet http://forum.planetisuzoo.com/viewto...712891#p712891

What I did instead was running around from one hardware store to another and some hydraulic shops. To make things work:

- the smaller one was #116 from a hydraulic shop.
- the larger one was #119 (though hardware store named it #19, as I recall)

Ether way, these o-rings made from Buna and are NOT all that great for automotive use!

IMO, best option is just to buy the above part numbers! Even with Honda's markup, they are only around $3 each, you just have to plan ahead!

BTW, both of my "original" orings were completely HARD and cracked the moment I attempted to remove them. I also had a few drops of antifreeze on the top of my block, so I suspect those orings were already failing and I just didn't know about it. I have no idea if they were already replaced with Buna orings or if this is what happens to OEM orings after 14+ years...