Last weekend I was flushing the cooling system of my 82 diesel long bed and as I expected the heater, the heater
hose and the hose to the oil filter base were all clogged with orange muddy rust. This required the removal of all
of these hoses and the heater core. The hose comming from the back of the oil filter thats connects to the steel
tube above the intake had an inline themostat in it. This item had to be removed with the hose as it was filled with
this rusty sludge and after cleaning it and replacing the hoses, I don't know which way to install the 'stat'. Would it
be right side up or up side down or is it even needed.
Thanks for any help
Fitzworld

There's an arrow under the 76.5C rating on the longest "half" of the unit, the arrow goes up. The unit restricts coolant from the head until it's warmed up, thereby not over cooling the oil and contributes to good fuel economy. Whether it's needed is up to the owner. When mine have gone bad, motor runs cooler than normal, soot goes up, fuel milage down. Damn expensive from Isuzu and I've never found another source.

Thanks a bunch Tom.

Fitzworld

What engine model are you guys talking about? Is it a C223 or C223T. I have an 86 Troop with a C223 (n/a) and I can't seem to find an in-line thermostat near the oil filter.

Should I have one? <img src="/forums/images/graemlins/confused.gif" alt="" />

Boyd,my experience it's both models. Look for it in the water hose coming up from the oil cooler before it reaches the top of valve cover, should be a bracket that surounds it & keeps it from vibrating. But due to this site I've become aware that Isuzu configured similar vehicles very differently around the globe, sometimes even in the same country, ie; my turbo has no EGR (thankfully!!) while another claims it was standard? Maybe no oil cooler means no thermo-valve!? If your rig runs OK, doesn't run too cool (is that even possible in that "humididity"?) I wouldn't lose sleep over it.

It's Isuzu part number 5-21770-001-2. It's called the oil cooler thermo-valve and St Charles has it for $49. Mine was shot so I took it out and just stuck in a piece of copper pipe and my truck does run much cooler. So much in fact that it failed emmissions three days ago, so I guess I'm going to have to cover the radiator partially to get it up to temp specs or buy the danged part...

Jesse