In the home stretch of a full rebuild of the 22re in my 93 pickup. Started as a head gasket job several months ago after overheating in traffic and blowing the head gasket.

Replacing the thermostat I noticed the old one has an extra spring at the end that is missing from the new OEM thermostat (and all 22re thermostats available for purchase that I could find). Curious if anyone knows why they're different (redesign? is the second spring a "2 stage" thermostat? was the old one the wrong thermostat?).

 

Every thermostat I have used on an R series engine looks like the new one you have. In my experience, the thermostat with the second spring is common on engines with the thermostat housing on the lower radiator hose, although there may be exceptions to that. I have always wondered what exactly that second spring is for, and after doing some reading it appears to be a bypass valve on a dual acting thermostat (not to be confused with dual stage). The lower disc blocks the bypass passage when the thermostat opens to allow more flow through the radiator, and the engine would need to be designed for this. I did pull one out of a 22RE some years ago when installing an OEM thermostat and it was not having cooling system problems, but I cannot see any benefit to using one on a 22RE which was not designed for this type of thermostat.

 

I agree with supernerd.
Seriously consider that your old thermo was incorrect for 22re application.

 

Thanks both, this tracks with what I've been able to gleen from the web. As far as I can tell the PO cut some corners so not surprising to find the wrong thermo. Hopefully between the new rad, fan clutch and thermo I'll have no more temp issues.