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Discussion Starter #1
2000-mile trip over the past seven days, noticed the temp gauge was sitting at 4 o'clock while driving 80mph on the interstate at 50°F ambient temps. Usually it's closer to 3 o'clock. Stopped overnight, ambient temp was 20°, and a five miles after starting out the CEL popped on. Had the code read at an auto parts store and they said P0128 but they wouldn't clear it. Disconnected the battery and the code went away, never to come back on again for the remainder of the trip, about 1500 miles in 15° to 55° temps.

I'm guessing that the thermostat isn't closing completely. Did an advanced search of this site of all three generation vans and came up with nothing for P0128. Replace the thermostat? I figure I'll replace that plastic thermostat housing/water outlet while I'm at it. Coolant was flushed when I replaced the TB/water pump about 13,000 miles ago.
 

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Hi Roader,
Interesting!
Please follow up. Use only Toyotas thermostat and keep in mind that the new stat does not come with a gasket, get that separately. A while back I changed my radiator on my 06 and renewed both hoses and the plastic inlet housing as well. Thats a good call to do that.
Part number 16321-0A040.....I believe for inlet housing...Cheers
 

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Discussion Starter #3
Thanks, Paul. I ended up buying an Aisin thermostat which is probably OEM, the seal, and that plastic housing/pipe for $44 shipped, with tax, from Amazon. Rock Auto had a similar price but they still won't ship to me in CO. Supposed to be decent weather for awhile so I'll install it next week.
 

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Discussion Starter #5
Replaced the T-stat. Put the jiggle valve up. Not too bad; about 2-1/2 hours on the ground. The FSM says the starter has to come out to replace the T-stat housing but no need to remove the starter cables. Just unbolt the starter and slide it back a few inches.
45651
45652


I'm glad I got that housing/tube because it broke when I tried to get the upper hose off. Very brittle.

Temp gauge is back to sitting right in the middle.
 
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