Unusual engine temps...need help

[Maistroyoda]

Hello everyone... I have a 97 LX with 136k that I bought about a year ago. I'm new to the site but not to toyotas. My LX is basically under heating. It takes 20-30 minutes city driving for it to get to normal operating temps (middle of the gauge). In highway driving it won't even get that hot, it stays just above the lower line. Two days ago I crossed a 8% mountain pass a total of 8 miles (4 miles up and 4 miles down). On the way up, it barely made it to the middle of the gauge. On the way down, the gauge went down passed the lower line on the gauge. It just recently started doing this and has progressively gotten worse. I think it may be the thermostat is stuck open. My brother thinks it may be a temp sensor. I'm not a mechanic at all but I understand how engines work, especially the 22r. Please help, let me know what you all think may be the issue. Thanks!

 

[Tools R Us]

The thermostat would be my first check, replace it. In this case, I prefer a dealer part.

 

[REKCUT]

If it were mine, the first thing I would do is add in a mechanical temp gauge or hook up a scan gauge so you can get real temps. Its very hard to get help with statements like "middle of gauge" or " just above the lower line". You need to be able to talk real temps. Mine runs around 198 almost all the time once it warms up. Will get a high as 210 on some real climbs.

 

[FrankTorres]

Check for a thermostat, it may be missing.
...what Rekcut mentions, Scangauge, ultragauge or mechanical gauge.

Good luck.

 

[CJF]

Classic symptoms of a failed t-stat. Couldn't be anything else, really.

 

[Maistroyoda]

I installed a Toyota thermostat today and did a thorough coolant flush using e9999's write up (very complete) but without all the gadgets and the problem is gone. The LX warmed up quickly as it should and maintained the temp going up and down the mountain. Thank you all for the input and advice!