Lq4 swap, then truck won't warm up.any ideas?

[Moe]

Heard that!! Nothing wrong with a little smack talk at all.

[88RCLB]

Don't need to drain it, just let it idle with the cap off and watch the fluid. Sometimes it helps if you give the upper hose a couple good squeezes to push some air out and suck some fluid up. My yukon takes 20 minutes on a 50* day to hit 210 idling. So I'd let it run at least that long to make sure the t-stat is opening. (this is assuming you don't have another problem.)

If you do drain it, throw a new t-stat in anyways since they're $5.

[Moe]

^ exactly what I did. Let idle with cap off squeezing upper hose evey few seconds, then added some fluid to too her off. Worked like a charm. Figured out why the gauge wasn't working at all too..... Wasn't plugged in lol