Overheating with brand new motor?!?!?

Sounds like its air locked to me. If it's not a factory thermostat remove the thermostat drill a 1/8 inch hole in the outer ring then it can't air lock.

 

Hey guys, meant to update this days ago but....jiggle valve down!!! Not sure if it actually makes a difference, but we took it out to check it (it was clocked at about 9) and put it back in with the valve facing down (as stated in the FSM), filled her back up and crunk her up. Sure enough once the temp gauge got to the middle (actually a tad below parallel) all the fluid disappeared below the fins in the rad...kept adding until it reached the top, topped off the reservoir, and down the road we went with a dead steady needle for the entire drive. Thanks again guys.

 

Problem solved. Congrats - glad you got her up again.

 

Just when you think it's all alright.

After 195 miles, 160 of which were perfect, she almost hit red again.

I flipped the heater over to cool for some normal air and the needle went up to about 95% after roughly a mile, I instantly flipped the valve back open to heat and the needle IMMEDIATELY went back to center. I just don't understand this thing...the expansion is filled to full and has remained there ever since the jiggle valve placement was corrected.

How can it be so completely inconsistent??? If it takes the heater core being open at all times then i guess i'll have to get a for sale sign before summer hits. Any ideas??

 

Did you do this:

with the heater on full hot?

 

Unfortunately haha.....i was also hoping there was a air pocket in the heater core. This was not the first time I've ran the cold air since the first "fix", this just happened to be the first time it's ran hot again since the "fix".

 

Another update....i'm getting suspicious between the initial destruction of the motor/poor maintenance, my rescuing it, and pulling/rebuilding of the motor, the temp sending unit might have got a little off. I bought a bluetooth OBDII scanner off newegg (elm327) and gave it a try with the torque app.

When idling at temp with heat on full the gauge reads 55-60%...the app reads 186-190F.
When cruising (50F outside air temp) with the heat on full the gauge reads 55%...the app reads 185-186.8F.
With the truck on full cold (no a/c) while cruising within 10 seconds of flipping the dial the guage reads 90-95% to red while the app reads 194-196F. (Same goes for A/C on)
When heat is turned back on, the gauge falls literally within 5-10 seconds...can it really fall from almost red to ~55% in 5 seconds?? Can i trust this bluetooth tool?? and most importantly, how can roughly 40 to 50% of the gauge be only 10 degrees difference??

 

Oem temp gauges are neither reallty accurate nor linear. It is hard to say which one is the accurate one, though. I'd be tempted to get a standalone temp gauge and check with that.

 

I was thinking the same thing, except i would prefer the oem gauge to read correctly...I placed a thermometer in the top of the rad with the truck off, my phone reported 176F and the thermometer read ~144F (makes sense to me since the phone was getting the temp from the ecu at the top rad hose neck while the thermometer was all the way across the top of the rad.) This also reassures me that the truck never ran hot to begin with and/or the truck has probably been fine this whole time...the gauge is just reacting much faster since its sensor is right in between the heater hoses and the two wire sensor is right in the top rad hose filler neck, so just gonna cross my fingers that all that has happened to the truck has boogered the single wire sensor and my head gaskets haven't been installed backwards or something that i can't fix for $20 has occured.

Needless to say, I will be rolling by toyota tomorrow and picking up a new single wire temp sensor for the gauge

 

Okay everyone, sorry to revive an old thread but I finally reached resolution with the truck. Replacing the temp sensor for the gauge only gave a more accurate look into what was really going on. After some more in-depth testing by the mechanic who assembled the motor....he pulled the heads and guess what...the head gaskets were backwards. Put new ones on the right way and she hits temp and the needle is dead steady, cold, hot, a/c, idling in traffic...it's almost like it was designed that way.

So just to hopefully shed some daylight for others who've just had the heads put on their 5vzs and it is seemingly fine but overheats when the heater valve is shut....yank the heads and try not to lose your lunch.

Thanks guys for all your help, those were all good ideas but unfortunately the problem was a little deeper.

 

Seen that mistake done more than once. Some engines it does not matter, but others it is vital to have the head gasket on properly. Good think it was worked out!