Potential overheat

Hey guys,

I recently swapped engines on my t100 3.4 and I'm afraid to overheat it. I've done heads, valve, timing belt, pump, replaced most coolant hoses on the new engine and installed a new denso radiator. The previous engine developed a small coolant leak on cylinder 6 after running around 203-213 degree. Decided to replace as the engine had 240k+ miles.

Things I'm concerned about:
1. Using duralast thermostat 170 degrees ( I bought an oem but it won't arrive until Saturday)

2. Heatercore ( prior to replacing thermostat I had a 180 on the previous engine and heat was running cold, flushed it and got alot of gunk out)

3. Lower hose ( Haven't replaced it but noticed that its significantly colder than the upper hose. The upper hose you couldn't touch but the the lower was cold instead of warm.
Current situation is the new engine Temps started creeping towards 200 (turned it off at 195 as I wussed out) degrees after letting the truck idle for 30 minutes. I'm running distilled water at the moment but have notice that water normally runs about 2 degrees colder than toyota's red coolant. I have the red coolant ready once I'm happy with the temps.

I tested the fan clutch on my taco beforehand (3.4 as well) and the temps were consistently between 186-188 degrees. By that I deduced that it's not the fan clutch but I have 2 extra spares to try as well.

I'll upload pictures later but for the meantime what do you guys think I should check while im waiting for the new thermostat?

Engine runs smoothly can almost add glasses of wine on top of it like the 1uz commercial.

Thanks in advance

 

Do you have an OBDII scan tool to check fuel trims for lean conditions?

Any chance of air pockets in the coolant system?

 

213F while on the warm side isn't gona cause engine damage, most cars don't even turn the cooling fans on until around 210-220F.

I wouldn't start getting concerned till 230F although on a properly functioning system you should stay in the 180-210F range unless it's really hot out.

Are you sure you had it full? An air pocket under the thermostat will cause it not to open.

 

Did you check the clocking of the jiggle valve on the thermostat? On those 3.4's they should be at the 6 o'clock position not the 12. It is in the FSM. It will run about 10 degrees cooler in the 6 position as long as everything else is okay with the cooling system.

 

Not sure if you remember, but on the 96s and some of the early 97s we got got unlucky with the headgaskets on the 3.4. Some worst like myself bought the truck which didn't get the recall/tsb done on.

 

Yeah I have the funnel to burp it only thing I didn't do with the heat running on blast. I'll check see the fuel trims once I get home.

 

Standard operating temperature on most vehicles since the late 80’s early 90’s is 210. I don’t think you’ve hit any temps to worry about yet.

 

Ended up being the thermostat, pulled it off today and tested it on boiling water and nothing. Now to wait on the oem one.

 

Just an update:
Got the oem thermostat early so I put it in, flushed the coolant and added new coolant. She now sits between 186-188. Now I'm going to tune the cables to drop the idle to 6××-7xx. Moral is to stick with oem parts.

 

is the fan shroud is on the radiator ?

 

It's on but honestly with it off I've only noticed a 3-5 degree difference while in stop and go traffic at 90-100 degrees (can't speak for the desert guys).