The radiator isn't designed to hold a vacuum. A standard cooling system pressure check and a Toyota radiator cap for starters. Is it overheating or just warmer than you expect under a load.
Use a IR temp gun and shoot the top radiator tank and hoses.
Is the clutch fan working correctly?
Throwing any codes?
Is the coolant in the reservoir disappearing?
New stat ? and where is the jiggle valve clocked?
Any oil or coolant contamination?
Maybe try a exhaust gas chem test on the radiator.

 

The temp is almost all the way to the top. WAAAAY past the middle.

I have to verify, because I don't recall exactly, but I think the bottom hose was HOT and the top was decently cool (to the touch).

No codes. Clutch fan is on (all the time, I do believe). But, the temp goes up while driving and while sitting. I mostly test drive it in a long(ish) rode, no traffic. 40-55 MPH with very minimal traffic/stopping.

New 190 stat, down to 180, and finally to 170 (for troubleshooting).

No contamination in the oil, or coolant.

I will test the rad for exhaust in the radiator. But, I think I will also replace the Heater core (might need to, anyways), and I think I want to fix it, and then do a V8 swap. I think it'll be a fun project (that I'm not looking forward to), plus it might make a good series on Youtube.

Thanks for all the knowledge and wisdom, SDSpeed. I'll check these things this weekend.

 

My T100 from new until now always run's at 3/4 on the temp gauge, common complaint. FWIW.
What temp does your scanner say it's running ?

https://www.toyotanation.com/threads/jiggle-valve-position-fer-the-5vz-fe-engine.346741/

I don't speak Spanish but this doen't look fun and I've done at least 100 heater cores in various vehicles over the years!

 

Ha. I've seen this video while looking into my options.

Basically everything has to come out (forward of the shifter). I dread doing this. But, I think it might have to happen. I forgot to say, when I'm driving (and specially when going up hills), is sounds like water flowing, from the right side of the car. Just a gentle stream of water. I'm thinking maybe a heater core leak. I'll do better research and troubleshooting, including finding the actual temp of the water. I'll look at the scanner temp, gauge temp, and infrared temp. But, the temp gauge stays in the exact middle for most of the drive, until it just goes up very quickly to the very far right side of the gauge. It happens decently quick (5-10 seconds).

I don't have my truck here with me (I live and work in two different cities). But, I'll check on it this weekend and give you a better answer.

Thanks for your advice and input. This is what makes these forums great, the wisdom and experience.

Cheers

 

Just to put this out there: The head gaskets are definitely LEFT and RIGHT. If you mixed those up you will get overheating. One of them I think the right side) placed on the wrong side covers a port that blocks flow. If you are 100% sure you got them correct, ignore this. If you were not paying attention when you put the heads on you might have to pull those back off and get new gaskets (do not re-use the old gaskets)

 

to be 100% honest, this is my biggest worry. The problem is that I am 100% sure that I put each one in the right place. However, I had to pull them off (the heads are also left and right specific, same head, but the mounting for the the accessories are drilled in different areas) to swap left and right head. I'm not 100% sure I did them back correctly. More like, 98% sure I did, but still... It was probably due to my frustration. But, that's the biggest issue I keep thinking of...

I'll see if I want to go down the rabbit hole of pulling the heads back off, or not.

Thanks for the heads up, though

 

Did you "burp" the cooling system?

 

I burped it multiple times using multiple methods. I even pulled a full vacuum, the last time I did it. So, I feel it is sufficiently burped.

 

HOW OLD IS RADIATOR? sometimes they look fine but can have small blockages... or even have sealer from a past owner..

 

We're looking at maybe a year old, but with probably less than a few hundred miles.

 

I had a similar problem with our 98’ C4 corvette and guess what? It was the heater core… I kinda of thought it was going but the dead giveaway was the glycol smell and the foggy windows. Replacing the heater core on that car is about a 16 hr job and I will die with a few scars I got in the process. The problem is that when the car cools, the cooling system will suck air in through a pinhole ao would have to burp the system again before it cools properly. What temp stat did you instal?

 

GOOD LORD, I've been thinking heater core, but I have been dreading it.

I will end up putting a heater core in, anyways. Just to have a fresh one if I ever sell that thing. But, I will not be happy.

It had a 190, I put in a 180 and ended up going with a 170 (pin clocked at 12 o'clock).

 

If you bypassed the heater-core, but still have some overheating then it is not the heater-core (or at least there is some other issue).

I am still wondering about those head-gaskets. Were they OEM or Felpro? Also, did you replace the thermostat with a new OEM thermostat?

 

I feel the same way, but I still think the heater core might be an issue anyways.

The head gasket was either Fel-pro or Mahle. I don't recall.

and thermostats are either OEM or OEM plus. Whatever I can get my hands on. Also, I test them before installing them. Always have, always will

 

I just wanted everyone to know the results.

I ended up selling the truck to a buddy. I basically sold it for what I paid for it, and just lost nothing but time and effort.

He took it apart and found that the new water pump's impeller was out further than it should have been. So, the pump was basically pushing out 1/2 the water it should be pumping.

So, in the end, faulty water pump. Which, when I look back, sounds about right.

Anyways, I hope this helps someone out.

Cheers to everyone!!!