Full Cooling System Refresh - (July 2019)
We were driving to Oregon to visit some family and I can't really remember why, but I plugged in my OBD II reader and noticed that the factory engine temp sensor was a lot higher than the speedhut temp sensor. The factory was sitting at 215F and the speedhut was around 185F. This was during highway driving.
The speedhut sensor is in the back of the passenger side head and the factory temp sensor is in the front of the driver side head.
Anyways - we ended up getting into some stop and go traffic and the factory temp sensor was starting to show 225F. I turned the heat on full blast and it came down a little, but then it got so hot in the car that the heater's circuit breaker tripped

.
Right when I was about to pull over, traffic started moving again and the engine cooled back off to around 210F. Strangely enough, the speedhut sensor was always lower than the factory sensor, but in the stop and go traffic would climb at a higher rate than the factory sensor until it would almost come to the same temp as the factory sensor.
I thought about what could be causing this...Fan clutch seemed obvious because of the worse overheating while not moving, but I tested the fan clutch and it seemed to be working fine. Thermostat seemed like a good culprit too.
Since the truck had around 145K miles on it, I decided it was time for a full cooling system refresh.
- New Thermostat
- New Waterpump
- New Fan Clutch
- New Belts
- New Hoses
- New Heater valve
- Clean Radiator
- Flush System
- New Coolant
I know this is overkill for some moderate overheating that probably could have been solved with a new thermostat alone, but I wanted to baseline the cooling system. According to the PO, none of the items listed above had been replaced (except he had the coolant flushed on a regular basis).
The heater core valve had a very small leak since I had bought the truck. You can see it was turning green. It may have been the original...
I replaced it with a new one [Part #: 87240-90A00].
Later on, I replaced it again because I foolishly way over-tightened the living daylights out of the worm clamps and the new heater valve was crushed/leaking...but this time it was leaking at the heater valve and where the hoses connect to the heater core

.
I decided I wanted to avoid the worm clamps and purchased the constant tension spring clamps for this size hose from Toyota [Part #: 90467-21010]. I have these clamps at the heater valve and heater core connections and so far there are no leaks!
This is the hose to attache the heater valve to the heater core - I had to trim it a little
Poor quality photo of constant tension hose clamps installed:
As I mentioned above, the heater core pipes were crushed because of the over tightening of the hose clamps and I had to figure out a way to get them round again. My dad is a plumber and uses Pex A (expansion style Pex) for his water pipe. I was able to take his expansion tool and very lightly re-round the heater core tubes. It worked amazingly well and they are back to being perfectly round

.
Below is the style of expansion tool I used...he also has a Milwaukee battery powered one that he uses for everyday use, but the manual tool is better for this application. You really want to be careful not to over stress the pipe and crack it!
Everything else installed pretty easily without any issues. I removed the radiator to give it a good flush and then spent a few hours cleaning the crap out of the fins. In retrospect, I should have just taken it to a radiator shop and had it boiled...
The temps came down to normal range after the system refresh. My temps at the factory sensor fluctuate between 195F and 208F depending on load and outside temperature, but it never really goes above that. The strange thing is that the speedhut sensor consistently sits around 180F unless we are sitting in traffic on a warm day. Then it slowly creeps up until it meets the temp of the factory sensor and they both sit around 205F. It must have to do with the different sensor placements in the heads. Maybe the speedhut sensor is getting the cooler water from the radiator in the back of the head and when its sitting in traffic on a hot day, the whole system is coming up to temp so the speedhut climbs to meet the factory gauge? just my best guess.