I recently purchased an '08 Limited with 210k miles. Aside from some age-related blemishes, it seemed to be in excellent shape. One thing I didn't catch until now is that the DS heat doesn't get above 75° when set to HI heat. The PS cranks out at 145°.
Initially, I thought it was the damper valve on the mixer block - so I replaced it (something I did on my '11 Sequoia). Unfortunately it did not fix my issue.
I then read the that heater core could be the culprit. After sourcing the proper coolant and flushing agent, I tackled the project this morning.
I disconnected the heater core at the firewall. However, as I tried to remove the hose from the tee that splits water to the rear core, the plastic tee snapped. Put more accurately, it crumbled. I don't know what kind of composite material they are made of, but it resembled brittle cardboard. Fortunately the local O'Reillys had a replacement set made of real plastic.
![Image]()
Anyway, using a heater core flush tool like this:
![Image]()
I was able to push pressurized water through the core. The amount of rust and debris that came out with just water was minimal. Pushing air in with the water agitated the core enough to release a ton of debris. Once it ran clear, I repeated it in the reverse direction, again dumping a bunch more debris.
A quick test revealed the DS temp up at 145°, just like the PS. I then drained the system completely, added the Prestone flush cleaner and water. I'll drive this for a few hours tomorrow, and then rinse/refill with OEM coolant.
Unfortunately, just as I was putting stuff away tonight, my son realized that the rear heat is also inadequate (80° on HI). I will flush to core (it can be accessed on the PS rear corner from under the vehicle) tomorrow and hopefully restore it as well.
Just thought I'd share.
Initially, I thought it was the damper valve on the mixer block - so I replaced it (something I did on my '11 Sequoia). Unfortunately it did not fix my issue.
I then read the that heater core could be the culprit. After sourcing the proper coolant and flushing agent, I tackled the project this morning.
I disconnected the heater core at the firewall. However, as I tried to remove the hose from the tee that splits water to the rear core, the plastic tee snapped. Put more accurately, it crumbled. I don't know what kind of composite material they are made of, but it resembled brittle cardboard. Fortunately the local O'Reillys had a replacement set made of real plastic.
Anyway, using a heater core flush tool like this:
I was able to push pressurized water through the core. The amount of rust and debris that came out with just water was minimal. Pushing air in with the water agitated the core enough to release a ton of debris. Once it ran clear, I repeated it in the reverse direction, again dumping a bunch more debris.
A quick test revealed the DS temp up at 145°, just like the PS. I then drained the system completely, added the Prestone flush cleaner and water. I'll drive this for a few hours tomorrow, and then rinse/refill with OEM coolant.
Unfortunately, just as I was putting stuff away tonight, my son realized that the rear heat is also inadequate (80° on HI). I will flush to core (it can be accessed on the PS rear corner from under the vehicle) tomorrow and hopefully restore it as well.
Just thought I'd share.
