HELP: Overheating Question

Alright Folks,

Hat's off to anyone that can properly diagnose this one. Haven't found any solutions on this site for what ails my 2011 4Runner SR5. She has 260,000 KM so it’s kind of expected that she needs some love but this one has stumped me and the local service department (albeit over the phone as I’m in the middle of a road trip from the Kootenays to Vancouver Island).

When driving on the highway, the temperature stays consistently in the mid range and AC blows somewhat cold...Things are good. However, when hitting forest service roads (FSR’s) and on steep inclines, the temperature gauge rises pretty quickly as the engine overheats and AC blows hot.

The first time it happened I didn’t notice until I parked and heard the coolant reservoir boiling. Let it sit for a bit but there was signs of coolant leaking/ boiling over and the reservoir was empty.

As soon as I got into town I picked up some coolant and topped off the reservoir but over a few days it seems to be losing coolant without any visual leaks. I stopped in at the closest Toyota for a quick visual inspection and topped off the rad and the reservoir. Unfortunately, they were booked solid so I wasn’t able to take it in but they said as long as it’s good on the highway then to avoid FSR’s until I can get it inspected and diagnosed further. They hinted that it could be the clutch fan based on the fact that it seems to only be overheating at slower speeds.

Have tried to read through forums and am driving myself insane trying to figure out the issue as it could range from a faulty rad cap to a blown HG.

Haven’t red lined it, oil is clear, coolant is clear and haven’t noticed any white smoke. The fan isn’t locking up but I’m not sure if it’s running at 100% because I’ve never took notice of it before.

Thank you for any help!

 

If its not leaking externally its leaking internally.

Get a pressure tester. You can prolly rent or maybe even get your local auto store to do it for you for free.

 

Sounds a lot like a fan/fan clutch issue. The way you can test it is to get something solid like a piece of wood/your hand and try to (gently) stop the fan while the car is running. If it stops fairly easily when the car is hot, you need a new clutch.

Be careful. Don't jam anything in there. Do it with the blades going away from you.

 

As stated above - if you’re fine operating at higher vehicle speeds and overheating when going slower it may very well be your fan. Another possibility would be the water pump. Your radiator is responsible for heat dissipation (cooling the coolant), your fan provides airflow across the radiator fins, and your water pump moves the coolant through the closed loop. At this point I would lean towards the fan.

 

Another possibility if the pressure check is good, and the fan clutch checks out: Regarding the water pump, if it is not a factory Toyota pump, such as a replacement from an auto parts store, the aftermarket impellers are not the same, and don't move the same amount of coolant. That would lead to a slow overheat in a situation such as you described.