Coolant leak *only when heater is on?*

[One Sick Puppy]

I've been aware of some previously mysterious coolant loss for a couple months now and finally observed the following:

- coolant dripping from passenger side, front engine area (see attached photo)
- haven't actually seen active dripping, only coolant wetness
- can't see where it's coming from looking down thru engine bay
- rad coolant level appears to only drop when the heater is used
- doesn't seem to leak when parked and engine off

I haven't tested running the engine and heater while parked to see if it starts spewing from somewhere, but this seems like a good test (will do this on the weekend when I have time).

Just wondering if I can rule out anything based on it only leaking when the heater is on? I.e. water pump, etc.

It's difficult to see exactly where the leak is coming from when I look under the vehicle, and I don't see any from looking down the engine bay. Any suggestions on where to start? Rad seems fine, if I were to guess it's something low in the engine area.

Thanks for any pointers

 

[JayRolla]

Bet it's the heater control valve. It will only leak when you have it open or on hot. Top of fire wall behind intake manifold. http://www.toyota-4runner.org/3rd-g...s-had-replace-their-heater-control-valve.html

 

[reelamin]

For sure its after the heater control and could be just about any hose or fitting. Wash it off...let it dry...fire it up...crawl under and wait. Mine had a leaky hose at the back of the block....was dripping down the back passenger side of the motor when it finally appeared.

 

[One Sick Puppy]

Checked the heater control valve. Clean and dry.

I've been stuffing my face up under my truck a couple times and all I see is this item. Doesn't look like a hose to me, but it looks cracked and also looks like the source. The rest of the items below it, like the bushing and arms, I assume are getting wet from the wind under the vehicle...