Mysterious Coolant Leak

I have a 2001 Tacoma V6 (PreRunner) that is leaking coolant in such a way that's leaving me puzzled. There doesn't appear to be any coolant in the oil, no smoke from the exhaust, nor any visible coolant leaks. The water pump / timing belt were replaced 62k mi ago, with 185k on the truck. The one strange thing that has me confused is there is a noticeable amount of water leaking from the AC drain hose in front of the passenger firewall / wheel well area. However, this appears to be just water, and not coolant. Still, I find it odd that so much water (perhaps a cup) is draining over nearly an hour once parked since I'm not running the AC (only the fan), and only drive 10 or so miles. The coolant appears to leak as the vehicle sits (over the next 30 to 1 hour) after driving. I was curious if anyone had any ideas, or could lead me in the right direction. Thanks.

 

The AC runs with any setting which includes defrost.

 

Well this answers one of my questions as I have been running the defroster. I'm not seeing any signs of leaking coolant beyond a diminished amount in my reservoir which leads me to question whether or not it could be the head gaskets...

 

Are you keeping coolant at proper level in reservoir? How much are you loosing over how long?

 

The reservoir level rises when engine is hot, level drops when cold. Thus the multiple fluid level lines on reservoir. If the level is constant hot or cold replace the radiator cap with a new OEM cap.

 

The AC drain hoses have been known to become clogged as well. Could be in an almost-clogged state, so any condensate from the AC unit is just draining slowly

 

the leak is more than likely from the thermostat bypass tube that is under the lower intake. It comes out the back of the "V" on the back of the block and goes to the heater core. The second place might be the core plugs on the back of the block... trans or motor has to come out to deal with these. I have a posting called "Mystery coolant leak found" under my name.

 

Here's a picture. The bypass tube is sealed with RTV. I saw this breaking down on the 21 year old engine that had 70,000 miles. Just keep you eye out for any any coolant vapors that may be coming up from below the lower intake manifold at the front of the engine just behind the timing belt cover.



Picture before cleaning to see how the old RTV is breaking down. It was a good time to replace the knock sensors and wiring harness.



Pipe installation with my enhanced knock sensor wiring harness. Lookout for steel gasket failure and gasket rash pitting around the head coolant ports. Those can begin to seep if the metal gasket rusts.