Mystery Coolant Leak

I’ve searched through the forum but haven’t necessarily seen the same issues so figured I would just ask.

My father in law has a 2011 Tacoma with a coolant leak he’s been chasing for a while now.

It started out with a leaking coolant by pass hose that was swapped out but he continued to lose coolant.

He determined that as long as he didn’t use the defroster it wouldn’t lose coolant for a trip or two but then would randomly start losing again.

He noticed that his passenger floorboard would intermittently be wet so we assumed heater core.

He bypassed the heater core and drove it today and after a couple hours had to add coolant again.

there’s no visible signs of leaking and the wet floorboard seems to be totally random.

he did tell me that he found the ac drain smells like coolant but I have no idea why coolant would be mixing with ac drain line. I’m not familiar with Tacomas at all so any insight would be much appreciated!

 

What engine does it have? 2.7L I4 or 4.0L V6

 

I’ll have to ask tomorrow but I’m pretty sure it’s the 4.0

 

Not really any common coolant leak points on the 4.0, if the heater core is bypassed it can't be going inside in cab. Now the A/C drain could be plugged causing the wet floorboard or there's an external water leak into the cab if it only gets wet when it rains.

Coolant leaks are typically pretty easy to find on Toyota's if they have the factory pink coolant, it usually leaves a white to light pink stain/crust around whatever is leaking.

 

I was finially able to ask and he’s got the 2.7L. Not sure how much different it woould be to the v6

 

Pick up a UV dye kit and add some to the coolant next time he has to top off. It is a heck of a lot easier to see the glowing residue, especially from odd angles, than it is to see the accumulated crust of cooked-off coolant. I chased a coolant leak for a long time and when I finally added dye, it jumped right out at me and I couldn't believe I hadn't seen it before.

If you do a thorough inspection with a UV light and don't find it, the unfortunate answer is that it's probably internal (head gasket or worse).

 

Water on floor is water on floor not coolant leak.

pressure test it.

 

Thanks for the response! Yea I have brought him my black light today and told him that was the only way he was going to find it. It’s such a big leak that it seems crazy to not be able to find it but it’ll definitely show itself with the dye

 

It was definitely coolant in the floor. You could smell it very strong inside the cab. It was just pressure tested when the coolant by-pass hose was replaced. He’s going to try the dye first and see if he finds that way.

 

As far as I know, the only way coolant gets on the floor is from the heater core. But that might not be the only spot it is leaking from. Check seams between radiator tanks and core, maybe? Look for pink and crusty anywhere there is a hose/connection.

 

X2 on the dye test. Let us know what he finds. Has the coolant leaked on the floor boards since he bypassed the heater core?