Help Diagnosing Coolant Leak

I need some help diagnosing a mysterious coolant leak. I bought a 2014 Tacoma with 72k miles about 2 weeks ago and everything checked out and looked good when I bought it. I recently noticed that my coolant reservoir was completely empty and so I refilled it and started looking for leaks (the truck never overheated though). When I drove the truck home it emptied about half way so I filled it again assuming that was just refilling what was lost in the cooling system. After looking everywhere I could think of on the truck I found no visible leaks and the oil looked normal (not even remotely milky). When driving the truck there’s no excess exhaust smoke or any water dripping from the exhaust so I’m hoping it’s not a blown head gasket. The only thing I noticed was that the overflow tube from the radiator into the reservoir was a little crusty and didn’t have a hose clamp on so I threw one on there (photo attached). It seems strange that it would leak that much from there but I guess it’s possible. I also took the truck to a local Toyota dealer that has been great with me in the past and they performed a pressure test and didn’t find any leaks. Still a little worried though since I went through about a reservoir and a half of coolant. Has anyone experienced this or have any suggestions as to what could be going on? For now I’m just keeping the truck close to home and keeping a close eye on the coolant. I appreciate any advice y’all can give.

 

The crusty hose on the reservoir is normal. No need for a clamp as there's even a overflow hole under/near the black cap where coolant can spill out if needed.

When the truck is cool, remove the radiator cap and check the level in there. It's possible the previous owner screwed up a radiator flush and the system simply is not full.

 

You have a worn hose connection at the res.

Coolant naturally evaporates. If you are in doubt do a pressure test and check for head gasket leak.

 

Take a look at your head gasket just under the exhaust manifold if there is a red /pink crust. Coolant leak are very common on the outside

 

Everything looks fine from the engine bay and I didn’t see anything around the exhaust manifolds. It looks like it’s still leaking somewhere cause the coolant level is slightly lower again today. Is it possible it’s the water pump and it just didn’t show when the shop did a pressure test?

 

I'd also check the waterpump. Look up from the bottom just below the large pulley that's attached to the water pump, my pump was going out and loosing amounts similar to yours over a 2-3 mo period. To see the leak I really needed to remove the skid plate and when I did I noticed a large pink crust buildup under the pulley, the water pump was leaking more then normal. A small amount of pink crust out of the weep hole is normal. Mine wasn't dripping on the ground nor getting hot, the only external indication w/o crawling under it was the coolant loss.

 

If your engine is a 2.7L 4 cyl, check the bypass tube around the area where it leads to the thermostat housing. Use a small flashlight and shine it in just in front of the oil dipstick towards the underside of the intake manifold and see if there is any sign of leakage there. It will show up on one of the two nuts or around the circumference of the bypass tube. The bypass tube was originally plastic but has now been superseded by a metal bypass tube with a slightly different design, IIRC.


The red arrow points to the bypass tube at the point of leakage, the yellow arrows point to the nuts where you may find small crusty deposits.



The other photo is the same area, cleaned up.