Intermittent Coolant leak, please help

Okay let me start from the very beginning. 4 months ago my gf and I had a plan to visit Yosemite. The weather was gonna be below freezing and I only had distilled water in my 2001 Tacoma 3.4L (I've ran straight distilled water for about 2 yrs) so I decided to take it in for a coolant change at a local shop. Well, they changed the coolant and we were on our way. When we were about 2 hrs into the drive we were in a hilly section (but I drive up big hills all the time), anyways maybe 2 mins past the hilly section I noticed coolant spewing from the engine. I then check the temp gauge and its at the red line so I pull over and check it out. I had a hairline crack in my upper radiator tank about an inch and a half long. So I got my car towed home and then replaced the radiator. After replacing the radiator I first burped the coolant system (with the car running) and drove the car about 5 miles round trip on a hot day. The temp gauge was at a perfect level and there were no leaks. 2 days later I go and sit in the truck with it running to enjoy it running again. I decide to turn the ac on with the engine idling, that's working and the temp gauge is still perfect. I don't drive it anywhere but sit in it for like 7 mins with the ac on and the car idling. Before I leave the car, I check under the car to look for leaks. Sure enough, it is dripping. Frustrated, I go back inside the house. I come back to it 2 days later and start it up again (with the ac and heater off). Sure enough, within 1 min it starts leaking. Starting with drips and eventually a small stream was pouring from somewhere. That sucks. Anyways, I turn the car off but it continues to leak for like 24 hours (in small drips). I come back to it like 3 days later and did a static pressure test. You could HEAR air escaping from somewhere but I couldn't tell where. So I put more water into it, and it started leaking w the pressure. I still couldn't tell where it was so I wrapped up for the day. 3 days later I do another pressure test but ITS HOLDING PRESSURE. I start it up and let it idle for like 15 minutes too and there are NO LEAKS. I take the thermostat out to test it and I find it works w the hot water test.

My dad told me to take the oil cooler off so I did and found out that was completely plugged up so I took it to a machine shop to get it cleared and then reinstalled it. We figured that was the problem. I put the truck back together and drove it for 3 days and there were no leaks (even took it for 2 long drives) and the temp was perfect. Today after I drove it somewhere close I checked under the car and there was a pool of coolant under the car and an active leak. I took it home and inspected it further and I saw coolant dripping from the lower timing cover. I dry things up so I can get a better view and come back to it 2 hours later where I do another static pressure test. This time there were NO LEAKS again so I started the car and did a dynamic pressure test. STILL NO LEAKS. I'm clueless please help.

 

I should add that the dynamic pressure test didn't show any signs of a blown head gasket/ cracked block and I have no other classic symptoms of one (milky oil, radiator constantly bubbling...)

 

IMO, if it’s spewing from the lower timing cover, might be an indication of a worn water pump. It’s either the WP gasket, loose WP bolts, or the peep hole on the WP. Unless coolant is leaking between the valley of the cylinder heads and pooling enough to run down from there.

 

I agree with @02hilux WP is most likely faulty and leaking from the weep hole. I’m thinking since you drove it two years with only water it caused the WP to fail due to no coolant lubrication.

 

That was my first instinct as well but I pulled the upper timing cover and looked at the water pump. It looks like there's an old trail running from the top weep hole downwards but I would expect the coolant to look more fresh.

 

But I suppose if it looks like a duck and quacks like a duck.. it's a duck.

 

I just static pressurized the coolant system and sprayed soapy water over the weep hole... sure enough there were bubbles