Mystery coolant leak

[DaveL]

About a month ago I found a slight coolant leak was apparent. Not the "cursed plug" at the rear of the head because it doesn't exist anymore.
Searched all over for about a month, no smell, no coolant in the cabin, and a compression test was good, i.e. no bubbles in the radiator and good numbers. Turns out it was a pin hole in the "T" coming off the thermostat neck. Got a replacement from Panicmotorsports and started the swap.
What a PITA that was, remove cam cover, front cover, water pump drive pulley, cam gears, plate behind the gears and finally the neck itself
where it now resides in a neighboring county after I hurdle the SOB.
Put everything back together and after 3 1/2 hours and a 100 mile, drive all appears well.
Just thought I would post my find in the event it may save others some grief.

[chavy]

i had a similar situation but my pin hole leak was on the coolant bypass pipe (the one by the header). luckily it was right by the hose so i pushed back the hose to cover it. i'll prolly replace the pipe when it's wp/tb time again

[DaveL]

I was hoping to do the same, but mine was almost at the joint. No luck using the hose to cover that.

[— kung fu jesus —]

stuff like that is why I am adamant about changing hoses and seals when doing the TB maintenance.

[MX595]

I too have a mystery coolant leak, no overheating, but coolant resorvior was basically empty, and it appears as if the coolant leaked towards the rear of the engine, and down the back, I recently did the TB/WP and recommended seals, this post was very useful, and I will also check out "T" coming of the thermostat neck, any other ideas considering where the leak is? Thanks

[— kung fu jesus —]

The rear of your engine, the heater hoses, water temp sensor, and the cap they plug into are the main culprits for a coolant leak on the back of the engine. Is it on the left or right side?

[Rogue]

2013-09-07_164722_1.jpg

[— kung fu jesus —]

Ugh...another tool I HAVE to buy.

[—RuckkehrMiata—]

My last miata had a "steam" leak coming out of the heater core hoses. The pipe was just barely dinged (my heater core was second hand) and shaped sort of like a pacman type dent in on the circumference.
It only lost coolant once the car was hot, and even at that it took like 2 weeks for it to lose an appreciable amount....


Well thats not entirely true, the radiator also had a hole in it so I threw a mishimoto in and the reservoir had hairline fractures in it from heat and age.
But the weird steam leak stuck around after.