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Prone to coolant overflow tank leaks?

4K views 5 replies 5 participants last post by  Milanomike 
#1 ·
When I was looking to buy a car, I was researching Mazda3's and Miatas. Miata NC's, with the 2.0 are prone to the coolant overflow tanks leaking, and because they only have an idiot light instead of a temperature gauge, by the time the light comes on, the engine is likely ruined. Savvy Miata owners replace that plastic POS tank with an aluminum Moroso tank, and then can stop worrying about the tank leaking. Problem is, those tanks are very expensive.

My 2012 Maz3 with a 2.0 Skyactiv has the same engine, I think. I was wondering if the coolant overflow tanks on these are prone to leaking, also. I am considering doing 1 of 3 things, if they are: 1) Replace with a new $50+ OEM plastic tank. Maybe they are better now. 2) Replace with a very expensive aluminum Moroso tank. 3) Put a bluetooth OBDII reader on the car, and an app on my phone or tablet so that I can see real-time diagnostics, including actual coolant temperature. But I am not sure if the Maz3 OBDII is advanced enough to output sufficient info for that. I could also hook up a separate real temperature gauge, but I don't want to run wires, and mount a gauge, and have potential coolant leaks because I screwed with the hoses and adding a sensor.

If these tanks are not prone to leaking, then maybe I am worrying about nothing. Anyone else here ever go through any of this? Anyone here ever have a coolant tank leak?
 
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#3 ·
When I was looking to buy a car, I was researching Mazda3's and Miatas. Miata NC's, with the 2.0 are prone to the coolant overflow tanks leaking....
What is the source of your information, and what's the frequency of failure? It's important to consider the vehicle age of the failures being described. IMO virtually EVERY 15 year old plastic coolant tank would be at risk for failure, simply due to the fact that all plastic deteriorates and degrades over time. However, your vehicle's 8 year old plastic tank is not yet in the category where failure might be expected at any moment. That said, it certainly wouldn't be a bad idea to proactively replace the tank with a new one. IMO a new plastic tank is perfectly ok, and it would not be necessary to use a metal tank.

Personally, I'm not concerned about engine damage due to overheating, simply because I am highly proactive about watching for ANY fluid showing up under my vehicles. So I'm going to catch any slow leak early enough to avoid issues, and a sudden major leak (i.e. tank bursting) is going to create steam which will alert the driver to shut down immediately. That works for me, but by all means replace the tank if it's something that keeps bothering you.
 
#4 ·
Thanks for the posts, so far. I now have the information I was looking for.

I keep a clean piece of cardboard under it, in my garage, so I can see if any fluid leaks develop. No matter how small, any drip at all prompts me to immediately try to solve the problem. Rear main seals are the only ones I am not likely to repair myself, because I am not fond of the thought of pulling any engine. And that is why I refuse to ever drive a FWD car with a manual transmission, because I would replace the clutch myself, as I never pay for any mechanic to do any work, besides installing tires and doing alignments. I don't mind pulling a transmission on a RWD car, though.

On another note, I sure do love this car. It is far more refined than the '09 that I used to own. Creature comforts are much nicer, electronics are vastly more evolved, ride is way smoother, and handling is almost as good, which is damn fine, BTW. I call it my sports car station wagon. And Hooligan. Very easy to get in trouble with this car.
 
#5 ·
Reviving this thread since I have an 04 3S and an 06 MX5. Miata forums have several incidents of plastic tank failures and recommendatios for a Moroso Aluminum replacement tank. I am considering doing that. However, I don't see a Moroso for the mazda 3.

Has anyone else had a failure with the pressurized coolant tank on an older (or newer) 3?
 
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