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I recently purchased a 2014 iSV which has a very low coolant level and I would like to make sure the system is in good shape. The previous owner didn't disclose the last time the fluids were checked or what kind of coolant was last used, but it looks to be an emerald green. I'm thinking of just picking up the FL-22 Mazda coolant and topping it off, but should I consider flushing the system first?

It's currently just under 97,000 miles.
 

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Don't top up. Drain, flush and replace.
Okay, will do! It'll be a learning experience for me since I've never done it before but the guide on CarCareKiosk looks like its pretty comprehensive. Would you recommend buying the coolant directly from Mazda or somewhere else?
Everyone is different, I today bought coolant for my 08' Mazda, went up to a Advance auto told them I needed coolant. They looked at the computer to see what exactly I needed and he gave me a yellow bottle of Prestone. Something like that. Around 20usd
 

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Everyone is different, I today bought coolant for my 08' Mazda, went up to a Advance auto told them I needed coolant. They looked at the computer to see what exactly I needed and he gave me a yellow bottle of Prestone. Something like that. Around 20usd
Coolant is quite compatible. Most is ethelyne glycol, so any type of that stuff will do. Some is better than the other based on additives. The other type is propalyne glycol, which is specific to GM. Its non toxic, but does not lubricate as well. This lead to premature pump failures so they abandoned it. It also turns to a gel when mixed with ethelyene glycol.

Before just topping up or flushing, I'd start by asking WHY the coolant is low. It generally doesn't evaporate as it is a pretty well sealed system. Low coolant means something is wrong. Start looking for leaks.
 

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Always change the fluids if things look questionable when buying a used car.
 

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Interesting, I got a engine code for my '08 Mazda, I went to 2 places and both said coolant levels and one said coolant levels and replace thermostat. I'm still taking it in, hope it's not the thermo.
 

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Interesting, I got a engine code for my '08 Mazda, I went to 2 places and both said coolant levels and one said coolant levels and replace thermostat. I'm still taking it in, hope it's not the thermo.
A failing thermostat doesn't really explain coolant loss as its sealed in its housing. If it failed closed, I suppose the increased heat could cause the coolant to spill out the overflow. Its not really clear as to how low the coolant is.

The thermostat is an inexpensive job in both labour and parts. My concern is if the car has been overheated and how badly. There could be other damage.

My mom recently did this with her car. Broke the belt and didn't notice. With nothing turning the water pump, it overheated. She didn't notice the overheating and drove it home. She's getting old, so it happens I guess. Result was a cracked engine head and a car sent to the scrapyard prematurely.
 

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Interesting, I got a engine code for my '08 Mazda, I went to 2 places and both said coolant levels and one said coolant levels and replace thermostat. I'm still taking it in, hope it's not the thermo.
A failing thermostat doesn't really explain coolant loss as its sealed in its housing. If it failed closed, I suppose the increased heat could cause the coolant to spill out the overflow. Its not really clear as to how low the coolant is.

The thermostat is an inexpensive job in both labour and parts. My concern is if the car has been overheated and how badly. There could be other damage.

My mom recently did this with her car. Broke the belt and didn't notice. With nothing turning the water pump, it overheated. She didn't notice the overheating and drove it home. She's getting old, so it happens I guess. Result was a cracked engine head and a car sent to the scrapyard prematurely.
Dang! Atleast the car is not overheating at all. It's just at almost 200k miles and been driven to the ground. My wife wants go change it anyway soon. Regardless I'm going to take it to a mechanic so they can do a proper diagnostic
 

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Dang! Atleast the car is not overheating at all. It's just at almost 200k miles and been driven to the ground. My wife wants go change it anyway soon. Regardless I'm going to take it to a mechanic so they can do a proper diagnostic
If you're unable to check it out yourself, that would be a good idea :) ask your mechanic to do a rad pressure test. They replace the rad cap with a hand pump and put pressure on the system. Forces coolant out any small leaks so its easy to find.
 

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Discussion Starter #12
Thanks for all the help, I think I bought everything I need so I'll get started early tomorrow morning. The CarCareKiosk video shows distilled water going through the system and then being drained only one time before putting the coolant in, but other places recommend two to four times. Is once enough or should I aim for more?

Before just topping up or flushing, I'd start by asking WHY the coolant is low. It generally doesn't evaporate as it is a pretty well sealed system. Low coolant means something is wrong. Start looking for leaks.
That concerned me too, even before I purchased, but I couldn't find any leaks and neither could the mechanic in the pre purchase inspection. That might change tomorrow though.
 

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I would drain the questionable coolant, rinse with distilled water until you are happy, then add your coolant of choice.

A no spill funnel will save you a lot of time and spills.
 

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That concerned me too, even before I purchased, but I couldn't find any leaks and neither could the mechanic in the pre purchase inspection. That might change tomorrow though.
Well its going somewhere....if its not coming out on the ground from a small leak, the only other place for it to go is into the engine and out the cylinders. But a blown head gasket would be extremely unusual with these cars. That's generally a thing of the past since they switched to multi-layered steel gaskets and torque to yield bolts.

Another thought is the heatercore. Might not notice it since leak would be behind the dash.
 

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Well its going somewhere....if its not coming out on the ground from a small leak, the only other place for it to go is into the engine and out the cylinders. But a blown head gasket would be extremely unusual with these cars. That's generally a thing of the past since they switched to multi-layered steel gaskets and torque to yield bolts.

Another thought is the heatercore. Might not notice it since leak would be behind the dash.
Actually, maybe not as unusual as you would think. I've heard that these engines can have issues that can cause head gasket failure. The cylinders are sleeved, with the sleeve inserted from the bottom. There is a small ridge at the top to keep it in place. This ridge is also part of the head gasket sealing surface. Under certain conditions this ridge can degrade and the head gasket will lose integrity. If this happens at the right spot a coolant leak could be the result. However I think if this were the case you might notice some pressurization of the coolant system.
Another possibility is the head has a crack somewhere. There is a coolant jacket around the lower part of the intake passages, and the wall is paper thin. It would not take a whole lot to cause a small leak.
A leaky heater core is pretty easy to spot. The windows will fog up for no reason and the cars interior will smell like old antifreeze....
 

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Actually, maybe not as unusual as you would think. I've heard that these engines can have issues that can cause head gasket failure. The cylinders are sleeved, with the sleeve inserted from the bottom. There is a small ridge at the top to keep it in place. This ridge is also part of the head gasket sealing surface. Under certain conditions this ridge can degrade and the head gasket will lose integrity. If this happens at the right spot a coolant leak could be the result. However I think if this were the case you might notice some pressurization of the coolant system.
Another possibility is the head has a crack somewhere. There is a coolant jacket around the lower part of the intake passages, and the wall is paper thin. It would not take a whole lot to cause a small leak.
A leaky heater core is pretty easy to spot. The windows will fog up for no reason and the cars interior will smell like old antifreeze....
Interesting about the head gasket...I thought that was mostly a thing of the past by now. If that is the case, they don't always blow gas into the coolant but it is common. That gas can also push coolant out the overflow...

I was avoiding head and block cracks since that is usually the result of overheating and usually the engine will run like ass...plus I'd rather explore the cheaper options first :p

As far as the heatercore....yeah it'll smell. But you'd be surprised what some people miss.

Let's hope something is found by a rad pressure test. They can always compression test if BHG is suspected.
 

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Discussion Starter #17
I got everything finished up last night, thought I would start before work but ended up starting after I came home instead. It went relatively smoothly and I didn't notice any leaks while working, except the coolant level has decreased a bit in the reservoir since driving it. Not sure if this is normal after draining or if I didn't properly bleed the system. I'll refill it a little and keep looking out for any changes, hopefully it's not leaking anywhere too costly! There are a number of other things I still have to get to.

As for a leaky heater core, I'm not really able to smell anything so if it is the heater core I guess I'll just have to pay attention to the windows. Thanks for all the help so far.
 

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That could be normal after a complete drain. There could be air trapped in the system and its working itself out. Give it a few days, keep an eye on how much you add and how often.
 
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