I've been losing coolant on my 2009 Mazda5 and not sure why. The coolant needs to be refilled every week or so. No obvious leaks. ANy ideas on the cause? Also, must I use the expensive Mazda coolant (looks yellow)? THank you!

 

No you do not need to only use MAZDA coolant. I have been using and frequently testing the coolant in my 2018 with less than 40K miles for about 3 years now!

The coolant does not evaporate so in your case you need to look closer to either find the leak, see if it is in your oil or if the cooling system is blowing it out the reservoir tank.

There are 3 test you could do.
A colling system pressure test and a fluid chemical test.
An oil sample analysis.
Chemical test of the cooling system

 

Ok, thanks for the quick reply. So what coolant are you using?

 

Currently AutoZone extended life not pre mixed. I run 60/40 water to coolant.

 

Okay thanks again - I will get some. Question - Hard to tell what's already in the reservoir (in terms of mixture of coolant to watter) other than sight lines...so do you premix before adding to the reservoir or is this only when you are changing the coolant for some reason? I have been adding straight coolant to the reservoir but only when needed and that's really not that often except for this recent incident.

 

Honestly I am not sure it too critical say no more than 60/40 unless you are not formulated your mix and do more than 70/30 for a daily drive? I filled my reservoir with straight water, and it still measured close to 60/40 after a week? Not totally conclusive method for a proper testing but on the other hand I have tested the coolant from new MAZDA supposedly having the 50/50 Mazda premix coolant using my refractometer and none were 50/50 mixture.

 

Ok. I have been running straight Mazda coolant in the reservoir since I bought the car new in 2009. My guess is its a mixture by now as I had the car serviced at the Mazda dealer a few times. I'm thinking just stay with the straight formula - not sure. Also, the reservoir cap is not the original as I dropped it years ago and couldn't find it so my wife found a cap from some food item in the house and we have been using that with a piece of plastic first to seal it. I was against it but gave in and years have gone by now. I know this sound lame. I need to get a reservoir cap any ideas on a source (going to try autozone soon).

 

The stuff you add to distilled water is antifreeze. The ethylene glycol in antifreeze has a heat capacity about half that of plain water, so it's half as efficient at carrying heat away from your engine. That's why it's mixed with distilled water, which does a better job removing heat. The antifreeze's job is to prevent the water in your cooling system from freezing during the winter and bursting your radiator tubes/pipes and potentially the water jackets in your engine. You could theoretically drain your cooling system in the spring and fill with only water (plus some anti-corrosion agents), and add antifreeze in the fall. But that's too much trouble for most folks, so they just run a mix year round. 50% antifreeze is good below -30ºF. Unless the place you live gets below that, using more than 50% antifreeze isn't any use. Have a look at this graph: 225502.pdf Most people in non-arctic areas just run a 50% mix. 50% mix is what's available in the store. Those who want to save a few bucks buy the concentrate and a gallon of distilled water, and mix ourselves. You just need a measuring cup and a half gallon jug. Measure half gallon of water into the jug, then top off the gallon of distilled water with antifreeze. Then pour the water into the now half full antifreeze jug. Presto, two gallon jugs of antifreeze/coolant at 50% mix.

 

Honestly the best thing to do for a DIY is but 50/50 coolant and not worry about it!

 

By far this is the best explanation I have ever read on coolant and coolant mixture requirements. Thank you so much for your time and efforts. The coolant reservoir is easy to find but I am completely ignorant of the location of the radiator and cap on this car. Is it under a shroud? Not visible looking at the engine compartment. 2009 Mazda5 seems like an earlier model as it has an oil filter inside a housing and not a spin-type. Another question on the coolant - in the reservoir - should that fluid also be a mixture or straight coolant (assuming a mixture). Thanks again for your time!!!
****Found the Radiator Cap**** Thank you!