Hey, everyone. I’ve owned my 2012 Mazda3 Skyactiv for almost 13 years now, and I hope to keep it for at least another decade, if not longer. The car has low mileage at almost 84K with no visible signs of rust on the body.

I recently had my brake fluid replaced since I had to get new front brakes and I also had a coolant flush. My mechanic had mentioned my coolant was fine, but I insisted it be replaced since the owner’s manual recommended replacement at 10 years. He’s a pretty no-frills kind of mechanic, which I appreciate because I save money in the short-term, but I do wonder if maybe he’s missing certain things.

My check-engine light has been on for months. My mechanic told me it was an oxygen sensor error code, but they so rarely fail, so he didn’t recommend I spend money to replace them since it might not remove the error code. He couldn’t seem to find the source of the error at my appointment this week. He checked for leaks in my exhaust, loose wires, etc. but nothing stood out. So my check-engine light remains on… I have no idea if this is doing long-term damage, but he doesn’t seem concerned at all.

Is there anything else you would recommend I service at this point? Power steering fluid and transmission fluid flush? Engine decarbonization? Timing belt replacement?

Thanks!

 

Your mechanic is obvious not really an Automotive Diagnostic technician and frankly not a very good mechanic. Sorry.
Driving for months with the check engine light on without knowing the cause.... BAD IDEA> Also "Guessing" or assuming it is an HO2 based on the DTC which is not how you do things is also a bad idea. And sorry to pop the bubble of bad information but who stated with facts that HO2s rarely go bad. We are replacing several every month about a complete diagnostic confirmation that they failed or were reporting bad information the the ECU/PCM
Your "mechanic" did not look at all the areas of the ECU/PCM when it was scanned otherwise you would be reporting more finding than what you had?
Back to questionable mechanic I can tell you based on your posting that your "mechanic" did not do a check of the coolant the way you were supposed to. otherwise, your information would have been much different. Like the % of coolant to water which tells the condition of the coolant. And while automanufactures state the service date remeber that adheering to them to the letter and not considering doing them earlier when your warranty has expired it now your $$$ to correct issues from less then more frequecnt and sooner servicing.

You did not mention if you had an automatic of manual transmission. if automatic I will presume that you have never had a basic pan removal filter and pan fluid change. So your Mazda is long over do for that.

 

Welcome to the forum

 

Callisto, thanks for the information and prompt reply. Something didn’t feel right when I had to insist on my coolant being changed. I wanted to change it two years ago, but he convinced me it was okay! I’m confused as to why he would recommend under-maintaining my car. Is it perhaps it would result in a more expensive repair later on?

As for my transmission, I have the automatic. I had a transmission flush only one year into owning the car as recommended by the dealer. I had less than 8000 km on the car at the time. I thought that was very premature, but I agreed to it like an idiot. Haha!

I’m going to look for another mechanic and get a second opinion. That check-engine light is driving me mad seeing it on constantly. I’m worried I’m burning more fuel than necessary too.

 

Sorry are you sure they did a transmission flush and not a simple pan filter and fluid replacement. A shop regardless independent or dealer really require doing the job correctly and properly if not safely for the transmission a Professional shop transmission service machine.

As for the coolant this is how you test the coolant. I resently duid mine at

 

I seem to remember it saying “transmission flush” on my invoice, but that was over a decade ago. It’s so hard to find anyone trustworthy. I do a search of mechanics on Google, and they all have stellar reviews, which some are probably bought and paid for. It’s so overwhelming because I don’t want to spend money on unnecessary repairs, but I also don’t want to under-maintain, leading to larger and more costly repairs down the road.

 

looking at your profile……(maybe take a illtle more time to complete a more informative profile?)
in your state , find a service shop that advertises ASE or has signage They can only legally post that if they at least have emplyoyed at least one ASE Automotive Mechanic or better Automotive Diagnostic Technican.

If yours did in fact get a “flush” (poor terminology if that’s what they called it) the cost would have been between 200-250+ dollars or more.
If they did a pan oil and filter service about $150-175+

 

If you want to do flush without much hassle, try draining and refilling with new transmission fluid three times over 2000 miles. It might not get everything, but it will get out majority of gunk. Also drop the pan and put in a new filter on your last drain and fill. I've got to do this with my wife's Honda Odyssey every 50k miles.

 

* The dilution method does not work. MYTH.
It will NOT get a majority of the accumulated “gunk”! You must drop the pan clean pan and magnets wipe valve body change filter. Then to do the fluid replacement correctly on most all automatic transmission from about 2009 to present really requires the use of a Shop quality grade transmission service machine .

because there is a part that do hold fluid even after drawing the pan ,valvebody , pump, torqueconverter to name a few the decades long MYTH of dilution method of changing transmission fluid we debunked decades ago.


If you wait 50 k miles you are are fooling yourself , want empirical proof get a sample analyzed next 50 k miles .

 

Regarding your coolant a specific gravity test with a Hydrometer is only 1/2 the testing required. The most important part is checking if the fluid is acidic or alkaline. New cooland will have a pH of around 8 which is alkaline. As the coolant ages it becomes acidic and the pH will drift towards 7 which is the danger zone for engine corrosion hence it should be replaced before it gets to this stage. Car manufacturers estimate from extensive testing when to change the coolant and for cheap insurance follow their advice. You can but pH test strips for easy checking. Castrol make an inexpensive one that will indicate the coolant concentration and the pH. I test every car I service weather it be 6 months or a year and for the DIYer for around $25 for 50 is a cheap addition to the toolbox. Which coolant to use? OE is the safest and in the big picture not that more expensive.