Clueless about PCV Valve

[jasonsthomas]

Hello,

I'm brand new to the form. I drive a 2009 Mazda5 Sport. It's the first car that I have ever owned. I'm a complete moron when it comes to car repair. My car has 66K miles on it and now that I'm on summer vacation (I am a teacher), I thought that it would be a good time to have my uncle show me how to do some basic maintenance. My car was previously a rental (I wanted a used Mazda5 so bad and it was the only used 5 for sale within 100 miles of me.). I bought it when it had 45K miles on it. I've recently done the brakes, rear shocks, replaced the cabin air filter, and bought new tires. A month ago, I had the transmission fluid flushed and it was almost black... So, needless to say I'm in full scale, 'I need to check everything mode', (Note to self: Never buy a rental) which leads me to my PCV valve question.

My next door neighbor said he changes his PCV every other oil change and was shocked that I have never changed my PCV. A friend of mine said every 2 years. Neither of them are cool enough to drive Mazdas. Is there a set interval for changing the PCV or even general guidelines? This is my only car and I'm a 'I'd rather replace it on summer vacation with my uncle's help, than pay someone to repair it during the middle of the school year when life moves a lot faster',-kinda person. Also, I've heard that you have to remove the intake manifold to get to the PCV. Is this true? Since removing the intake manifold involves replacing the head gasket and what not, I don't want to ask my uncle/spend extra $$$ unless I really need to.
Any other maintenance suggestions would be appreciated as well.
Thank you in advance for your assistance,

 

[Robotazky]

I can't comment on where it is and how much trouble it is to access. PCV stands for positive crankcase ventilation. You know how if you have a vacuum leak the car will have trouble? That's because it's basically a big pump. Sometimes it produces pressure instead of vacuum. WHen that happens, it vents through the PCV, usually to the air intake box or somewhere upstream of the throttle body. At other times, it is pulling air from there. It's just there as a check valve to maintain the proper pressure conditions.

When you find it, it will pull out easily. Remove it and shake it up and down. If the part inside can be heard moving up and down freely, it's fine. If it seems gunked up and not moving freely replace it. It's just a check valve that opens and closes as the engine pulls the diaphragm closed or pushed it open. That's why such a simple test is all that required.

If you're having no idling or other minor performance issues, and the PCV is a pain to get to, I wouldn't worry too much about it. If it's easy to get to, it can't hurt to spend 1-2 minutes checking it.

Comment on the tranny fluid: I'm not surprised it was black. That's common for that mileage. I don't see any other part of the car wearing that quickly so don't be alarmed. Just stay on top of the tranny fluid and you'll be fine up through 100K.

 

[Silentnoise713]

Welcome!

+1 to Robo's comments.

Not sure what car your neighbor has or reason why he replaces it every oil changes but a PCV is NOT a routine maintenance item -not on any car that I heard of. It is a very simple device. Are you sure you two are talking about the same thing? It should last you ~100K miles before maintenance for the typical owner. I recall from a Mz3 discussion that is under the intake manifold so that has to be removed (tedious but not hard), and this has nothing to do with a head gasket (seal for top end and bottom end of an engine block).

Here’s a quick tip: the Mz5 and Mz3 are mechanically identically. If you can’t find specifics for the Mz5, Google the same question for a Mz3 b/c there are much more owners who work on their cars.


And yes, NEVER EVER buy a rental - EVER!

 

[jasonsthomas]

Thanks for the replies and tips! I'm learning slowly but surely about this whole car ownership/maintenance thing. Thankfully, I own a Mazda, so there's not as much to worry about. As a teacher, the joy of summer vacation is having the time to do and learn about stuff like this.
Thanks again!

 

[thaxman]

Congrats on the Mz5 purchase. I have to warn you that it will set unrealistic expectations for all your future car purchases tho, as really no reliable vehicle is this much fun and very few fun cars are this reliable.

Your neighbor who pops in a new PCV every other oil change must have a V8. Old-school pushrod V8s have the PCV coming out of the valve cover on one bank of cylinders. Easy to find and get to, since you just look for a little hose that goes from the air cleaner to the engine. They cost $3 and are the same technology they were in 1974. New OHC VVT engines wrap the PCV in the most unusual locations and involve dismantling part of the engine to get to them. My Volvo has it wrap all the way around the block only to terminate in an oil trap and breather component dead under the intake, completely inaccessible without removing EVERYTHING air and gas run through before entering the cylinders. But its this extra attention to PCV functionality that lets them go 100K w/o needing to be serviced. I say relax, keep up on the oil changes and when you begin to see oil start to disappear between oil changes or idling quality issues, its time to look at the PCV.

If you haven't done so yet, now is a good time to switch to full-synthetic oil. Used to be that syth was for mullet-headed Camaro drivers and fake-boob Cougars in Corvettes, but with the price of the stuff coming out of the ground ever-increasing, the fake stuff (which works BETTER, incidentally) gets more affordable by comparison. Don't worry about which brand is better, since a little 2.3L NA engine isn't going to notice much if you aren't taking it to the track and you keep oil changes no farther apart than 7500 mi. My personal opinion tho is to not mix brands, as since its not dino, the diff brands could theoretically be made in much different ways, so they may not be compatible w/each other.
Watch your AT fluid color, as you already learned. Ditto on keeping an eye on the PS fluid. These cars use an electric pump and to be frank, the pump sucks. Mine constantly bleeds fluid from somewhere and the pump is always soaked. What can you do? its actually a warranty replacement. Be aware that the interior plastic parts aren't very beefy, so use a light touch with things like the visors and the little clips that keep the 4 back seatbelts up against the body when not in use.
Rotate the tires like its your religion. Although its supposed to be remedied in 07, some 09 owners have complained about throwing away the rear tires prematurely. If they make their way around all 4 positions over their lifetime, they should last much, much longer.
Back to oil: Rental businesses keep track of their cars' mileage and are supposed to flag them for maintenence, but it never happens. Theoretically, your engine could have had oil in it 3-4X longer than it should have. In OH, that's probably not as big a deal as in places like PHX, where 90% of all car renters leave PHX, elev 1000' and travel to Sedona, Payson or Flagstaff, all over 6000' elevation and about 100 mi away. 5000' in 100 mi will really work your oil, and if its old, it will lose its lubricating abilities (sheering) and the metal begins to wear on other metal parts making permanent microscopic grooves. Keeping your oil fresh will prevent additional wearing and good oil will partially fill in the grooves, so you won't really have to worry about the abuse the engine may or may not have received in its previous life as a rental car.

 

[phunky.buddha]

Congrats on the Mz5 purchase. I have to warn you that it will set unrealistic expectations for all your future car purchases tho, as really no reliable vehicle is this much fun and very few fun cars are this reliable.

I would put my S2000 up against my MZ5 for higher fun factor and higher reliability.

And my MZ5 is an 09, definitely had rear tire wear issues.

 

[jasonsthomas]

Thanks for all the insight. I'd have to say that my V6 '08 Fusion was more fun to drive, but my Mazda is perfect now that I have a wife and 2 young kids. I hear ya with regards to Arizona... We used to live there and boy you are correct about the utter beating that a car takes driving from PHX up to Flagstaff/Sedona. I'm glad that I bought my car after I moved here. I've also experienced the tire issue that you mentioned and replaced all 4 with top of the line all-seasons. Oh how happy I am to drive a car that will easily hit 200k-250k if I take care of it.

 

[Robotazky]

I would put my S2000 up against my MZ5 for higher fun factor and higher reliability.

And my MZ5 is an 09, definitely had rear tire wear issues.

I'm assuming what you're calling an MZ5 is a 5. I have an '09 5 with no abnormal tire wear after 40,000 miles on the same set.

 

[Silentnoise713]

I'm assuming what you're calling an MZ5 is a 5. I have an '09 5 with no abnormal tire wear after 40,000 miles on the same set.

The original Toyos on my '08 didn't have any uneven wear either. Down to 2/32 @ ~35k per my tire gauge. My rear end is squeeking like hell tho!


On rentals, the main thing that gets abused is the transmission. Motor oil can be monitored by mileage and rev-limiter (auto) pretty much protects the engine. I travel a bit for work and go through rentals and gas is comp. let's just say I can understand why there were fire incidents resulting in the recall... Don't go near any rental that has a manualmatic transmission.

 

[phunky.buddha]

I'm assuming what you're calling an MZ5 is a 5. I have an '09 5 with no abnormal tire wear after 40,000 miles on the same set.

Yup, Mazda 5. Thought that was the normal convention around here- MZ3 = 3, MZ5 = 5, MS3 = Mazdaspeed 3. I bought mine at 52k miles and it probably had the original shocks on it, so they didn't last much longer after I bought it.

 

[Robotazky]

Yup, Mazda 5. Thought that was the normal convention around here- MZ3 = 3, MZ5 = 5, MS3 = Mazdaspeed 3. I bought mine at 52k miles and it probably had the original shocks on it, so they didn't last much longer after I bought it.

I'm curious what your mileage is now and are you still getting uneven wear with replaced shocks. I have heard quite a few times that the wear issue was resolved in the '08+.

 

[phunky.buddha]

I'm curious what your mileage is now and are you still getting uneven wear with replaced shocks. I have heard quite a few times that the wear issue was resolved in the '08+.

We're WAY off topic now... but no weird tire wear in the last 5k miles, and averaging about 28mpg on the highway, 20-22mpg in the city... but we drive the piss out of it.

 

[thaxman]

We're WAY off topic now... but no weird tire wear in the last 5k miles, and averaging about 28mpg on the highway, 20-22mpg in the city... but we drive the piss out of it.

Topic? Well, that was a few exits ago...

Wish I could get 28mpg hwy. We'd take the dang thing out of town. 21 mpg across the desert w/AC @ 78-80 mph. Sux.

But I can squeeze 24 mpg out of city driving, and that's 99% of its duty as a runabout, so its nearly all win.

 

[phunky.buddha]

Wow, that's it? Ouch.