Turbo failure + Engine blow-by 2010 CX-7

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2010 CX-7
Hey all--we have a 2010 CX-7. Our turbo went out about a year ago at 84,000 miles, and we got it replaced at the dealer. We brought it back to the dealer for an oil change about a week ago and oil was low. After a test, they are saying there is blow-by on several cylinders and will need a new engine.

I'm frustrated because we spent about $3k on the turbo, and wouldn't have had we know of the engine issues which seem like they had to have been happening at least somewhat when we got the turbo replaced less than a year ago. Hoping Mazda will help us out to me it seems crazy that a turbo and engine would go on a car with 92,XXX miles.

Looking for some opinions. Is this common on this car; should the dealer have caught and told us about the engine issues at the time of the turbo replacement; do you all think there is, any chance of either a refund on the turbo from the dealer, or for mazda to replace the engine?
 

sm1ke

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Canada
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'18 CX-9 Signature
I wouldn't expect much from the dealer with an eight-year old car. You might get lucky and they may cover the work required as a gesture of goodwill, but what I would do before anything else is research what blow-by can do to an engine. From what I know, blow-by can cause a build up of carbon on the intake valves - this causes the car to idle and accelerate roughly, and can impact performance (maybe mileage as well). Usually this build up can be cleaned by sandblasting with walnut media or a chemical clean, but if it goes untreated for a long time, the general consensus is that it can be very harmful to the engine and cause misfires.

I would ask them to show you exactly why you need a new engine. You have every right to ask for pictures of the build up, and proof of the engine misfiring. Are you noticing oil leaking anywhere? Consider that your problems may just be a minor oil leak and dirty intake valves, both of which are relatively small costs compared to replacing an engine.

I know this sounds like I'm a jaded customer who's trying to pin it on a shady dealer who's just trying to squeeze money out of you - I'm not saying any of those things. We just need to remember that at the end of the day, the dealership is there to make money, that's their bottom line. So it becomes very important to do your due diligence, just in case.

Also, if you have no luck with the dealer, contact Mazda Corporate / MNAO. Good luck.

When you get everything sorted, I would look into installing an aftermarket oil catch can. It will catch a lot of the blow-by and slow the carbon build-up down greatly.
 
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Avoidin Deer

Zoom Zoom, baby
Contributor
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Central Virginia
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2019 CX-5 Reserve
I wouldn't expect much from the dealer with an eight-year old car. You might get lucky and they may cover the work required as a gesture of goodwill, but what I would do before anything else is research what blow-by can do to an engine. From what I know, blow-by can cause a build up of carbon on the intake valves - this causes the car to idle and accelerate roughly, and can impact performance (maybe mileage as well). Usually this build up can be cleaned by sandblasting with walnut media or a chemical clean, but if it goes untreated for a long time, the general consensus is that it can be very harmful to the engine and cause misfires.

I would ask them to show you exactly why you need a new engine. You have every right to ask for pictures of the build up, and proof of the engine misfiring. Are you noticing oil leaking anywhere? Consider that your problems may just be a minor oil leak and dirty intake valves, both of which are relatively small costs compared to replacing an engine.

I know this sounds like I'm a jaded customer who's trying to pin it on a shady dealer who's just trying to squeeze money out of you - I'm not saying any of those things. We just need to remember that at the end of the day, the dealership is there to make money, that's their bottom line. So it becomes very important to do your due diligence, just in case.

Also, if you have no luck with the dealer, contact Mazda Corporate / MNAO. Good luck.

When you get everything sorted, I would look into installing an aftermarket oil catch can. It will catch a lot of the blow-by and slow the carbon build-up down greatly.
Interesting suggestion.

After reading your comment I found this Road & Track video explaining exactly what a Catch Can does.
https://www.roadandtrack.com/car-cu...es-it-work-and-why-doesnt-every-car-have-one/

Your comment caught my eye because I'm all wrapped around the axle looking at new cars, and they all seem to have direct inject, which I've been led to believe causes a similar carbon buildup. I still don't understand if a Catch Can would help prevent this in D.I. engines, and if I'd end up having to empty the thing weekly.

Do you have any thoughts on this, or am I way off base?
 

sm1ke

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Canada
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'18 CX-9 Signature
Interesting suggestion.

After reading your comment I found this Road & Track video explaining exactly what a Catch Can does.
https://www.roadandtrack.com/car-cu...es-it-work-and-why-doesnt-every-car-have-one/

Your comment caught my eye because I'm all wrapped around the axle looking at new cars, and they all seem to have direct inject, which I've been led to believe causes a similar carbon buildup. I still don't understand if a Catch Can would help prevent this in D.I. engines, and if I'd end up having to empty the thing weekly.

Do you have any thoughts on this, or am I way off base?
I had the same thoughts when I first came across oil catch cans. Excess engine vapors (oil/fuel/water aka "blow-by") are vented out of the engine via a positive crankcase valve (PCV) to the intake manifold, where it mixes with the air and gets reintroduced to the engine. Because a direct injection engine doesn't spray fuel onto the intake valves, the blow-by can build up on the valves. The PCV on the CX-9 has an oil separator installed from the factory, which, by itself, reduces the amount of blow-by that makes its way back into the intake manifold. An oil catch can forces the blow-by vapors to condense even more, meaning that there is even less blow-by that makes it back into the intake manifold.

I used to own a 2008 Lexus IS250, which has a DI engine. These cars were susceptible to carbon build-up issues (along with a bunch of other manufacturers like Audi). The issue was such a point of contention with owners that Lexus eventually put out a TSB for the carbon build-up issue in the US. Most owners then started looking into oil catch cans as a preventative measure. Personally, I had never experienced any symptoms in the 60,000 kms / 3 years that I owned my car, but if I had kept it a little longer I probably would have installed a catch can myself.

Turbo engines are also more likely to experience excessive blow-by, which is why you'll see many modified turbo engines with single/dual oil catch can systems.

Regarding how often to empty it, most say that it should be emptied with every oil change, but that is highly dependent on how big your catch can is and how much blow-by its catching. I recently installed a catch can on mine and plan to check how much is in it every 1000 kms to start, then go from there.

If you'd like to read more about oil catch cans, check out the oil catch can guide I wrote (link in my sig). It's a great place to get started.
 
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