No Oil

Well, they poured 3 quarts into the motor and started it up. From the sound they are saying bad rod bearing.

“From the sound they are saying bad rod bearing”

…and they are probably correct.
Rather than spending the money to tear down this engine in order to replace all of the rod bearings and main bearings, you would be better-off just finding a low-mileage replacement engine from an auto recycler (aka junkyard).

Your son should bear the entire cost of this misadventure, in the hope that he will learn to be responsible regarding the basics of car ownership, which includes good maintenance, frequent checking of fluids, and immediately shutting-down an engine which is making new and unusual noises. If you bail him out of this situation, he may never learn to be a responsible adult.

Apparently the mechanic heard the “Rod Knox.” It’s a distinctive sound that I am sure several here would recognize quickly.

Yes, get an estimate for a used engine. It is by far the preferred method of dealing with catastrophic failure in popular late model cars these days.

Yes, my mechanic quoted me both a used and a rebuilt engine. He said if it was his car he would go with the used. He said his experience is that rebuilt engines last about half the time of new. We’re going with used. Also, in my son’s defense losing oil quickly is not all that uncommon with the 2.3L Mazda 3 engine, something I learned just today.

What does it sound like to YOU?? A bad rod bearing will produce a subdued, dull thump at idle and if you “goose” the throttle in neutral, the thump will turn into a “rap” …A clunk-clunk kind of sound…Idle oil pressure is usually near zero or way below normal…

Today, few cars are worth the price of rebuilding or exchanging the engine…I would drive it until it will drive no more…

There was still at least one and probably two quarts of oil left in the engine…It’s not like it was run dry…

Yup, heard a few rod knocks . . .

The last time, a colleague of mine was working on an expedition, which had been driven with a very low oil level

He corrected the oil level, but there was a knocking noise

I told him to cancel cylinders one by one, until the noise dissipates. When he found the cylinder with the rod knock and canceled it, the noise dissipated. I told him he’s got a rod knock, and the truck wasn’t worth repairing, in my opinion. It was an older model fleet truck, with a lot of hard miles, law enforcement

ultimately, the vehicle operator may have been to blame. They’re supposed to check fluids and tires from time to time. However, some of them don’t do it, and the truck suffered for it

An engine with a rod knock is beyond nursing a few more miles. And an experienced mechanic should know the sound. I once poured 3 cans of STP in a Ford V-8 and nursed it 75 miles with a rod knocking but I was heading home and every mile I drove was a minute that I wouldn’t be waiting for a wrecker. I would never drive away from home in that condition.

Boy, it can’t be repeatable in mixed company.

IMHO a 2005 Mazda 6 is, if it’s otherwise in decent shape, worth fixing, but your son will now have to choose between four options:

  1. a boneyard motor
  2. a rebuilt motor (long block IMHO; as the top end parts have probably sustained damage too)
  3. rebuild the existing motor
  4. a remanufactured motor (more extensive than a rebuild)

I’ve tried to list them in the order of the most risky (but least expensive) to the least risky (most expensive). Which option is the best will depend on the overall condition of the vehicle.
If it’s beat up, high mileage, and/or other maintenance has been ignored, option (1) is IMHO the best.
If it’s in otherwise excellent condition, low mileage, and other maintenance has been kept up, and your son can afford to do it, option (4) is the best option. With a remanufactured motor the car should have many more good year left… if the oil is no longer ignored.

Others may disagree, but that’s my perspective.

What did it sound like to me? The first time I heard it when my son drove up it reminded me a bit of a diesel, just louder. When my mechanic put some oil in it it sounded like a loud rattle with a knock. He immediately said bad rod bearing. I asked how he could be so sure, and he said “many years of experience.” They found a used engine. Overall the car is in good condition, my son put a new clutch in it last year. He can’t afford to buy a new car right now so fixing it is the cheapest option. I told my son to put a reminder on his phone to check the oil every two weeks.

I took a look at the garage floor where my son parks. No oil on the ground. In doing a quick search on the web I find a lot of discussions about the 2.3L Mazda engine suddenly consuming a lot of oil when it reaches 100K. One guy said he had a similar thing happen and when he checked the oil it was 3 quarts low. He said he had checked the level only 2 weeks prior and there was no sign of a leak and he never saw smoke coming out of the exhaust. I spoke with my Mechanic about running the “new” engine on a heavier oil as some say that this helps alleviate the issue (the engine is supposed to run on 5-20). Some speculate that the PCV could be the cause of this so I will have my mechanic look at this. Here is a link from the APA that was posted on one of the Mazda sites:

I have to say that my mechanic said he had the same thing happen to another customer with the same engine. In my own experience I once had to replace the engine in a 1988 Chevy S-10 Blazer at 84,000 miles (2.8L engine). I never ran it low on oil and had it serviced per the manufacturer’s recommendations. I had a different mechanic back then but he said that was not uncommon with that motor. Last Chevy I ever bought.

IMHO checking the oil and other fluids every two weeks is too long (better than never doing it though) I check my ‘fleet’ of 3 cars every Saturday morning. It is also a good time to look over tires and general condition of the cars. Does not take too long either, just need to get in the habit of doing it regularly. If the cars are driven a lot, several hundred miles in a day, they should be checked more frequently. Each time you fill up is another good time to do it.

how many miles on new motor?

I think that depends highly on the car and its use. When I commuted, I checked my fluids every week. For one year in the '80s I worked 103 miles from home and commuted (long story not car related). Now that I’m retired, I check perhaps three times a week… it gives me something to do.

I think once weekly is great for starters until one knows ones vehicle, but if it’s a new(er) vehicle that uses little oil and mileage is only a few hundred miles a week, every few weeks is perfectly fine. With the addition that it should be checked at least daily for a few days after an oil change to ensure that it isn’t leaking out due to a bad filter gasket or loose plug.

But it’s highly personal without any right or wrong periodicity. The only absolute is that never checking ones fluids, or only checking ones fluids when they get low, is a virtual guarantee of trouble. If someone knows their vehicle uses a quart every two months, they should be checking every week.

SteveCBT I also check oil every Saturday and tire pressure every other Saturday. My previous and current car never used oil between changes and current car has TPMS but I still check oil and tires.

Why not replace the bearings? Gotta be cheaper than a used motor. Can you get to the bearing easily on this type of motor? Rocketman

@rocketman The trouble is that the crankshaft will also be damaged.

…and the cylinder walls may have been scored.
There are just too many possibilities for damage to that engine for it to be repaired economically, hence the recommendation of installing a new (used) engine.

I have a different perspective. If your son was checking the oil regularly and the car was not loosing oil, then whatever caused this failure was a semi-catastrophic failure causing large oil consumption. If he knew about it, maybe he could have babied the car for a few weeks, but that engine was probably toast either way.

I am OCD, but my engine oil checks vary based on the car. If I know the car and it has not been burning any oil, I usually check every 2 weeks. If I know a car has some seepage or other issues, I keep a closer eye on the oil. I always check the garage floor and when I pull out of a spot, so I would know about a major leak immediately.

I am OCD, but my engine oil checks vary based on the car. If I know the car and it has not been burning any oil, I usually check every 2 weeks. If I know a car has some seepage or other issues, I keep a closer eye on the oil. I always check the garage floor and when I pull out of a spot, so I would know about a major leak immediately.

That’s the way I am too. If I buy a new…used car…I check the oil daily for the first week. if there are no signs of heavy usage, then I go to every two weeks.
I also seem to notice those oil stains where we park and if I had not, my wife would have probably burnt up two cars this past year. Somehow she has been lucky enough to have something (road debris) puncture the oil filters on two of her cars…all within about 2 months. They were not bad leaks, but enough to leave a puddle where she parks. She never noticed.
The problem is that her ears are going and she keeps the radio so loud…she’d never hear the engine clatter from a lack of oil.


Put oil in it and hopefully noise goes away. If it does my guess is the car will die before the engine does if you maintain the oil level after this incident.

If noise is gone make it a regular habit to check/top oil every 2-3 fuel fillups and the car will likely live a decent life.