measured

Hi all, wondering if someone can help.

The opinion I've had from an official garage, and a third party garage, is that the eccentric shaft bearings have been damaged due to a lack of oil. But I never ran it out of oil.

So my question is, does anyone have either:
- a precedent for an rx8 running out of oil (for however long/short a time) and then being driven for ~2000mi before failure
- a suggestion as to how the rx8 can run the bearings dry, without a loss of oil pressure and when the oil is full

Original post with video here:
https://www.rx8club.com/trouble-shoo...9/#post4385770
The car is now on ~62000 miles

Many thanks for any help you can give!

RIWWP

iTrader: (2)

The oil may be full now, but your post indicates that you ran out of oil at some point previously?

You are aware that we burn oil intentionally right?


Bearing failure is not common at all, but the times it has occurred it is usually oil related. Either out of oil or insufficient viscosity (like starting with a 5w20, and then running that too long as our engines break down the viscosity quickly, often by 2,500 miles for dino oils)

shadycrew31

iTrader: (6)

Did you install new coils plugs and wires yet?

measured

Riwwp: No, it wasn't run out of oil - I'm very aware that it gets used, and regularly checked it, and topped it up. It never went below 3/4. Your point about the viscosity is interesting - it had fresh oil in it when I bought it, and I topped it up with 5w30 as recommended by mazda. I'm trying to determine if it's possible that damage occurred before I purchased the vehicle.

Shadycrew: No, the garage said the bearings have gone and it needs a new engine, so am not spending more cash yet...

RIWWP

iTrader: (2)

Yes, it's possible that the damage was dealt by the prior owner.

HiFlite999

iTrader: (2)

I'd bet you can get that failure by redlining with cold oil. It takes quite a bit of easy driving before the oil temp get reasonable, and in very cold weather, it may never get warm enough.

ASH8

What garage..you are in UK ...was it a Mazda Dealer or Mazda Rotary Specialists?

Get a compression test done at a Rotary specialist who knows what they are talking about...(Hayward Rotary)

Can you tell me 'how' the garage diagnosed 'bearing failure', no one can without really removing and pulling your engine apart.

What 'shady' suggested is worth looking into and much cheaper.

However, car has done 62K (miles) on I guess original engine?

It may need a rebuild.

BTW: Fill out some details about your location/car in UserCP.

shadycrew31

iTrader: (6)

I've seen/heard engines with completely failed bearings and they did not make any noticeable noises.

RIWWP

iTrader: (2)

What would you think about the possibility that it is more like a shattered bearing, and a rotor is so completely out of balance that the banging is the rotor hitting the housing?

shadycrew31

iTrader: (6)

According to the 7 club if the front and rear stationary gear bearing fail you can get diesel noises.

However you would see the front pulley wobbling slightly if that were the case.

If you aren't going to get new plugs, coils, wires, as suggested then your only option is to pull the motor and tear it down.

There is nothing else here for you.

Karack

unlikely it is a stat bearing or bearing at all.

nor do i believe it is an out of balance rotor, rotors don't bang into the irons and make clattering noises even when they do touch.

what it could be is something that you probably aren't even looking for like an exploded clutch disc hitting the bellhousing and transmitting noise to the front of the engine bay. easiest way to check this is with a borsecope through the removed starter hole.

or

a faulty accessory, like A/C clutch bearing, water pump or maybe even alternator(but i have never heard an alt sound like that, but cameras can make noises sound much worse than they are). remove the belts and run the engine and see if the noise goes away.

or worst case, a balooned up rotor face due to oil overheating. i have seen these on occasion but it is a rather rare issue. basically the knocking noise is the rotor face hitting the rotor housing chrome surface.

edit: who on the 7 club claimed it would make a diesel sound? i'm curious.

nycgps

iTrader: (1)

Have you ever changed the belts? sometimes the belts can make weird sound like that, not from this car but I heard it from another car that has 105K miles.

shadycrew31

iTrader: (6)

Wierd Knocking Sounds Like A Diesel - NoPistons -Mazda Rx7 & Rx8 Rotary Forum

Karack

nopistons, less feedback. and they never came back and said it was in fact the problem. if his pulley had slack the front thrust bearing probably failed and the balancer was knocking on the front iron. but the FD has a pull clutch and pulls the front balancer towards the rear of the engine, the 8 has a push type clutch and shouldn't give the same characteristics, a failed thrust bearing may still cause some strange noises though. the fact it started after a clutch job, it was probably clutch related.. like long bolts through a lightened flywheel hitting the rear stat gear mount bolts. there's many things it could be but if it started after work was done that work should be checked first.

easy check is push and pull on the front main pulley, if the slack is almost nonexistent then your thrust bearing should be fine.

a ballooned up rotor face can also be checked with a borescope through the leading plug holes. the rotor face will be shiny and metallic in a certain spot.

shadycrew31

iTrader: (6)

It could be a number of things...

I would start with getting the easy stuff out of the way then pulling the engine to inspect drive train components. lastly I'd tear apart the engine to check for any other issues.

9krpmrx8

iTrader: (46)

What are you basing this statement on? I have only seen several torn apart in person and several here and a bunch have shown bearing wear down to the copper.

RIWWP

iTrader: (2)

Was the cause of the failure just the bearings? or was something else is what failed and you discovered the bearings were wearing and would go eventually?

I'm not saying it's not a problem. But it's not what kills the engines first. All the other issues are the common ones. I can't recall a single failure on here being due to exclusively the bearings. They probably have happened, but in the face of all the other methods, failing on the bearings alone is indeed not common.

9krpmrx8

iTrader: (46)

Hard to say what exactly caused the failures but the bearings were toast. Knowing what caused the failure is not always possible and depending on who you ask, you will get differing opinions.

Does an out of balance engine or an engine ran with a thin oil or ran on low oil create out of round worn bearings which then in turn causes a loss of compression due to worn or broken apex seals?

Karack

copper showing does not mean the bearing is bad, but the renesis does eat through the bearing material faster than previous engines. it does this because of the lighter engine oil which is to supplement emissions and mileage. but it seems to me that the recommended oil is too light, which causes friction wear.

the front bearing usually has the majority of the wear, because it has the loading from the accessories off the front of the engine to deal with. the belts are not symmetrical so there will always be wear on the topside of the bearing, usually at the 12 o'clock to 2 o'clock area.

these engine blocks are also not line bored very well, nor do they really need to be. as mentioned, copper showing is rather normal and nothing to be worried about unless it is excessive. up to 1/4 of the bearing surface showing copper will not cause any major issues. if it was a piston engine you would likely be getting a rod knock way before that point, except the e-shaft is always loaded in that certain position and doesn't really vary from it.

you will also note the rest of the bearing shows almost no wear whatsoever. with the thinner weight oils you will note oil pressure drop more with that particular wear which is why higher mile engines should not use the recommended 5W-20, but something more conventional like a 10W-30 after 50k miles.

9krpmrx8

iTrader: (46)

Yeah the wear I have seen was pretty significant. I have seen some with minor wear that I agree was probably normal considering the mileage, oil used, etc. The type of oil is definitely important.

Here locally we were able to see my engine (mobil1 / 0W-40) and Houstonrx8ers engine (Castrol 5W20 dino) torn apart at almost the same mileage (both were Mazda remans) and mine had zero copper showing or any real wear at all and his had quite a bit of copper showing.

Karack

also has a bit to do with how tight the belts are run.

ASH8

type of oil Important!...REALLY

I have been saying this for the past 7 years that 0W20 or 30 is a crap oil for all Rotaries, and still do.

Slight bearing wear is not unusual in any rotary, it is happening more in the RENNY because of OIL...

As for parts used, Mazda still uses the same machinery and processes for the past 30 years.

shadycrew31

iTrader: (6)

10w30 with no bearing wear at 125k I'm sure 160k will show the same results.

Karack

40+ now actually.

9krpmrx8

iTrader: (46)

I can't wait to see