Brettus

iTrader: (2)

LOL - didn't occur to me that there might be a different term for it in the US .

ken-x8

Until someone comes up with a definite reason why these engines sometimes fail:

17) Be born under a lucky star.

Ken

pistonhater

Exactly. I was referring to the hype about "cleaner" burning. Some people go crazy arguing about what brand burns cleaner over the other, blah, blah, blah.....

LOL

monchie

I drive less than 10 miles a day. My commute from home to work and back home is around 6 miles only. Maybe, i'll cruise around the neighborhood before i go back home...lol

j9fd3s

i was referring to the thermal pellet. when the oil temperature is under ~65c, there is a bypass on the Eshaft that is open, thus lowering the oil pressure to the bearings. there is a period where the water temp gauge shows normal temp, but oil temp is not over 65c yet.

i am otherwise at a loss to explain why the Rx8 engines have bearing problems, when the FD, and all of the competition engines after 1980 use the same bearings without any trouble.

cturbo28

iTrader: (1)

You needed to use an accent.

wcs

iTrader: (2)

I'm with Ken

Doesn't seem to be much rhyme nor reason to it ... but I'm not in the Engine rebuild industry so WTF do I know

dannobre

iTrader: (3)

Likely the 5/20 oil at lower oil pressure. This is also likely why they raised the pressure in the Series 2 motors

ken-x8

I get the impression that most of the failures are low compression from side seal failure, with carboning-up of the exhaust ports being a cause. Occasional major failure from an apex seal breaking. Doesn't seem like oil weight would have much to do with that.

I think the pictures of every torn down engine posted here have shown wear on the eccentric shaft bearings, which would be from wimpy oil. I don't think I've seen any posts about engines coming apart from that, though.

Just figuring from stuff I'd read here over the years, not from any real knowledge.

Ken

j9fd3s

me too… and we do have to admit the vast majority of engine failures were under warranty, so we didn't see the inside of those engines

dannobre

iTrader: (3)

I was talking about the bearing wear only.... the oil weight shouldn't be an issue for seal failure

JimmyBlack

Good thread topic. To do it right it should include a summary of the most common failure modes of the Renesis, then identify the maintenance steps required to address each of these.

Had a quick search (at work) but didn't find a summary of common engine failure modes. Anyone care to find and link? I'd be very surprised if one doesn't exist already.

j9fd3s

loose clearances would explain why there is so much variability in engine life. some engines will be (and are) fine, some wont. this would also explain why they exhibit different modes of failure too.

i don't know that i've seen enough engines to draw any conclusions myself

poacherinthezoo

I've long held the belief that the legend of the renesis reliability stemmed from tolerance issues due to it being more "hand built" than an average piston engine (vaguely remember that the side seal springs were done by feel? not sure though - EDIT: found the video from mazda: part 3: http://www.mazda.com/mazdaspirit/rotary/howto/ ). Some were put together correctly, others were doomed from the start.

Brettus

iTrader: (2)

The overwhelming failure mode (from what I have gleaned over the years)would be - major loss of compression resulting in hard starting and poor performance.

Loose clearances would explain some minimal loss of compression but I don't think that is what causes the failures . The biggest loss of compression is carbon buildup on the apex/corner and side seals causing them to stick and fail to follow the contours of the compression chamber .

Perhaps there is some correlation between poor clearances allowing gases to bypass the seals initially and gradually cause the carbon to build up ......... but it seems unlikely to me . I believe the carbon is going to build up either way.

This buildup is a result of the engine being used as a commuter vehicle by owners who don't really understand why a rotary wont last long under these conditions.

JimmyBlack

Interesting - build quality (I.e. tolerance issues) would explain why some regions seem to have experienced a higher than average engine failure rate.

Here are a few other common causes of engine failures that I've seen on the forum:
- inadequate OMP delivery caused by faulty OMP system (did 9krpm have this issue and it cost him a few engines?)
- inadequate OMP delivery caused by low OMP rates on older PCM flashes
- carbon build up caused by granny driving

Feel free to add to this list or debunk.

New Yorker

Sigh... if only I was "stuck" where I am with every car I've owned.

poacherinthezoo

Very true. The differences between the series 1 and series 2 cars is the closest we'll ever get to knowing what Mazda's research actually said were areas for improvement.

twospoonstn

I'm at 142,000 miles (2004 model) on my original engine. I've not done oil changes every 3K miles, sometimes I went as long as 10K. I've only replaced coils once and spark plugs once. I've not replaced any other parts on the car.

Mazda upgraded the starter for free one time. The car has been flooded 3 times total.

Around 100K miles the car would not idle, and was really hard to start when warm. I then started premixing which resolved those issues.

I did a decarb at the Mazda dealer recently (at around 141,000) and that made the car idle better, but warm starts are even worse (5-6 seconds).

The only thing I can say I have done reliably is drive the car hard.

RIWWP

iTrader: (2)

Sounds like your engine probably would have failed a compression test back at 90k. Rotaries are like that though, you can keep driving them long past failure.

twospoonstn

I feel like this problem is not going to get any better (the warm starts), so passing emissions today was a hassle. I'm torn between paying for a rebuild (I live in middle TN, so I don't know of any reputable shops around here), or trading it while it still runs.

I love the car though, so it's hard to part with it. There is nothing quite like it out there.

RIWWP

iTrader: (2)

Actually, you are reasonably close to one of the few shops that people here are willing to recommend. Contact Rotary Resurrection, he is 1hr east of Knoxville. Solid work and reasonable pricing for basic rebuilds.

Hi Flying 8

iTrader: (2)

Get a good rebuild and keep your car as you won't be able to find anything else that will give you as much enjoyment for whatever a good rebuild will cost. This is especially true if we never see another Rotary produced commercially. That is definitely my plan when I have to face this dilemma.

DanBas

I don't agree with this. My experience says that overfilling the oil can be as bad as underfilling it. If it's slightly over, particularly on earlier cars, it's very easy for oil to travel through the filler neck breather hose and get sucked back through the air intake. This can gum up the filter, contaminate the MAF and throttle body, cause very rough running and has a small chance of causing serious engine damage. It's also a pain in the **** to clear up.

I would say best practice would be to keep oil about halfway between your top 2 marks, I.E around 2/3rds full.

Raptor75

You are running an expensive time bomb here. I have gone through it so let me share. My coils failed around 35K miles I did not notice at first, car started losing power and very noticeably on the way home one day. I tried to get home with it but that was a mistake. CAT started to over heat and glow red. Apparently when the coils start to go bad the fuel is not burning all the way in the combustion chamber and is being dumped into the CAT which then burns it and melts the CAT.

I towed the car home and replaced the coils. About a year or two later the the O2 sensor failed and needed to be replaced. I brought it to a repair shop I trusted and he told me the CAT was melted. So since it was under warranty I brought it to Mazda. The service center would not replace the CAT without replacing the coils, I told them they were about a year old and they said they tested them and they were bad and wanted $600 to replace them. at this point I bought the BHR upgraded coils and Mazda then replaced the CAT and O2 sensor under warranty. I figure the coils would be a good invest to keep the new CAT long lived, it is very expensive to replace.

So moral of the story don't depend on the OEM coils, you may have been lucky so far but when they go they will take out the CAT with them and your be looking at a few thousand to replace it all.