Oval Bore Syndrome - 1ZZ

[Anonymous]

1ZZ now fubared.

No oil consumption at all until yesterday, pulled off the motorway, horrible internal knocking on coasting. Only on one cylinder though - I think it is the oil control problem causing the bore wear rather than pre-cat material in the oil - would expect to have all four rattling if that was the case....

Pulled over, no oil. Engine will start and does run on 4 cyls, I'll check the precats tomorrow, but assume they are powder.....Had just booked it in to have them removed as well...

2001, 64000 miles, using Mobil 1 5W60, changed every 3000.

Going to try the dealer but I doubt they will help as the car had no service history when I bought it......

Gutted! Just been made redundant too! Sympathy gratefully accepted......

  s:( s:(

[Wabbitkilla]

Suitable sympathy given, please accept a manly hug mate.

Sorry to hear on both counts.
Even if you have only partial service history it's worth a try with Mr T, good luck.

[muffdan]

So sorry for you, it never rains but it pours.

Jason

[rmowbray]

Sorry to hear that mate. Gutted.   s:( s:(

[Anonymous]

Mine has suffered this, I feel for you.

I have been through both worth cases with the 2 now.

[Anonymous]

Thanks for the comments guys...

Unfortunately, right pre-cat beginning to break up, so it's either no. 1 or 2 cylinder.

I'll ring Mr T today.......

 s:-( :-( s:-(

[kanujunkie]

folks, whenever you do a service on the car its imperative that you use engine oil flush, the issue is not with the rings or the precats but with the oil feed holes coking up and restricting oil flow, so do the engine a favour and clean it properly

[markiii]

stu, not disagreeing with you, but since this is a new argument, do you have some evidence to back it up?

[SteveJ]

stu, not disagreeing with you, but since this is a new argument, do you have some evidence to back it up?

IIRC didnt Jason find his oil control rings had clogged up causing the demise of his engine.

The oil control rings on my old engine were pretty well choked up with sticky crap as well. Although it's demise was running lean on one cylinder and rich on the other due to the bit's of plastic from the inlet explosions   s:shock: :shock: s:shock:  which resulted in the valve seats burning out.

I'm not sure that a flushing agent will clear the problem though - the best cure is prevent the problem in the first place - use decent fully-synth (real stuff NOT the marketing hype stuff thats really dyno-juice that has been heavily processed)

[markiii]

stu, not disagreeing with you, but since this is a new argument, do you have some evidence to back it up?

IIRC didnt Jason find his oil control rings had clogged up causing the demise of his engine.

The oil control rings on my old engine were pretty well choked up with sticky crap as well. Although it's demise was running lean on one cylinder and rich on the other due to the bit's of plastic from the inlet explosions   s:shock: :shock: s:shock:  which resulted in the valve seats burning out.

I'm not sure that a flushing agent will clear the problem though - the best cure is prevent the problem in the first place - use decent fully-synth (real stuff NOT the marketing hype stuff thats really dyno-juice that has been heavily processed)

but stus saying it's not the rings that are teh problem

[SteveJ]

but stus saying it's not the rings that are the problem

  s:oops: :oops: s:oops:  Should have read his post more thoroughly.

There is evidence however of the oil drain holes in pistons clogging up, causing the oil control rings to jam resulting in excessive amounts of oil getting past and then clogging the compression ring grooves which in turn then allows the oil into the cylinder during the intake stroke. Result - bye-bye pre-cats and oil, followed very quickly by the big-ends.

This is only a working theory based on what Jason reported and what I have observed from the engine I have stripped that wasnt using oil at the time but I'm fairly certain from the nasty state of the pistons (and in particular the ring grooves) it would have started to in fairly short-order.

I would like to take a look at the state of my current engine given that the oil that came out of it when I bought it was practically new (it was a VERY low mileage celica) and since fitting it has only been fed with Silkolene Pro S and has covered ~38k. I just dont want to strip it down at the moment as (fingers crossed, touch wood etc) it isnt giving any problems.

[Anonymous]

I am fairly sure it was some sort of excessive wear problem in the bore / piston / rings which has caused the cat breakup, not the other way round.

I have been checking the pre-cat's condition every month or so and they have been immaculate. The only reason I didn't gut them is because I couldn't get one of the manifold nuts off, even with a Dremel and removing half the rear end, so I had it booked in with a local garage to do the work in December. Bearing this in mind I have been checking the oil weekly and pulling the O2 sensors regularly to check.

I have also been listening to the engine whilst starting up and driving. The only symptom I can recount is a bit of (very) mild pinging on decelleration when warm. No CEL light, ever and I check the codes regularly JIC. As for the fateful journey itself, no symptoms at all, it was a completely uneventful motorway run from Lancaster to Manchester, 4000RPM all the way in 5th. I only had to downshift once the whole time. The engine was as responsive as usual, comfortably in the high-duration zone all the way, I only knew something was wrong when coasting on the slip road, it sounded like going over speed bumps but without the jolts.

It would tend to suggest an oil starvation problem, or perhaps excessive wear / carbon on the oil control rings causing gumming / scraping. Thus the change to 8 drain holes and a groove in 2003 and the3 comments from the Toyota guy on the sticky.
I doubt the pre-cats had ANYTHING to do with the failure, as the right hand one has only just started to degrade.

[Wabbitkilla]

Y'know you've been taking very good care of that car.
Sorry, how many miles has it done?

After witnessing Ste's rebuild i'm wondering if you'd get away with a rebuild using new pistons, honing the cylinders and maybe new "end" bearings? Obviously ditching the pre-cats at the same time   s:wink: :wink: s:wink:  

I'd say it's definitely worth the try.

[roger]

IMO there has never really been a definitive answer to which comes first (bores or pre-cats) though Toyota have recognised both as problem areas.

Of course looking at the precats through the o2 holes only shows you the top end. Any damage at bottom end is out of sight. You could have broken bottoms, which did the engine in, then all the oil did the tops.

I'm afraid the diagnostics is very circumstantial, however sorting the engine becomes your number 1 task - and best of luck with that.

[muffdan]

My opinion is that the bores oval due to a design flaw in the piston oil feed holes (too small or too few of them) causing excessive wear to the cylinder walls and then excessive amounts of oil to be burned. Toyota later revised the piston design which seems to have fixed this oval bore problem. The excessive oil burning kills the pre-cats though and the broken pre-cat material can then destroy your engine in a matter of miles.

If you gut the pre-cats you can run with the oval bore problem for a long time (at least 30k with a turbo for me), you just have to top your oil more regularly.

You won't be able to repair the block with just a hone of the cylinders. You are going to be missing large amounts of metal from your cylinder walls, hence they are oval. The only solution is to sleeve the block or bore out and fit larger pistons. Its more cost effective to buy a whole replacement second hand engine.

You could just replace the pistons/big ends/anything else damaged, hone the cylinders and see what happens. You would still have a high oil consumption and I imagine the new rings wouldn't bed in at all. Without my knowledge a garage did this to my engine after a pre-cat failure and I ended up running 30k with a turbo on a block with oval bores. This was discovered when rebuilding after a head gasket failure.

I'd go for a new engine from a 03+ car.

Jason

[Ilogik]

Or fit a 2zz :p

[Anonymous]

Can a 03+ engine go straight in a preface lift model or would it need the ecu changing aswell?

[Wabbitkilla]

Can a 03+ engine go straight in a preface lift model or would it need the ecu changing aswell?

Straight swap, no problem.

[Anonymous]

I'm going for a post-2003 1ZZ or a Mr. T shortblock, assuming I can persuade them to pay for it!

As for the failure itself, in my case I realise that the actual sequence of failure is moot.

I've read the various stickys and know you guys have done this subject to death - however in my experience building and running high-horsepower V8s of various specifications, and having experienced bore damage before (most of it self-inflicted!), I have yet to see any material at all from the exhaust side ever getting into a combustion chamber - even when running silly overlap / lift with 2" exhaust valves, part throttle (i.e. a lot of inlet vacuum) and EGR. It's clear that the damage in my case was during the high duration regime, and that I appear to have caught it early enough that so that the rest of the engine is still serviceable.

What I have seen several times, is cylinder damage due to detonation / lean combustion or overheating. Even then, piston material tends to exit the chamber with the exhaust gases, the damage to the bores being due to the rings floating in damaged grooves. The only thing I've seen causing an oval bore in a single isolated cylinder is overheating or oil starvation. And as Toyota have radically altered the oil control groove in the piston, I would assume they have identified the problem as such. The oil can't drain away, it oxidises, laquers, the rings burn out, you lose oil control and voila - an oval bore. This would also account for the lack of noise whilst the damage is going on. I have heard bits of piston break before and you can certainly hear it happening, even with an open exhaust.

The damage to the pre-cat material would appear to be secondary in my case. There are several large bits of pre-cat material evident in the manifold, all far too big to get past the exhaust valves, and I'm fairly sure as said before the damage is confined to a single cylinder, although I'll know more when the engine is pulled. It could just be a big end or rod bearing.....but I doubt it.

Once the engine is pulled I'll post the results here. All I have to do is figure how to drop the engine without a ramp / pit. Is it possible to get the body high enough?

[ChrisGB]

Sorry to hear of the demise of the engine and loss of work at the same time  s:( s:(  

Is W60 recommended for this engine? Too high a viscosity can cause problems in itself in some engines.

Does the car get fully warmed up when used most times? Not getting the oil up to temperature will affect how well it cleans the engine. Oil as a cleaner, like any detergent or solvent, works best when it is really hot.

I would hope that running fresh Mobil 1 changed every 3000 miles would keep the oily bits really clean. I have used the lower viscosity Mobil 1 in the past and stripped engines that were immaculately clean inside, rings grooves included. Now using the later generation oils like Motul 300v, the engine should be spotless inside. Hope I never get to have a look at the rings though.

Good luck for getting it fixed. If you do strip it, let us know if it was clogged oilways. Maybe a previous owner used cheap and nasty oil (I know one of the local Mr T dealerships uses Magnatec, which I would avoid)?

Chris

[Anonymous]

Hi Chris,

Yes, it generally gets at least a 30 second warm-up. On the morning in question, it had about 5 minutes - enough to defrost the front and back windows....

And a full flush on every change.

[ChrisGB]

Hi Chris,

Yes, it generally gets at least a 30 second warm-up. On the morning in question, it had about 5 minutes - enough to defrost the front and back windows....

And a full flush on every change.

I was more thinking does the car get used for long enough journeys to really get the oil up to full working temperature and boil off the contaminants (unburnt fuel and water). A car generally needs a good hour on road on a regular basis to keep the oil free of water and fuel. A tell tale of this is when you run the car for shortish journeys for thousands of miles with no oil usage, then do a long fast journey and the oil level drops a lot. Oil temperature is probably lagging about 5 - 10 miles behind water temp, so when you think it is warmed up (on the temp gauge), the oil may be somewhere down in the 50 - 60 deg C range. That leaves it a bit thick for giving it full throttle in some engines and with thicker oil too. Not got oil temp gauge in my car, but have seen this on previous cars.

Having said all that, you have changed the oil every 3000 miles, so I cannot see that being the problem. I reckon you have looked after it better than most in respect of oil maintenance. Just bad luck, definitely not neglect.

Chris

[Anonymous]

...and removed. You can see the varnsh / gum / tar mixture that binded the rings up and caused oil usage


Nearly finished cleaning stuff up. To be continued soon.....

A prime demonstration of why a good synthetic is a good idea. I have never seen so much gunk on the inside of an engine owned by me. Having said that, I have seen a lot more on engines owned by others that I have rebuilt. Could it bet that the famous precat failure is caused by gummed oil control rings?

Chris

Wear due to piston side-load

Piston rings are subject to wear as they move up and down the cylinder bore. To minimize this, they are made of wear resistant materials such as cast iron and steel and coated or treated to enhance the wear resistance. Two-stroke port design is critical to ring life. Newer modern motorcycle manufacturers have many single function but sererated ports to retain the ring. Typically, top ring and oil control rings will be coated with Chromium, or Nitrided-possibly plasma sprayed or have a PVD (physical vapour deposit) ceramic coating. For enhanced scuff resistance and further improved wear, most modern diesel engines have top rings coated with a modified chromium coating known as CKS, a patent coating from Goetze. The lower oil control ring is designed to leave a lubricating oil film, a few micrometres thick on the bore,as the piston descends. Three piece oil rings, i.e. with two rails and one spacer, are used for four-stroke gasoline engines.

[ChrisGB]

When the control rings get gummed up, the car will leave too much oil on the bores in places, or can scrape too much off the bores in others, so could well be a contributory factor. How about a combination of not enough oil feed (from the inadequate piston design) contributing to gunge staying in the control ring lands?

We know the Avensis (that has no precats) suffers the same issue of oil consumption, so I think we have established that the precats are not the primary cause.

Where did you dig that up from Les?

Chris

[Anonymous]

Chris, I think you have hit the nail on the head.

I'm fairly convinced the pre-cat damage is secondary in my case.

Now, can somebody tell me if it is possible to drop a 1ZZ without using a ramp or pit?