Accelerated Ring Wear 4

[Elihu]

A local Nissan dealer just told a lady friend that her 2005 V-6 w/96000 miles had suddenly begun to burn oil at a high rate because the catalytic converters were disintegrating. They claimed that when she went downhill and lifted her foot the pieces were being drawn up into the combustion chamber causing the sudden ring failure. They’d done all of her service work since purchase - so she believed them.

I need some replies to help her see the light.

 

[IRstuff]

That's BS, but's this is a question for CarTalk

TTFN
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[MacGyverS2000]

Unless she was hanging from a tree with the nose facing the ground, there's no way cat pieces got back through the exhaust runners... not to mention the constant flow of gases exiting said runners (which, I assume, is where they were attempting to make the argument letting her foot off of the gas created a vacuum there).

Sounds like a lawsuit (if she got that in writing... doubtful).

Dan - Owner

http://www.Hi-TecDesigns.com

 

[MikeHalloran]

More likely the extra HC from the failed rings clogged the cats and the high DP fragged the honeycomb.

Time to produce the extended warranty contract if she has one...



Mike Halloran
Pembroke Pines, FL, USA

 

[Lou Scannon]

Surely the emissions warranty should cover both the oil burning and the pooched cat; unless the result of neglected maintenance.

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

 

[MikeHalloran]

I think the mandated emissions warranty has been quietly scaled back to 50,000 miles, under industry pressure.
... but it's worth trying to make a claim anyway.


Mike Halloran
Pembroke Pines, FL, USA

 

[tbuelna]

The exhaust cat on a 2005 Nissan is covered for 8 years or 80,000 miles by US federal law. At 96,000 miles and with the problems described, your lady friend is likely facing a several thousand dollar repair bill. Unless the car has sentimental value it's probably not worth fixing. Tell her to sell it and buy something new. And remind her to change the engine oil on a regular basis.

 

[Tmoose]

what is the "high rate" of oil consumption? More than 1 qt / 1000 miles? I've heard that limit applied by dealers from decades ago applied to new Subarus (it's right in the owners manual) , even though most do a lot better.

Is there more info about testing done to arrive at the "worn rings" disgnosis?
If just based on oil consumption then I call criminal malpractice.

A compression and leak down test could provide some indication if ring condition.

What is the view under the oil fill cap?
Any external leaks? Be a real shame to overhaul an engine because the cam cover or oil pan gaskets are bad, or the fasteners just need tightening.

Adding a quart every week or 4 is way cheaper than engine repairs and just might get her to 200 kmiles.

Regardless I think I'd check that the various Crankcase ventilation breathers and whatnot are clear. PCV testers of various forms are available to clamp over the oil fill hole. Some would say a decent test is to set the unscrewed cap in place, and if it lifts or dances with the engine idling there is excess pressure. Others advocate observing whether a sheet of saran wrap elastic banded to the filler neck is concave (good) or convex (bad). While I'd vbe interested in those results a test at idle is not as tough as at highway loading.

Some cars maintenance schedules are pretty weak in that PCV system maintenance area. Excess crankcase pressure will force oil out somewhere, and make the seals wear even faster. The pressure can be excessive because worn rings are allowing lots of blowby, OR because even normal amounts of blowby in an engine in fine shape have no place to go due to a resticted or plugged PCV system.

 

[waross]

They’d done all of her service work since purchase - so she believed them.

My first reaction;
During a scheduled service they forgot to put the oil back in.
Now they are covering their ASSets.
They will not admit voluntarily that they may have negligently destroyed an engine.
Contact a factory rep and avoid that dealer. DO NOT confront the dealer. That will give them an opportunity to refine their story.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[MikeHalloran]

Star for Bill. That's entirely plausible.


Mike Halloran
Pembroke Pines, FL, USA

 

[Tmoose]

My aspiring gear head young MSME buddy owns 2 late Subaruz and a 76 Corvette. His wife's 'Roo is sometihng like 4 years old, bought new. When changing the oil around 5 kmiles sometimes it is REAL low, like off the stick. He considers that excessive oil consumption. Once when debating if he dared drive the off-the-stick car to buy oil for an oil change, or maybe to buy a quart because his wife said the oil pressure light stayed on a while He read me a line like this from her owner's manual - "If the oil consumption rate seems abnormally high after the break-in period, for example more than 1 quart per 1,200 miles..." I guess we know what the dealer is likely to say about ~ 1 qt/2000 miles.

http://techinfo.subaru.com/proxy/71914/pdf/ownerManual/071914_2014_Forester/MSA5M1403BrevSTIS_17.pdf

His (newer) "roo has an oil level warning light, which he has set off a time or two.
I think his lack of periodic oil checking reflects badly on his parents and to a small extent even me.

I guess "Excessive" oil consumption is to some extent clearly in the eye of the beholder.

 

[Lou Scannon]

None my ancient cars burns an appreciable amount of oil, but two out of three leak it at a disgraceful rate. In one case, I believe the leak is the rear main which took a set during extended storage. In the other the obvious culprit is an air-to-air oil cooler installed as a upgrade (on a heavily turbocharged and modified engine), which has either sprung a leak in the core, or at one of the fittings. But the cooler is buried in the front bumper, so I haven't had time to investigate.
As mentioned above, the cost of top-up oil is quite low. The real issues are the mess and potential embarassment, if one is finicky about that sort of thing.

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

 

[Tmoose]

I may have missed it, but I don't recall reading what rate of oil consumption is being deemed excessive, nor if there are symptoms like blue smoke, an oily underbelly, unclean parking spot, poor running, etc

 

[140Airpower]

Going downhill and lifting the foot is normal driving. The fact that there is a manifold vacuum PROVES the engine is pushing air out the exhaust. It doesn't mean the engine is dematerializing air. The idea that the engine will suck anything back through the exhaust valves is the purest and smelliest BS I've ever heard.

 

[jons999]

Actually i have seen this a few times on Nissan 4 cylinders (QR25DE i think). The cat converter integrated into the exhaust manifold comes apart and gets pulled back into the cylinders causing oil consumption and/or engine failure. There was a Nissan TSB that covered this and possibly a warranty extension. Im not sure if the bulletin applies to V6 engines and i can't access that info from here at home.

 

[jons999]

Found some info online, there was a recall on the issue and they redesigned the manifold.

-----------------------------------------------------------------------------------------------------------------------
Reference: Date: NTB03-070c November 17, 2006

VOLUNTARY RECALL CAMPAIGN ALTIMA AND SENTRA QR25DE ENGINE EXHAUST PIPE HANGER PIN AND PRE-CATALYST

CAMPAIGN I.D. # NHTSA #: R3007, R3014, R3015, R3016, & R3017 03V-084

APPLIED VEHICLES:
2002-03 Altima (L31), with QR25DE Engine 2002-04 Sentra (B15), with QR25DE Engine

APPLIED VINS:
Altima: 1N4AL11**2C100000 - 294952 1N4AL11**2C700001 - 719020 1N4AL11**3C100003 - 311983
Sentra: 3N1AB51**2L700019 - 730181 3N1AB51**3L716572 - 736783 3N1AB51**4L727627 - 730593 3N1AB51**4L736618 - 738436

INTRODUCTION
Nissan has determined that some 2002-2003 model year Altima and 2002-2004 model year Sentra vehicles equipped with the 2.5 liter engine have defects that relate to motor vehicle safety. For 2002-2003 model year Altimas, there is a possibility that the exhaust pipe hanger pin may catch debris from the road that could be ignited by contact with the catalytic converter and cause a fire. In addition, for 2002-2003 model year Altimas and 2002-2004 model year Sentras, there is a possibility that certain engine operating conditions may cause damage to the pre-catalyst. Material from inside a damaged pre-catalyst could enter the engine and result in increased oil consumption. If the engine oil level is not checked on a periodic basis and drops below the low level, and the driver continues to operate the vehicle ignoring noticeable engine noise, engine damage may occur which could result in a fire.

 

[TheBlacksmith]

Yes, a few cars have the "mani-cat," probably to allow for the fastest light off of the cat. So the distance is not as far as a conventional after the Y pipe/under the car setup, but still, the engine sucking the exhaust. Would like to see the bulletin before I push the "I believe" button.

 

[jons999]

The bulletins usually don't provide too much detailed information beyond a basic cause and the updated parts or repair procedure. Maybe the catalyst pieces are being pulled into the engine through the EGR system?? I know that exhaust system leaks a few inches downstream of an oxygen sensor can affect its readings slightly at idle so there is some upstream movement to the exhaust at certain times. When exhaust is flowing out of the exhaust valve and the valve slams shut there must be a slight amount of vacuum created there, whether or not it is strong enough or exists long enough to pull material towards the valve i have no idea but it does seem unlikely.

 

[BrianPetersen]

140Airpower, the net airflow may still be from intake to exhaust, but all it takes for debris in the exhaust close to the exhaust valve to be sucked back in is a momentary reversion flow, and in shut-throttle coasting conditions, that condition WILL exist.

There is overlap between intake valve opening and exhaust valve shutting, during which both intake and exhaust valves are open. Under high intake manifold vacuum conditions, reversion flow will occur during the valve overlap period.

Also during shut-throttle coastdown with no fuel supplied (and deceleration-fuel-cut is the norm!) the pressure in the cylinder at time of intake valve closure is well below atmospheric, and in those conditions, nothing happens to it between then and exhaust valve opening, so the cylinder pressure will still be well below atmospheric at the time of exhaust valve opening. What happens ... Reverse flow from the exhaust manifold to fill the cylinder, then forward flow (out of the cylinder) during the last part of the exhaust stroke, then reversion during valve overlap. The net flow when all of these are added up is indeed from intake to exhaust, but there is plenty of opportunity for instantaneous flow from the exhaust manifold into the cylinder at certain times.

 

[golfpin]

Good day gentlemen'
seems as though the gremlins in motor trade are the same world wide great replies as always from all.
Here in South Africa cats and the like are unheard of, only being introduced certainly perhaps in the last few years!! My point is that Vw SA in the hand book state that a litre of oil per 1000 kms is ok if that is the case what about pollution!? However I think I digress, from a personal experience re exhaust debris being drawn back into engine.......... Mazda rotary fitted to a Puma car {Brazilian VW] based sports car fabricated exhaust system remember noise on them things a few 1000 K,s down the road bang engine gone no evidence of ingress of foreign particles rebuilt fitted started bang no compression stripped found mechanical damage and bits and pieces from the baffles from the silencer. High exhaust pulse ??? no evidence of rust causing the breakage of the baffle silencing medium but it was sucked back into the engine . Hope not too far off the point hope the lady gets some form of recompense.
Cheers Golfpin