OT: So much for Honda reliability

[A.K. Boomer]

Saltmine that's another extremely common misconception about piston ring wear and you nailed it exactly! Whenever an engine starts burning oil the first thing most people think of, including a heck of a lot of mechanics, is worn rings when almost every time it's valve guides/stem seals! Worn rings cause blow-by and oil is lost by it literally being forced out of the engine and by the fact it becomes so diluted by unburned fuel getting past the rings, by far most of that smoke coming from the tail pipe is oil getting past the valve stems not somehow getting into the combustion chamber past worn rings. People have spent tons of money rebuilding the short block or even replacing it while only giving the heads a "lick and a promise" then blame the continued oil consumption problem on improper break-in of the rebuild. In the vast majority of the cases those simple "re-ring" jobs (a half arsed approach anyway) would have accomplished a heck of a lot more by rebuilding the heads instead but there-in lies another problem. Most mechanics idea of rebuilding the heads simply consists of grinding the valve/valve seats and little or no consideration is given to the condition of the guides and wear on the valve stem itself. On most OHV engines excessive valve stem and guide wear occur way before the rings and cylinder walls wear out but some mechanics seem to think that a simple valve grind and seal replacement is all that's needed. Whenever I went into an engine for a rebuild, top overhaul or a complete overhaul, I always installed bronze guide bushings and often replaced the valves if they had detectable wear on the stems, even if the wear was only slight the fact is it had already started and the guides/stems had only little serviceable life left in them so it made no sense to me to reassemble the engine in that condition.

yes and no, seen plenty of both, yet not due to wear of the rings but the rings getting sludged and locking up...

have also brought many an old engine (like the one in my car) that was consuming about 1 quart every 6 or 700 miles around to going about 1500 to 2000 before needing any, with a diet of good synthetic and adding rislone when it gets a quart low...

have to be careful because you can plug an oil filter real quick if the engines been on conventional oil for all it's life,,,

just too many tear downs in the past only to find that everything is in good tolerance but sludge is creating a situation that is keeping things like ring tension from happening,,, you know this when you remove a piston and the rings don't expand when you pull it out of the bore,



But I agree about half the time it's hardened valve guide seals though too...

You can't really test whilst running to find out if it's rings or valve guide seals because both will act up on deceleration - it's high manifold vacuum and will draw oil up past the rings and also draw it past valve guide seals,,,

so the way to help distinguish is to let the car sit overnight and then fire it up and watch the tailpipe,,, if it smokes allot it's valve guide seals as they will drain down, if it doesn't it's rings as gravity is in you favor there....

this test is for conventional engines --- if it's an old volkswagon or a subaru it won't work...

[Danl]

Getting back to the original post, I had a 2003 Accord until this year. Several years ago I took it in to have the timing belt changed and felt like a dummy when they advised me this was the first year for that particular VTEC in the Accord that had a timing chain. I was told the cam was showing signs of wear, and that this was a known manufacturers defect in these particular engines, first year for the specific cam design characteristics. I had them replace the cam a year or two after that for $700, and it was running fine when I sold it.

Danl

[A.K. Boomer]

Did you get to see the old cam? or keep it?,
first iv heard of it as it's most likely a roller rocker engine and cam should last forever...

[radkins]

yes and no, seen plenty of both, yet not due to wear of the rings but the rings getting sludged and locking up...

have also brought many an old engine (like the one in my car) that was consuming about 1 quart every 6 or 700 miles around to going about 1500 to 2000 before needing any, with a diet of good synthetic and adding rislone when it gets a quart low...

have to be careful because you can plug an oil filter real quick if the engines been on conventional oil for all it's life,,,

just too many tear downs in the past only to find that everything is in good tolerance but sludge is creating a situation that is keeping things like ring tension from happening,,, you know this when you remove a piston and the rings don't expand when you pull it out of the bore,



But I agree about half the time it's hardened valve guide seals though too...

You can't really test whilst running to find out if it's rings or valve guide seals because both will act up on deceleration - it's high manifold vacuum and will draw oil up past the rings and also draw it past valve guide seals,,,

so the way to help distinguish is to let the car sit overnight and then fire it up and watch the tailpipe,,, if it smokes allot it's valve guide seals as they will drain down, if it doesn't it's rings as gravity is in you favor there....

this test is for conventional engines --- if it's an old volkswagon or a subaru it won't work...

Well actually it's fairly easy to tell, worn/stuck rings will result in excessive blow-by while valve stem seals will not, also a simple compression test (doing that to a 3.0 Ford Ranger just today!) will determine ring seal condition. The bottom line is that very often the valve seals can be causing serious oil consumption while the bottom of the engine is still in serviceable condition but it's just about unheard of for it to be the other way around, that is the rings/cylinders worn out but the heads still in good shape. By far most of the time when a reasonably well maintained engine starts to burn oil the valve stem seals/guides are the main culprit and the point was that this all too often gets overlooked and money gets spent repairing the wrong problem.

[Danl]

Did you get to see the old cam? or keep it?,
first iv heard of it as it's most likely a roller rocker engine and cam should last forever...

No, never saw the old one, but the rough idle that was getting progressively worse was fixed when I got it back.

Danl

[A.K. Boomer]

Well actually it's fairly easy to tell, worn/stuck rings will result in excessive blow-by while valve stem seals will not, also a simple compression test (doing that to a 3.0 Ford Ranger just today!) will determine ring seal condition. The bottom line is that very often the valve seals can be causing serious oil consumption while the bottom of the engine is still in serviceable condition but it's just about unheard of for it to be the other way around, that is the rings/cylinders worn out but the heads still in good shape. By far most of the time when a reasonably well maintained engine starts to burn oil the valve stem seals/guides are the main culprit and the point was that this all too often gets overlooked and money gets spent repairing the wrong problem.

yeah like I said not my experience with higher mile engines,,, some of the viton valve guide seals that are at least being used on what I work on (japanese) are nothing short of amazing,,, seems about half the time even @ close to 1/4 million miles they are still hanging in there,,, I did say about half the time,,,

as far as the lower ends, they too are in great condition as far as wear goes like you say, but at least half the time they are sludged out --- I work on mostly little high strung engines that get allot of work done for their displacement --- the pistons are literally roasted, cheap oil thermally breaks down and ends up as "coke" in the ring lands --- this is the other half of the equation, so no ------ not always valve guide seals,,, if that was the case I would not be able to bring many of these engines around simply by changing their oil diet's...

Incidentally --- a compression test is not always going to show what might be causing oil consumption --- upper compression rings can still be free to prevent excessive blow bye yet the oil rings or scraper rings can be gridlocked... this will show good on the psi gauge yet the engine will still consume copious amounts of oil...


like I stated earlier, one of the best simplest tests without doing anything but turning the key is to park the car hot, let it sit awhile and then start it up with a cold cat, if you immediately see lots of oil smoke you know it's valve guide seals --- if you don't then it's most likely piston rings...

[justanengineer]

The part that sucks is it is pretty much impossible to do an overhead cam motor with gear drive. I believe we are getting close to no valvetrain drive though. Solenoids will replace chains, belts, rockers, lifters, cams, the whole bit.

Depends on the application and particular engine more than anything. A lot of diesels are OHC or cam in head (two different concepts) and gear driven, but theyre also low RPM comparatively.

Personally, I think one of the biggest problems with today's engines is folks just plain rev them too high. I hardly ever push a gasser over 3k bc of the effect on longevity, but with automatics today most folks romp them up to 4-6k regularly.

[saltmine]

Interesting experiences, and theories. I've worked on hundreds of Vega engines. I have yet to see a piston ring failure. For those who don't know, the cylinder bores of a four-cylinder Vega, after the final etching and honing process is complete is a 7 on the Mohs scale of hardness (diamond is a 10). The pistons are actually electroplated with several layers of tin, and then iron. Rings are chrome molybdenum. Since the aluminum particles in the block casting ride against the flash-coated iron, wearing out the cylinders, pistons or rings is virtually impossible....save for the lack of lubrication. Many Vega engines were destroyed because of the valve stem seals. And, since Chevrolet marketed the Vega as a low-cost, entry level car, it was subjected to poor maintenance. Block problems that Boomer described were initially caused by the lack of water passages causing cavitation between the cylinder castings at the top of the block, which was open, to be sealed by the head. Once cavitation was discovered, a clever GM engineer, armed with a 6mm cutter made a slot between each cylinder about 18mm deep. That cured the overheating problem and it was subsequently used on all blocks from then on. Yes, the Vega had its problems. But, many people don't realize that due to corporate pressure, the Vega was in production before all of the engineering bugs were worked out. Ed Cole once said that they were redesigning components as the cars were going down the production line. Many made it to the distribution lot, and off to dealers before a lot of the redesigns could be applied. It was an innovative car, and many components are still used on cars today. One particular innovation is the annular oil pump, which mounts on the front of the crankshaft and is driven directly by the crank. All of the Chevy LS engines use an identical pump, as does the 4L60 transmission. The only difference is the transmission pump uses a variable displacement feature to regulate the pressure and flow of fluid. The innovative Reynolds A-390 alloy was bought by Porsche of Germany for roughly $6 million dollars, and the aluminum alloy is found in many German sports cars to this day.

[Royldean]

Personally, I think one of the biggest problems with today's engines is folks just plain rev them too high. I hardly ever push a gasser over 3k bc of the effect on longevity, but with automatics today most folks romp them up to 4-6k regularly.

This is ridiculous. If I didn't rev my cars past 3k, I'd never be able to merge into traffic on an on ramp or stop sign. Manual transmission combined with less than 2 liters of displacement, the only way to develop HP is to rev it out. This isn't new. My 89 Suzuki Swift GTI would rev to 8k all day long....

[A.K. Boomer]

I totally agree, I see more engine damage from "lugging" than RPM's --- I take it too extremes in the other direction and normally shift @ or above redline...

if your running clean oil and staying within specs you will generally be fine,,, high RPM's get a bad rap (no pun intended)
because things can go boom, what people don't realize is lugging can lead to a very slow painful death....

just depends how you want to go, very rare for an athlete to have a heart attack while he's putting out immense effort but yes can happen and it's horrid when it does,,, yet everybody thinks for some reason that if it happens on your couch whilst choking down your daily bag of pork rinds then it's ok...

Pop's always used to tell us to hang on in the 390 country squire station wagon because he was going to "blow out the cobwebs" My Dad was not extremely mechanically inclined but I kinda think he had something there, and nobody ever got hit with anything molten hot coming into the cab, in fact that POS always got us back home...

[hareng]

Interesting one a mate with Honda VTEC had excessive chain stretch and packed up no warning at 110k, luckily was at a set of lights.
Recent purchase he did about 2k, new chain etc fitted some 20k before which turned out to be an aftermarket kit and of course stretched.

The GM 2.2 ZE22 and 2.4 are chain, early ones circa 2001 to 2003 plagued with chain problems. These were a global engine used by 7 other manufacturers inc Subaru, Alfa, Vauxhall, Opel, Chevrolet and some others. Plenty of scrap engines at less than 8k from new blamed on the small oil feed to chain. Had mine done at 65k and took it to 137k where I scrapped the car.

[flylo]

I did on a Subaru I bought with just over 50,000 miles & took to the dealer for something minor. The dealer said "make sure to change the belt at 60,000? I thought he was selling belts. It broke at 60,500 but no other damage. It was one of my best cars, a 4WD wagon getting 35 mpg in the late '80s.

Has anyone actually experienced a timing belt failure that was not brought on by the failing of some other mechanical part?

I run Audis. Not new ones, they are a bit spendy. All the Audi officianados are anal about "timing belt changes". I prefer to call the service a "water pump and tensioner pully change", for those are the only parts I have seen fail in normal service. The timing belt takes a bad rap for the other parts! ;-)

One case of dissatisfaction does not undermine the many satisfied stories unspoken!

[flylo]

Maybe instead of a check engine light, a check driver light should come on that looks like this $$$$$$$.

[justanengineer]

This is ridiculous. If I didn't rev my cars past 3k, I'd never be able to merge into traffic on an on ramp or stop sign. Manual transmission combined with less than 2 liters of displacement, the only way to develop HP is to rev it out. This isn't new. My 89 Suzuki Swift GTI would rev to 8k all day long....

Why do you need power? Torque is what gets you going from a stop. Ive loaded my lil 2.2L S10 w/1k+ lbs and had no problems merging into Chicago traffic, the stick actually helps by giving me total control over the engine torque output. By revving an engine higher all youre doing is wearing it out faster and wasting gas.

If you look at a lot of high-end cars and OTR semis you might notice many have big engines and more gears. They need a big displacement engine to get enough torque to run those extra gears (ie. 6th on many cars), which gives them more pulling power. When run slow tho, those extra gears give them the advantage of better fuel economy. Running slow also allows them to last longer, multiple million miles in the case of some semis.

[flylo]

That's the secret of diesels for. Low HP for low fuel burn & high torque to move the load. My 12 valve Cummins has 160 HP & 460 ft #s of torque.