OM60x Piston oil ring expert - PeachParts Mercedes-Benz Forum

ah-kay · #1 05-18-2014, 02:19 PM

Bought a set of Beck Arnley New Old Stock ( NOS ) piston ring. The set is 87mmx3mm. The oil ring comes with an expander. However, I cannot fit the expander behind the oil ring. The groove is not deep enough. There is no way it will fit. What is it for, for piston with deeper groove? Can I do without it? This is what I think I will do. It is the ring shown in the middle of the picture.

Any ideas?

jt20 · #2 05-18-2014, 03:43 PM

The purpose of the expander is to expand the oil ring, it is significantly weaker than other rings and needs assistance for increased lifespan.

Unless you cannot compress the ring once it is on the piston, the expander should be working fine (unless boxed incorrectly) - it should provide resistance to compressing

Did you clean the piston grooves out well? How well?

jt20 · #3 05-18-2014, 03:45 PM

I would not assemble an engine without them if I planned on smoke free combustion or if I wanted my pistons to last more than 30,000 miles

ah-kay · #4 05-19-2014, 12:47 AM

Quote:

Originally Posted by jt20

The purpose of the expander is to expand the oil ring, it is significantly weaker than other rings and needs assistance for increased lifespan.

Unless you cannot compress the ring once it is on the piston, the expander should be working fine (unless boxed incorrectly) - it should provide resistance to compressing

Did you clean the piston grooves out well? How well?

I soaked the piston in solvent and cleaned all carbon out. I suspect it is boxed wrongly as the instructions has diagrams, one with expander, one without. The depth of the oil rings differ between the with and the without. There is no way I can put the expander behind the ring and put it back into cylinder.

Maxbumpo · #5 05-19-2014, 01:59 PM

Did the original rings have expanders?

Diesel911 · #6 05-19-2014, 02:03 PM

On Gasoline Engines Piston Ring Instructions that come in the Box seem to be made to cover every possible Piston Ring that that particular Manufacturer makes and it is up to the Mechanic to pick out which on of the Instructions matches the Piston Rings that He got.

And, there is always a possibility that something got boxed wrong. That happens less often at the Manufacturer and most often after the Seller gets them.

jt20 · #7 05-19-2014, 04:44 PM

I would compare the new oil ring to the old ones and compare their structure - does the new one seem more robust? more metal? thicker cross section?

I would also contact the supplier or, even better, the manufacturer if there is any identifying information.

jt20 · #8 05-19-2014, 04:47 PM

It will last for an indeterminate amount of time if you gamble and use the ring w/o the expander.

Although these rings do not experience incredible stresses, wear will accumulate fast if they do not maintain contact with the cylinder wall. Small bits will eventually find their way between the cylinder wall and the piston skirt - bad news.

ah-kay · #9 05-19-2014, 10:10 PM

Quote:

Originally Posted by jt20

I would compare the new oil ring to the old ones and compare their structure - does the new one seem more robust? more metal? thicker cross section?

I would also contact the supplier or, even better, the manufacturer if there is any identifying information.

Jt20 - Thanks for the info. I have attached the old ( broken ) and new oil rings. The new one is much beefier and stronger than the old one. That is why the expander cannot be put behind it. The old one has a spring coil and new one doesn't. I suspect the expander is for a different piston, my psiton hopefully should be fine without it.

OM603 · #10 05-19-2014, 11:22 PM

Quote:

Originally Posted by ah-kay

Jt20 - Thanks for the info. I have attached the old ( broken ) and new oil rings. The new one is much beefier and stronger than the old one. That is why the expander cannot be put behind it. The old one has a spring coil and new one doesn't. I suspect the expander is for a different piston, my psiton hopefully should be fine without it.

The purpose of the oil ring is to regulate the oil lubricating the cylinder wall and as part of that function it scrapes the oils on the down stroke removing hot oil aiding in cooling the engine.

An incorrect oil ring will probably cause a number of problems in both the short and long run. If the ring does not seal against the cylinder wall correctly the lubrication of the wall and the compression and 2nd ring will be incorrect, maybe too much maybe to little, either way accelerated mechanical wear would be likely, if the oil ring doesn't seal it will not remove the hot oil causing overheating of the cylinder wall and the rings. If too much oil is on the wall it might end up getting past the rings, burning and smoking, too much might cause the upper rings to become fouled and inhibit their function which requires them to move around a bit when running.

If the Oil ring seals too tightly the cylinder wall/ring interface could suffer a "lubrication starved" condition which would cause accelerated wear, probably more accelerated than too much lube I'd bet.

If you're just trying to get an engine to run half arsed for a reasonable length of time you can probably get that done this way, but if your time and energy are worth anything it seems a rather poor investment to not use the parts designed for the task, which the parts you have are obviously not.

http://www.hastingsmfg.com/Race_Catalog_Pdfs/Piston_Ring_Functions.pdf

ah-kay · #11 05-20-2014, 10:46 AM

Quote:

Originally Posted by OM603

If you're just trying to get an engine to run half arsed for a reasonable length of time you can probably get that done this way, but if your time and energy are worth anything it seems a rather poor investment to not use the parts designed for the task, which the parts you have are obviously not.

I take exception to this. The parts is designed for the car. Beck/Arnley part # 013-8174 is the correct part for the piston. Google it if you like. I am just concern what is the purpose of the oil expander in the box. It probably is boxed there for a different car with a similar piston. The spec of the oil ring is 87mmx3mm and is correct. It is so beefy that the oil expander cannot be fitted.

OM603 · #12 05-20-2014, 11:29 AM

Quote:

Originally Posted by ah-kay

I take exception to this. The parts is designed for the car. Beck/Arnley part # 013-8174 is the correct part for the piston. Google it if you like. I am just concern what is the purpose of the oil expander in the box. It probably is boxed there for a different car with a similar piston. The spec of the oil ring is 87mmx3mm and is correct. It is so beefy that the oil expander cannot be fitted.

Well, I'm sorry that you do!

You may or may not know that Beck/Arnley has never been and is not a manufacturer of the parts they sold, they are a re-boxer of parts they sell. While there may be some listing somewhere that claims the parts you have are "for" a certain application, it seems that you've invested in believing some unverifiable sales pitch rather than your own lying eyes in this case.

The original equipment is completely different design (multi piece), are you for the sake of some dollars assuming that the engineers at MB are less than competent and that the second tier parts buyers at Beck/Arnley are superior in their reasoning and understanding of the differences in the design characteristics of the simple ring vs. the OE multi-part oil ring design? On the surface it seems that's the reasoning being applied.

The rings you have bought might fit within the parameters of the original physical specifications but there is no question that the design and function of your Beck/Arnley parts are nothing like the original MB parts that have lasted for hundreds of thousands of miles, right?

My contention is that your Beck/Arnley parts might not induce a complete failure instantaneously, but it is virtually guaranteed that they can not and will not perform as suitably as the correct design and specified original parts per MB.

It is interesting that you are arguing that the expander spring is not for your application and was incorrectly included in the boxing of these parts, when your own description and photo show that the original parts had an expander, why have you decided that the inclusion of the expander is incorrect and not concluded that the oil ring which is obviously a completely different design and a completely different physical dimension is not the part incorrectly included in the box of parts claimed to be appropriate for that engine?

Your original post asked about the expander you have "what is it for", it's for use with an oil ring the same specification as the Original Equipment, a thinner ring that is designed to function with the expander supporting and assisting its design function and operation.

The oil ring included in that set of parts while meeting the most basic requirements of circumference and thickness which allow it to fit into the dimensions of the groove in the piston, does not follow the design specifications and functional specifications of the original parts, of that there is no question whatsoever.

It's your engine and your choice, I was simply responding as to what the potential overall effect of using parts that are dis-similar to the originals particularly in a fairly critical application. Good luck!

jt20 · #13 05-20-2014, 11:54 AM

OM603 - I believe he mentioned that the instructions suggest installation with the expander and another option without the expander. 2 separate installation options for this oil ring.

AHKay - certainly, you have your own opinion about what is reasonable and practical for every application and their limits. This being a case where an unknown manufacturer has designated this the proper part for your application - seems good enough to suffice. On the other hand, it is not as desirable as the 3 piece OE part designated by MB.

I would install without the expander if I was in a tight spot, but prefer to contact the supplier or manufacturer or buy an OE set that had the coil spring expander.

I would ABSOLUTELY check ring end gap before installing this ring on the piston!!!!

And ring clearance!!!

Regardless of their quality and reputation, non-european parts suppliers have often left me unsatisfied when it come to Mercedes and the like - too many failed items and bad fitments that I have witnessed personally (I am not a seasoned professional, and that is limited experience, but a pattern exists)

Regardless, I am very suspect regarding this ring, but certain you could make it work if it is the proper part sold by the retailer.

jt20 · #14 05-20-2014, 12:11 PM

Assuming you are sure it is the correct part and you are satisfied with its design - use it without the expander. It most likely as you state, which is that this ring has many other applications and they use it generically.

Please check ring end gap and ring clearance before install.

Being a generic application, its not worth the gamble.

The ring is clearly more robust, thus they have made the decision to rely solely on the strength and durability of the ring material to maintain outward force on the cylinder walls.

The expander's installation would normally be behind the oil ring in the designated groove pushing the ring outward.

moon161 · #15 05-20-2014, 12:15 PM

How many parts are harder to access and service than a piston ring?

or phrased another way,

How many parts have greater associated labor & machining to replace?

or more simply, what is the cost of being wrong about this?

What is cost & lead time for OEM ring set?

So most simply:
What is the cost of being wrong?

compared to-

What is the cost of being right?

I'd be at the local benz parts counter. Load up on free cookies & coffee while you wait, if it will make you feel better.