7.3 Piston rings
 

New to forums in general. Looking for help on why my piston rings on rebuilt 7.3 haven't seated yet. 12k on engine since it was rebuilt. It blows some blue smoke on take off. You can see the blowby when the oil filler cap is removed. The engine builder used Mahle pistons and rings that were installed on the new pistons. Is there anything that I can do to get the rings to seat or did engine builder break an oil ring when building it.

RE: 7.3 Piston rings
 

Sounds like somethings wrong.

RE: 7.3 Piston rings
 

That's why I'm here. Trying to figure out what to do next. Rebuilt it in hopes of not having to buy a new truck. Truck runs great. I'm wishing that I had spent the money on a new one now.

RE: 7.3 Piston rings
 

What year 7.3?

RE: 7.3 Piston rings
 

I've heard of people dusting a little bonamy powderthrough intake inolder style Gasser's to seat rings but i never tried it does it use any oil because i think u would get a little blow by on diesel if not using oil its probably normal rings should be seated in that many miles

RE: 7.3 Piston rings
 

2001 7.3L I put some extras on it while I was rebuilding it. It has new Alliant 100 hp injectors, new Garrett GT38 ball bearing turbo, high pressure crossover hose, 4" exhaust turbo back,new air intake, triple disc billet torque converter,etc. I actually did this for pulling my fifth wheel not racing. The fuel milage is not too bad either. Old motor had 123k on it when it broke a piston and it was totally stock. The wrist pin scarred the cylinder wall so bad that the block had to be replaced. I just bought the wife a new Ford Fusion and wanted to keep my truck until I could pay off her car. Couldn't get anything for the truck with a bum motor anyway. I am still almost as scared of the new 6.4L as I am of a Dodge.

RE: 7.3 Piston rings
 

It does use a little oil. Not really sure how much as I noticed an oil leak coming from the oil cooler and have not repaired it yet waiting to see if I'm going to have to pull the motor again to find out about the blowby. I did a compression test on the engine this last weekend and then was told that my efforts were fruitless due to the oil rings being on the bottom of the piston.

RE: 7.3 Piston rings
 

Some blow by is normal,,but if it's excessive, it'll show up in the inlet to the turbo, and the intake elbow wet/oily,and eventually asoil build up in the CAC tubes.. Excessive blow bywould indicate loss of compression,most likely not just oil ring/s, and might be easier detected with a leakdown test through the glow plug hole to pinpoint either one bad cylinder or multiple..Kind of a balance test.. If you could pin it to one cylinder a bore scope might reveal the piston top washed from passing oil if a single damaged ring.. All washed would mean bore problems, or ring issues.. Could have been bored (replacement was bored?) out of spec, or honed to coarse, rings gaps not offset ect.. I'd think if it were a bad/damaged oil ring, it would smoke at cruise speeds.. How much is 'some' smokeon launch? What help has the engine builder offered?

RE: 7.3 Piston rings
 

Engine builder asked me to switch to Rotella 30 instead of 15w-40. I did that roughly 1000 miles ago.He said that maybe it is overfueling and washing the cylinder walls and wants to unplug the chip and run it like that for a while.
No smoke that I can tell at cruising speeds. It may even be getting better at not smoking on take off. It is not a lot of smoke. Hard for me to quantify the amount of smoke. I did take the intake tube off when doing the comp. test and there was some oil residue in it. The thing that concerns me the most is when you take off the oil filler cap you can see what appears to me to be oil mist or steam or something to my untrained eyescoming up 6" out of the fill tube. He wants to run the truck longer and see if the rings will go ahead and seat. I use the truck to pull my travel trailer and to get back and forth to work. I just want for it to be right. I don't want to have a major problem when I'm off with my family and maybe no telling how far from home.

RE: 7.3 Piston rings
 

Can you explain the leak down test and how that works?

RE: 7.3 Piston rings
 

A leak down test 'or' cylinder differential test generally uses a two gauge set, one registers/measures the compressed air being forced into the cylinder, and the other measures the 'percentage' of pressure being lost.. Done with the cylinder at TDC (valves closed) or can[/i] be done at BDC with the rockers pulled ect. to test for a cylinder crack.. A leak down test can help to prove worn or damaged parts like bad exhaust valves,, leaking or bleeding air out the tail pipe, intakes out the intake manifold or plenum.. Compressed air leaking past the rings, valves can be heard sometimes as a ‘hiss’ or howl, and felt at the outlets.. Leaking rings may show up as air escaping from the oil fill/cap.. During a leak down test you can rock the piston up/down slightly to check for worn ring lands, or at times verify unseated rings.. Leak down is also a good way to check for head gasket leaks between cylinders, or as a test for combustion leaks into the cooling system from block/head cracks, or failing head gaskets..

If you were over fueling, I'd think you'd see at least 'some' black smoke as well if enough to wash the cylinder walls..

Going toa 30wt. may result in some 'romping' in cold conditions

RE: 7.3 Piston rings
 

Thanks a bunch for the info. Sounds as though this test may be just what I need. I do not think it is overfueling either. You can make it blow the black smoke if you stand on it but it is not smoking with just normal driving down the road. It appears to me as though if it were overfueling, especially enough to wash the cylinder walls, it would be blowing black smoke or a least a tinge of it at cruising speeds. What did you mean by "romping"? Again, thanks for your help! I'll let you know what I find out.

RE: 7.3 Piston rings
 

Romping is somewhat normal for the 7.3.. On a 'cold' start, (more so very cold) lower the temps more the increased chance, what can happen on initial start up is the engine will have series of idle RPM spikes/lows and will make a "romp, romp, romp" for a second or few.. Increasing the viscosity in colder loctions or seasonal lows can make the romp more prominent along with the closed back pressure valve/gate..

Not a big deal, and generally clears after a few seconds... Annoys some folks...

RE: 7.3 Piston rings
 

Ok I've seen that before and didn't know what was causing it. Found out some good stuff today and will try to get back on tomorrow and elaborate. May be something for others to look for in the future.

RE: 7.3 Piston rings
 

Also have seen the seals inside the turbo leak oil into the intake side and create this issue as well.

RE: 7.3 Piston rings
 

I may have stumbled on something yesterday but am not sure yet. I took the truck over to a diesel truck shop yesterday and the tech did the same as everybody else in that he took off the oil filler cap and pulled the dipstick a little. His immediate response was that the blowby was excessive. He asked about the honing of the cylinders and I could not answer his questions so I stopped at my brother in laws place on the way home. The engine builder builds race car motors for him. He also builds NHRA and a lot of other racing motors for every different kind motorsports there is. This is part of the reason I got him to build my motor in the first place and the second was that as a friend he would build it for me for substantially less money. I asked my brother in law about the honing. The general consensus from him was that the engines that the builder is used to building are all very high horsepower gassers and that one of the things that they do different when building these high HP motors is to hone the cylinders very slick/fine. His thought was that if this motor was honed this way and with the extra hardness of the diesel rings that it might be where the problem is. Sounds reasonable to me so I guess this is where I'll start checking next. It is not smoking enough to warrant me to belive that it is a problem with oil leaking into the combustion chamber and I still have the blowby issue which does lead me to believe we are on the right track.

RE: 7.3 Piston rings
 

I had a 1970 4x4 f250 360 motor new motor 428cj .30 over rv cam 1960 3 duce ran goood uesed oil for 6 mo .. old man tolded me to drive for a hr for motor to get hot in 4th gear https://www.fordforum.com/micons/m2.gifgo 60 or 70 mph let off to 25 or 30 mph putt foot in it go to 60 or 70 mph and keep doing it till it pu up speed you will feal it start to pu up speed and will seat the rings the old way ITS WORKS per ratlermike.. old man now oldddd!!!! good luckhttps://www.fordforum.com/micons/m13.gif https://www.fordforum.com/micons/m6.gifhttps://www.fordforum.com/micons/m12.gif