[Dexter314]

HI All

I rebuilt my 1980 SD33T recently. I used a 3-ring piston kit obtained from Noordeman Diesel. The original pistons were the 5 ring pistons. I kept the original sleeves as they looked and measured good. A machinist checked them too and honed them.

So the engine runs good but was using a lot of oil. Way more oil than normal , not acceptable. I had issues in the first 500 to 750 miles with a blocked fuel flow so it never got up to speed until after I found the blockage . So maybe the rings never seated properly and this is causing the oil consumption. Also, I did not do a good job checking ring end gap, could have installed some with little or zero end gap. I am pulling the pistons now, one is out, the other 5 later today. I plan to clean them up, re-ring with new rings. Quick re-hone and reinstall pistons.

Here are some questions:

1. Has anybody here done a rebuild like this with the Noordeman or similar 3-ring piston kit? Any tips for piston / ring installation?
2. There is no suggested ring end gap in engine manual or piston ring kit. The RIK rings say to file to fit. I am guessing it should be about .013 to 0.014 inches. Any suggestions about this?

 

[james008]

Specs for rings gap and whatever other measurements you'd like to know can be found in the SD service manual.
Linked in the supplement for the SD33T as you have used 3 ring pistons. 0.013-0.014 is alright for the top ring, on the large side for the second, and out of new spec for the third (oil control) ring.

SD Series Diesel Engine Service Manual - SD33T Supplement | MQ-Patrol.com

Even during inital break in oil consumption shouldn't be too excessive but some is normal of course. How much oil were you adding, and how often?
Are you positive the engine is consuming the oil? If so valve stem seals may be suspect.
If there is no drain point in the bellhousing, or it is clogged, it may be worth a look, likewise the cooling system, ensure there is no oil there. Any other leaks would likely be external and fairly obvious with excessive oil loss.

 

[Dexter314]

Specs for rings gap and whatever other measurements you'd like to know can be found in the SD service manual.
Linked in the supplement for the SD33T as you have used 3 ring pistons. 0.013-0.014 is alright for the top ring, on the large side for the second, and out of new spec for the third (oil control) ring.

SD Series Diesel Engine Service Manual - SD33T Supplement | MQ-Patrol.com

Even during inital break in oil consumption shouldn't be too excessive but some is normal of course. How much oil were you adding, and how often?
Are you positive the engine is consuming the oil? If so valve stem seals may be suspect.
If there is no drain point in the bellhousing, or it is clogged, it may be worth a look, likewise the cooling system, ensure there is no oil there. Any other leaks would likely be external and fairly obvious with excessive oil loss.

Hey, thanks so much for the information. My SD manual is from 1980 and only has information for the 5 ring pistons. I appreciate the link to the later manual.

First, to answer your questions. The oil consumption was as bad as around a quart per 200 to 300 miles. or about 2 liters per 500 km. The oil consumption was nearly 100 percent thru burning as there were no apparent leaks in engine. The coolant was clean and The machinist checked head and the valves and found no issues. I had already resolved the rear main seal leak by installing a factory new seal.


I just finished pulling the 6 pistons. I believe I found the issue of oil consumption:

As far as the piston/ring work that I did. It was my first complete piston/ring job on this engine. I must have not been paying attention or had too many beers as I had 3 compression rings installed upside down! Two caused the upper compression rings to get carbon fouled and the rings stuck in the piston grooves. Amazingly it appears there is no damage to the cylinder walls , although I still need to put a micrometer and bore gauge on them to be sure. I can still see the honing crosshatch from the machine work done about 4k miles ago. The ring gaps were about 0.014 inches for top ring, a little less for 2nd ring and only about .006 in at the oil ring gap. This seems to match good with what you mention above. I will read up on the manual you attached above when I install the new rings and pistons. I will of course be more careful so that the install has no upside down rings or other badness.

Since there is less than 5k miles since the machinist honed the cylinders, I am planning to just clean up and oil the cylinders when I install pistons. No additional honing. I have gotten away with this before so I think it is probably better to not hone. Of course I will make sure the cylinders check out with my micrometer and bore gauge before installation of pistons. Advice would be appreciated as far as honing vs not honing.

If anybody has some tips that would help ensure a good piston/ring installation, that would be great!

I will post some pictures when I get a chance.

 

[james008]

Yep, pretty good chance the rings will do it. I'm surprised it didn't have oil leaks everywhere, crankcase pressure must have been pretty high.

Good to hear the bores are okay, if you can still see the cross hatch theres a good chance they will still measure up just fine.

 

[Dexter314]

Yep, pretty good chance the rings will do it. I'm surprised it didn't have oil leaks everywhere, crankcase pressure must have been pretty high.

Good to hear the bores are okay, if you can still see the cross hatch theres a good chance they will still measure up just fine.

Yes, bores measured up fine! 3.268 inches on all 6 measured in several places. And almost no taper or out of round (max I found was about .001 to .002 in), manual says up to 0.008 is acceptable. The 1980 version of sd33T they put in the IH Scouts have a downdraft tube (no pcv valve) so it is nearly impossible to get crank pressure very high. Not surprisingly, the downdraft tube was chugging smoke more than usual. I'm going to clean everything, then install new rings/pistons/rod bearings. Got the parts on the shelf, just need the time to do it. This time I hope to get the rings to seat well and be done with the repair! I am planning to use "Driven" break-in diesel engine oil 15w45. Then will switch over to Rotella 15/45.

More updates and pictures to come.

 

[Dexter314]

I meant to say 15-40w. Hey its back together and running strong. Rebuild kit says to retorque head after break in. Its not leaking, so I don't see the point.

Can someone explain the process for retorque? I know I need to drain coolant. Not sure how to retorque. One at a time, or loosen all and retorque.

 

[Bathy]

I meant to say 15-40w. Hey its back together and running strong. Rebuild kit says to retorque head after break in. Its not leaking, so I don't see the point.

Can someone explain the process for retorque? I know I need to drain coolant. Not sure how to retorque. One at a time, or loosen all and retorque.

Once you've heat cycled the Engine,
A composite head gasket will soften and is able to be compressed more, allowing for a good clamp of head to liners and precombs.
If you don't retorque there's a good chance the head clamp force isn't what it should be and it the head gasket will fail.

Do it hot, 1 at a time in the correct sequence, usually from middle to ends
and you shouldn't have to drain the coolant unless something is stopping you getting to the head bolts?

Edit: i used to mark the all head bolts, with a line longitudinally, it is surprising how much more the head bolts do up with a retorque.
it also helps show if you missed one.

 

[Dexter314]

Once you've heat cycled the Engine,
A composite head gasket will soften and is able to be compressed more, allowing for a good clamp of head to liners and precombs.
If you don't retorque there's a good chance the head clamp force isn't what it should be and it the head gasket will fail.

Do it hot, 1 at a time in the correct sequence, usually from middle to ends
and you shouldn't have to drain the coolant unless something is stopping you getting to the head bolts?

Edit: i used to mark the all head bolts, with a line longitudinally, it is surprising how much more the head bolts do up with a retorque.
it also helps show if you missed one.

Thanks for the reply. I like your idea of marking the bolts. In my opinion, the reason for draining some coolant is to keep it from getting in between the gasket and head/block when the bolt(s) are loosened. Although loosening one bolt at a time, probably not going to let something get in. The head gasket is steel, Im skeptical about the softening, but it is so easy to retorque im not opposed to still doing the procedure.

It is interesting how many different suggestions I have found from the two forums I am on (this one and BinderPlanet/Diesel Tech). Some are from known professionals, but it is a little concerning how many different suggestions:

1. Just check to be sure bolts are tight without loosening.
2. Drain some coolant, loosen all bolts and redo the sequence (main -sub, main -sub) . Engine cold.
3. Drain some coolant, loosen one bolt at a time in sequence and retorque . Engine stone cold.
4. Dont drain coolant, loosen one bolt at a time and retorque. Engine hot.

Maybe the engine hot vs cold or drain coolant vs not drain coolant depends on the engine?

So what to do? Maybe take a poll? Im leaning toward #3. #1 I wont do since in order to check a torque one must start with a loose bolt and trust the wrench. If it is just to make sure a bolt wasnt missed, that is different.

 

[Bathy]

If it's a MLS Gasket (Multi layer Steel) it' won't need to be re-torqued.
If it's a Composite Gasket, i would retorque, number 4, hot.
Done thousands of truck engines, lot's of UD's (Nissan trucks) and most other makes too exactly like that.

 

[Dexter314]

Well, darn it... I retorqued the head and now I wish I hadnt. After retorquing the head, I now see that my coolant is pressurizing. The coolant is be pushed into the overflow but not flowing back. There is pressure in the radiator still after sitting overnight. My guess is that when I retorqued the head, I caused a (likely small) leak so that now excessive pressure is leaking at the headgasket. There is absolutely no blow by noticed out the downdraft tube so I dont think the new pistons were dammaged. I am running a new Merc Turbo and have boost as high as 12PSI. Could the high turbo boost be contributing to the issue? There is no oil in coolant, no coolant in oil. It has a lever type 16# radiator cap and no coolant leaks at all.

Ive had the engine apart too many times, it is really trying my patience. Any suggestions on what to do next?

 

[james008]

Well that's not good news.

How did you re torque the head? Back off the bolts then tighten again, or just attempt to tighten? Warm or cold engine?
The Nissan service manual just specifies torque checking at 1000km or 600mi on a warm engine.
I don't know if I've ever personally checked a warm engine though....

Unfortunately now that the gasket has been torqued, heat cycled and torqued again, it'll need to be replaced.
If you can source a genuine one, I'd go that route.