Consuming 4 liters oil per 600km!

[philip]

SNIP- So now i start to search for a piston and rings

Maybe. The manual lists "Service" limit of .004" (0.105 mm) for the pistons (measure at the skirt). BE SURE you get the single piece oil rings (has a wire/spring behind). NO twin rail/expander oil rings ... like the gasoline engine has. NO low RPM version pistons with 5 rings type.

The cylinders must be x-hatched again ... 45 degree.

[after oil]

from the nissan dealer:
ring set 12033 L2006 $$298 canadian
piston 12010 T7205 $135.66

anyone know what they mean by grade 1 or grade 2 pistons?
anyone got any spare rings?

[asavage]

the mechanic finally came today. he determined that the rings on piston 1 are shot . . .

This is the cylinder that had 410 PSI. Either that has changed (ie the rings on No. 1 died/broke after you performed the test), or the test was performed incorrectly, or the rings are not broken after all. Choose one of the above.

There is no way to achieve 410 PSI with a broken compression ring.

[philip]

Tentatively, I vote for: no "broken" rings.
Tentatively, I vote for: compression rings that are just worn out (way excess ring gaps).

AND ... I have yet to hear back on my question about how those intake guide seals were replaced. I want to SEE ... after a valve spring is removed.

By the way, I just change the engine oil and filter. 2,900 miles lost 1 qt of NAPA 15w-40.

The odometer says 179,925 + 12,656 on the orginal odometer (the original owner wanted a speedo WITH a "trip" meter ... with the orginal truck did not having one (which I now have in the box).

My my ... how things keep turning up.

[after oil]

The rings are in japan :

This is the cylinder that had 410 PSI. Either that has changed (ie the rings on No. 1 died/broke after you performed the test), or the test was performed incorrectly, or the rings are not broken after all. Choose one of the above.

There is no way to achieve 410 PSI with a broken compression ring.

i understood that its the oil ring thats shot and it can still have compression

Tentatively, I vote for: compression rings that are just worn out (way excess ring gaps).

so worn compression rings are replaced?

AND ... I have yet to hear back on my question about how those intake guide seals were replaced. I want to SEE ... after a valve spring is removed.

i didnt take off the manifold, hoping i wouldnt have to. its such a PITA, and ill have to buy a gasket again.

i always seem to get really confused by conflicting diagnoses from you guys and various other mechanics. but if you're suggesting that i might discover something by removing the manifold, and that perhaps i wont have to buy pistons and rings, that would be very nice.

[asavage]

Understand that few of us are experts. I am giving you the best advice I can.

Yes, it's possible for the oil control ring to be ineffective and have working compression rings . . . it's just not very common, because the same things that break or wear an oil control ring also breaks or wears the compression rings.

I am suspicious because the huge increase in oil consumption occurred after the head was worked on and the head gasket replaced. As they say, "When you hear hoofbeats, think horses -- not zebras," meaning look for the most likely things and not the less common.

Which is why I'll ask a third time for pictures of the valve stem seals as installed. They can be seen through the springs without disassembly or manifold removal. While it would be difficult for as much oil as you're using to be consumed through the intake valve guides, it's possbile -- and more likely than the likelihood that one oil control ring broke at the same time as you had the head off. Oil control rings do not control all of the oil from getting to the combustion chamber from the cylinder wall, they only help. They have no pneumatic pressure against the cylinder wall as do the compression rings, and should last "forever" if the oil is kept clean.

I can't see the condition of the oil control rings changing when you change a head gasket.

The reason I asked about the intake manifold is to see if oil was sitting in there. If there is, then the PCV system (and blow-by) would be indicated. Blow-by comes back to rings.

But the monkey in all this guessing is: why did it change after all the work that was done? The most likely answer is that something happened during the work, or the head was assembled incorrectly (ie missing or damaged valve stem seals).

[philip]

AND ... I have yet to hear back on my question about how those intake guide seals were replaced. I want to SEE ... after a valve spring is removed.

i didnt take off the manifold, hoping i wouldnt have to. its such a PITA, and ill have to buy a gasket again.

"after oil": It was NOT me to make a manifold suggestion. It was me who asked for a view a valve spring to view a valve guide seal. All required is to pull off the valve cover. Takes 3 minutes. From that point further, each valve spring (total of 8 each) can be removed in less than 30 minutes. I use a trick little compresser clamp. No need to pull off the cylinder head! Every decent mechanic has one of these compresser clamps too.

Your engine is not "young." So I would expect to see a little bit ... here and there ... the cleared off carbon that I photo'd earlier.

Let's not run off paranoid first. Let's get these intake valve guide seals looked at REALLY close. Even when new seals are installed, there are various kinds which while new ... don't do the job. For example, the seal requires a lip oil seal. But some people install those High Zoot high heat nylon that won't stand up valve guides in a loose guide guide. OR... the mechanic slamed the new seals into the guide which teared them at the oil lip.

JUST thinking out loud.

[asavage]

That's what I'm wondering too: did the shop use the plastic sleeve over the valve stem to install the guide seals? If an apprentice was doing the work, perhaps he just shoved them on (I've seen it done). The seals look OK, but the sealing surface is chewed up by dragging it over the valve spring retainer keeper grooves.

Still, I wouldn't think that even eight damaged seals would allow quite that much lube oil in. The top of the valve guide is not under oil, it's just sprayed with it.

[philip]

SNIP- Still, I wouldn't think that even eight damaged seals would allow quite that much lube oil in. The top of the valve guide is not under oil, it's just sprayed with it.

Thoughts:
1) Crankcase is slightly pressured while intake manifold is consideral less air pressue (vacuum). It is the intake seals that will allow oil to the combustion chamber.
2) Because this is a four cylinder engine, there is a lot of air turbulence pushing back and forth as two pistons go up while two others go down. This becomes less and less as more cylinders are added together.
3) To this turbulence, add the oil passing off the rocker arms, and the rockers reciprocating fast. Try this yourself by removing the valve cover cap -while- the engine is above 1500 rpm.
(NOTE: Next time you refill the engine oil, try filling the valve cover quickly. You can overfill the valve cover quickly ... because ... the oil return passages are rather small.)
4) Exhaust seals leaking will allow very little oil (relatively) adding to the exhaust gases because exhaust pressure is higher than crankcase pressure.

History bit. Long ago, I owned a BMW R100rs motorcycle back in early '80s. The "Boxer" two pistons reciprocated toward and then away from each other. THAT much of crankcase air turbulence was horrendous. So ... BMW made up a reed valve to control crankcase pressure. The result was atmosphere crankcase pressure when the pistons were BDC and then slightly below when the pistons reached to TDC. Without this reed valve, oil would seep out through everything!

The SD25 has a similar reed valve on the valve cover. Air Control venting

[asavage]

Quite a bit of oil can make it in via the exhaust valves' stem seals, but not nearly as much as in the intake.

The reason this idea is so attractive is that it corresponds with the both the symptoms and the timeframe: reasonable oil consumption before taking off the head, unreasonable after. And Paul didn't do the head work so he doesn't know for certain what transpired or how it was assembled. Which is why I've asked three times to look at the valve stem seals: not because valve stem seals are a real likely candidate for that much oil consumption, but because it's possible and it fits the whole scenario, unlike the other guesses.

[philip]

Ah yes Dr. Watson. Indeed sir yes ... indeed you could be more right!

It is also possible that because I agreed that we both could be mistaken.

[after oil]

Oh, I understood from the photos of the valves stems that the manifold was off. I've uploaded pics of the valves, and springs, with the springs on, I hope thats what you're looking for.

I found rings and pistons in Canada for much cheaper made by Hastings manufacture, distributed by piston rings services and retailed by Lordco (I had to work backwards from the manufacturer down to the retailer to find them) $120 for ring set, and $45 for a piston!

But, alas, maybe I won't need those.

[after oil]

here we go:

[asavage]

I can't tell what I'm looking at. Are there seals installed or not? And if so, are they OK?

[TDI_Joe]

Here are some photos showing an example of bad intake valve guide seals.





Valve 4 seal is good, all others show some indication of leaking.



These injectors were rebuilt 4,000 miles ago. Note number 2 has much oil residue. Oil use was about 1qt per 1000 miles.