Thread: 2.6l 6-pot oil in cylinder #6 - Where is it likely coming from?!?!?!?

Well thought out and well written. As I was reading it, I too was thinking along the lines of your possible causes 1 to 4. It's been decades since I worked on a Landrover 6c, but I can tell you that accessing the stem seals on a 4c is easy and I can't see why the six would be any different. The solution is to put compressed air into the cylinder via the spark plug hole to hold the valves up while you remove the springs (4c) or intake spring (6c). From memory it doesn't take much pressure, just 4 to 6 psi (piston at TDC) or something and you won't do any damage. On the 4, the valve stem seals would harden over time and using the above method they could all be changed over very quickly.
The stem seals would certainly be the easiest things to check, so that's where I'd start. Also, if your rings are in good condition and the gaps not aligned, the compressed air should not leak out for quite some time. You could check no 6 against one of the other cylinders as a reference.

G'day All,

A quick way to determine if inlet valve stem seals are leaking oil into the cylinder is to first warm up engine to normal operating temperature.

Then let the engine idle for about 2 minutes then operate the accelerator with a quick operation to see any blue smoke from the exhaust. I note only one cylinder is effected with oil so may only be a small amount of blue smoke.

Blue smoke is an indication of leaking valve stem seals after a period of idle condition.

If the inlet stem seals are O ring type, looks like you have to removed the head to replace them!. (Your machine shop may have modified the inlet valve guides to take an external seal?)

Good luck with it.

Chris

If you put compressed air in as suggested above, the loss of compression will show up as air leaking from the cylinder. If it is a valve, you should hear air leaking into either exhaust or intake manifold. If it is a head gasket you should get bubbles in the coolant, and it is rings, you should be able to hear air coming into the crankcase.

I'm afraid that my guess is rings - valve stem seals will certainly get oil into the cylinder, but will not affect compression.

I suspect you have either ring gaps lined up, or, more likely, a ring is broken, perhaps due to insufficient gap, or being cracked during installation. The mileage since overhaul should mean it is not wear. I suppose it could be a cracked piston, but I cannot envisage how that could happen without a major event such as overheating.

Originally Posted by DieselLSE

Well thought out and well written. As I was reading it, I too was thinking along the lines of your possible causes 1 to 4. It's been decades since I worked on a Landrover 6c, but I can tell you that accessing the stem seals on a 4c is easy and I can't see why the six would be any different. The solution is to put compressed air into the cylinder via the spark plug hole to hold the valves up while you remove the springs (4c) or intake spring (6c). From memory it doesn't take much pressure, just 4 to 6 psi (piston at TDC) or something and you won't do any damage. On the 4, the valve stem seals would harden over time and using the above method they could all be changed over very quickly.
The stem seals would certainly be the easiest things to check, so that's where I'd start. Also, if your rings are in good condition and the gaps not aligned, the compressed air should not leak out for quite some time. You could check no 6 against one of the other cylinders as a reference.

thank you all!!! As I was reading the post about using the compressed air to compress the spring it made me think that I could have stuck valves!! Since I know from the leak down test that I have compression loss somewhere, and I didn’t hear air escaping through the bottom end and out the oil filler, then I have to suspect one or both of the valves could be sticking. And if they were sticking badly enough then wouldn’t that be the obvious cause of oil getting into the cylinder? And since it is unlikely that the oil would “climb” up from the exhaust valve then it is likely a stuck intake valve and possibly a bad o-ring.

if you all think I’m going down the wrong path then let me know. But if it’s a stuck valve there’s probably not a way to fix that without removing the head right?

I’m gonna remove the intake valve cover and position #6 on TDC on the compression stroke and use my smoke machine and fill the cylinder with air and smoke via the spark plug opening and see if it escapes into the top of the head. I can check the exhaust pipe for smoke as well but my theory is that I will see a constant stream of smoke coming out of the top of the head via the valve opening on #6.

thoughts? Not sure why I missed thinking about a stuck valve.

love that method about using the air to compress the valve springs. That’s genius!!!!

A stuck valve in conjunction with a bad valve stem seal is something that could cause both oil in the cylinder and compression loss.

But I think you are wrong about "it could not be an exhaust valve" - when the engine is idling, there is quite a high vacuum in the cylinder during every intake stroke, and if an exhaust valve is not closed it could carry oil into the cylinder if there is any coming along the stem, and exhaust flowing back in from the manifold will carry it along. However, certainly the intake valve is more likely as it also has a vacuum in the manifold. Intake stem seals are the usual culprit.

As a sort of aside - if the compressed air test shows compression leak is from a valve, make sure that there is tappet clearance on the valve - it may not be actually stuck, but not closing completely because of no clearance.

As you suggest though, doing anything about a stuck valve will require the head off. There is a possibility that the "stuck" valve actually has the valve or seat sealing face damaged or has something stuck to it.

Thank you. I don’t much about these 2.6l so I just assumed that the position the exhaust valve is in would not allow oil to get back in the cylinder. Very good to know.

I’m gonna run my compressed smoke machine through it and see where the smokes comes from and narrow it down from there.

Question: Do you all use the metal head gaskets or the composite for a series III 2.6l?

Originally Posted by JDNSW

A stuck valve in conjunction with a bad valve stem seal is something that could cause both oil in the cylinder and compression loss.

But I think you are wrong about "it could not be an exhaust valve" - when the engine is idling, there is quite a high vacuum in the cylinder during every intake stroke, and if an exhaust valve is not closed it could carry oil into the cylinder if there is any coming along the stem, and exhaust flowing back in from the manifold will carry it along. However, certainly the intake valve is more likely as it also has a vacuum in the manifold. Intake stem seals are the usual culprit.

As a sort of aside - if the compressed air test shows compression leak is from a valve, make sure that there is tappet clearance on the valve - it may not be actually stuck, but not closing completely because of no clearance.

As you suggest though, doing anything about a stuck valve will require the head off. There is a possibility that the "stuck" valve actually has the valve or seat sealing face damaged or has something stuck to it.

I can't really answer that - I don't work on the six (my relevant knowledge is from extensive reading and consultation, and from my Series 1 four with a similar engine.

As a follow-up gentlemen to the mystery surrounding the oil in the cylinders, fouled plugs, smoke out of the exhaust and oil consumption, I want you all to weigh-in on this. I ran my smoke machine down each spark plug hole for each cylinder with that cylinder on TDC on the compression stroke and watched for smoke to work its way through. I never saw smoke push through either of the valves. I did see smoke come out another cylinder spark plug hole?!?!?!?!? Just to set the stage, I removed the exhaust and intake covers. I have pressurized smoke being put in to the spark plug hole on #6 at TDC on the compression stroke. Smoke comes out of #5 and #1 cylinder?!?!? At this point, I'm thinking to myself I have ring problems in #6 for sure. Not sure how smoke is making its way to #5 and #1. I'm still perplexed and would love input. My first thought was that I have more than a ring issue on #6 but also on #5 and #1...except that both of these cylinders (#5 and #1) performed excellently in the leak down test. Help!?

Continuing on. I pulled the head and other than some carbon on the intake valves, everything in the head checked out: the o-rings around the intake valve stems where in place, the valve springs, rocker arms, and rods were fine on both the intake and exhaust. The head gasket looked fine with no apparent failure anywhere. Again, I'm thinking that the poor leak down test results combined with the smoke test on #6, which didn't push smoke through either valves (intake or exhaust), but also didn't create pressure in the cylinder, leads me to believe I've got a ring issue at least in #6.

I pulled #6 cylinder and it was very easy to see what the culprit was of the low, almost non-existent, cylinder pressure (SEE PICTURE). The rings had aligned. Which brings me to another question. I know the rings rotate around the cylinder head as the engine is running. And they all rotate at different speeds due to their purpose and location. Am I just to assume that these rings aligned and that was just "unlucky"??? Is there anything that the workshop manual doesn't explain that you guys are doing to prevent these rings from aligning? I have noted in my journal that I kept while rebuilding this truck that I clocked all the rings (two compression and one scraper) to 120 degrees apart. Is that wrong?

any other suggestions?