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General Tech Leak Down Test

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KVH

KVH

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I lose 1/2 quart every two weeks. I'm going nuts trying to find the cause. I'm seeing smoke out the exhaust when I punch the accelerator or shift at high RPMs, and my plugs are black sooty around the outer ring, not the center. I'll try new plugs. But the loss of oil is bugging me. So, I bought a leak down tester. All cylinders are perfect with 5 to 10 percent leakage. What does that tester tell me about my loss of oil? This is the same car where two months back I nearly had a fit after seeing I was over 2 quarts low and heard a knocking. There's no knocking now, and I run great. But the exhaust smells like gas and I'm losing oil.

My friends say the exhaust smoke on shifting is black, but the other day, to me, it looked more grayish.

I guess for giggles I could replace my carb jets, but that seems desperate to me. I already replaced my floats and needles.

I'm just wondering if somehow I really am burning up that oil despite the leak down test. I'm also wondering I could be throwing oil from the rear main seal while driving, and while driving only.

Oh, well.
 
Any puff of smoke on start-up? If so, it could be leaky valve seals. A leakdown test won't show it because the valves are closed when testing the cylinders. Although leaky valve guides are unlikely to cause a huge oil consumption unless they're really leaky.

Might also be worn oil scraper rings but good compression rings.

But if you're smelling fuel, I'd start with mixture adjustment and see if that cures it. Could be as simple as a little wash-down.
 
Dunno what you're driving, but I don't think 3s have valve seals. Check your moss catalog to see if they are illustrated for your model. Very helpful would be determination of smoke color so as to identify what system to tinker with. Black is gasoline and blue is oil. Could of course be two problems at once.
Bob
 
I wonder how many miles you've driven in those 2 weeks...If not many, it could be a gravity leak while sitting vs burning when the engine is running.
If burning during actual driving and you have good compression, it might be the oil control rings responsible, not the compression rings.
With some brands of oil control rings, it's possible that ends of the middle spacer overlapped during installation rather than staying butted together.
 
A half quart of oil would make a huge puddle - so I'd lean towards the oil control rings if observation suggests that it is oil smoke.

The plug color you describe is somewhat ambiguous - the black 'ring around the collar' with a cocoa brown tip is what I sometimes see even when I am convinced the mixture is right.

Maybe I need to follow you on a desert drive?
 
Geo Hahn said:
A half quart of oil would make a huge puddle - so I'd lean towards the oil control rings if observation suggests that it is oil smoke.

The plug color you describe is somewhat ambiguous - the black 'ring around the collar' with a cocoa brown tip is what I sometimes see even when I am convinced the mixture is right.

Maybe I need to follow you on a desert drive?
Click to expand...

Yes, I'll call you, set it up, or finally make it to a club run. I was pretty careful with those oil control rings. I'm fairly certain I did not overlap any. Now it haunts me of course.
 
As noted, no valve stem seals originally on TR2-4A. But the puff of smoke on shifting is a classic symptom of worn intake valve guides. Do you by any chance have one of those external oil feed lines fitted?

The rear main seal does only leak while the engine is running, because it is above the static oil level. But the oil doesn't find it's way to the ground instantly, so you're almost certain to see at least a few drops each time you stop if that is where the leak is.

Another thought is the crankcase vent system on a 4A. If you have some extra blowby, the PCV may be sucking oil mist from the rocker cover. You might try disconnecting the line to the valve and see if it either stops burning so much, or you get a lot from the disconnected line from the rocker cover. (Plug the inlet to the valve but leave the line from the cover open and directed into a temporary catch can of some sort.) I've owned cars (tho not a 4A) where just a few minutes of nearly full throttle driving would blow a quart or more.
 
To check the integrity of your piston rings you can do a very simple test. All you need is a rubber band and a latex glove. Place the glove over the oil fill opening and slip the rubber band tight around the glove. If the glove blows up you have bad, broken, or stuck rings. Good luck!
 
Poolboy might be right. The flexible center ring type of oil compression has caused a problem with two recent builds here. The ends of the tabs that touch together break off and the engine burns oil. Replacement of those oil rings with a solid type solved the problem of oil burning in both engines.

Jerry
 
I'll try responding (below) to several of you in the hope I get some resolution short of tearing things down again:

From Randall:

TR3driver said:
As noted, no valve stem seals originally on TR2-4A. But the puff of smoke on shifting is a classic symptom of worn intake valve guides. Do you by any chance have one of those external oil feed lines fitted? MY INTAKE VALVES ARE ALL NEW, ALL INSTALLED BY A GREAT SHOP. I HAVE NO OIL FEED LINE FITTED.

The rear main seal does only leak while the engine is running, because it is above the static oil level. But the oil doesn't find it's way to the ground instantly, so you're almost certain to see at least a few drops each time you stop if that is where the leak is. I ALWAYS HAVE A FEW DROPS BACK THERE, SO MAYBE THAT'S WHERE AND WHEN I'm LOSING THE OIL. I DID FIT A NEW VITON SEAL BACK THERE SO I WOULD'VE HAD TO SCREW THAT UP, TOO.

Another thought is the crankcase vent system on a 4A. If you have some extra blowby, the PCV may be sucking oil mist from the rocker cover. You might try disconnecting the line to the valve and see if it either stops burning so much, or you get a lot from the disconnected line from the rocker cover. (Plug the inlet to the valve but leave the line from the cover open and directed into a temporary catch can of some sort.) I've owned cars (tho not a 4A) where just a few minutes of nearly full throttle driving would blow a quart or more. I REMOVED MY PCV VALVE ALREADY AND HAVE A TUBE RUNNING DOWN. WHETHER IT'S BLOWING OIL OUT I'M UNCERTAIN. AT STOP, THERE'S ONLY AN OIL RESIDUE THERE, PERHAPS THREE DROPS WORTH.
Click to expand...

From Blue Max:

[Quote: All you need is a rubber band and a latex glove. Place the glove over the oil fill opening and slip the rubber band tight around the glove. If the glove blows up you have bad, broken, or stuck rings. Good luck!]

I can do that easily. I'm fairly certain it will blow up, though, because, at least prior to my rebuild, I recall there was considerable air pressure coming out of the PCV valve outlet pipe from the valve cover. In other words, with or without a PCV valve, there was pressure and air escaping the valve cover outlet pipe.

From Jerry:

[Quote: Poolboy might be right. The flexible center ring type of oil compression has caused a problem with two recent builds here. The ends of the tabs that touch together break off and the engine burns oil. Replacement of those oil rings with a solid type solved the problem of oil burning in both engines.]


Are you referring by "center" as that funky oil control ring between the upper and lower band rings? I installed new County Pistons and Rings. Who offers a different kind of center control ring? I have a spare set of "Grant" rings, and those come with very specific instructions to avoid overlapping the ring ends. As I recall, the County ones aren't supposed to overlap either, and I believe I verified they weren't overlapping. I guess pulling a piston to verify isn't all that awful. Maybe next week. Beats watching the confirmation hearings.
 
Here's a very good example of a engine that is making good compression. If the glove inflates your compression is bypassing the rings and pressurizing the crankcase. That oil then is push up and passing the rings back into the combustion chamber which is burned.

New pistons and sleeves installed? Rings properly gaped? Rings staggered correctly? Were the rings installed right side up? If reusing old pistons, were the ring land gaps carefully check? Were the bore dimensions checked for taper and honed properly?

https://www.youtube.com/watch?v=uQ2ARnW4574
 
BlueMax said:
...All you need is a rubber band and a latex glove...
Click to expand...

Or, for a more colorful display, you can perform the test with a latex product available for pocket change in any truck stop restroom.

The oil control rings that seem the trickiest to me are the ones with the two colors on the ends (red & green?) that are there to show that the ends have not overlapped once the outer rings are in place. The simplest are probably the one-piece version - hard to see where one could go wrong with them.
 
This isn't the sharpest of pictures but it does illustrate Grant's spacer for the oil control rings...temporarily butted together.
 
Yeah, the tricky bit is maintaining that as you snap on the two control rings. Okay, not terribly tricky but something that must be confirmed after they are both on.
 
That picture of the oil ring above was the problem with two out of 3 engines all built together in my garage. The colored tabs had broken off! Even though the rings were fitted and had enough gap in the cylinders. The third engine had a solid oil ring and no problems. We replaced the bad rings with Hastings one piece rings and solved the problem.
 
Jerry said:
Poolboy might be right. The flexible center ring type of oil compression has caused a problem with two recent builds here. The ends of the tabs that touch together break off and the engine burns oil. Replacement of those oil rings with a solid type solved the problem of oil burning in both engines.

Jerry
Click to expand...
Who sells the the solid type oil compression ring?
 
Jerry said:
That picture of the oil ring above was the problem with two out of 3 engines all built together in my garage. The colored tabs had broken off! Even though the rings were fitted and had enough gap in the cylinders. The third engine had a solid oil ring and no problems. We replaced the bad rings with Hastings one piece rings and solved the problem.
Click to expand...

I built 700+ HP engines for years and never had an issue with the 3 piece oil rings. There can't be anything wrong with the design. Before this forum I had heard of maybe one oil ring failure, and that was on a high mileage car. So I wonder what is going on with the Triumph rings? Was there a bad batch or were people installing them wrong?
 
I don't think there is anything 'wrong' with all 3 part oil control rings, just the Grants pictured with the butt type spacer. I had to get them out of my TR6 engine.
By contrast I have been very happy with the Hastings 3 piece FlexVent oil control ring which is a different animal than the 3 piece Grant.

The fault could have been mine but oil consumption went from 1 qt/800 miles with Grant to practically Zero/2200 miles with Hastings
 
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