Burning Oil

[dmen]

Can someone help me with where I begin? I am having oil problems with my TR6. It is using a quart about every 100 miles. I don't know where to start diagnosing the problem but I know it could be anything. When I rev the engine really high I see black smoke come out some time. When I hold my hand up next to the tail pipe I see little specks of black on my hand. Where do I get started. I don't want to have to overhaul the engine if I don't have to. Can some give me a list of things to check? From easiest to worst? Thanks!

 

[Harry_Ward]

Check the drain plug first to make sure it's on and oil tight. Ok that was easy now do a compression test on each cylinder to see which cylinder's valves, rings, piston, or gasket seal is worn or blown. Also stop reving the engine really high as this could make for more problems if the ring, or piston, decides to let go inside the engine. The oil may just be leaking out a seal. Do you see oil on the floor after it is parked sitting or running sitting? The smoke may also just be improperly adjusted carbs if once in a while but black smoke is an indication of oil getting into the combustion chamber which is not good and requires compression testing to determine where it is leaking.

My usual disclaimer...I own a 3 and I'm sure some of the 6 guys will help you out further.

 

[gjh2007]

do the compression test first & write down each one, shouldn't be more 10-20 lbs diff between high & low. I think you should be somewhere in the 130-160 psi range if I remember correctly. I tis best to do the compression with a screw in tester, that holds the highest psi read.

Then squirt a little oil in each cyl one at a time & see if compression jumps up, that would indicate worn rings, low compression after the oil likely indicates worm valve stems or seals.

Keep us posted.

 

[AltaKnight]

Wow, a quart every hundred miles ia a lot.
Assuming it's not leaking out underneath then you should see PLENTY of BLUE smoke out the tailpipe, I would think it's likely a piston ring problem.
You can do the work with the engine in the car if you have a set of ramps or sturdy jackstands.
While you're at it you may want to replace rod, main and thrust bearings.

 

[Alan_Myers]

Hi,

It would also be helpful to know some history of the engine: overall mileage, any work that's been done on it you know of, etc.

What viscosity oil are you using?

Are you using a synthetic oil?

Does your car have one of those supplementary oil feed lines for the rockers & valves?

Is the PCV valve in and working? Has any of the emission control stuff been messed with or removed?

The compression test is a good idea, but even better is a similar test called a "leak down". That can tell you a lot more about what's worn inside a cylinder, if anything. Just about any auto repair shop can perform this test for relatively little cost.

 

[aeronca65t]

Blue smoke usually is oil.
Black smoke is usually excess gas (rich mixture).

Check carb float to see if the thing is stuck. Or look for dirty air filter. Really rich mixture can wash oil off bores and cause heavy oil consumption.

Also, look at PCV valve. If it's stuck, the car will suck oil out of the crankcase like crazy.

Finally, be sure that dipstick is correct....an overfilled sump (due to wrong dipstick) will burn-off excess oil quickly.

I like to do a fully cold and then hot (engine warmed up) compression test....big differences indicate big problems.

 

[Deleted member 451]

Let the engine warm up and drive it around the block. If it's not smoking like a mosquito fogger then it's not burning that much oil. If it is smoking then if it smokes more accelerating it's probably rings. If it smokes more when you let off the gas then it's valve guides.
That much oil usage I would be looking for a crankcase ventalation problem. Look under the car my bet is that it is coverd with fresh British undercoating (oil).
My reasoning on this is an old MGB that sat with a broken rod for a couple of years. When I fixed it the valve seals were gone and it burned a quart every 200 miles and smoked like crazy. I also had a Jensen-Healey that used a quart every 250 miles and never somked a bit but the bottom of the car was covered with oil from the crankcase vent pipe.

 

[Alan_Myers]

[ QUOTE ]
be sure that dipstick is correct....an overfilled sump (due to wrong dipstick) will burn-off excess oil quickly.

[/ QUOTE ]

Agreed!

Plus, be sure you are reading the dipstick correctly!

I was chatting with a Morgan (w/TR 4-cyl. engine) owner the other day at a car show. He was very concerned his dipstick showed the oil quite low. But he was just reading it wrong and was planning to put 1 or 1.5 quarts too much oil in the sump!

You probably aren't making this mistake. But, there are two engraved lines on the dipstick. The oil level should be in between those two marks, preferably up close to the top one. (Also, there should be a felt gasket/seal on the dipstick, that will raise it slightly in the hole.) The Morgan owner was looking at filling to the second folded metal end on the dipstick (that forms the spring to keep the dipstick from coming out of the hole.)

Overfill the TR 4-cylinder motor and it will very quickly push the extra oil out the rear main scroll "seal" (not really a seal at all)! The 6-cylinder has a true seal in there, which might be damaged along with other seals and gaskets, if the sump is filled with too much oil.

Let us know what you find.