Engine Oil Burning Question

[bobrogg]

I'm burning oil when I drive my car and thought that I may need to replace the rings. The plugs are oily when removed, plugs 1 to 5, with 6 being a nice brown color. The cylinder pressure testing I did today have given me the following results (cold engine, all plugs removed).

#1 130
#2 135
#3 132
#4 135
#5 140
#6 132

So where or what do I look at next?

Thanks,

Bob

[Peter Cobbold]

Bob,

The compressions look good - ie consistent. Try measuring with and without a squirt of oil down the bore. If oil does not change the reading the compression rings are probably OK, and unless they have been replaced without the scraper rings too ( unlikely) look elsewhere for oil entry - eg valve guides?

 

Has the oil burning started suddenly? can you see blue smoke in exhaust? what is oil consumption?

 

Could it be spark plugs that are too cold - ie not getting hot enough to burn off normal oil contamination? Try a grade or two hotter.

Peter

[bobrogg]

I did the wet (a small amount of oil in each cylinder) and the reading increased by 10 PSI in each cylinder

 

#1 130 dry, 140 wet

#2 135 dry, 145 wet

#3 132 dry, 140 wet

#4 135 dry, 145 wet

#5 140 dry, 150 wet

#6 132 dry, 148 wet

[Motorsport Mickey]

Bob,

 

As Peter said the compressions are even, this means whatever it is affects all the cylinders equally. I think the rings are not bedded into the bores and the excess oil is being burned. No history available as to how old the engine is since rebuild etc but even engines which have been run for a couple of years ok need to avoid glazing the bores.

 

Try the easy fix first, give it some Teddy !

Not revs, power. Drive the engine in top gear at the area of BMEP, (brake mean effective pressure) this gives the most pressure throughout the power stroke to the piston and rings and helps expand the rings to give best scraping action and therefore bedding into the cylinder walls. The BMEP area normally coincides where the engine develops maximum torque and if you select top gear and give it the beans in that area whilst travelling up a long gradient or even level road it will deglaze the bores.

You need to continually drop the speed below the start of the torque area and drive the car through it's range (easier if it's up a gradient where you can hold the car on a steady revs in the range). Or give it a rolling road session for about 40 mins where the operator can load the engine whilst holding the revs in the torque area.

 

Even my daily driver Ford S Max needs to be kept deglazed, normal running trickling about on part throttle on A - B roads don't help so I do the above about every couple of months, or tow a 1700 kg caravan about 6 times a year, that seems to do it, lol.

 

Mick Richards

Edited October 12, 2013 by Motorsport Mickey

[Ashley James]

Oil consumption may not be caused by rings, often worn valve guides do it. In either case I'm not sure of the value of a compression test for anything except indication of a burnt or bent valve.

 

I don't know TR6 engines, but if the car smokes after accelerate away from the bottom of a hill you've just descended, then oil is going down the guides. However if there's lots of smoke from the breather and from the rocker cover oil cap, then all the rings are worn, probably bores too and finally, if everything is fine, but the car is using oil, it may just be oil control rings not functioning as they should. I had this with my 3A and new rings fixed it.

 

I'd take the head and sump off and check it all out.

[GT6M]

Most T engines will burn oil.

BUTT, not always the fault of the engine but the oil.

 

All 20/50 oils , or what ever other grade, { apart frae straight 50,40 30 ect }

are just a 20 weight oil with modifiers to thicken it up as it gets hot.

BUTT, after a while, the oil looses its thickening qualities, and reverts to a straight 20 0r 25

NOT the 50 top rting it has when new.

 

I find that when the oil gets older, over about 3-3.5k miles, the engine starts to pink,

this is an indicator to me tht oil is on its way oot. as oil is thinning and getting into cylinders.

 

So try a oil change to some thing newer, and maybe thicker, seeing as ye in California,

as it be hot there,!!!

 

As a note, I got 4 tins of Castrol Edge RS oil, 10/ 60, v v cheeeeeep.

totally useless, 3 litres of oil in 500 miles of mainly M Way running, { OK in the MX though }

just never got up to temp, stopped as a 10 -15 weight, and poured thru into chambers.

rings and valves covererd in the darn stuff.

pinking like mad, till backed of 10 degs all over, and exhaust was v v blue smoke.

 

Markus

[bobrogg]

Thanks to all for your inputs. I do not have a lot of history on the car/engine other than it had been sitting for several years before I bought it. I do not know (and the previous owner did not know) if the heads were ever converted to run unleaded fuel. I am going to pull the head of soon to verify if the conversion has ever been done and to have it rebuilt, the oil usage is a concern since I had not planned on a engine rebuild until late next year.

[Motorsport Mickey]

Why pull the head to check about unleaded fuel ? are you planning to do 30,000 miles in the next year ? use additives until you want to do the engine build late next year, more convenient.

 

Mick Richards

[Nick Jones]

Plugs are wet oily? Or just dry black?

 

I dread to think how much oil you need to use to be getting wet oily as my previous PI engine was doing just 300 miles to the litre (and smoking offensively) but even that wasn't getting wet oily plugs, just rather dark dry brown.

 

This engine also taught me that compression readings have little to do with oil use (or maybe the oil control was so bad every compression test was a "wet" one) as it it had good, even compressions (180 - 195psi). That was caused by a long period standing (15 years) resulting in rust-pitted bores.

 

Dry black is more likely to mean rich running.

 

Nick

[bobrogg]

^{Today was an interesting day with the TR6, I took the spinoff oil filter and found that the rubber oil rings were completely degraded. The large outer ring was not a ring at all but only bits of rubber, the inner ring was not that much better but still recognizable at least. I had a new Moss spin-on filter unit so I replaced the whole thing. My oil pressure now is much higher after warm up and I no longer leak oil}

[bobrogg]

Plugs are wet oily? Or just dry black?

 

I dread to think how much oil you need to use to be getting wet oily as my previous PI engine was doing just 300 miles to the litre (and smoking offensively) but even that wasn't getting wet oily plugs, just rather dark dry brown.

 

This engine also taught me that compression readings have little to do with oil use (or maybe the oil control was so bad every compression test was a "wet" one) as it it had good, even compressions (180 - 195psi). That was caused by a long period standing (15 years) resulting in rust-pitted bores.

 

Dry black is more likely to mean rich running.

 

Nick

They are oily black, I'm going to rework the oil vent lines and hope that part of the problem is crank over pressure

[Andy Moltu]

What's your oil consumption? Are the plugs wet with fuel or are they oily?

 

 

There are really only two ways for the engine oil to get into the the combustion chambers-

Past the oil control rings or down the valve guides.

 

Has it got an external rocker feed kit? If so remove it & see if that improves things.

 

If the car has stood for a long time it is possible the oil control rings may have stuck and may settle with time.

Your compressions suggest the bores are unlikely to be hugely worn so with luck it's gummed up rings but it's odd for that to affect all 6.

Glazed bores may be a factor if the engine has been re-ringed without adequate glaze busting or run in too gently so the rings didn't bed in adequately.

Have you any history with the car to know if that might be the case - if so it may settle with time. If not you may eventually end up stripping the engine down and to find out.

 

If your crank case breather is blocked that will increase consumption & leaking.

[bobrogg]

What's your oil consumption? Are the plugs wet with fuel or are they oily?

 

 

There are really only two ways for the engine oil to get into the the combustion chambers-

Past the oil control rings or down the valve guides.

 

Has it got an external rocker feed kit? If so remove it & see if that improves things.

 

If the car has stood for a long time it is possible the oil control rings may have stuck and may settle with time.

Your compressions suggest the bores are unlikely to be hugely worn so with luck it's gummed up rings but it's odd for that to affect all 6.

Glazed bores may be a factor if the engine has been re-ringed without adequate glaze busting or run in too gently so the rings didn't bed in adequately.

Have you any history with the car to know if that might be the case - if so it may settle with time. If not you may eventually end up stripping the engine down and to find out.

 

If your crank case breather is blocked that will increase consumption & leaking.

Since I replaced the o-rings on the spin-on oil adapter my oil leaks seem to have stopped. I used a oil flush chemical, added new 20W50 oil and a better oil filter than what I had, now I can accurately track my oil usage this week to see how much oil I use.

[Motorsport Mickey]

I'm confused, we started off this thread with "I'm burning oil" and then went to "I'm going to pull the head to check if unleaded valve seats fitted but I didn't want to do this till next year" to "I'm going to use it to see if the oil LOSS" has stopped ??? To many variables and not enough sensible feed back, I'm out of here.

 

Mick Richards

[bobrogg]

I was having a heck of a time setting up my weber carbs and finally broke down and took it to my local Triumph shop. as part of the service they redid my compression test and confirmed my reading, the gentleman who did the test told me the rings are fine. Part of the oil consumption issue was insufficient negative pressure from the valve cover vent line. I'm making the changes to correct this and will resume the oil use monitoring to determine the next step.

[Andy Moltu]

You shouldn't need negative pressure - the crank case should vent OK at atmospheric pressure.