Did a lot of work on the car over the summer as it ate a big end bearing. Ended up taking the time to do a lot of PM while the engine was out.

Replaced one connecting rod, crank (damaged by con rod), cam (worn), lifters (seemed stuck). I used gage pins to check valve stem diameters and they were all within spec. I hand lapped the valves using 3 micron diamond paste (and yes, cleaned it all out) and installed new valve seals. All new timing parts, oil pump, updated it to the cageless oil filter housing. Put in ARP head studs instead of bolts, so should have good tightness there...

The car has been running strong and starts on the first crank. Tested compression and all cylinders were 150-155 psi (after several compression cycles, I didn't record first, second, etc). Leak down test gave me 3-7% on each cylinder.

I parked the car for a week in the garage with cardboard under it and didn't find a single drop. So, definitely not leaking. Coolant is not dropping. Coolant does not appear oily or discolored.

BUT, I am consuming 1 quart of oil (5W-40 Pennzoil Ultra) every 200-300 miles.

I saw a big puff of smoke just once on startup. Doesn't seem to do it every time.

Any ideas?

 

I don't have any ideas besides the crank position sensor O ring but you mentioned no drips on the cardboard.

Only other question I have is oil weight you are using ... Is that the right weight? I am fairly certain you should be going with 30 weight oils.

Let us know what you find out

 

Thanks, I did replace that o-ring when I was doing the engine work. I don't think slightly heavier oil is hurting me here - should be helping.

Mini/BMW doesn't specify a single weight of oil. The manual for my Gen I MCS just specifies oil that meets BMW LongLife-01 (LL-01). There are some 5W-40 oils that meet LL-01, and the one I mentioned is one of them.

The pennzoil ultra euro 5w-40 "meets or exceeds" LL-01 but doesn't say "certified to", which suggests that Pennzoil has not paid BMW to certify it, but rely on their own testing to claim it "meets or exceeds". It is a small difference and has become a subject of argument in the past. That is a subtle difference and I don't think I have a subtle problem...

 

Edit - I was looking at the owners manuals online. The 2002 manual says LL-01 oils. The 2003 manual says "Use only approved MINI High Performance Synthetic Oil.If you are unable to obtain MINI High Performance Synthetic Oil, you can add small amounts of synthetic oil in between oil changes. Only use oils with the API SH spec-
ification or higher" and "Approved oils are in SAE classes 5W-40 and 5W-30."

 

Really doubt it it is an oil quality issue...
Did you re-ring it when it was open? If so how many miles?
My guess the oil is getting burnt...hense the smoke...
One more thought...
Look at the oil pan gasket, cps o-ring closely...maybe spray some cleaner (brake clean is fine I think) to make it dry and clean...drive it a few miles...look for drips!!

 

I did not re-ring it and have been kicking myself ever since. I did clean the rings and pistons extensively to make sure they were free in their grooves.

143k total. Only 1000 miles since the rebuild.

 

Since the rings were cleaned, I'm guessing they will need to "re-seat" themselves..... They might not be as tight as new ones, but assuming there is still tension, and they need to conform the position walls in their new, though similar, positions....
I'd give it more time...watch the oil level, and hope for the best...as long as it seems to run OK, and starts OK, compression must be "good enough", and it might take a bit of time...

 

Did you de glaze the cylinders or just stick the pistons back in? Sometimes removing the ring of carbon at the top of the bore will increase consumption depending on the wear in the bore at TDC. I would suggest running the car hard to try and re seat the rings. Lots of throttle, mid rpm, higher gears, uphill as long as possible. You don't have to rev it high, you want to make it work. Hopefully you didn't break any rings when you re installed the pistons.

 

I did not deglaze it as it the cylinder walls seemed to have good cross hatch still. I have pretty consistent 150-155 psi on the compression test - while it is not great, I think it would be lower with broken ring(s).

I will run it harder to help with the break-in. I have not been running it hard. Anyone see value in putting in "break-in" oil compared to the usual synthetic? I am not sure what is even in "break in" oil, but saw it for sale online.

 

While that is high consumption, when I used High Detergent oil in my MCS it consumed about 1/2 qt per 1,500 miles. Stopped using that type of oil and consumption stopped, so maybe it's a combination of factors combined causing this.

 

Unfortunately, I think this is the answer.
I hate to say it but: "penny smart & pound foolish". When doing a job of this magnitude (valve job, new crank, bearings etc, etc) not doing the rings is a kick in the nuts.

Fortunately it's not a catastrophic mistake (like not indexing the oil squirters), and it's one that can be managed with weekly fill-up checks.


EDIT:

ZOINKS! I just read the consumption rate!!!

 

Don't bother with "break in oil" while good for new engines [higher ZDDP content] the single weight usually SAE30 may cause some starting issues with cold weather. It wouldn't hurt to use a 5w 30 conventional oil while you try to reseat the rings. If it doesn't improve things you will be out just that much less money by using cheaper oil and if it is still burning it at the present rate it will be pretty much self changing
I took off across the country in a loaded Dodge van that used a quart per tank. The consumption decreased the further west it went and by Colorado it was down to almost nothing. Gas mileage seemed to rise too. So drive your car and make it work, you've got nothing to lose.

 

Correct me if I'm wrong, but in these engines, the rings are seated in less than 20 minutes of the engine running.

There's nothing he can do at this point (assuming the consumption is blow-by) short of tearing the engine down and resurfacing & re-ringing it.

 

are you sure your not routing oil into the gas line and making a two stroke mini cooper?


all joking aside, that's a lot of oil to be burning, that you would definently see coming out the tail pipe. did you make sure your ring gaps where 180deg apart from each other? cause I think youd still have higher compression if the ring slots where on top of each other

 

On a freshly honed bore with new rings they will seat quickly. On used bores the microscopic sharp edges left by the hone have been worn so mating will take longer and require higher pressures to seat. As said before nothing is to be lost by trying.

 

It is not that smoky. Wish I was 100% sure it was burning it and not leaking somehow/somewhere. I did orient the ring grooves 180-degrees apart. 1000 miles is 15-30 hours of driving. I think they would have seated by now if they were going to...

But, anyway, it looks like I need to prepare for my penance for my ill-conceived attempt to save some bucks on rings.

I've had the oil pan off with the engine in the car and think there was sufficient access to reach the connecting rod bolts. Any thoughts on simply removing the head and oil pan, and removing the pistons from the top rather than complete engine removal? I will hone the block and re-ring the pistons..

 

if the pan is already off, I wouldn't see why you wouldn't be able to pull the pistons from the top, granted ive never pulled pistons out of a mini.


theoretically if you can access the rods from underneath and the head can come off without pulling the motor, you should be able to pull pistons. I hope this solves your issue! I see why you didn't replace the rings, shouldn't have needed to since everything was in working order

 

Spent some time troubleshooting last night - decided to try a dry/wet compression test. Results were a little surprising. Still getting compression values around 150-160 psi, but they barely increase when I add a little oil to the piston and do it "wet". These aren't great compression values, but are well within the acceptable range. Hard to believe there is a ring problem.

BUT, I think I received a good clue out of the shadows. I let the car idle in the driveway to get it warm before doing the compression test then moved it into the garage. When I popped the hood, in the weird garage lighting, A curl of smoke rose from the exhaust manifold. My feeble mind starting thinking exhaust leaks, but then I realized that perhaps the valve cover gasket is oozing when hot and it is burning off on the exhaust manifold so it leaves no drips. I am guessing that it has to be above the exhaust manifold - if the head gasket was oozing, I think it would ooze down the block and not burn off on the exhaust manifold - I will investigate this more thoroughly tonight....

 

How did your head gasket theory turn out ?

 

I pulled the valve cover and found the valve cover gasket (not head gasket) was split in the rear, right over the exhaust manifold - either bad luck or perhaps that is where it gets hottest. It was a Fel-Pro, so now I am concerned about their intake and exhaust gaskets, too. Installed a new MINI valve cover gasket and driving it to see if the oil level stays up - will update when I know...

 

Sadly, 250 miles since I replaced the valve cover gasket and I'm a quart low again. Guess I have to go back to the drawing board - rings, valves, valve stem seals, etc.

This was my first time doing a wet/dry compression test and I saw little difference. How much faith should I have in that as an indication the rings are ok and to focus more on the head/valves?

 

You need to do a cylinder leak down test to determine where to turn next.

 

Leak down test (was the first post) is 3-7% across the various cylinders. Compression is in the 150-155 psi range and barely increases when I add a little oil to make it "wet".

 

At that rate of consumption with no visible signs of leaks it has to be burning it up. How does the engine run, any misfiring or hard starting ?

Maybe check the spark plugs look for oil deposits from leaky valve guides/worn rings.

 

Spark plugs have a dry gray residue to being very slightly oily. It's been starting easy and running without misfires.

I do have the nice exhaust burble on deceleration with a borla exhaust, but I think that is a feature and not a symptom.

I am resigned to pulling the head and changing rings and valve seals. Unless it is really obvious that it is one or the other. Parts are not expensive, and I'm doing the work myself, so will just do both. I will be really dejected if it turns out not to be one or the other....

Giving myself a little pat on the back for choosing head studs and not bolts on the last-go around. Paid for themselves now...