Hi, im new to here, I have brought a mini that has a misfire, turns out no compression on 2, seemed like a valve problem... so I have stripped the head down and the valves had a lot of carbon build up, would this likely be the cause, I was told it used a lot of oli too which I know I normal for a mini, it would tick over fine, just not full power and if left on tick over for 10 mins then rev it up smoke would come out then clear . I'm thinking they just need a good clean and seals changing, whats your thoughts. Thanks View attachment 281243 View attachment 281244

It could very easily be the coked valves, I have just recently finished my N12 rebuild, the head was also very coked up. I'd rather bring the cylinder head to a machine shop to test it, re seat the valves and change the valve stem seals.

Also check the cylinders for wear, you can usually feel it on the upper part of the cylinder where the piston ring does not travel.

 

A decent machine shop will get that sorted easy and have your head as good as new. As above check the bores for wear.

Those engine take a lot of caring for.

 

I take it this is an N14 or N18 engine. I noticed you haven't removed the intake camshaft. That (and the eccentric shaft and stands) will need to be removed before you go to the machine shop. Remove the bearing bracket too.

For the sake of orientation with the head flipped over for your picture, cylinder 1 is on the right hand side; cylinder 4 is on the far left side. Notice how the cylinder 1 intake valves are much cleaner than the rest. Now look at cylinders 3 & 4; I would suspect the head gasket was leaking and oil was entering the combustion chamber. You also have evidence of a sealing problem between cylinder 2 & 3. That would also explain the oil consumption. Is there any chance you performed a lead-down test before you removed the head?

When you take the head to the machine shop, ask them if the head is warped. I'll bet you lunch it is. The longitudinal straightness limit is .003". The lateral limit is .001"

Make sure you tell the machine shop that the valve seats tend to fall out of these cylinder heads ... especially after machine work. The shop can ping the valve seats to keep them from falling out. There's nothing worse than putting your refurbished head back on the block only to have one of the valve seats drop out shortly after you've reassembled the engine. It's happened to me.

When the shop planes the head, ask them how much they took off. You may have to go with the thicker .120" head gasket. The stock gasket is .090"

Funny, I just posted a head reassembly video last night.

How to reassemble your cylinder head after a visit to the machine shop - North American Motoring

R56 :: Hatch Talk (2007+) - How to reassemble your cylinder head after a visit to the machine shop - Hey folks! I just created a series of how-to videos for reassembling your cylinder head components. My Craigslist special had a hole in the #4 exhaust valve, and the head needed some TLC at the...

www.northamericanmotoring.com

 

I take it this is an N14 or N18 engine. I noticed you haven't removed the intake camshaft. That (and the eccentric shaft and stands) will need to be removed before you go to the machine shop. Remove the bearing bracket too.

For the sake of orientation with the head flipped over for your picture, cylinder 1 is on the right hand side; cylinder 4 is on the far left side. Notice how the cylinder 1 intake valves are much cleaner than the rest. Now look at cylinders 3 & 4; I would suspect the head gasket was leaking and oil was entering the combustion chamber. You also have evidence of a sealing problem between cylinder 2 & 3. That would also explain the oil consumption. Is there any chance you performed a lead-down test before you removed the head?

When you take the head to the machine shop, ask them if the head is warped. I'll bet you lunch it is. The longitudinal straightness limit is .003". The lateral limit is .001"

Make sure you tell the machine shop that the valve seats tend to fall out of these cylinder heads ... especially after machine work. The shop can ping the valve seats to keep them from falling out. There's nothing worse than putting your refurbished head back on the block only to have one of the valve seats drop out shortly after you've reassembled the engine. It's happened to me.

When the shop planes the head, ask them how much they took off. You may have to go with the thicker .120" head gasket. The stock gasket is .090"

Funny, I just posted a head reassembly video last night.

How to reassemble your cylinder head after a visit to the machine shop - North American Motoring

R56 :: Hatch Talk (2007+) - How to reassemble your cylinder head after a visit to the machine shop - Hey folks! I just created a series of how-to videos for reassembling your cylinder head components. My Craigslist special had a hole in the #4 exhaust valve, and the head needed some TLC at the...

www.northamericanmotoring.com

The engine on the pictures provided would be either the N12 or N16, as the N14 does not have the springs for the vavletronic system.

When I did my cylinder head I told the machine shop about the valve seat issue, but I don't think they did anything about it. Make sure you mention this.

I would not remove the eccentric shaft at all, as the manual says the head will be "damaged" in some way when the right bracket screws are released. I released mine before I had the chance to read this, and I assembled it back again with no problems at all. Now that I know this I would not want to risk anything.

Another thing is all the intake rockers (all 16 of them) are numbered from 1 to 5, and you don't want to mix them up.


This engine has it's quirks that you need to be careful with.

 

I ran across the same warning when I had my '07 N12 cylinder head in the shop. The machine shop removed the bearing bracket after I told them about the warning. So, I went to talk to the shop foreman at my local MINI dealer. He said they remove the bearing bracket all the time with no issues. I think the machine shops have to remove the bracket to get the head to clamp in correctly before they plane it.

I posted a how-to for reinstalling it; I had to figure out a way to do it since the book didn't cover it, and the machine shop removed it.

How to reinstall your cylinder head bearing bracket - North American Motoring

How to - How to reinstall your cylinder head bearing bracket - Greetings everyone. They say that necessity is the mother of invention, so here's how I solved my cylinder head problem. The machine shop removed the bearing bracket after I gave them the technical data that says not to remove it...

www.northamericanmotoring.com

You're correct about the N14, but the N18 has the same VANOS spring configuration.

 

No, the non-return check valve is item 14 in the picture below. It's function is to keep the oil in the upper end of the engine from draining back in the block/oil pan thereby ensuring quick lubrication/pressurization of cylinder head components on engine start.

The oil pressure switch on the N12/N14 engines is item 4. You could tap into the oil pressure switch port for pre-lubrication, but (to correct my comment in the video), you will not get oil to the lower end due to the non-return valve.

My recommendation for the N12/N14 would be to follow BMW's instructions (see attachment) for pre-lubrication, essentially, disable fuel and ignition and crank the motor.

 

Thanks for clearing that up 👍👍👍

 

I just thought of something. It is possible to remove the non-return valve and install a plug in the port; then you could tap your pre-luber into the low pressure switch port and flow oil to the upper and lower end of the engine. Just make sure to reinstall the non-return valve when you are finished.

 

What I usually do is just turn the engine over quite a few times by hand, after this start cranking without the coils plugged in, or fuel pump.

I had my oil pressure gauge connected and it did need quite few cranks to get up to pressure.