Jump to content

Engine Refresh for a 2006 Mini R56 Cooper N12B16, done as a do-it-yourself project.


Recommended Posts

I purchased my Mini Cooper at the end of 2022 after it failed its MOT, as I said in my opening post.

The vehicle has served me well and I have really enjoyed using it. Additionally, I have performed a significant amount of regular and preventive maintenance on it, including tasks such as brake repairs, repainting the front subframe, addressing different oil leaks, replacing the front wheel bearings, and installing a new thermostat. The vehicle is in excellent overall condition considering its age. It has always shown reliability and has facilitated several memorable journeys, such as the one to climb Scafell Pike.

The vehicle's mileage now stands at 149,000 kilometres, and it has successfully passed its MOT inspection for another year without encountering any problems. Nevertheless, it has consistently shown a somewhat irregular idle and sometimes stalls during idle, posing an exasperating and vexing issue. Incidentally, it seems to use a quite little quantity of oil, definitely insufficient for me to see it as a concern. Regardless, I brought it to a skilled someone last year (who was excellent) and he thoroughly examined it, identifying a couple issues (a cracked PCV valve and a non-standard PCV pipe) which I promptly rectified. Although this did provide some improvement, the primary problem still persists. In addition, he saw a significant quantity of leaking from the camshaft oil seals, accompanied by a substantial amount of blow-by. Consequently, he recommended that a complete engine overhaul would be the most effective course of action. In January 2022, the automobile coincidentally had a new timing chain installed. Mike verified that the timing was accurate and found it to be precise.

Therefore, I have made the decision to myself do the engine refresh and proceeded to disassemble it using conventional methods:



I reached my maximum progress, but then concluded that I had to detach the front end due to the insufficient room for removing the exhaust manifold, among other components.Mike I attempted to rock the engine back in order to create more space, but I found this task to be rather challenging, so I reluctantly decided to go with it.



The disassembly process proceeded successfully, albeit it was time-consuming. The task of removing the inlet manifold is challenging due to the presence of two inconvenient 10mm bolts located beneath. Moreover, extracting the object might be somewhat challenging due to the presence of several connections, clips, and other components. After some time, I successfully removed both manifolds, drained the coolant, and managed to remove the thermostat, although it was somewhat challenging. Now I can proceed to work on the cylinder head. It is pleasing to see the absence of any indications of oil leakage from either the vacuum pump or the oil filter housing, both of which had their seals changed last year.




Armed with my inexpensive £24 timing tool set from Ebay (apologies to Mike! :)) I was pleasantly astonished to find that it was a flawless match, even down to the bottom locking pin. I verified the timing (which remained accurate) and briefly inspected the cylinder head. From my inexpert perspective, it seems to be in excellent condition, without any visible damage or marks, and possessing a pleasing coloration.


Presented are the current camshaft sprockets, with uncertainty on their condition (since it is unknown whether they were replaced simultaneously with the timing chain in January 2022). I would appreciate hearing other perspectives on this matter:



I successfully removed the remaining timing device and various additional components, except for the fuel rail which posed some difficulty due to the obscured bolts. However, I ultimately managed to detach the head.


My intention is to extract the pistons and install new rings while also honing the bores, using one of Mike's refurbishment methods. However, I am open to receiving any feedback about the condition of the pistons (do they seem notably deteriorated?). Are there any glaring problems? Or is this level of wear and tear typical for a vehicle with 150,000 miles?Colon

Here is the cylinder head. It seems dirty, but this may be expected given the mileage.


I illuminated the exhaust ports with a light in order to see the valve stems. They appeared to be quite dirty, and at least four of them exhibited noticeable indications of oil leakage from the cylinder head down the valve stem. Consequently, I will definitely be replacing the valve stem oil seals. (Attempted to get an image of this, but, it lacked enough clarity). The intake valves seemed pristine, exhibiting a flawless condition.

Having removed the head, I will now proceed with the process of disassembling and reassembling. Presented below is the existing strategy, open to receiving any recommendations:

    Place your head on the bench
    Disassemble the exhaust camshaft assembly
    Perform maintenance by cleaning and repositioning the exhaust valves, as well as replacing the valve stem oil seals.
    Examine the camshaft oil seal journals (the areas where the rectangular rings are placed) for signs of deterioration. Please provide photographic evidence of any findings.
    Consider addressing the inlet side, which poses a greater challenge owing to the presence of the Variable Valve Timing (VVT) mechanism. According to Haynes, dismantling this component is strictly forbidden.

Thank you for reading. I appreciate any comments and hope that someone may find this information valuable as well.



Link to comment
Share on other sites

Haynes lacks knowledge in this area. However, I am well-versed in this task and can assure you that no specialised tools are required. Simply utilise a flat screwdriver with a slot cut into it to push the spring fingers away from the upright followers. This will allow them to rest against the camshaft. This method eliminates the need for the expensive £300 BMW tool designed for the springs. Once the springs are removed from the uprights, proceed to undo the two 8mm bolts from the posts. Levering the thick plates out will aid in removing the centre bolts from the posts as well. Repeat this process for all components, except for the first one which cannot be removed. It must remain in place while lifting the camshaft and all posts off as a single unit. To reassemble, repeat the aforementioned steps. Best of luck!

Link to comment
Share on other sites

I recall that you provided me with verbal instructions during our last encounter, but I appreciate having the information presented in paper form. I recalled and familiarised myself with the screwdriver tool technique.

What is your opinion about the condition of the camshaft sprockets? Do they seem worn to you? Do you believe it is necessary to replace them routinely as part of the refresh?


Link to comment
Share on other sites

Simply replace the worn-out components, since continuing to use them will simply accelerate the wear on the new chain. Additionally, there is a high likelihood of experiencing vanos failure if you choose not to replace the components. I refuse to install partial kits on any vehicle.

Link to comment
Share on other sites

Thank you,SlayNeo . I made some progress on the cylinder head this evening. The work went well overall, but I did encounter a little accident, as seen below. Initially, it is preferable to begin with a well-organized and uncluttered workspace, ensuring that refreshments are easily accessible:


I removed the exhaust camshaft and examined the journals for any signs of wear (please forgive me if my terminology is incorrect):


While the location of the rectangle on the journal is visible, there is no noticeable groove worn on the journal. Even if I run my finger over the slight discoloration, it does not catch. It is only slightly textured. I believe the camshaft and journal are in excellent condition, and I anticipate no difficulties in installing the replacement rings. However, should I consider polishing them?

After removing two valves, a calamity occurred when I imprudently released my valve spring compressor, causing the collets to be propelled across the garage. I successfully retrieved one portion, however the other portion remains missing. Despite conducting a meticulous search in the vicinity, where I mistakenly identified every dead woodlouse as a valve collet, I ultimately abandoned my efforts and acknowledged my failure. Nevertheless, considering the whole context, the situation is not too severe, as it seems I can get a replacement collet set for around £5.

From this valve, it is evident that there is a little leakage of oil along the stem seal.





My subsequent action involves extracting the remaining exhaust valves, purifying the cylinder head, and refining the valves by including new stem seals. However, it seems that I must first disassemble and refine the intake side before reassembling the exhaust side, since there are accessibility concerns. I am open to receiving guidance on this matter.

Aside from the mistake, everything is progressing well.


To summarise, this is our current position.


Link to comment
Share on other sites

It is necessary to polish the end caps in order to minimise the likelihood of wear. Additionally, it is essential to install new rectangular rings that meet the newest specifications.



The component numbers provided are only for BMW vehicles.


Previously, I used a drill together with a Dremel pad for the purpose of polishing. This process typically takes a few minutes to complete.

Link to comment
Share on other sites

I continued with the disassembly process this evening, successfully removing the remaining exhaust valves. Afterward, I used a makeshift tool to detach the VVT springs, which was not very refined but got the job done.


This functioned well, except for the finger positioned on the far left when seen from the front of the automobile. Consequently, I used Mike's method, as previously explained, and retained this last finger in its original position. I cautiously removed the camshaft by unscrewing it and made an effort to raise the whole assembly. However, it slightly shifted out of position while the last finger was still exerting pressure on the rockers, if that is really the correct phrase. However, this issue might be alleviated by rotating the camshaft in such a manner that the lobes are oriented in the opposite direction from the "rockers". Overall, a simple task.

Next, I detached the 4 spring assemblies by unscrewing the 3 8mm bolts for each assembly, and placed them aside. However, I did not proceed to remove the intake valves, although I do not anticipate encountering any difficulties in doing so. As of tonight, here is our current status:


Incidentally, I have some positive news to share. The misplaced collet that I believed had been forcefully propelled across the garage yesterday has unexpectedly been discovered within the spark plug hole labelled as number one. This discovery has provided me with a sense of relief.

Upon inspection of the eccentric shaft, its design is intriguing, featuring 4 sets of lobes, where the lobes within each set are not perfectly identical....resulting in a situation where, depending on the shaft's position, one valve in each pair opens to a greater extent than the other, until the shaft completes a full rotation (presumably when the engine is under maximum load), at which point both valves open completely. Intelligent content.

I have ordered valve grinding paste and Scotchbrite pads to do the task of lapping in and cleaning the valves. This will be my next course of action.  Is the replacement of valve stem seals a separate task within the scope of MPD, or are they included as part of a comprehensive kit?

I appreciate your help so far.



Link to comment
Share on other sites

In order to address the issue with the spring, it is necessary to create a more pronounced indentation in the screwdriver. Additionally, while reassembling, it is important to carefully position the upright follower in its original location before placing the camshaft assembly on top of it.

Link to comment
Share on other sites

Please sign in to comment

You will be able to leave a comment after signing in

Sign In Now
  • Create New...