Long story short but my Mini is an 02 R53 and she's sitting just shy of 290k miles. I had to replace my timing chain tensioner and did so only to run low on oil and develop a similar ticking noise to a bad tensioner. I removed the head, suspecting a broken timing guide rail and discovered I was right. So figured I would pull my oil pump off and replace the gears and chain and tensioner as well guides. I removed the oil pan since that was also another source of leakage and cleaned it out. Then removed my oil sump and cleaned the bits of guide rail from the screen. Reinstall with new gaskets, new oil pump, new timing kit, tensioner, idler pulley and harmonic balancer. Filled with new oil and the car ran great. I actually think my timing may have been off before. The car was making about 17-18psi after the work whereas before I was only getting 13-14 occasionally 15psi. So I think I had a gear off a tooth.
The car lasted about 3 weeks and one night I drove her hard, high revs quick shifting and didn't notice anything until I got home that the car was knocking again. I left it over night then started it up the next day the knocking there and had some belt squeaking. Which it's never done. I drove it to work then to my shop where I work on it(around the corner from my work). And ran a compression test. Pulled 128/120/131/65 psi. Thought well the bottom end was real tight. I had no coolant in my oil or oil in my coolant whatsoever. There was however an excessive amount of steam on my oil cap which looks milky. After draining fluids I was able to rule out any cross contamination. I have every bolt on including a race cam and flash tune. I removed the head and found multiple cracks in every cylinder all running from the valve seats to the spark plug threads. Some going several threads up. Cylinder 4 was the worst. I had a shop perform a valve seal check and they were all sealing sub par and had some leakage. Though this wouldn't check any leaks from the cracks I had into water jackets. My car blew the core welds on a CSF radiator, it's blown fluid out around the coolant cap a couple of times and broken some 3 way fittings. Overheated 2 or 3 times. I didn't bother to test for warpage at this point it doesn't matter. Head is garbage. I'm going to replace the head and do a compression test with the new head. I believe my knocking was from the unbalanced crank pulley wobbling more than usual from cylinder 4 being down so low. And it was causing strain on my belt tensioner because the damper strut closes to the idler pulley has etched into my oil pump/timing cover.
Some photos. The last one is before I cleaned up the pistons and gasket surface. That's cylinder 4 on the valve angle of the head. Big cracks. I just hope throwing a new head on doesn't put strain on my block. However there is practically no wear on my cylinders. You can't feel the ring wear at all. Not even with your finger nail. That's pretty amazing for nearly 300k miles.
Pulled my trans off. Is it possible this was the OEM clutch. It had been slipping here and there the last couple months I drove the car. Primarily in hot weather. It says luk on everything. Isn't that the OEM brand?
And I was feeling sorry for myself a couple weeks ago for having to tear apart the front end of my R53 to replace the supercharger (worn bearing)....your situation certainly trumps that!
I don't think you'll find many here that can provide advice of what to replace at 290k miles...I feel like my car is a mere babe at 122K....HaHa
I figure every time I expose the water pump, crank sensor, and related items in that area I should replace them...the water pump only had 30k miles on it, but who wants to have to tear everything apart to get to it later?...I went ahead and replaced it along with the supercharger and all related seals. My crank sensor o ring was toast and leaking oil, so replaced that again as well.
I suspect you'll be replacing all the seals that get touched in route to the head, right?
What oil are you using?...and what is your maintenance routine?...I'm impressed with the lack of wear!
Cary, North Carolina
2004 Chili Red R53 with "Just a few mods...."