I am a relative noob with car repairs. I do a lot of repairs on my '97 Chevy K25, but have left my Coopers to the pros. A year ago, I made a terrible mistake. I bought a 2005 MINI Cooper S Convertible (R52) privately, didn't take it to the mechanic right away and drove it for a few months and sure enough it just up and died on me. Towed it to the best shop in town and the verdict was "engine damage" -- to replace with a used engine would be more than I paid for the car. First, what I don't need are replied telling me that I'm an idiot -- of course I am. I also don't need advice telling me that I probably need to get a new engine -- I've already been told that. What I'm after is someone willing to read the details below and give good advice about whether or not this could simply be due to a broken timing chain tensioner. Thanks!

Towed it home and opened it up and found the following:

1) Car clearly had not been maintained well: very low oil level, oil very dirty, coolant very dirty, air filter completely fouled, oil leaks around intake manifold gasket, broken air intake boot, etc.

2) Oil level was very low, but not completely empty. No sign of smoke or overheating before it quit.

3) Timing chain was off the sprocket, but intact, i.e., not broken.

4) Plastic covering on timing chain tensioner was completely missing, although pieces of it were found in the timing chain area.

5) Crankshaft turns easily -- not seized.

The timing chain went back on easily and the crankshaft still turns over. Valves are working. So, I could replace the tensioner and see what happens. My worry is that the timing chain being off the sprocket is a sure sign of damage elsewhere (like to the bearings), but I don't have enough experience to know whether or not those two things always go together.

Any helpful advice (e.g., yes, they always go together) is really appreciated.

Cheers,
Tom

 

I would pull the engine cover off and inspect the chain and sprockets , replace the chain and sprockets. I would think if you skipped a tooth the valve would make contact. Its a chance , but i would pull more stuff apart and inspect.

 

^He already did that^.

I think it's worth trying to throw chain guides at the motor to see if you got lucky: they're cheap. Set the timing correctly, ensure that your tensioner is functioning, replace the guides, reassemble, and turn the motor over. At this point, what's the worst that can happen? I'm afraid that you probably did damage to a valve or two when the chain popped off of the sprocket, but I think it's worth rolling the dice on a guide and tensioner.

Even if your valve train is damaged, it's not the end of the world, you can get them fixed for a reasonable price.

 

Thanks for the feedback, Eric. Will try it this weekend.

Tom

 

Yep, saw that , was just laying out train of thoughts before I cranked it over with the tensioner. Also to double check the chain and guides before the tensioner and cranked over, started. Its a chance , fingers crossed that everything is ok.

 

Thanks for the tip. Chain and upper sprocket seem in good shape, but I will check again when installing the guides.

Cheers,
Tom

 

Got the new tensioner and installed it with the chain lined up. Put everything back together with new gaskets. First time doing this with a MINI, so pretty fun. Turned the key and it started!

When cold, it runs well for about 1 minute, then starts to run rough and eventually stalls. It throws codes P1126 and P1126, and sometimes those two plus P0638 and P1688.

These are throttle body and intake manifold sensor codes, so my first shot was at simply cleaning the sensory wire harness contacts. That didn't change anything, so am now considering removing the throttle body for a good cleaning. Any other suggestions?

Thanks,
Tom

 

Make sure the plug on the throttle body terminal are clean and its clipped in all the way , the plugs on the throttle body are known to be touchy with age on the clip. Also test it with a volt meter to make sure there are no splits on the wire harness.

 

Did you remove the timing cover and confirm the lower timing marks were lined up, did you "pop" the tensioner before closing the engine up?

If you didn't do either of those you may still be out of time, but the throttle body codes may all just lead back to the connection being fouled.

1688 can also be a slipping or broken crank pulley/ after market SC pulley, as well as MAP sensor problems or throttle body.

 

Is there a diagram of the Mini engine anywhere, with exactly where the timing chain, tensioner, etc are all working?

 

The diagram for the Gen 1 MINI timing:

Timing chain:

http://www.realoem.com/bmw/enUS/show...diagId=11_3095


Engine block:

http://www.realoem.com/bmw/enUS/show...diagId=11_3081

Timing Cover on the side of the engine block:

http://www.realoem.com/bmw/enUS/show...diagId=11_3083