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Discussion Starter #1
found a little project 2007 mini cooper s JCW spares repair 60.000 miles on it full service history very nice car, this guy paid a lot of money for it 9 months ago, and one day coming home from work it went bang started smoking really bad and running on 3 cylinders etc, he took car to garage who informed him the turbo had failed and had taken out the engine etc,,,, so after a full day and a proper diagnostics checks found number 4 cylinder had no compression dry test and after a wet test it went up to 40psi so piston issue,,, so striped the car when i removed the turbo checked it found there to be nothing wrong with it,, when removed the cat found it had a handful of black chucks of cat honey comb melted in the pre cat end closest to turbo and also found it had oil burning deposits on all piston and on back of the valves the inlet valves had bad build up of carbon as they do this was part of why it destroyed its number 4 piston where unburnt intermittent firing of the fuel that had washed down between the piston rings etc and when ignites blows them apart also found the timing chain to be stretched two teeth out,, so this engine had no chance really,, so the fix is new pistons and rings new big bearings head gasket and bolts stem seals etc the cause of all this started with inlet valves and carbon holding them off the seats and washed the bore,, also retarded timing over heated valve stem seals and oil blocked the cat and unburnt fuel also added to it and melted the cat,
once ts back together its going to be decat'd and put on rollers see what can be had from it,
 

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Similar happen to me on one of the piston last year when I took the car in for timing chain service and walnut blast :ROFLMAO:, blow out black smoke out of the exhaust.
 

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Similar happen to me on one of the piston last year when I took the car in for timing chain service and walnut blast :ROFLMAO:, blow out black smoke out of the exhaust.
its the mixture of oil burning and petrol and add the timing chain also retarding it turns the cat in to a furnace and melting it, have seen a fair few like it easy way to tell is on compression test do a wet test as well if compression jumps up its piston and if dont then it valve issue as a rule, i'll stick a set of pistons in and put scotch brite pads on my hone tool as the stones are to rough on the bores, i got all the valves out so these will be cleaned and polished and new stem seals little tip for anyone when installing stem seals just add a tiny bit of well seal on the part they clip to on the head and then use socket and hammer and tap them home, have seen them leak oil past if dont from the bases, then rest of the engine is perfect,,
 

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Discussion Starter #4
little update today finished stripping it found the rest of piston oil control rings were cracked so has been drinking oil as last owner said,, also cut the cat apart and taken some pics of how melted and blocked it was,, all 4 pistons have signs of being washed with petrol down the sides common when inlet valves get gummed up also the blocked cat was the finishing blow ie back pressure and heat etc surprise it even ran to be honest,, word of warning to all out there who there car uses a lot of oil and smokes and has not had a timing chain replaced ie this car was 58.000 miles and to be honest it needed doing around 40k on this to have stood a chance of avoiding this out come...
today i cleaned all valves and head lapped all valves in all ready for new parts when they arrive, i also scotchbrite pads on hone tool on bores and all 4 look like new , also turned pistons 90 degrees to check if oral bores as a guide all near perfect so with be a really good engine when done, no wear on crankshaft fitting new big ends bearings and new conrod bolts as stretch type will add red locktight to threads,,
 

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Discussion Starter #6
Is that CAT from the downpipe or further down to the back exhaust?
thats the down pipe one i cut the top around the weld so can re-weld back up along the factory weld so by time welded back wont be able to tell its decat now, only thing i would say to anyone with a oil burner with some miles on it and having head off anyway its worth the extra £55 for ring set, £35 for bigends £15 from bmw conrod bolts use red thread lock on them as well i found all the oil control rings to be cracked, i feel this was from retarded running due to chain 2 teeth out the oil blocked the cat cause a furnace effect rings could not cope with extra heat the oil rings are no more that 1.2mm thick each one there are two as such but install as one ring if that makes sense,, also the bores were glazed from oil burning so i use scotchbrite pads cable tied to the arms of the hone tool this is just enough to remove the glaze and dont hurt the low friction bores , i have used the stone hone tool once before on the bores and never got a good result it used oil like hell after,, this is why i always se seafoam engine flush on my stuff it stops carbon build up on the rings as carbon build up also hurts the rings,
 

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Thanks mike1967.

I'll also probasbly need a new sports cat downpipe for mine.

Does de-catting the downpipe not fail MOT unless the tester can fiddle with the test?
 

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Discussion Starter #8
its is mot fail for sure, but if car is mapped correctly where on fast idle the fuelling is leaned it will reduce the output from exhaust hence why its a must have mapped out bit must keep the 02 sensors running as part of the test is lamda readings, so by keeping the stock filter case its possible to set it up so it dont stand out if that makes sense. also where car gets mot's makes a difference ie if use big garages or companys then they love failing stuff for the slightest reasons, if do have it mapped out talk with mapping company about who they use mot wise etc,, or fit a sports cat thats got smaller honeycombe thats does have a effect of altering the CO and co2 levels,, but if mapped for pops and bangs then decat is only way as the pops and bangs will blow the cat apart
 

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Discussion Starter #9
added bit is when mapped we lean the engine out on fast idle running and also map a difference in to pre and post 02 sensors readings ie fouls ecu to thinking a filter is there still etc so when mot'd the screen asks for 2200revs at this pint the ecu is set to lean out the readings, it does lose a bit of low down power by doing it but makes the top end more of a surprise when done right
 
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