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Matt
Matt, Mechanical Engineer
Category: BMW
Satisfied Customers: 20611
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have an s reg 520 petrol that I have bought and am

Customer Question

hi, I have an s reg 520 petrol that I have bought and am currently restoring to former glory, I have what seems to be internal oil loss as I have a dry dipstick very noisy engine and there are no patches on my drive. the oil light flashes on now and then but not all the time, I can throw a litre or two of oil in it and it will be dry the next day. if I top up and leave it over ight it seems to struggle starting in the morning and then goes with a puff of smoke.. the cr smells like a two stroke engine so I was just wondering is there anything common where it could be leaking into the bore??
Thanks,
Dave
Submitted: 4 months ago.
Category: BMW
Expert:  Matt replied 4 months ago.

Hello

The first thing I'd check is the crankcase pressure relief valve (PCV) these are sprung loaded and are only meant to 'burp' excess pressure every now and then. The exiting gas is piped back to the inlet, however should the valve stick open then the engine tends to suck the air out of the crankcase all the time and this carries oil over with it.

If you remove the air intake pipe and look inside where the crankcase breather is plumbed in you may find evidence of oil.

If you do find oil replace the valve

. If this is all OK then its possible that the valve stem seals are past their best and are drip-feeding oil into the intake. These can be replaced without removing the head by a competent garage in half a day or so

an engine flush may also help if you've got a sticking oil scraper ring so its worth a go, as for the oil if you go up a grade / use slightly thicker oil then this is less readily drawn into gaps and less likely to be burnt off

Expert:  Matt replied 4 months ago.

Hi

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