Hey everyone! I'm not new to rebuilding cars, but I am new to the R53. I owned a 2010 R55 before but I wasn't a fan of the N14. Anyhow, I picked up an 03 MCS with 151k on it last week and its a huge turd. The PO had no maintenance records, but from what Ive seen, it wasn't cared for. Oil leaks from pretty much everywhere and theres noticeably low power. I noticed on the test ride that its really sluggish in the bottom end. I pulled the codes and didn't see anything related and there wasn't a CEL or anything lit up. I pulled the spark plugs and they looked good. My first thought was either the SC BPV or a vacuum leak from somewhere, but both of those seem to be OK. I ran compression check and got the following: CYL1 90 psi CYL2 120 CYL3 118, CYL4 100. Not great, but Ive seen worse. Im guess my next step is to pull the cylinder head and see whats going on in there. 150k seems soon for needing rings. Im thinking the valve stem seals or guides might be the issue, but it doesn't misfire or anything. Im also planning on pulling the oil pan (since its pissing from the gasket anyhow) to see if theres any surprises. Im just looking for any pointers or a sanity check before I tear this thing down. If the cylinders look OK, I'll probably send the head to Way Motor Works for rebuild, fix all the leaks and throw it back together. Anything Im missing here?

 

Since it is so new to you, I'd run it for a week or two, get used to it, find out its little foibles. Maybe a quality filter & oil change, fresh plugs, decent gas, injector cleaner.
Then do the compression test again with the throttle wide open - your numbers are not that bad & I'll bet they'll improve.

 

What brand tester? If its a cheapie lik eharbor freight they are known to run like 40 psi low
If it is really low first thing I would do is pull valve cover and timing cover and verify Cam timing is not off a tooth.

 

BETOOLL 8pcs Petrol Engine Cylinder Compression Tester Kit Automotive Tool Gauge https://a.co/d/5ucJ7Y5

Heres the compression tester I have. It was pretty accurate on my last rock crawler engine, but who knows. The valve cover is coming off this diving to check timing ( and because it’s also leaking).

 

DBC
Before you start dismantling, can you do a leak-down test?
If the valve timing is off, all 4 cylinders will leak; if it's just a gummed-up or burned valve, only that one will leak (we hope).

 

I need to do that. I was trying to avoid buying a leak down tester but I might as well get it over with. I just ordered one from Summit Racing. That would be sweet if it was just a valve.