e91 N53 325i - lack of compression on Cylinder 6
Discussion
So, need a bit of help diagnosing an issue with a car I recently purchased.
In effect, I did the usual, bought it on eBay, late at night, after a few glasses of wine. Naturally, I did this unseen, knowing full well that the car had a fairly obvious misfire and was using a bit of oil. Previous owner apparently couldn’t be bothered to fix it, so bought something else and plonked this on eBay. Being that N53’s are renown for their issues with coil packs, spark plugs & injectors, I took a punt on it. BMW had carried out a “quality enhancement” in 2011 and replaced all the injectors with Index 9, along with new coil packs & NGK spark plugs. Being that anything prior to Index 11 is generally useless, I simply assumed they had failed again. What’s the worst that could happen … well …
Cold start it starts instantly, runs ok for 5 seconds or so, then starts to jump about (really bad), with EML lights appearing & misfires on cylinders 5 & 6. After running for a couple of minutes, it struggles to start again, starter spins for quite a while.
Initial fault finding so far has resulted in:
Cyl 1: Unknown brand coil pack, NGK spark plug – smells of fuel.
Cyl 2: Delphi coil pack, NGK spark plug – smells of, & appears damp with fuel.
Cyl 3: Unknown brand coil pack, NGK spark plug – no fuel smell.
Cyl 4: Bosch coil pack, NGK spark plug – no fuel smell.
Cyl 5: Unknown brand coil pack, NGK spark plug – no fuel smell.
Cyl 6: Unknown brand coil pack, NGK spark plug – smell of fuel, very wet tip.
I cleaned all the plugs, re-inserted, then restarted the car, Cyl6 was instantly wet with fuel, all others were fine.
Then swopped the coil packs around, misfire stayed with Cyl5/6. Did the same with the spark plugs, misfire stayed on 5/6.
If I pull the oil cap, the idle stays the same, i.e. doesn’t get any/even worse.
Cylinders 6,5,4,3,2,1:
Untitled by Sir_Dave, on Flickr
Cyl6 Spark Plug:
Untitled by Sir_Dave, on Flickr
After buying a new 12mm adaptor, I then did a compression test (tested cold, all other plugs left in):
Cyl 1: Compression at 120
Cyl 2: Compression at 130.
Cyl 3: Compression at 130.
Cyl 4: Compression at 130.
Cyl 5: Compression at 110.
Cyl 6: Compression at 0.
At this point, after swearing a little, having read that a completely failed DI injection can occasionally cause compression pressure to bleed away giving a false reading, I bought a new Index 11 injector & de-coupler. Having removed the old one, I was faced this this, appears covered in white gunk?
Cyl6 Injector:
Untitled by Sir_Dave, on Flickr
New injector fitted and coded with INPA, re-started, still misfires. New compression test, this time done without any plugs in, all 155-165, barring cylinder 6 at 0.
Cylinder 5 sounded like this:
https://www.youtube.com/watch?v=lI8h4GN2vKg
Cylinder 6 sounded like this:
https://www.youtube.com/watch?v=iR76uSY3Og8
When up to temperature, there is a decent amount of white smoke, this appears to have quite a nice smell to it. The previous owner said that since the misfire had started, it had started to burn a lot of oil
Now, ive had a head gasket go on an e46 M3 between cylinders 5&6 a few years back, but from memory, it wasn’t at zero (just 5/6 comps were lower than all the others) and being that that’s a closed deck block, there was no coolant usage etc as the break was between the cylinders. The last time I saw zero compression was on my R53 Mini I after a bit of a valve broke off and prior to that failing completely, it also smoked blue like a chimney on cold start. The 325i has no blue smoke, which in my mind, would be the normal indicator of valve and/or piston ring issues?
Just need a bit of advice really, I don’t really have the time, or inclination to take the head off myself, so am trying to self-diagnose prior to either sticking it back on eBay, or taking it to a specialist.
Thanks in advance.
In effect, I did the usual, bought it on eBay, late at night, after a few glasses of wine. Naturally, I did this unseen, knowing full well that the car had a fairly obvious misfire and was using a bit of oil. Previous owner apparently couldn’t be bothered to fix it, so bought something else and plonked this on eBay. Being that N53’s are renown for their issues with coil packs, spark plugs & injectors, I took a punt on it. BMW had carried out a “quality enhancement” in 2011 and replaced all the injectors with Index 9, along with new coil packs & NGK spark plugs. Being that anything prior to Index 11 is generally useless, I simply assumed they had failed again. What’s the worst that could happen … well …
Cold start it starts instantly, runs ok for 5 seconds or so, then starts to jump about (really bad), with EML lights appearing & misfires on cylinders 5 & 6. After running for a couple of minutes, it struggles to start again, starter spins for quite a while.
Initial fault finding so far has resulted in:
Cyl 1: Unknown brand coil pack, NGK spark plug – smells of fuel.
Cyl 2: Delphi coil pack, NGK spark plug – smells of, & appears damp with fuel.
Cyl 3: Unknown brand coil pack, NGK spark plug – no fuel smell.
Cyl 4: Bosch coil pack, NGK spark plug – no fuel smell.
Cyl 5: Unknown brand coil pack, NGK spark plug – no fuel smell.
Cyl 6: Unknown brand coil pack, NGK spark plug – smell of fuel, very wet tip.
I cleaned all the plugs, re-inserted, then restarted the car, Cyl6 was instantly wet with fuel, all others were fine.
Then swopped the coil packs around, misfire stayed with Cyl5/6. Did the same with the spark plugs, misfire stayed on 5/6.
If I pull the oil cap, the idle stays the same, i.e. doesn’t get any/even worse.
Cylinders 6,5,4,3,2,1:
Untitled by Sir_Dave, on Flickr
Cyl6 Spark Plug:
Untitled by Sir_Dave, on Flickr
After buying a new 12mm adaptor, I then did a compression test (tested cold, all other plugs left in):
Cyl 1: Compression at 120
Cyl 2: Compression at 130.
Cyl 3: Compression at 130.
Cyl 4: Compression at 130.
Cyl 5: Compression at 110.
Cyl 6: Compression at 0.
At this point, after swearing a little, having read that a completely failed DI injection can occasionally cause compression pressure to bleed away giving a false reading, I bought a new Index 11 injector & de-coupler. Having removed the old one, I was faced this this, appears covered in white gunk?
Cyl6 Injector:
Untitled by Sir_Dave, on FlickrNew injector fitted and coded with INPA, re-started, still misfires. New compression test, this time done without any plugs in, all 155-165, barring cylinder 6 at 0.
Cylinder 5 sounded like this:
https://www.youtube.com/watch?v=lI8h4GN2vKg
Cylinder 6 sounded like this:
https://www.youtube.com/watch?v=iR76uSY3Og8
When up to temperature, there is a decent amount of white smoke, this appears to have quite a nice smell to it. The previous owner said that since the misfire had started, it had started to burn a lot of oil
Now, ive had a head gasket go on an e46 M3 between cylinders 5&6 a few years back, but from memory, it wasn’t at zero (just 5/6 comps were lower than all the others) and being that that’s a closed deck block, there was no coolant usage etc as the break was between the cylinders. The last time I saw zero compression was on my R53 Mini I after a bit of a valve broke off and prior to that failing completely, it also smoked blue like a chimney on cold start. The 325i has no blue smoke, which in my mind, would be the normal indicator of valve and/or piston ring issues?
Just need a bit of advice really, I don’t really have the time, or inclination to take the head off myself, so am trying to self-diagnose prior to either sticking it back on eBay, or taking it to a specialist.
Thanks in advance.
Interesting one.
Looks like the injector staining is coolant? HGF causing the injector to fail due to coolant contamination? Or other way round - a failed injector on 6 dumping too much fuel and causing the HG to pop. Strange that it's at zero comp though! That's more of a valve problem I'd have thought. Still, being an n53 index 9 it could have been leaking for ages and in the meantime the valve fails. One pot two faults.
Looks like the injector staining is coolant? HGF causing the injector to fail due to coolant contamination? Or other way round - a failed injector on 6 dumping too much fuel and causing the HG to pop. Strange that it's at zero comp though! That's more of a valve problem I'd have thought. Still, being an n53 index 9 it could have been leaking for ages and in the meantime the valve fails. One pot two faults.
Could be bore wash on No.6 resulting in chronic ring wear. Either way, it's shagged.
Get rid. Plenty of heroes! I'd fire it through Copart tbh, better than Ebay for moving stuff like this.
To fix that will cost a bloody fortune.You *could* get the head removed and see what's occurred but I've seen enough of these with bore/ring problems. It would be worth firing some engine oil down the plug hole, spinning it on the starter before another compression test. If it perks up a bit, could be rings. If it doesn't it could be a valve burnt out or the side of the piston blown away. I have somewhere a piston from an N53 E60 523i as a paperweight - an injector went bananas, washed the bore clean and tried to seize and one side ofd the piston has melted, leaving the rings intact, sort of. Utter s
te.
Get rid. Plenty of heroes! I'd fire it through Copart tbh, better than Ebay for moving stuff like this.
To fix that will cost a bloody fortune.You *could* get the head removed and see what's occurred but I've seen enough of these with bore/ring problems. It would be worth firing some engine oil down the plug hole, spinning it on the starter before another compression test. If it perks up a bit, could be rings. If it doesn't it could be a valve burnt out or the side of the piston blown away. I have somewhere a piston from an N53 E60 523i as a paperweight - an injector went bananas, washed the bore clean and tried to seize and one side ofd the piston has melted, leaving the rings intact, sort of. Utter s
te. So after a bit more tinkering, i ruled out HG failure (bought a tester), rings seemed ok (wet compression test), then stuck an endoscope down the spark plug hole and the top of the piston looked ok. At which point, i was leaning towards valves, most likely inlet, due to the excess white smoke out the exhaust (probably unburnt fuel), but before i take off the head, it made sense to get a second opinion...
So today i had a leakdown test done at BMS Surrey; they confirmed that the inlet valve on Cyl6 is stuck open slightly. Realistically, its quite difficult to tell whether the cause is bending/sticking as you can only see so much with a borescope, but he said that whilst the area around the valve looks a bit damaged, the top of the piston & cylinder walls seem to look ok.
To speed up getting it back on the road, i've just bought a used cylinder head complete with cams/valves etc, so the idea is to simply swop them over, then strip the old head & sell the unused parts.Currently trying to decide whether i can bothered to do it all myself, on the drive, in the cold & wet, or just pay them 12 hours labour to do it ...
So today i had a leakdown test done at BMS Surrey; they confirmed that the inlet valve on Cyl6 is stuck open slightly. Realistically, its quite difficult to tell whether the cause is bending/sticking as you can only see so much with a borescope, but he said that whilst the area around the valve looks a bit damaged, the top of the piston & cylinder walls seem to look ok.
To speed up getting it back on the road, i've just bought a used cylinder head complete with cams/valves etc, so the idea is to simply swop them over, then strip the old head & sell the unused parts.Currently trying to decide whether i can bothered to do it all myself, on the drive, in the cold & wet, or just pay them 12 hours labour to do it ...
bmwmike said:
Could the inlet valve be held open with carbon? Seems unlikely to me but who knows.
Btw if your boroscope is small enough you can see the back of inlet 6 via the hole for the inlet manifold MAP sensor..
I think you mihght have mentioned this on one of the other forums actually - i did pull off the MAP sensor and put the endoscope in there, but well, the inlet is full of black gunk so i couldnt get far enough to see anything (lense kept getting dirty)!! Super amounts carbon buildup me thinks, which in turn made me think about how gunked up the inlet valves must be and whether that would be enough alone to hold them open ...Btw if your boroscope is small enough you can see the back of inlet 6 via the hole for the inlet manifold MAP sensor..
Unfortunately, if they are being held open by carbon, the head will still have to come off as everything needs to be closed for walnut blasting
Bit of an update on this, just in case anyone else suffers similar and contemplates setting fire to their 325i 
In the end, whilst the garage had quoted a very reasonable £1200 in labour/parts, that, plus the cost of the 2nd hand head at £500, seemed rather a lot to stomach. Being that i like a bit of a challenge/something to tinker with, i thought, "if its broken already, i cant make it anymore broken" and decided to have a go at doing it myself.
Weekend of the 30th/31st April, i made a start to the 325i's strip down ...
Starting point
Untitled by Sir_Dave, on Flickr
Inlet manifold removed
Untitled by Sir_Dave, on Flickr
Valve cover removed
Untitled by Sir_Dave, on Flickr
Organised chaos
Untitled by Sir_Dave, on Flickr
Well hello there broken valve spring:
Untitled by Sir_Dave, on Flickr
Turned the car over by hand a few times and by peering through the inlet opening, it appeared that the valve was still moving within its guide, but only to a certain point - meaning that the valve was still open say 5mm or so. Upon looking at the valve spring with the valve cover off, it appeared that i had a broken spring; naturally this would stop the valve closing all way as its not being pulled all the way back out of the cylinder head. Its VERY difficult to see as its rather close to the bulkhead, but i decided to order the N53 timing tools and have a proper look before even considering pulling the head off.
Then 2 weeks ago.
Valve cover back off, timing tool fitted:
Untitled by Sir_Dave, on Flickr
Timing chain tensioner removed, vanos hubs removed from cams, top half over inlet cam cover removed:
Untitled by Sir_Dave, on Flickr
Both cams & their ledges removed:
Untitled by Sir_Dave, on Flickr
Untitled by Sir_Dave, on Flickr
Hydraulic lifter removed & valve spring on cyl6 inlet side is confirmed as the issue:
Untitled by Sir_Dave, on Flickr
At this point, i realised that my recently purchased ebay cheapo overhead valve spring compressor wouldnt fit. FFS.
Then last weekend.
Testing my new Laser overhead spring compressor tool on the spare cylinder head i bought for "practice":
Untitled by Sir_Dave, on Flickr
Then doing it on the cylinder head proper:
Untitled by Sir_Dave, on Flickr
In order to stop the valve dropping down into the cylinder, i held it very lightly with some padded plyers held together with masking tape. Whilst the compressor tool is fine for one-handed use, removing the valve spring keepers was definately a job that required two hands!!
One very broken valve spring:
Untitled by Sir_Dave, on Flickr
All replaced and now i have a valve that seats correctly:
Untitled by Sir_Dave, on Flickr
New rocker cover gasket & rocker cover back on again:
Untitled by Sir_Dave, on Flickr
Nearly there:
Untitled by Sir_Dave, on Flickr
Then time to get the jump leads out, crack upon a beer to calm my nerves and start it...
Success!!
https://www.youtube.com/watch?v=_B0IWLZUggQ
https://www.youtube.com/watch?v=9FbnsnD_Ymw
Being that there isnt much info out there for the N53, i used the following N54 guide for the tear down, barring the turbos, it would seem they are very similar in terms of process: https://www.e90post.com/forums/showthread.php?t=10...
The N53 specific tools purchased were as follows:
12mm spark plug socket
Gunson 12mm adapter kit
Laser 5153 Chain Tensioner Tool
N53 Timing Tool
Laser 5258 Valve Spring Compressor
I also needed to purchase a Teng 3892ag 5-25nm 3/8" Torque Wrench for lower torque nuts/bolts as my Halfords one only went down to 30nm.
Repair parts:
Low Pressure Fuel Sensor (13537614317)
Elring Rocker Cover Gasket (11127544368)
N53 Valve Spring (11347563459)
2 x N53 Camshaft Bolts (11367524954)
All in all, very happy!!
In the end, whilst the garage had quoted a very reasonable £1200 in labour/parts, that, plus the cost of the 2nd hand head at £500, seemed rather a lot to stomach. Being that i like a bit of a challenge/something to tinker with, i thought, "if its broken already, i cant make it anymore broken" and decided to have a go at doing it myself.
Weekend of the 30th/31st April, i made a start to the 325i's strip down ...
Starting point
Untitled by Sir_Dave, on Flickr
Inlet manifold removed
Untitled by Sir_Dave, on Flickr
Valve cover removed
Untitled by Sir_Dave, on Flickr
Organised chaos
Untitled by Sir_Dave, on Flickr
Well hello there broken valve spring:
Untitled by Sir_Dave, on Flickr
Turned the car over by hand a few times and by peering through the inlet opening, it appeared that the valve was still moving within its guide, but only to a certain point - meaning that the valve was still open say 5mm or so. Upon looking at the valve spring with the valve cover off, it appeared that i had a broken spring; naturally this would stop the valve closing all way as its not being pulled all the way back out of the cylinder head. Its VERY difficult to see as its rather close to the bulkhead, but i decided to order the N53 timing tools and have a proper look before even considering pulling the head off.
Then 2 weeks ago.
Valve cover back off, timing tool fitted:
Untitled by Sir_Dave, on Flickr
Timing chain tensioner removed, vanos hubs removed from cams, top half over inlet cam cover removed:
Untitled by Sir_Dave, on Flickr
Both cams & their ledges removed:
Untitled by Sir_Dave, on Flickr
Untitled by Sir_Dave, on Flickr
Hydraulic lifter removed & valve spring on cyl6 inlet side is confirmed as the issue:
Untitled by Sir_Dave, on Flickr
At this point, i realised that my recently purchased ebay cheapo overhead valve spring compressor wouldnt fit. FFS.
Then last weekend.
Testing my new Laser overhead spring compressor tool on the spare cylinder head i bought for "practice":
Untitled by Sir_Dave, on Flickr
Then doing it on the cylinder head proper:
Untitled by Sir_Dave, on Flickr
In order to stop the valve dropping down into the cylinder, i held it very lightly with some padded plyers held together with masking tape. Whilst the compressor tool is fine for one-handed use, removing the valve spring keepers was definately a job that required two hands!!
One very broken valve spring:
Untitled by Sir_Dave, on Flickr
All replaced and now i have a valve that seats correctly:
Untitled by Sir_Dave, on Flickr
New rocker cover gasket & rocker cover back on again:
Untitled by Sir_Dave, on Flickr
Nearly there:
Untitled by Sir_Dave, on Flickr
Then time to get the jump leads out, crack upon a beer to calm my nerves and start it...
Success!!
https://www.youtube.com/watch?v=_B0IWLZUggQ
https://www.youtube.com/watch?v=9FbnsnD_Ymw
Being that there isnt much info out there for the N53, i used the following N54 guide for the tear down, barring the turbos, it would seem they are very similar in terms of process: https://www.e90post.com/forums/showthread.php?t=10...
The N53 specific tools purchased were as follows:
12mm spark plug socket
Gunson 12mm adapter kit
Laser 5153 Chain Tensioner Tool
N53 Timing Tool
Laser 5258 Valve Spring Compressor
I also needed to purchase a Teng 3892ag 5-25nm 3/8" Torque Wrench for lower torque nuts/bolts as my Halfords one only went down to 30nm.
Repair parts:
Low Pressure Fuel Sensor (13537614317)
Elring Rocker Cover Gasket (11127544368)
N53 Valve Spring (11347563459)
2 x N53 Camshaft Bolts (11367524954)
All in all, very happy!!
helix402 said:
Top job! Always good to get feedback on rare problems.
Thanks! Having spent ages researching the issue when i first bought the car, i did find that quite often people dont come back with the actual solution to their problems, which is a tad infuriating
bmwmike said:
Fair play to you!!
Those inlet valves look fairly clean too.
Hope no dirt fell into those open injector connectors... what index are they out of interest?
Edit index 9 & 11 as stated above
Wonder why the valve broke, just one of those things ?
Yeah, the valve on 6 was super clean, although i assume that was because, for once, the fuel was cleaning it off nicely! The rest of them were a bit gunked up, but not so bad that i thought "OMG i must clean this" though. If i keep it and put on a 3 stage manifold i will give them a once over with the toothbrush however. Those inlet valves look fairly clean too.
Hope no dirt fell into those open injector connectors... what index are they out of interest?
Edit index 9 & 11 as stated above
Wonder why the valve broke, just one of those things ?
Re: the valve, i guess it must have just been bad luck/manufacturing defect etc, a money shift would have killed a few more things i would imagine
Injector wise, all open "things" were covered with masking tape to stop things falling in, injectors/injector rail/inlets etc. I also put the rocker cover back on after working on it, just to make sure no little critters decided to make their way into the engine somehow to make a little house lol
Touring442 said:
Top work! I used to feed a ball of string down the plug hole and turn the engine so the piston would compress it against the valve and hold it shut.
A nice cheap fix and we like those.
Yes, all about a good bodge/ingenious feat of engineering when it comes to these things ... I did read about the string trick funnily enough! It seems that if you go back a few years/trawl youtube enough, there are all sorts of ingenius ways to get by. The modern advice just seemed to be "take the head off", which, even with no labour charges, still would have cost considerably more money than the fancy Laser tool and masking tape modified pliers A nice cheap fix and we like those.
Sir_Dave said:
Yes, all about a good bodge/ingenious feat of engineering when it comes to these things ... I did read about the string trick funnily enough! It seems that if you go back a few years/trawl youtube enough, there are all sorts of ingenius ways to get by. The modern advice just seemed to be "take the head off", which, even with no labour charges, still would have cost considerably more money than the fancy Laser tool and masking tape modified pliers
Yes, it's great to read the solution for a change - thanks for posting it. 
And good to read that you didn't need to take the head off!
Funnily enough I watched an episode of Wheeler Dealers earlier this week and Ed connected an airline via the spark plug hole and blew air into the cylinder to keep the valves closed - but then we don't all have a workshop like Ed.
Gassing Station | BMW General | Top of Page | What's New | My Stuff