E60: Engine Rebuild 4 - Replacing Pistons, the easiest way.

EDITED August 2015:

** I never completed this job as I ended up replacing the entire engine, but did get pretty involved in it and thought I'd somewhat finish the guide anyway. **

If you're only replacing one or two pistons then the engine does not need to come out and the crank can stay on, but this is still a hardcore task. Still, I was determined to replace two of mine this way until a crack in the timing-case and other issues made me swap the engine, which was a lot more work and cost. Pistons are about £250 each new, but with 2nd-hand ones and new rings you could probably replace two for about £300, including gaskets and fluids. 

The biggest problem with accessing the bottom-end of the E60 engine is that the sump is an all-cast-alloy design that sits very snugly into the power-steering rack and front subframe. It also bolts completely to the gearbox bell-housing at one end. You will need an engine-crane to lift and support the engine an inch, then a bit of guts to unbolt and lower the subframe with the engine hanging precariously above you, so if this is beyond what you think you can do then it's time to bung the car over to someone with ramps, as you cannot get the sump off without doing it.

This thread on Bimmer-Forums [http://www.bimmerforums.co.uk/forum/f15/2003-e60-530d-whats-secret-getting-sump-off-please-t109192/] puts the process of trying to get the sump off without all the effort, then realising it is essential, quite succinctly and was a huge help for me.

You will need:

• Ramps
• Engine crane
• 1 or 2 Trolley jacks
• 1 or 2 spare Axle stands

You will need to remove:

• Cylinder head etc. [See this post].
• Engine under-trays and metal reinforcer-plate.
• Prop-shaft at gearbox end.
• Exhaust from back of turbo.
• Turbo hosing.
• Engine-mount top nuts.
• Front anti roll-bar centre-mounts.

Basic Process:

• Suspend the engine so the front is raised about one inch.
• Remove all the screws holding the sump to the block and the gearbox-housing.
• Unbolt the front subframe, the one the engine mounts sit on. The rear two bolts may not need fully removing.
• Have someone pry down the subframe and work the sump out from the rear of the engine.
• Bolt the sub-frame back up.
• Lower the engine back onto the mounts.
• Remove the bottom-end guard.
• Remove the big-end from the affected piston.
• Use a wooden drift to knock the piston(s) out of the top of the block.
• Fit the new piston(s) and repeat the process to refit the sump.

** As I say, I did not complete this job. I lifted the engine and lowered the subframe a bit, but could not get the sump out first try. A second try never came before I decided to engine swap, though I'm sure it would have come out. Refer to the thread linked above for far better instruction. **

E60: Engine Rebuild 2 - Mashed up piston re-grind - ghetto style...

Bits of swirl-flap doing the skinhead moon stomp inside your cylinder is not good. It batters the top of the combustion-chamber in the head and the piston-crown good style, though in most cases won't score the cylinder-wall bad enough to need honing or re-lining. I went and swapped in a re-con cylinder-head as mine needed too much work, but the piston was a bit more of a head-wreck.

Firstly it's quite difficult to find spurious or 2nd-hand single pistons. There are plenty of other pistons on eBay, so I guess it's just waiting for an M57N to come up, otherwise it's over to BMW themselves who will charge about £250 for the part. It doesn't just double the cost of the job, but doubles the work too - the plastic and metal under-trays need to come off, along with cross-members and engine-mounts, the gearbox needs supporting, then the sump comes off and the big-end shells, finally the piston is knocked out of the top of the block with a hammer and block of wood.

I was working on gravel and moving the car onto ramps was out of the question, so in the end I went cowboy style and reground the damaged piston-crown while it was still in the block. Using a die-grinder I leant into the cylinder and remove as much of the sharp metal protrusions as possible, getting it pretty flat for the most part, but the worst bits are at least rounded into small bumps, rather than spikes that could break off and do more damage. I can't imagine combustion is as good as before, but as long as it compresses then I doubt any difference will be noticeable.

PIston 4, second from bottom, took a few valve strikes, worse on the exhaust side and needed a little bit of grinding left and right. At the top of the piston in the pic it seems a few bits of swirl flap did some damage, however the lower side is totally clear. I seriously doubt any performance will be lost on this cylinder.

Piston 6 took the brunt of the swirl-flap and was entirely covered in sharp peaks. The top and bottom faces came flat again with a few hours spent grinding, but the left and right really needed some work. About 5 hours spent in total leaning right into the engine and holding a steady hand and still its like the surface of the moon, but better than all that work to remove the piston and all 6 cylinders appear to firing great after 50 miles.

E60: Engine Rebuild 1

This was complicated, but a totally realistic DIY job if you have the time. It is a lot easier than it has to be by 3 factors:

1. No need to remove the front-bumper, radiator, aux. belt and pulleys as chain is not replaced.
2. No need to fully retime as lower tensioner keeps chain on lower cog even though upper-cog is removed, pump chain is separate.
3. Obtaining a 17mm allen-key type socket to undo a front-plug and access the chain-tensioner. This is actually the only 'special tool' you need.

Hand-ground pistons and block get a final clean before new gasket is put on.

Recon head from a twin-turbo X6 diesel mates up with new Febi head-bolts and crazy torquing sequence.

Once the front plug (where the allen-key is sticking out under the belt) is removed with a 17mm male-hex (allen-key type) socket, the tensioner can be accessed. A 10mm nut below the tensioner is released to free oil-pressure, then the plunger can be pushed all the way back and a pin inserted to hold it in place - the 3mm allen-key in the picture worked for me. The oil-pressure nut is retightened after the chain is back on and the tensioner released.

Unable to turn the engine, camshafts had to be positioned by eye based on photos of before the chain was removed.

Nice dollop of fresh oil on the rockers / guides / bearings and caps.

Rocker-cover is the most involved part of the job as all the injectors / fuel pipes plumb into it.

E60: Engine Autopsy Verdict.

Well, contrary to my earlier verdict of no damage to the head, a bit of informed explanation reveals the corroded surfaces in cyl. 6 are in fact battered metal from the where bits of my swirl flap were bouncing around inside it. Not good!

After having my photos pored over by the engine diagnosis experts on BMW Land, the best version of events of that fateful Tuesday are below:

1. Swirl flap no. 4 breaks up and bits enter cyl. 4.

2. Inlet valves jamming open on cyl. 4 cause a backfire and blasts the loose remains of the swirl flap into the intake plenum.

3. The turbo forces the swirl flap remains along the plenum, with bits ending up in cyl. 5 and the majority entering cyl. 6.

4. Cylinders 4 and 5 continue to fire with slight lack of compression.

5. Trapped debris in cyl. 6 begins to ricochet around, causing damage to the alloy piston-crown and the top of the combustion-chamber in the head until the inlet valves cannot close fully and compression is lost entirely.

Worst bits:

• Cylinder-head is finished. Valve-ports on cyl. 4, 5 and 6 need regrinding and fitting with some new valves. The top of the combustion chamber in cyl. 6 needs completely regrinding into shape.

Best bit:

• The engine still turns freely, cyl. 4 and 5 are virtually damage free and do not need replacing.
• Piston 6 compresses in the block still, so no damage to piston-rings.
• There is no damage or scoring to the cylinder walls.

THE REPAIR [in theory...]

• Repairing the head will cost ~£350, the cheapest Birkenhead-Engines can do and may still need further work, so a replacement is needed. Birkenhead-Engines say they have one such in stock, removed from another E60 530d, though what year they are unsure. It is not re-con and they say I can take my chances for a mere £200, but at least they know the valves etc. all work so it looks like this is the way to go.
• As long as I remove any tiny debris from cyls. 4 and 5, I am happy that they are working 99% as well as they should and do not need any repair.
• Cyl. 6 is battered and, although it is compressing in the block, the jagged metal crown will mess up proper combustion even if it fires ok. Worse, bits of the jagged alloy will probably break off during combustion and ping around the cylinder some more, potentially messing up the valves again so really the piston needs replacing.
• Not only is finding a single replacement piston very difficult, the job to replace it requires removal of the sump and big-end shell. This, with all the under-trays and cross-members is a colossal task in itself and, with the car parked on loose gravel, it's looking like a no-go.
• The short-cut solution to piston-6 looks like it's going to be a jenky regrind with the piston still in the engine. I will turn the crank by hand so that piston-6 is in its topmost position and get in there with a die-grinder, removing all the proud bits of metal and re-shaping the 'swirl-pot' and piston-crown as well can be. This ultimate bodge could be the end of a relatively unscathed engine. It could also be the only way to get the E60 back on the road quickly and with a minimum of fuss... Fingers crossed.

COST:

• Replacement cylinder-head: £225. [Birkenhead Engines]
• New head-gasket: £85.55. [Euro Car Parts]
• New head-bolts: £37.48. [eBay: dusty789blue]
• Swirl-Flap Blanking Plates: £20.99. [eBay: myldanautodesignltd]
• New thermostat: £33.99. [I broke the housing - Ebay: carpartssaver]
• Oil: £85.98. [Halfords, own-brand BMW Fully Syn. 5w30]
• Coolant: £22.99. [Halfords, Comma G48]

TOTAL: £511.98.