BMW 525i -- June 26th, 2005

Time to disassemble the head! Once disassembled, it can be cleaned, skimmed, and the broken studs replaced.

The head is securely clamped into an adjustable workbench.

The oil spray bar, rubber rocker shaft caps, and rocker/cam keeper have been removed. See that big rubber hammer? I always keep a big hammer handy because big hammers are good.

Twelve plastic cups, one per valve, are taped to a table. These will be used to keep track of the rockers, valves, valve springs, keepers, and other bits. Never mix them up! They must go back exactly where they came from, or rapid wear will occur.

Here's another view of the head. The #1 exhaust rocker clip has been removed and put in its corresponding cup.

Removing the camshaft and rocker shafts is a bit of a trick. The problem is that no matter where you rotate the camshaft, there are always at least three valves open. This puts pressure on the camshaft and rocker shafts, which makes them impossible to remove unless the pressure is relieved.

There are two generally accepted ways to relieve the valve spring pressure and disassemble the head.

The first method is to use the so-called "Iron Maiden" head tool. It looks like this:

I found the preceding pictures at Apparently, the special tool costs $1400USD direct from BMW, and it's manufactured strictly on demand by one guy somewhere in Germany. Bleh.

The second method, advocated by the Haynes 5-Series BMW manual, is to use screwdrivers to pry the rockers away from the camshaft, thus liberating it and allowing it to be removed. This requires several people manning the screwdrivers, or creative use of rope or strong wire to hold the screwdrivers.

Here's what I did, and what you can do if you have to do the same thing:

1. Align the timing marks on the head and the cam pulley.

2. Pop off all the rocker clips, and stick them in their corresponding cups.

3. Stick screwdrivers in the rockers to show which ones need to be levered.

It looks something like this:

If you actually try this, you'll immediately discover that the screwdrivers have to be specially modified, i.e., bent, so that they'll lever the rocker without colliding with the head. If you bend a screwdriver that's small enough to fit in the rocker, you'll find that the pressure of the valve spring is sufficient to bend it back, thus causing it to collide with the head and re-extend the valve spring back to where it started.

In other words, that's not gonna work.

As it turns out, it's possible to disassemble the head without levering anything against the valve spring tension. In fact, it's almost stupidly easy. It goes something like this:

4. Loosen all the valve clearance adjusters, and turn them all to maximum clearance. Tighten them slightly so they stay there.

5. Slide the loose intake rockers along the rocker shaft so they're as far from their corresponding valves as possible. You'll have to slide the exhaust rockers as well. One intake rocker is pushing a valve and can't be moved.

6. Rotate the camshaft just enough to free the intake rocker that's pushing a valve. Slide the rocker away from the valve. Rotate the camshaft until the timing marks are aligned.

7. Now the intake rocker shaft is free. Push it out. Once you've done so, the head will look like this. I've left three intake rockers sitting in place, so you can see what three intake rockers left in place look like:

Be sure to put all the rockers in their corresponding cups. Here's a close-up of the head and three loose rockers:

Now the rest is easy.

8. Slide the free exhaust rockers so they're as far from their corresponding valves as possible. Two rockers will still be pushing valves.

9. Rotate the camshaft until the two rockers are free.

10. Press out the exhaust rocker shaft, and put all the rockers in their corresponding cups.

11. Remove the two bolts that secure the cam seal, remove it, and carefully extract the camshaft. Support it so you don't scratch the cam journals!

If you're unlucky, you'll discover something like this:

That, my friends, is a nasty, evil crack! It runs, quite irreparably, through the cam journal. In fact, it runs through four cam journals. The head is suitable only as a doorstop -- which is precisely what I intend to use it for. Now it's off to eBay, and various and sundry used parts sources to get quotes on a replacement head.