BMW E31, E32 AND E38 V8 SPARKPLUG REMOVAL
MISFIRE REPAIRS (M60-M62)

This procedure shows how to remove the sparkplugs on the V8s and clear the oil from around the sparkplugs and HT stub leads. Most of the V8s suffer from this at some time or other and the symptoms are very similar to Nikasil wear in that the car rocks at tick-over. There often is a pronounced lack of power that can be intermittent, getting worse in damp conditions. It differs from Nikasil wear in that the power loss is evident at all revs whereas Nikasil has a pronounced lack of power at low revs and is less significant at higher revs. This fault and a split PCV valve (aka bellows) are quite simple faults to fix on the V8 and you can often pick up a rocking V8 for next to nothing because it is perceived as Nikasil wear.


Oil down the sparkplug holes on V8's is quite common, just a small leak from the rocker cover bolts or gaskets and the oil has no-where to go except for around the plugs. Although oil is an insulator, it damages the stub HT leads eventually causing the rubber to disintegrate and allowing the spark to travel through the rubber and straight to the head. Before the complete failure of the rubber it becomes loose on the sparkplug and sparks can travel down the side of the insulator. With the high compression ratio (10:1) on the V8 the spark likes to go anywhere except across the electrodes of the plug!

The oil tends to accumulate on the rear pair of cylinders initially due to the backwards cant of the engine but after a while they will all get filled up and certain gasket failures will fill up odd plugs rather than travel all the way to the rear cylinders.

Repair can be as simple as clearing the oil from the apertures and fitting 'O' rings to the stub HT leads that have been damaged. Where the stub HT leads are disintegrating they can be replaced as separate items from BMW for around 5 per coil, there is no need to replace the whole assembly.

These instructions include sparkplug removal.

First of all, you need these tools; all except the 10mm socket and wrench are available in the normal E32 toolkit........



Start by removing the top and side covers. The 10mm nuts are covered by little plastic covers, which can be levered out. After a while, these get quite brittle and the clasps may snap off so lever them carefully. Replacements can be bought from BMW if you break them.



Remove the soundproofing from the top of the manifold....



Start with the drivers side bank........This is what is under the side covers.......four HT coils each held in place by two 10mm nuts with captive washers.....



A clip holds on the connector on each coil. Get your fingers behind the clip and pull it towards you as shown. As long as the clip is fully forward, the connector should lift away from the coil. Leave the connector sitting on top of the coil.....





Undo the two nuts on the coil and put them somewhere safe, you do not want them falling down the sparkplug holes later on!
Pull the coil upwards.... they should come off with a 'pop', if they don't the rubber is probably failing.....



Here is a picture of the head after the coil is removed showing evidence of oil. There is not much here; most of it had ended up on the back plug whereas the other three are dry..



Remove all the coils (work on one bank at a time to reduce the possibility of something disappearing down the bores). Make sure that you indelibly mark the coils with the cylinder number; they should go back to the cylinder they came from. Here's a picture of the coil stub HT lead that is furthest back....Yep....covered in oil!.......



Before the plugs can be removed, you need to clear the oil from the plug(s). To do this remove the insert from the plug spanner.....



Wrap a single layer of cloth around the spanner and stuff the spanner over the plug. Keep lifting the spanner and moving the cloth to a new dry bit and stuff it back in again until most of the oil is removed.....



Stick the spanner back over the plug without the cloth and ensure the spanner does not look like this!.....



You will not get all the oil out but most of it ends up on the sparkplug threads when you remove the plug (at least it won't seize up!) .......



On my car the AC pipe work gets in the way on cylinder 1 and I can only get the plug spanner on when the insert is not fitted to the spanner. So I always start with cyl 1 and then refit the insert for the rest of the plugs......


With all the plugs out you get to work removing all the oil from the cavities. Use the other end of the sparkplug spanner and cloth to get to the bottom of the sparkplug wells. Use your fingers and a cloth for the rest of it......



Clean all the oil you can from the stub HT leads. Give them a good stretch.... if they survive the rubber is probably OK. However, the lead must fit tightly over the plug and the plug should come out with a 'pop'. If the rubber is slightly loose but does not disintegrate then a repair can be made by fitting a couple of 'O' rings on the lead as shown. Ensure it is a tight fit again. If the rubber is beyond repair then they can be obtained separately from BMW.....



Fit four new plugs not forgetting that cylinder 1 needs the insert removed from the plug spanner (at least it does on my car)......When you refit the coils guide the stub HT lead over the plug and place the connector over the socket, as you push the coil down push the connector on at the same time, this reduces the strain put on the wiring......



Make sure each clip is fully home on the connector. Do not over tighten the nuts on the coils; the studs are in an aluminium casting. If a stud does pull out, coat the stud with Loctite 270 and screw it further in than usual, allowing just enough thread to fully fit the nut. Loctite 270 cures better with heat and will lock fast when the engine warms up. Note where the earthing strap connects to coil number 2, it must go back in the same place it came off.....


Once all coils and nuts are refitted stuff the plastic cover back on to stop anything falling on the cylinder head. It's a bu$$er to get a nut back out when the coils are re-fitted!......



The passenger bank is the same process except that the spanner fits all the plugs with the insert in place.....but you still need to take it out to get oil out from around the plugs.

When both sides have been done refit the soundproofing over the inlet manifold and carefully align the four studs into the centre cover. DO NOT OVERTIGHTEN the nuts on the centre cover as you will find that the studs will rotate and tear the rubber mounts that bond the two halves of the raised stud assemblies. Refit the plastic covers over the nuts.......

All done, time for a cup of tea (and a Osteopath as bending over the engine will kill your back)........

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