Spark plug change (tips and pics)

[Jazz_89]

Alright everyone, time for spark plug replacement on the 535i E34 (first time for me). I am not an expert, but a few tips and the pictures might be helpful.
Here are the tools you need:

The sockets are 21mm. Only use the correct spark plugs for the engine (Bosch W8LCR in this case). The garden hose is a good tool for this job Required time: 2-4 hours depending on experience.


I heard that you should work only when the engine has completely cooled down and that you should not use anti-seize on the plugs, so I followed this advice.
The gap should be between 0.7mm and 0.8mm for these particular spark plugs, but it depends on the model I guess. Mine are Bosch W8LCR. It is probably a good idea to widen the gap a little bit, but I am not an expert on this. There is an extra tool for this job, but mine were approx. 0.7mm to 0.75mm wide so I did not change anything.

Start by removing the air filter cover and then the air filter box itself ( sorry that it looks so rusty and dusty ):


Unplug the HT-Leads one at a time. Try to pull them out from the base, as close to the engine block as possible. Make sure that the key is NOT in the ignition.
Here is the spark plug on cylinder #1:


Add some WD40 and then wait for a while for it to sink in. Carefully try to remove the plug with the spark plug tool (the one with the black handle). If it doesn't work try to tighten it a little bit and then try to loosen it again with small movements. I also had to use the torque wrench to remove a few of the plugs. Be very gentle in order to prevent cross-threading the spark. (actually I have the bad feeling that at cylinder #6 I almost cross-threaded the plug, because I could not tighten it correctly with the torque wrench :/ ). Try to listen for grinding or squealing sounds while you turn it out.
When you remove it compare it with new new for thread size, thread length, and make sure it is the same type. Also check if the washer rings are there. The last thing you want to happen is the piston to slam against the plugs because you used the wrong ones.

Then use a small 1/2" inch garden hose to insert the new spark plug. Like this:

The garden hose will act as an universal joint and make the replacement process easier.

According to the manufacturer and various manuals, these spark plugs should be tightened with 28-30 Nm. After getting them in the head with the garden hose, I turned them with the spark plug tool until they seated and then used the torque wrench, first with 10Nm, then with 20Nm and finally with 30Nm, always looking and hearing for signs of cross threading. Make sure the torque wrench is exactly perpendicular to the plug when you torque it. This is the most critical part IMO. Before moving to the next cylinder reconnect the cable. Do not screw the firing order or you will damage the engine.
Repeat the process for the cylinder #2, #3... until #6. The last three, at the rear of the engine are tricky to remove. Removing the ignition coil from its attachment point, may provide some extra space, but be careful to not touch any high tension cables under any circumstances.

Here is the plug hole for cylinder #6:

This is probably the hardest to install since the space is very limited. The thread appeared to be slightly damaged, since I torqued the plug with 30 Nm but then it kept rotating under slight force...:/


Here are the old plugs. In my opinion they look pretty descent:


Any help on how to diagnose these? (the shining liquid is only WD40 I think) :


Cylinder #1



Cylinder #2



Cylinder #3



Cylinder #4



Cylinder #5



Cylinder #6

[whiskychaser]

FWIW, they also make a special tool for bending the ground electrode. Did you manage to tighten the no. 6 plug fully? I see problems ahead if not

[Jazz_89]

I know, but I did not find this tool, so I installed them anyway, since the gap was ok (slightly more than 0.7mm)
Actually I tightened the #6 carefully with the spark plug tool by hand until it seated. Then I torqued it with 10Nm and it clicked. Then with 20Nm and it clicked again. But at 30Nm it continued to turn about 30-40 degrees and it didn't really clicked. I suspect that the thread on the head was slightly damaged before, since the old spark plug was stubborn coming out. :/ But with the spark plug tool it appears to be very tight.
There were no visible gases escaping the head or unusual noises/vibrations when I started the engine. I even turned off all the lights and checked for flames or sparks-nothing.
On the other hand, with six cylinders, one of them misfiring is tricky to diagnose for a noob I guess

[whiskychaser]

Well, you seem to have got the right replacement plugs and torque figure. Some previous owner probably cross threaded that plug and damaged the thread. Not much you can do without major surgery. Just get it as close to spec as possible without it slipping and keep an eye on it. Old plugs look in very good shape. Based on that I'd say there isn't a lot wrong with the engine

[632 Regal]

It could also be the crush sleeve. When I changed them on the E36 I pretty much freaked out until I felt it actually seat. That's when I realized it needed to turn about 1/2 turn after contacting the seat.

[Jazz_89]

It could also be the crush sleeve. When I changed them on the E36 I pretty much freaked out until I felt it actually seat. That's when I realized it needed to turn about 1/2 turn after contacting the seat.

I hope this is what happened
I will check the plug tension again after a few hundred miles.