Recently on a trip I had a breakdown. On inspection the center electode on the 4 center plugs (six cylinders) were broken off. this car a BMW 635csi uses Bosch silver plugs. Other than the missing center electrode the plugs are in great condition. It appears that the valves are busted up (no compression).
My question has anyone heard of this happening and if so on several plus at once and what caused this?
bmw 635csi uses Bosch silver plugs
Is the porcelain insulator broken?? If not, the plugs are clearly defective…If the porcelain is broken, foreign material has been ingested into the engine, destroying it…
There is more to this story…
Two possibilities. One is that someone has cranked too much advance into the ignition timing. This will eat up an engine top end pretty quickly once a car is out on the highway. So think back to any servicing, tune-up, etc. and whodunit.
The other is coolant entering the cylinders (head gasket, etc.). Hot anti-freeze being burned under compression will eat up valves and plugs very quickly.
In addition to the timing being advanced too far, I believe that this could also have resulted from using gas with too low an octane, coupled with “hard” driving. This combination will result in “detonation” that can be truly destructive.
As far as I recall, this engine calls for 91 octane gas. Have you (and other drivers of the car) used gas of that octane consistently?
Have you (or other drivers of the car) been in the habit of doing “pedal to the metal” acceleration?
Timing belt or chain failure
Is the Bosch silver plug the OEM replacement plug?
While timing chain (or belt) failure was the first thing that came to my mind, I’ve also heard of aftermarket “gimmick” plugs that penetrated the cylinder too deeply being hit by pistons and the electrodes breaking off.
The electrodes are just gone. There are neat holes in the insulator.
Insulator is in perfect condition except for the holes where the electodes were.
The plugs are OEM.
The car is equiped with a Motronic system. There are neat little holes in the insulator where the electodes were. I have been using the same octane gas for 25 years. The car has 277 000 miles on it.
Engine turns over but no compression in the four center cylinders. Which I suspect is due to the valves meeting the detached electrodes.
The car has a Motronic system, advnce is controled by a ECU. There are neat little hole where the electodes were. The ground electodes are perfect. The valves have been damaged for there is no compression in the four center cylinders… I suspect that the valves met the detached electodes. I won’t be able to evaluate the damage until the head is taken off. Hopefully it is only a couple of bent valves.