Re: Drowning plugs?
Plugs get tighter and tighter, in aluminium heads particularly. If it's that tight odds-on they've never been changed, or not for a very long time. If the plug nose is longer than the thickness of the casting where it is threaded, you get a build up of coke on the tip of the plug. This will, over time, spoil the thread in the head. I undo the plug a bit then turn it back, then undo it some more and turn it back, and some more.... about 1/4 turn at a time or even less maybe. This helps a bit. In the case of aluminium heads you have the added problem of electrolytic corrosion between plug and head amking ti tighter still. MOST important to use something like coper grease on the new threads.
NB IMO thread-chasing without head-off is not totally harmless, take care, maybe use a vacuum cleaner to try to collect as much debris as possible.
This problem can get so bad that you risk twisting the plug in two or taking the flats off it. Then it is head off.
Doesn't say that in the manual
Last edited by Wrenched; 14-08-07 at 13:50.
Reason: more info