I am in the process of changing spark plugs and wires, and for some reason I am having a problem installing a spark plug on cylinder#6. I doubt that it is a cross tread problem because i am only trying to start threading it by hand, but could not even start threading it. It just wont bite, plus it is quite hard to see and align. any ideas would be appreciated.

thx

What do the threads look like on the plug that came out of the #6 hole?

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Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.

Hopefully you're using a dab of anti-seize paste on the spark plug threads. One idea is to use a short section of rubber hose to grip the spark plug, yet avoid any tendency to cross-thread. If the hole is already cross-threaded you might need to use a tap to clean the threads.

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Fred Hoelzle

There may be a burr at the start of the threaded hole. There are thread "chasers" available that will clean the threads and are typically used when any machine work is performed on the head. A foreign car parts store will have your size. Coat the inner channels on the chaser (it is like a tap) with a heavy grease like wheel bearing grease to catch any small metal chips and prevent them from dropping into the cylinder.

Tim

Make sure you are using Bosch plugs. They have (always did in the past) a special coating on the plugs to prevent galling when installed in aluminum heads. Shouldn't need anti-seize on that basis. Also, if using anti-seize, must cut back on the torque or can strip the head threads.

DO NOT use champion plugs.

Thread chasers are cool and helpful.

thank you all for your inputs.

I had looked at all the plugs that I had removed, and do not see any particular one with messed-up threads. And yes, I use Bosch plugs per spec.

The thread chaser sounds like what I need to get. Any suggestions where I might find this tool?

Thanks again. I will update the forum soon...

The best advice from my experiance!!! Just use a clean thread chaser! Unfortunatly, it may or may not help depending on the condition of the threads. I had a similar problem with one of the spark plug ports in my 560 and it wouldn't take the plug. Now in my case I had to remove the heads for other reasons, however, the machineist ran a thread chaser through and siad it was okay. Before I re-installed the head I used a sparkplug just to make sure all the threads were clean before installation. The spark plug port would not take the spark plug. What ultimatly fixed it was running a tap from the inside out. The first thread on the outside has become flattend somehow.

You should be able to fix this without removing the heads. As I said, I had them off anyway, so I was able to use a sure-fire fix.

Good Luck!