Glow plug cross threaded

Been having some cold starting issues lately so bought a new set of glow plugs for the 300tdi. I removed the first three no problem but the fourth (nearest bulk head) was very very tight, eventually it came out which is when I realised the reason it was so tight it was because the previous installer had cross threaded it going in !!

The one at the back is a bit of a funny angle and access isn't as easy as the others, so I guess they fudged the last one. Needless to say I couldn't get the new plug in, I have however managed to get the old one back in but here's the problem..

It won't go all the way in, theres about 3-4mm of thread still showing, the car started OK, so basically is it alright to leave like this? Or should I tap the thread and get it in properly, also can you tap the thread with the head on?

hi m8 tbh i had the same problem but i managed to put the new one in with some thread left .it was tight going in so i just left it and its been fine ever since i wouldent worry about it.it will be fine.

If the threads are fooked on both it would be obviously better if you tapped it out maybe a helicoil. But to do it properly is head off jut incase of swarf dropping in. Having said that I did manage to tap a spark plug hole In another vehicle about a year ago by dipping the tap in copper Grease so all the bits stick in the Tap. I then with the piston at tdc stuck straight length of copper brake pipe down the hole attatched to the end of a blowgun And a few squirts shot the rest of the **** out, its still going today...I'd atleast put the new plug in so it's a tighter fit... If you decide not to do it right. Hope it helps

Cheers thanks for the help. I was bothered it might effect the compression with it not fitted right, seems to run OK but still had trouble starting this morning, although of course the faulty plug could be the knackered one I put back in!

Really needs the threads repairing, pity your not a bit closer as this is the type of job I do on a daily basis as you will get a carbon build up further up the glowplug which could make future removal very difficult if it has not screwed all the way in.