Spark plug thread repair

[Iceberg_172]

My number 3 plug decided to blow out the head a while back, i managed to replace it and the threads seemed ok.

Just after that i had the beauty of cambelt failure hit me lol so got the head rebuilt and completely forgot all about number 3 plug or i would have got it seen to then.

Got it all up and running again with new valves, fitted new belts etc but it was misfiring slightly on number 3 cylinder. Decided to pull the plugs out and check them and surprise surprise number would no longer tighten up.

My question is, is it possible to repair the thread with the head still on the engine? Really dont want to take it back off.

 

[steviet]

If you were thinking of helicoiling it, you need to tap a thread for the helicoil to run down, which I cant see being easy to do in situ without getting bits of swarf down the hole.... Thats even if its feasible to use a helicoil for an area under that much stress...

 

[Iceberg_172]

Think any repair needs a thread tapped. Surely and swarfcan be blown out using an air line?

 

[steviet]

True. Id doubt you could guarantee getting all the swarf out though... maybe run the risk of blowing any swarf into the edges of the bore/ up around the back of any open valves etc.... Id speak to one of the specialists on here TBH

 

[Iceberg_172]

Yeah will see what options iv got before i need to take the head off again

Cheers

 

[MicKPM]

If it were me... Head off and use a timesert I'm afraid. I really hate helicoils and there's no way I'd risk doing one in-situ as you cannot guarantee getting all the swarf out before it does some damage.

Mick

 

[ozclio03]

had mine done by a guy called thread doctor, he came to my house, smeared some grease in the hole tapped a hellicoil in and then simply pulled out the grease with a stick or something. looked really dodgy and I thought if this works im selling the car but of course it worked, they dont call him the thread doctor for no reason. and of course i couldnt sell my car because a clio sport the best daily a man could ask for

 

[ozclio03]

oh and its been fine for the last 10k, not bad for $80 AU and he came on Fathers Day even!

 

[Iceberg_172]

Gonna try the "sav a thread" repair kit. I'll make up an attachment for the hoover to get all the swarf out.

 

[Dan519]

Timesert 100%. Helicoil's are very strong, but not the right thing in this case.

put lots of grease on the tap and back it out to wipe the swarf off frequently. then dip a stick with grease on it as mentioned above

Cranking the engine over with the plug removed should blow any stray shards out the plug hole.

 

[Iceberg_172]

Yeah trying to avoid the heli coil by all means as i think it may work itself loose. Hav got access to an airline now aswell so should help

Thanks for replies. Will post how i get on

 

[MicKPM]

The worst thing about Helicoils is they can un-wind which isn't nice when you're simply trying to service a vehicle and the owner didn't know/care to inform you about it. As you can't see them in the spark plug wells its often too late by the time you've noticed so it leaves the servicing mechanic in a difficult situation.

It's the same with sump drain plugs... I had one in last week that had been over tightened and thread locked in so it's no wonder it was leaking badly. It ended up needing an oversized tap and new plug in the end to finish it correctly.

 

[Iceberg_172]

The plugs are pretty new so wont be coming out for a good few thousand miles. Gonna buy the draper kit with the solid black inserts. Atleast theres no tab to snap off and go in the cylinder.

 

[Iceberg_172]

just an update on this

managed to get hold of the bergen/sealey kit (similar to the timesert kit)

great piece of kit and very easy to use, very happy with the repair, minimum amount of swarf entered the combustion chamber because you leave the tap in when cutting the seat so its easilly removed! and hooray my misfire is gone and the car is running very good.

got pictures so will write up a guide for people to use incase it happens to them. I strongly reccomend using the same kit i used though

mot time and get it on the road and mapped in time for summer

so relieved! thanks guys