Hi

While changing my plugs recently for the first time i had difficulty unscrewing/tightening one plug.All i can think of is a stripped thread.Has anyone had experience of this and if it is the case how does a loose plug affect performance?Car seems to be running ok apart from the usual hesitation problem(MY99 turbo 4-door).One for Mr.Crooney?

TIA

Pete

 

Is it damaged or not? Only way to answer that is to take it out and check for damage on the spark plug threads...if the plug threads show damage then there will probably be similar damage on the thread in the cylinder head.

Very light damage may be able to be cleaned up with a spark plug thread chaser (try Halfords etc). Otherwise you may be looking at having a helicoil insert fitted, this isn't really a DIY job.

Plugs with a (new - i.e. uncompressed) compression washer should be seated then angle tightened 90 degrees max. It's a good idea to use copper based grease on the threads to stop them seizing.

Paul

 

Thanks for the reply.The funny thing is the thread on the plug is fine-no damage at all.The reason i think it's stripped is that no matter how much i turn the plug it never tightens fully.Is there any other way of telling what the problem is?How much would a slightly loose plug affect the cars performance?

TIA

Pete

 

i wouldn't have thought you would have seen any damage on the spark plug thread as these are steel and the head is aluminium there fore a lot softer. i've only seen one other scoob which was a legacy do this and to get around it you can buy a kit which has a tap you use to retap the threads slightly bigger then you get a top hat shaped insert which you screw on to the spark plugput some threadlock around the outer threads and then screw it in to your newly tapped hole. screw it in tight to compress the washer on the spark plug and job done it cant screw in to the cylinder like a helicoil can and if it sticks to the plug when you change them again just use a new insert i think they are brilliant but i cant remember their name sorry

 

Peter

If the plug never tightens up then it does indeed sound like the thread in the cylinder head has gone. You may get away with it in the short term but long term you should get it fixed. Recommend that you have this done professionally to avoid turning the head into scrap.

Paul

PS I would be interested to know the product name of the system mentioned by Scoobyboy

 

If you retap the hole wont the cuttings go in the cylinder?

 

If it does not tighten, then I would suggest you get it done straight away. It is possible that the small bits of metal that were the threads are already flowing around your engine?

Take it to a garage, get it helicoiled and ask them to check the bores etc for any scoring, full oil and filter change straight away and another one within 4 weeks to be on the safe side?

helicoil would mean removing that cylinder head and would not be done on the vehicle, It would be impossible to get at on the vehicle. Stuff wouldn't "drop" in as cylinder is not vertical, but I wouldn't risk it..

Mike.

[Edited by Mike Tuckwood - 10/23/2001 12:32:08 PM]

 

Thanks for the advice Mike but is there any way i can tell it's stripped without taking the engine out?eg performance,sensors,etc.
If it does need major surgery is there any chance it would be covered by the warranty?

TIA

Pete

 

personally i wouldn't use helicoils because if the plug goes in funny it could wind the coil in to the cylinder as there is nothing to stop it . as for bits going in to the cylinder when retapping put some grease up the gaps in between the cutting thread the loose swarfe then sticks to this. i will try to find out the name of the system as i think it's the best out there.