My own salutary lesson but not meant to panic you, just take your time and be careful.
When I bought my Zetec engined 4/4 from Allon White, it was "fully serviced" and MOT'd before I took delivery.
It came with a very comprehensive service history so one bored evening, I decided to read through it all in detail.
I discovered that about 3 years before I took delivery the garage that serviced it (not Allon White) reported that they could not get numbers 1 & 2 plugs out but as it was fitted with platinum plugs they would not need changing anyway.
The owner therefore decided to leave them in and only had the other 2 checked which were fine.
When I discovered that, I went straight into the garage to use my superior skills to entice the plugs to free themselves.
Tried everything above and more. Left penetrating fluid for several days etc but still they wouldn't budge.
At this point I decided to stop because I knew that if I persevered I stood a real chance of stripping the thread.
I therefore notified Allon White and asked them to change the plugs for me and informed them about the service history note which they had missed and I asked them if they had taken the plugs out when they serviced the car.
They said that because of the type of plug fitted, they did not need changing so they had not removed them.
After a short and amicable discussion they agreed that if I got the car back to them, they would remove the plugs, check them and replace if necessary.
Guess what, the plugs were absolutely stuck and they ended up stripping the threads on numbers 1 & 2 cylinders.
However, the car was still under warranty and without question AW arranged for the head to be repaired with the correct thread insert (Similar to Helicoil but specific for spark plugs threads).
Ultimately great service from AW but IMHO they should have checked them before I took delivery and what would have happened if I had not discovered the problem until the next service was due when the car would have been out of warranty.
2 lessons.
1. Ask the dealer if they have removed the plugs when the car is serviced.
2. When you buy a secondhand car with an Aluminium head, check the service history thoroughly.
I was very lucky as it's an expensive job to put thread inserts in a cylinder head.
