DerkBarrington

A few weeks ago the CTT suddenly started making a high pitch popping noise which I figured was caused by the failure of the AOS rubber membrane. Sure enough when I checked the membrane it was torn but this was not the cause of my problem. When the noise persisted after the new part was installed I discovered the plug in cylinder #4 (back LHS) was just sitting loose in its bore. The sound I was hearing was the cylinder pressure being pushed passed the plug and coil. I suspect the previous owner cross threaded the plug and it failed over time.

I'm debating how to fix this ... should I install a Time-Sert? How difficult is it to remove the cylinder head with the engine in place or does the engine need to come out?

I'm not looking forward to this repair ... I just finished installing a new timing chains on the wife's Touareg VR6 and now this...

Any advise is greatly appreciated. Thanks!

VulcanGrey

That apparently happened to a 2006 CTT that I test drove before buying my 2004 CTT. The owner said at first the dealer told him he needed a new engine, and then they apparently fixed it for ~$1k... Probably a thread insert, installed in situ.

It could have been that they tried to torque or remove the spark plug while the engine was hot, the aluminum threads are much more likely to strip when hot.

curtsr

I hear about this often with Hondas (my Fit blew one) but not P-Cars. Timesert time.

19psi

Was it sitting loose within the threads or did it back all the way out?
Inserts are easy to install, the hard part is not getting shavings in the cylinder when you tap for the insert. Even with a ton of grease on the tap, there's still a chance of shavings dropping down.

DerkBarrington

I have to get it in the garage with a bore scope to determine the extent of the damage. It looks like it backed out since the plug threads are undamaged but the new plug just spins and will not tighten ...

My plan is to first determine if the plug was repaired in the past with a helicoil etc., if not I will purchase the appropriate Time-Sert kit. I'm concerned about the filings and am wary of using grease since grease laden filings may fall into the head making it difficult to get them out with compressed air. I think I will use wd-40 on the tap and then take my time getting the filings out using a compressed air and shop vac. I'll use the bore scope to confirm I get all the fillings out.

ScootCherHienie

Presumably the metal on the plug is high-temp/high strength steel. Steel is harder than aluminum. It should not be surprising that the threads on the plug are still in-tact. And it does not mean the plug "backed out". The threads were likely damaged previously and the plug blew out the damaged threads, then bounced around inside the hole getting rattled one way and another by high pressure air (and maybe fuel) blowing out the hole past the plug.

PigsInSpace

FYI. You can not remove the head with the engine in the car. In the workshop manual when taking off the cylinder head it says:
Step 1. remove engine from the car.

DerkBarrington

I figured you couldn't remove the head without dropping the engine and the plug took the aluminum threads with it. I think a time-sert kit is in my future.

J'sWorld

Yes you CAN remove the head with the engine in and I recommend rolling right past the time sert to a Big Sert.