spark plug thread problem?
 

Hi all:

I was checking, cleaning, regapping my plugs today with no trouble (I mean, how hard is it?) until I tried to re-install and tighten the last plug. Well, it seems that the metal in the head is pulling out when I attempt to install the plug. It's coming out of the head in a shaving like pattern, like a coil. What to do? Is this going to be a big pain in the rear?

David

Chances are that you have a cracked head...The 2.0 engines are notorious for cracks in the chambers, leading to the plug hole. This crack weakens the plug threads and causes this exact situation.

There are several methods of repair for this:

: Heli coil thread repair, works but not my chosce

* ream it oversize, and hope that a sparkplug thread insert will install, without the same problems

* remove the head, have the source repaired, instaed of rying to fix the symptoms.

Alot of rebuilt heads are re welded in this srea, if yours has been, drilling and tapping is a waste of time, as most of the weld material; is super soft, and will not hold threads.

This is the reason that I always have 12,, sparkplug holes installed in the 2.0 heads, it solves these problems.

Jake,

Thanks for the speedy reply. The car is indeed a 2.0, although it's in a 912E.

Would evidence of a cracked head be apparent? I'll go take a look-see, but with all that tin around the motor, it's tough to actually see the head.

The motor was rebuilt only about20k ago, paid for by the PO, so I don't know what was done to the heads. I have the receipts, but I never looked b/c I never had a problem.

I'll go and take a look. What kind of cost is involved to have this done right? Any kind of temporary but safe fix available to me? I drive the car daily, and would like to get it running today if possible.

David

The temp fix is the "heli-coil" or "time cert" fix. Should work for a while.

Was that plug more difficult to remove then the others? If it was then you may have had galling and just stripped the plug theads. If as Jake says, you have a cracked head you will need to procure a replacement head to use while that one is being rebuilt. If the crack goes unrepaired the seat can drop and ruin the motor.

Was that cylinder running lean? Is all the 912E tinware in place? The thermal reactors, air pump still there? If they aren't 20,000 miles is very few miles to expect a new crack.

JP
76 912E a/c sunroof, 16" Fuchs
75 914 2.0L a/c, 5-stars ATS
74 914 1.8L rust-o-ration
72 914 1.7L chop-chop

The car has been converted to dual 40 Webers. The tin is there. It was not more difficult to remove that plug than any of the others, nor more difficult than usual to remove any of them. I was not concerned until I couldn't get it to thread.

Is it possible to buy a pair of re-worked and ported/polished heads? Or, is it to my advantage to have my own heads "done"? This is not an experience I've gone through before. I'm not sure what to expect.

Thanks,

David

The cracks are in the chamber....It does not matter if the heads or engine were rebuilt 20K ago, if very particular procedures are not followed with the 2.0 heads, they will crack again. I can help you with the rebuilding chores, e mail me...

The heads are the single most important part of the engine, and especially with the 2.0...We install 12mm plugs in all of these, 14mm are way too big, and close to the seats..

Thanks Jake. I'm studying for my law school end of year exams right now. When that nightmare is completed in a few weeks, I'll be looking for some P car solutions. I'll email you. Thanks so much for your help.


David

It is also possible that you are seeing a Heli-Coil coming out of the head. In other words, the plug hole may have been stripped already at some point, and someone chose to use a helicoil to repair it. They can sometimes come out--it's uncommon, but possible.

I don't think you can simply install a new one when the old one has come out. But I could be wrong on that.

--DD

The Heli coil could be starting to tear away from the threads, chances are that a crack is the cause of this as well....

I had a heli-coil spin in a 2.0 head in which the PO had cross-threaded the plug and had run the car that way. I tore the engine down and had the heads rebuilt with big valves and some porting, and the shop told me that repairing the heli coil was no big deal. (?)
Probably not related, but one head was cracked between the exhaust port and the valve - very difficult to detect - it would have been impossible with the head in the car. I didn't notice it through the carbon even when the head was removed.
A side note - I gather that if there is a leak at the exhaust port, the head can crack and if the head cracks, the exhaust valve can drop a seat and...
The devil is in the details!

Dave