03-11-04 ENGINE - MUSTANG COBRA - TICK NOISE FROM ENGINE - COBRA VEHICLES EQUIPPED WITH ENGINES BUILT BEFORE 11/1/2002 ONLY*
Some 2003 Mustang
Cobra vehicles with engines built before 11/1/2002 may exhibit an unusual engine tick noise that is present at all temperatures during idle. This noise may be due to valve guide wear in the left bank cylinder head. Guide wear manifests itself as a tick noise which can be heard at the rear of LH head, through LH catalyst, at the LH front wheel well and may not be heard with the hood open.
Use the diagnostic Service Procedure listed below to evaluate the vehicle condition and replace the cylinder head if applicable.
In order to diagnose noise, the following items must be checked:
- Verify noise by placing a stethoscope on the back of the left head near the exhaust ports.
- Verify that the noise is heard in the left side exhaust system (left side wheel well or catalytic converter, from underneath the vehicle).
- Try to isolate the noise by cancelling the cylinders, by unplugging the injectors one at a time (start with #8 cylinder).
- Verify that there are no exhaust manifold leaks.
- Check to make sure that the camshaft spacers are in place. If not, install cam spacers (per Workshop Manual Section 303-01C) and retest vehicle.
- Check for proper cam sprocket bolt torque, retorque to spec listed in the Workshop Manual Section 303-01C.
- Check for spongy lash adjusters (refer to Section 303-00 in the corresponding Workshop Manual).
- Verify that the timing chain tensioner pin has been removed.
The part numbers for the latest Cobra heads (to fix the tick issue) are:
Left side head
Part # 2C5Z-6049-BAB
Right side head
Part # 2C5Z-6049-CAB
* Please note that this issue was NOT confined to 2003 Cobras built before 11/1/2002 as was originally believed. It has happened on both 2003 and 2004 Cobras. Even on Mach 1s. Also note that the actual percentage of affected Cobras is very small. Also note that the original TSB stated that the then available replacement head was to be used if the driver's side head was confirmed to have the issue. However, it did not solve the problem as some cars with this early replacement head again developed the tick issue. ONLY the replacement head released in 01/2005 (and later) effectively solve the problem as the coolant passages were redesigned on this head. Lastly, this issue has affected a very small percentage of 2003-2004 Cobras. So the odds of any one Cobra developing the issue is minimal.