You might not believe this, but not every 2.9L, 3.0L or 4.0L V6 Ford factory cylinder head cracked and failed. Nor did every 706 GM 4.8-5.3L with the “battery” emblem. Cylinder heads fail for a reason. Now the difference between success or long life and failure may be a very fine line, but it usually takes some form of neglect or poor maintenance to bring out the weak link. If you don’t want this same type of failure to happen again, especially not while under your warranty period, you would be doing yourself a favor to point out a few things for your customer to check and make sure are in good operating condition, before the vehicle leaves the shop. — A faulty or sticking thermostat will cause an engine to run hotter than it should. Incorrect ignition timing and uncontrolled burn may cause elevated exhaust temps, which will cause excessive heat in the head. A leaking head gasket due to insufficient clamp­ing force from the head bolts can allow exhaust gases to enter the cooling system, again causing elevated temperatures. Severe warping to the head due to a warped cylinder block deck can impose force on a thin casting causing it to crack — There are many forces like torque tension and engine temperature working on the head every minute the engine is running, all looking for a weak spot to finally give way to failure. Doing a little post-mortem investigation of the old head, gaskets and cooling system may lead to the reasons why it failed. If you write it off to the idea that “they all do”, you may be proven right and see the one you just shipped come back as proof.

Dave Sutton
Stering Bearing Inc
Minneapolis, MN
February, 2017