ASE A1 Engine RepairCylinder Head and Valve TrainMedium
A technician is using a straightedge and a feeler gauge to check for warpage on a cylinder head after an engine overheated. The service manual specifies a maximum allowable warpage of 0.002 inches (0.05 mm). The technician places the straightedge across the cylinder head in various positions and measures a gap of 0.003 inches (0.076 mm) at one point. What is the MOST appropriate next step?
- AApply a thicker layer of RTV sealant during reassembly.
- BInstall the cylinder head with a new head gasket.
- CResurface (machine) the cylinder head.
- DReplace the cylinder head.
Show answer & explanationAnswer & explanation
Correct answer: C. Resurface (machine) the cylinder head.
The measured warpage of 0.003 inches exceeds the maximum allowable warpage of 0.002 inches. Since the warpage is relatively minor and often correctable, the most appropriate next step is to resurface (machine) the cylinder head to restore its flatness, assuming sufficient material can be removed without compromising structural integrity or compression ratio.
Why the other options are wrong
- A. RTV sealant is not a substitute for a flat mating surface and a proper head gasket; it will not seal significant warpage.
- B. Installing a warped head, even with a new gasket, will likely lead to another head gasket failure and potential engine damage.
- D. Replacing the cylinder head is an option, but resurfacing is a more cost-effective repair if the warpage is within machinable limits.
Cylinder Head Warpage
The deformation of a cylinder head's mating surface, typically caused by overheating, which prevents it from sealing correctly against the engine block.
- Measured with a straightedge and feeler gauge.
- Exceeding specifications requires repair or replacement.
- Can lead to head gasket failure and coolant/oil leaks.
Memory trick: Warped head, check the gap, then machine the cap.