Reader Question: Just acquired a 97 F-150 with the Ford 4.2L engine, with rod bearings out. Considering rebuilding the engine instead of replacing. Keep hearing talk about an internal coolant leak that seems to be contributing to this type of failure. Anybody know the facts? Is it fixable with the same block and heads or is it a design flaw that requires a new one of these items?
Answer: It would be nice to know how many miles is on the engine. However, there seems to have been a problem with head gasket leaks or cracked cylinder heads. Either way will allow water or coolant from the radiator to enter the cylinders. This engine is a candidate for a rebuild. The coolant leak that this engine is well known for is from the intake manifold. This engine uses a twin intake port manifold and the front and rear cylinders have coolant passages that run really close to one of the intake ports. The engine uses the plastic intake gasket with o’rings.
When the gasket gives up, the coolant is sucked into the cylinder using engine vacuum, and hydraulically locks the piston and rod combo in the cylinder when the piston tries to compress the water or coolant, which won’t compress. Which in turn bends the piston to crankshaft connecting rod and when the rod gets short enough the counter weight on the crank starts banging the bottom of the piston.
The noise this makes at first can easily be mistaken for lifter noise. However after a short time the rod gets short enough that it is a solid knock. Under many circumstances the rod or the piston may break.
We don’t see an unusual amount of 4.2L engines for rebuild. There is no big secret to a successful rebuild. It all starts with good habits and a sold knowledge of how to rebuild engines and having the most up to date tech and parts info available. Our protocol requires replacing the intake gaskets with the new improved ones from Fel Pro and the problem is solved.
Obviously we put every engine that gets rebuilt through the rest of the required procedures and updates to exact a better engine. If said engine had a particular issue, you can bet plenty of solid research went into the development of a solution. Our job is to provide the best rebuilt engines available anywhere, with the value rebuilt right into the engine. Some rebuilt engines get shipped free, all get shipped within 24 hours. Call now.