replace defective plastic intake manifold on 1998 Mercury Grand Marquis

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I have a coolant leak at a crack in the intake manifold at the top-front of the 4.2(maybe 4.6?)Liter engine. The leak stopped when I put in a stopleak "mud" and held through the winter. Then it leaked after a 3500 mile trip coating the engine with a fine-coating of fine mud/dust. (I have a competent mechanic for whom I had the engine compartment pressure washed ... the motor is clean like new. The engine runs good.) What will it cost to flush the coolant and mud, then replace the intake manifold and refill coolant?
(1) Answer
(2) Comments
It's a 4.6L V8.

This is a common issue that at one time Ford offered warranty coverage for (not any more).

I believe all in you are looking at $500-700 for this job, depending on your labor cost, and using an aftermaket intake manfiold.

Hopefully your stop leak has not contaminated components that you did not want it to impact.
Well the cost estimate made my heart stop, but like another mechanic posted: proper maintenance is preferablle and least costly than replacing an otherwise fine car. Thanks for the answer. The cost will be honest because I (and my family) have had him work on our cars for many years. He has always been fair, honest, and dependable. And the cars always last a looong time with his keeping the maintenance top-notch.
A good relationship with a good technician is nothing to be taken for granted! Nice to hear.

Nothing you could have done, of course, with the coolant leak. It was a factory flaw and yours lasted years longer than many.

Good luck!