Ford Aerostar 1986-1997 Repair Guide




See Figures 1 and 2

  1. Remove the cylinder head.
  3. Remove the camshaft.
  5. Remove the camshaft followers.
  7. Using a spring compressor, compress the valve spring and remove the retainer locks, retainer and spring. Remove and discard the stem seal.
  9. Remove the valve from the cylinder head.

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Fig. Fig. 1: Exploded view of the 2.3L cylinder head

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Fig. Fig. 2: Exploded view of the 3.0L and 4.0L engine cylinder head

To install:
  1. Install the valve in the guide.
  3. For the 2.3L, 2.8L and 4.0L engines, coat the new seal with clean engine oil, then place the new seal over the valve stem. Using a driver, tap it into place on the guide until it bottoms.
  5. For the 3.0L engines, coat a new stem seal with clean engine oil and place it over the valve stem. Use a 5 / 8 in. deep well socket and drive the seal into place.
  7. Install the spring and damper assembly, compress it and install the retainer and locks. Make sure that the locks are fully seated.
  9. Apply a coating of multi-purpose grease, such as Ford No. D0AZ-19584-AA, or equivalent, to the contact surfaces of the camshaft follower and install the follower.
  11. Install the camshaft, as described later in this section.
  13. Install the cylinder head, as described earlier in this section.


See Figures 3 and 4

Refer to the Engine Rebuilding Specification charts for the specific tolerances allowed for the following inspection procedures.

Install each valve into its respective guide bore, then run the valve up and down in the guide to check for binding. Remove and inspect the valve. Repeat this procedure with each valve.

Measure the valve seat width and reface the valve seat if the width is not within specifications.

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Fig. Fig. 3: Valve stems may be rolled on a flat surface to check for bends

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Fig. Fig. 4: Use a micrometer to check the valve stem diameter

Check the valve seat runout with a dial indicator. Follow the dial indicator manufacturer's instructions for installation on the cylinder head and measurement procedure. Seat runout should not exceed 0.0016 in. (0.04mm) on 2.3L engines; 0.0015 in. (0.038mm) on 2.8L and 4.0L engines; or 0.003 in. (0.076mm) on 3.0L engines. If the runout exceeds the service limit, the valve seat will have to be refaced.

Check the valve stem-to-guide clearance of each valve in its respective guide with a dial indicator. Move the valve back and forth in its guide and take a measurement at two axis, 90° apart. If the readings exceed the values given in the Engine Specifications chart, the valve guide will have to be reamed to the next oversize valve stem size.

Inspect the valves for minor pits, grooves or scoring. Minor pitting may be removed with an oil stone. Check the valve stem diameter and face angle, as well as any bend in the stem itself. Discard any excessively worn or damaged valve train parts.


Refacing of the valve seat should be closely coordinated with the refacing of the valve face so that the finished seat and face will be concentric and the specified interference angle will be maintained. This is important so that the valve and seat will have a compression-tight fit. Make sure the refacer grinding wheels are properly dressed. Grind the valve seats of all engines to a true 45° angle. Remove only enough stock to clean up pits and grooves or to correct the valve seat runout. After the seat has been refaced, use a seat width scale to measure the seat width. Narrow the seat, if necessary, to bring it within specifications.

On the valve seats of all engines, use a 60° angle grinding wheel to remove stock from the bottom of the seats to raise them, or a 30° angle grinding wheel to remove stock from the top of the seats to lower them. The finished valve seat should contact the approximate center of the valve face. It is good practice to determine where the valve seat contacts the face. To do this, coat the seat with Prussian Blue and set the valve in place. Rotate the valve lightly and remove it to see where the blue contacts the valve. If the blue is transferred to the center of the valve face, contact is satisfactory. If the blue is transferred to the top edge of the valve face, lower the seat. If the blue is transferred to the bottom edge of the valve face, raise the seat.

If the valve face runout is excessive and/or to remove pits and grooves, reface the valve to a true 44° angle. Remove only enough stock to correct the runout or to clean up the pits and grooves. If the edge of the valve head is less than 1 / 32 in. (0.79mm) thick after grinding, replace the valve as it will run too hot in the engine. The interference angle of the valve and seat should not be lapped out. Remove all grooves or score marks from the end of the valve stem and chamfer it as necessary. Do not remove more than 0.010 in. (0.025mm) from the end of the valve stem. If the valve and/or valve seat has been refaced, it will be necessary to check the clearance between the rocker arm pad and the valve stem with the valve train assembly installed in the engine.

Lapping The Valves

Because of the high quality of machining processes and because of the harder materials used in engine manufacturing techniques, lapping the valves is no longer necessary. However, if you are in doubt as to whether you should lap the valves or not, refer to your automotive machinist to ascertain whether it is necessary for your particular cylinder head. If your machinist maintains that lapping the valves is necessary, perform the following procedure:

  1. Invert the cylinder head so that the combustion chambers are facing up.
  3. Lightly lubricate the valve stems with clean oil, and coat the valve seats with valve grinding compound. Install the valves in the head as numbered.
  5. Attach the suction cup of a valve lapping tool to a valve head. You'll probably have to moisten the cup to securely attach the tool to the valve.
  7. Rotate the tool between the palms. changing position and lifting the tool often to prevent grooving. Lap the valve until a smooth, polished seat is evident (you may have to add a bit more compound after some lapping is done).
  9. Remove the valve and tool, and remove ALL traces of grinding compound with solvent soaked rag, or rinse the head with solvent.

Valve lapping can also be done by fastening a suction cup to a piece of drill rod in a hand egg beater type drill. Proceed as above, using the drill as a lapping tool. Due to the higher speeds involved when using the hand drill, care must be exercised to avoid grooving the seat. Lift the tool and change direction of rotation often.