Tech Tip: Oil Leak Repair for 1990-’93 4.0L Ford V6 Engines – UnderhoodService

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Tech Tip: Oil Leak Repair for 1990-’93 4.0L Ford V6 Engines

The 4.0L Ford V6 has been a problem engine for oil leaks for years. This engine has been used in the Aerostar, Explorer and Ranger pickups. The most common oil leak on 1990-'93 4.0L engines is often diagnosed as a rear seal leak, but in most cases, the problem is usually found to be the rear of the oil pan gasket.

Underhood Service Staff Writers
By Underhood Service Staff Writers

The 4.0L Ford V6 has been a problem engine for oil leaks for years. This engine has been used in the Aerostar, Explorer and Ranger pickups.
figure 1
The most common oil leak on 1990-’93 4.0L engines is often diagnosed as a rear seal leak, but in most cases, the problem is usually found to be the rear of the oil pan gasket. Since 1990, when the 4.0L was first introduced, Ford redesigned the gasket twice and even the oil pan casting to eliminate the leaking issue.

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The following installation tips from Canada Engines should help to prevent this costly and aggravating oil pan gasket leak.

The ’90 to ’93 gasket set will include a plastic wedge seal that goes into a groove in the main cap. The diagram (Figures 1 – 5) explains the steps to take for a successful installation.
figure 2 - the 1990 to 1993 model years use gasket a along with the wedge seal b (figure 3) on the rear main cap.
Source: Canada Engines LTD.
figure 3 - use gasket a (figure 2) along with the wedge seal b on the rear main cap.figure 4 - the oil pan was redesigned in 1994 and so was the gasket shown c. the wedge seal is no longer used because its shape is built into the gasket. silicone is still necessary across the main cap and in the cavities between the cap and the block.Figure 5 - The oil pan must be aligned with a straight edge to the back of the block before it is torqued down.


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