Line Pressure Test

WARNING: This page is about a different car, the 2007 Lincoln Mark LT and 2007 Ford Pickup. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Locating Transmission Pressure Taps

Courtesy of FORD MOTOR CO.

Item	Part Number	Description
1	-	Direct clutch pressure tap
2	-	Forward clutch pressure tap
3	-	Electronic pressure control (EPC) pressure tap
4	-	Intermediate clutch pressure tap
5	-	Line pressure tap

CAUTION: Carry out the Line Pressure Test prior to carrying out the Stall Speed Test. If the line pressure is low at stall, do not carry out Stall Speed Test or further transmission damage will occur. Do not maintain wide open throttle (WOT) in any transmission range for more than 5 seconds.

This test verifies that the line pressure is within specification.

Connect a pressure gauge to the line pressure tap.

Start the engine and check line pressures. Refer to the Line Pressure Chart to determine if line pressure is within specification.

Applications	Range	Idle		WOT
Applications	Range	EPC	Line Pressure	EPC	Line Pressure
All	P, N	34-276 kPa (5-40 psi)	276-689 kPa (40-100 psi)	N/A	N/A
	OD, 2, 1	34-276 kPa (5-40 psi)	276-689 kPa (40-100 psi)	689-793 kPa (100-115 psi)	1,172-1,586 kPa (170-230 psi)
	R	172-207 kPa (25-30 psi)	689-862 kPa (100-125 psi)	586-655 kPa (85-95 psi)	1,124-2,068 kPa (250-300 psi)

Place the ignition switch in the OFF position. If line pressure is not within specification, check EPC pressure.
Connect a pressure gauge to the EPC pressure tap.
Start the engine and check EPC pressure. Use the line pressure chart for specifications.

If the EPC pressure is not within specification, go to Pinpoint Test D to diagnose the EPC operation. If the EPC operation is OK, refer to the Line Pressure Diagnosis Chart for line pressure concern causes.

LINE PRESSURE DIAGNOSIS CHART

Test Results	Possible Source
High at Idle in All Positions	Wiring harnesses Run Quick Test. Refer to the INTRODUCTION - GASOLINE ENGINES article. EPC solenoid Main regulator valve
Low at Idle in All Positions	Low fluid level Restricted inlet filter Damaged inlet tube seal on inlet filter Loose main control valve bodies Sticking main regulator valve Excessive leakage in pump Damaged gaskets on separator valve Case bolts Case Separator plate EPC solenoid
Low in Park Only	Valve body Low/reverse servo
Low in Reverse Only	Separator plate Low/rear servo or valve body Reverse clutch
Low in Neutral Only	Valve body
Low in Overdrive Only	Forward blutch Valve body
Low in 1st Position	Forward clutch Valve body Low/reverse servo
Low in 2nd Position	Intermediate clutch Valve body Forward clutch