Technical Service Bulletins
|Publication Date: JANUARY 2, 1997|
|1995-1996 ECONOLINE, F-150-350 SERIES|
This TSB article is being republished in its entirety to update the part to latest level and revise Figure 1.
A “buzzing, rattling or chattering” noise may be coming from the right front of the engine compartment at idle, especially after a warm start. After 30-120 seconds, the noise stops. A cold engine may also exhibit a “knocking” noise. This may be due to the air check valve diaphragm pulsating which causes the various noises. The check valve may also cause back pressure, resulting in a knocking noise on some vehicles when cold.
Replace the upstream air check valve. The revised check valve has a different diaphragm which should minimize the chance of the noises recurring. It also has less restriction which should reduce the knocking noise when cold. Refer to the following Service Procedure for removal and installation details.
- Locate the upstream air check valve which is in-line between the exhaust manifold and the diverter valve. Refer to Figure 1 for the 1995-96 model year system description.
Figure 1 – Article 97-1-14
- Start the engine and listen for buzzing noise in the engine compartmemt near the check valve. A vibration may also be felt in the hose between the check valve and diverter valve. The buzzing noise will occur when air is pumped upstream to the exhaust manifold, usually just after engine start-up, and will last 30-120 seconds. The noise will then quit as the air is diverted to the catalyst. The noise is more noticeable when the engine is warm. A knocking noise may only be evident when the engine is cold.
- If the buzzing noise continues for more than 120 seconds, the check valve is not suspect. Attempt to isolate the noise by the use of a technician’s stethoscope.
- If the buzzing noise does not last for more than 120 seconds, replace the check valve which is in-line between the exhaust manifold and the diverter valve and confirm the noise is gone.
|PART NUMBER||PART NAME|
OTHER APPLICABLE ARTICLES:
Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage And Emissions Warranty Coverage
|970114A||Replace Check Valve – Econoline||0.7 Hr.|
|970114B||Replace Check Valve – F-Series||0.5 Hr.|
|BASIC PART NO.||CONDITION CODE|
497200, 702000, 702100, 703000, 703100