TSB 97-01-14 Cold Start Buzzing or Knocking, 4.9L Engines
Publication Date: JANUARY 2, 1997
LIGHT TRUCK: 1995-96 ECONOLINE, F-150-350 SERIES
ISSUE: 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.
ACTION: 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.
SERVICE PROCEDURE
1. Locate the upstream air check valve which is in-line between the exhaust manifold and the diverter valve. Refer to the figure for the 1995-96 model year system description.
2. 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.
3. 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.
4. 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
F5TZ-9A487-B Check Valve
OTHER APPLICABLE ARTICLES: NONE
SUPERSEDES: 96-22-12
WARRANTY STATUS: Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage And Emissions Warranty Coverage
OPERATION DESCRIPTION TIME
970114A Replace Check Valve - Econoline 0.7 Hr.
970114B Replace Check Valve - F-Series 0.5 Hr.
For other TSBs, check
here.
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TSB 95-08-08 4.9L Engine Knocking on Cold Start
AFFECTED VEHICLES:
LIGHT TRUCK: 1984-95 BRONCO, ECONOLINE, F-150-350 SERIES
This TSB is being republished in its entirety to include the 1995 model year.
ISSUE: An engine knock of about 3-5 seconds may be heard on initial start-up, after an extended soak time (eight hours or more). This may be due to insufficient oil at the engine bearings, caused by engine oil drainback from the engine oil filter.
ACTION: Install an anti-drainback engine oil filter adapter. Refer to the following procedure for service details.
SERVICE PROCEDURE
1. Drain and discard engine oil.
2. Remove and discard engine oil filter.
3. Remove and discard engine oil filter adapter insert.
4. Install the service replacement anti-drainback engine oil filter adapter insert (E4TZ-6890-A).
5. Tighten the anti-drainback insert to 15-35 lb-ft (20-48 N-m).
6. Lightly lubricate the gasket surface of the new oil filter (FL-1A).
7. Install the new engine oil filter to the cylinder block and rotate the engine oil filter one-half turn after the gasket contacts the sealing surface.
8. Fill the engine with the proper grade and amount of engine oil, as specified in the appropriate Owner Guide.
Parts Usage:
E4TZ-6890-A Engine Oil Filter Mounting Insert
Labor: 0.4 Hr.
SUPERSEDES: 94-11-22
