There is a bulletin that may help find a resolution, 94-10-19 is the number. I will forward the literary portion of it right now, it has quite a few pictures that I am not able to attach at this point.
Accessory Drive Belt - Chirp or Squeal Noise
ACCESSORY DRIVE BELT - FEAD BELT "CHIRP"/"SQUEAL" NOISE AND BELT EDGE WEAR OR LOSS - VEHICLES WITH 4.9L ENGINE
ENGINE - 4.9L - FEAD BELT "CHIRP"/"SQUEAL" NOISE AND BELT EDGE WEAR OR LOSS
NOISE - "CHIRP"/"SQUEAL" SOUND FROM FEAD BELT - VEHICLES WITH 4.9L ENGINE
1987-94 ECONOLINE, F-150-350 SERIES
This TSB article is being republished in its entirety to provide specific bolt number references in Figures 3 and 4.
Front-end accessory drive belt (FEAD) belt noise may be heard and excessive belt edge wear or loss may occur.
The "chirp" noise may occur at constant engine speeds and all engine loads. It is caused by belt/pulley misalignment.
The belt "squeal" noise is intermittent and is heard during engine speed variations, usually at engine start up. The noise is caused by belt slippage.
Belt edge wear and/or belt loss is caused by belt mistracking across the automatic belt tensioner. If the automatic belt tensioner is out of parallel, the belt can be "driven" to either flange of the pulley, causing belt edge wear and in some cases, the loss of the belt.
Use the following service procedure to correct these conditions.
1. Start the engine and while idling, wet the ribbed side of belt by spraying water on the belt where it enters the A/C compressor pulley.
2. Listen for belt "chirp" as the belt dries at the entrance point of each grooved pulley to identify the noisy pulley.
3. If the "chirp" is at the power steering pulley entry, check for belt mistracking on the tensioner pulley, otherwise go to Step 13.
4. Check press of the power steering pulley. The pulley hub should be flush with the end of the pump shaft.
5. If the pulley is flush, start engine and while idling, visually compare the size of the gaps between the belt and front and rear flange of the tensioner pulley. If the larger gap is twice as wide as the smaller gap, Figure 2, proceed with Step 6, otherwise, go to Step 13.
6. Mark the accessory drive belt with an arrow to denote rotation of belt. Remove belt.
7. Loosen all fasteners attaching A/C bracket to cylinder block and cylinder head. See Figures 3 and 4.
8. Tighten nuts # 3 (and, on 1987-93 model only, bolts # 4) on side of cylinder block to 62 N-m (46 lb. Ft).
9. Tighten bolt # 2 on side of cylinder head to 47 N-m (35 lb. Ft).
10. Tighten bolt # 1 on front of cylinder head to 47 N-m (35 lb. Ft).
11. Install the accessory drive belt. Be sure belt is installed with arrow mark denoting original rotation of belt.
12. Start engine and check for belt "chirp" noise.
13. Remove the accessory drive belt and replace it with a new service replacement belt. See Figure 1 for correct belt usage.
BELT SQUEAL - F-SERIES
1. Remove the accessory drive belt automatic tensioner assembly. Refer to the appropriate Truck service Manual, Section 03-05, for the removal procedure.
2. Replace it with automatic tensioner assembly (E7TZ-6B209-G). Refer to the appropriate Truck service Manual, Section 03-05, for the installation procedure.
3. Replace the accessory drive belt.
BELT SQUEAL - ECONOLINE (A/C EQUIPPED MODELS ONLY)
1. Remove and discard the accessory drive belt.
2. Remove 90 mm diameter pulley from automatic tensioner assembly. Discard bolt, pulley and bearing dust shield. Refer to Figure 5.
3. Install new 76 mm pulley, bearing, dust shield and bolt assembly (E7UZ-8678-A) to automatic tensioner assembly. See Figure 5.
4. Install new accessory drive belt. (1987-93 models - E7UZ-8620-J, 1994 models - E8TZ-8620-S).
BELT EDGE WEAR AND LOSS
1. Remove and replace accessory drive belt with new service replacement belt. See Figure 1 for correct parts usage.
2. Start engine and while idling, observe location of belt on automatic tensioner pulley. If belt tracks near the pulley flange, Figure 2, replace with automatic tensioner (E7TZ-6B209-G).
3. Start engine and observe belt movement. If belt moves too far rearward on tensioner pulley, proceed as follows:
a. With belt installed, loosen all A/C bracket fasteners. Belt tension will pull A/C bracket inboard towards the engine. (Refer to Figures 3 and 4 for bolt and nut position identification.)
b. Tighten bolt # 1 on front of cylinder head to 47 N-m (35 lb. Ft).
C. Tighten bolt # 2 on side of cylinder head to 47 N-m (35 lb. Ft).
D. Tighten nuts # 3 (and for 1993 and prior model years, bolts # 4) on side of cylinder block to 62 N-m (46 lb. Ft).
4. Start engine and observe belt movement. If belt moves too far forward on tensioner pulley, proceed as follows:
a. Remove accessory drive belt and loosen all A/C bracket fasteners.
B. Pull A/C bracket toward driver's side of vehicle.
C. Tighten bolt # 1 on front of cylinder head to 47 N-m (35 lb. Ft).
D. Tighten bolt # 2 on side of cylinder head to 47 N-m (35 lb. Ft).
E. Tighten nuts # 3 (and for 1993 and prior model years, bolts # 4) on side of cylinder block to 62 N-m (46 lb. Ft).
OTHER APPLICABLE ARTICLES: NONE
Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage For 1992-94 Models, Basic Warranty Coverage For All Other Models, Emission Warranty For Belt Loss On Vehicles Equipped With Thermactor Pumps
Tuesday, June 14th, 2011 AT 3:58 PM