Middleby Marshall PS638, 740 & 745 Series Oven Cleaning & Preventative Maintenance
Middleby Marshall conveyor ovens allow operators to cook a variety of foods such as pizza and sandwiches quickly. Since proper care is important, this guide covers cleaning and preventative maintenance instructions for PS638, PS740 and PS745 series pizza ovens so you can keep your unit in good working order.
Supplies List
- Stiff Nylon Brush
- Clean Cloths
- Small Vacuum Cleaner
- Shop Vacuum Cleaner
- Screwdriver
- Warm Water
- Mild Detergent
- Light Food Grade Lubricant (extended shaft and interior of the hollow shaft)
NOTE: To avoid damaging your oven, don’t use a water hose, steam-cleaning equipment or large amounts of water. Also, don’t use a caustic cleaner as it may damage the baking chamber surfaces.
Pre-Maintenance Checklist
- Step 1. Cool down the oven - Turn the oven off and allow it to cool down. Never perform maintenance on an oven while it’s warm as this may lead to injury.
- Step 2. Disconnect the power - Unplug the unit and turn off the circuit breaker(s).
- Step 3. Disconnect the gas - If you have to move a gas oven for cleaning or other maintenance, be sure to first disconnect the gas supply.
Daily Cleaning
- Step 1. Clean the fan grills and vent openings - Use a stiff nylon brush to clean the cooling fan grills and vent openings.
- Step 2. Wipe the exterior - Clean the oven exterior with a soft cloth and warm, soapy water.
- Step 3. Check the cooling fans - Make sure the cooling fans are operating properly. If not, replace the part immediately since operating the oven without proper internal cooling can damage the unit.
- Step 4. Brush the conveyor belts - While allowing the conveyor to run, stand at the end and brush off the crumbs as the conveyor belt moves.
- Step 5. Clean the crumb trays - Remove and clean the crumb trays.
- Step 6. Clean the window - Without uninstalling it, clean the window with a soft cloth and warm, soapy water.
- Step 7. Rinse the oven - Use a damp cloth to wipe down the unit to remove soap suds or remaining crumbs.
- Step 8. Dry the oven - Use a cloth to dry the unit.
Monthly Preventative Maintenance
- Step 1. Remove the crumb trays, drive chain, conveyor, air fingers and blank plate - If necessary, refer to illustrations in the manual for instructions. Be sure to note the original location of each finger so you can reinstall them in the correct order.
- Step 2. Disassemble the air fingers - Remember to note the original location of each disassembled piece because incorrect reassembly of the air fingers will change the baking properties of the oven.
- Step 3. Clean the air fingers - Use a damp cloth and a vacuum cleaner to clean the disassembled air fingers.
- Step 4. Clean the interior - Wipe the oven cavity with warm, soapy water and a soft cloth. If necessary, use a small vacuum cleaner to vacuum up large food particles.
- Step 5. Rinse the inside of the oven - Use a damp cloth to clean up any remaining soap suds or food particles.
- Step 6. Dry the interior - Soak up any remaining moisture with a clean, soft cloth.
- Step 7. Reinstall parts - Return the crumb trays, drive chain, conveyor, air fingers and blank plate to their position in the oven. If necessary, refer to the manual for instructions.
Quarterly Preventive Maintenance (Every 3 Months)
It’s strongly recommended that the quarterly preventative maintenance procedures only be performed by a Middleby Marshall Authorized Service Agent.
- Step 1. Vacuum the blower mounts - Use a shop vacuum to clean the blower mounts and their surrounding compartments.
- Step 2. Tighten the electrical terminal screws - Use a screwdriver to tighten the electrical terminal screws.
- Step 3. Disassemble the split belt - Remove the conveyor end stop, crumb trays, chain cover, drive chains, end plugs and conveyor assembly. Next, take out the master links, roll up the belts and then remove the conveyor adjustment screws and the idler shaft assembly from the conveyor. Refer to the manual for instructions if needed.
- Step 4. Clean the idler shaft - After pulling apart the two sections of the idler shaft, clean them with a soft cloth.
- Step 5. Lubricate the idler shaft - Once the shaft is clean, lubricate both the extended shaft and the interior of the hollow shaft with a light food grade lubricant. Don’t use WD40 or a similar lubricant since these products can cause the shafts to wear rapidly.
- Step 6. Disassemble and lubricate the drive shaft - Following the same procedure as with the idler shaft, disassemble, clean and lubricate the drive shaft.
- Step 7. Reinstall the conveyor belt - Replace all uninstalled components. Refer to the manual for detailed instructions.
Blower Belt Inspection (PS740 and PS745)
- Step 1. Remove the rear panel - After loosening the six screws holding the rear panel in place, take off the rear panel.
- Step 2. Check the blower belt - Make sure the blower belt has the proper deflection at the center (1/4" or 6mm). Additionally, inspect the belt for any cracking or excessive wear. If needed, replace the belt.
- Step 3. Adjusting the blower belt - Both an overly tight or overly loose belt can cause issues. So, loosen or tighten the four motor mounting bolts to adjust the tension of the belt to achieve the correct deflection.
Bi-Annual Preventative Maintenance (Every 6 Months)
It’s strongly advised that the bi-annual preventative maintenance procedures only be performed by a Middleby Marshall Authorized Service Agent.
- Step 1. Clean the burner nozzle - For gas ovens, inspect and clean the burner nozzle and the spark electrode assembly.
- Step 2. Vacuum the blower mounts - Clean the blower mounts and the surrounding compartments with a shop vacuum.
- Step 3. Check the conveyor - First, tighten all electrical terminal screws. Then, check the conveyor drive shaft bushing and spacers for excessive wear. Replace if necessary.
For more information about cleaning and maintaining your Middleby Marshall oven, take a look at our collection of Middleby Marshall manuals.