This is an authentic replacement part manufactured for use with small engines. Seals can deteriorate overtime, and it is recommended to replace worn seals when servicing an engine. This seal is the lower seal in the engine's sump, the seal is sold individually.
Seal-oil 399781S
OEM part for: Briggs & Stratton Engines, Toro
Part Number: 399781S




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Compatibility
This Seal-oil will fit the following 17502 machines. Confirm this part works with your model, and view the detailed model diagrams and repair help we have to offer.
Displaying 20 of 17502 matching models.
17502 total model matches. Try the above search to narrow your results.
This is the official OEM part for the following brands:
- Briggs & Stratton Engines
- Lawn Boy
- Toro
This item works with the following types of products:
- Engine
- Generator
- Lawn Mower
This part replaces obsolete part #: 399781
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Customer Repair Instructions ?
All our customer repair instructions are solicited directly from other customers just like you who have purchased and replaced this exact part.
Leaking lower crankshaft seal.
Tool Type
Lawn Mower
Difficulty
Easy
Time
30-60 minutes
Tools Used
Screwdriver, Socket set
Parts Used
bottom oil seal leaking
Tool Type
Lawn Mower
Difficulty
Medium
Time
15-30 minutes
Tools Used
Screwdriver, llarge pry bars
Parts Used
2 drained oil
3 removed blade
4 had a hard time when I was removing blade hub had to heat up and pry off took some time
5 popped out leaky oil seal on engine bottom pan
6 cleaned shaft and oil from housing
7 installed new oil seal
Leaking oil from crankcase
Tool Type
Engine
Difficulty
Easy
Time
15-30 minutes
Tools Used
Socket set, Nutdriver
Parts Used
Bent crankshaft
Tool Type
Lawn Mower
Difficulty
Medium
Time
30-60 minutes
Tools Used
Screwdriver, Socket set, Wrench Set, Nutdriver, Drill/Driver with adjustable clutch, inch #s torque wrench
Removed gas tank
Removed engine flywheel cover
Removed spark plug
Removed flywheel
Removed crankcase cover
Removed governor assembly and cam shaft
Disconnected piston rod end cap and pushed piston forward to clear path for crankshaft removal
Removed cranked shaft
Cleaned all parts and engine crankcase
Replaced crankshaft lower seal
Oiled all parts during reassembled in reverse order. Torqued all bolts to spec.
Reinstalled engine onto mower, new oil, fresh gas and mowed the yard!
very little compression ex. valve leaked
Tool Type
Lawn Mower
Difficulty
Hard
Time
More than 2 hours
Tools Used
Screwdriver, Pliers, Power Drill, Socket set, Wrench Set, Nutdriver
honed the cylinder, regrind both valves
reassembled all parts by changing out all ordered parts.
Seal leaking at out put shaft,letting oil drain out and locked the motor up.
Tool Type
Engine
Difficulty
Medium
Time
1-2 hours
Tools Used
Screwdriver, Pliers, Socket set, Wrench Set, Adjustable Wrench
Parts Used
OEM stands for Original Equipment Manufacturer and means the part you’re buying is sourced directly from the manufacturer who made your product. At eReplacementParts, we sell only genuine OEM parts, guaranteeing the part you’re purchasing is of better design and of higher quality than aftermarket parts.
Learn MoreOur product descriptions are a combination of data sourced directly from the manufacturers who made your product as well as content researched and curated by our content & customer service teams. This content is edited and reviewed internally before being made public to customers.
Our customer service team are at the ready daily to answer your part and product questions. We have a dedicated staff with decades of collective experience in helping customers just like you purchase parts to repair their products.
All our part reviews are solicited directly from other customers who have purchased this exact part. While we moderate these reviews for profanity, offensive language or personally identifiable information, these reviews are posted exactly as submitted and no alterations are made by our team.
All our customer repair instructions are solicited directly from other customers just like you who have purchased and replaced this exact part. While we moderate these reviews for profanity, offensive language or personally identifiable information, these reviews are posted exactly as submitted and no alterations are made by our team.
Based on data from past customer purchasing behaviors, these parts are most commonly purchased together along with the part you are viewing. These parts may be necessary or helpful to replace to complete your current repair.
All our installation videos are created and produced in collaboration with our in-house repair technician, Mark Sodja, who has helped millions of eReplacementParts customers over the last 13 years repair their products. Mark has years of experience in selling and repairing both commercial and residential products with a specialty in gas-powered equipment.
This data is collected from customers who submitted a repair instruction after replacing this exact part. Customers can rate how easy the repair was to complete and how long it took. We aggregate this data to provide a repair rating that allows customers to quickly determine the difficulty and time needed to perform their own repair.