Medium
30-60 minutes
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 and Stratton, Toro, Lawn Boy
Part Number: 399781S
$8.38
In Stock
Order within the next 12 hours and your part ships today! 
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Compatibility
This Seal-oil will fit the following 11426 machines. Confirm this part works with your model, and view the detailed model diagrams and repair help we have to offer.
Briggs and Stratton
Toro
Lawn Boy
Show More Compatible ModelsThis item works with the following types of products:
- Engine Parts
- Generator Parts
- Lawn Mower Parts
This part replaces obsolete part #: 399781
Customer Part Reviews ?
Average Rating (out of 5):
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Oil leak, no oil leak
The oil seal and sump gasket arrived as promised, fit perfectly and pressure washer is up and running with no oil leak.
Rich -
August 16, 2023
Verified Purchase
Worked as expected
Fit perfectly, easy replacement, fixed my oil leak
Steven -
June 16, 2022
Verified Purchase
great part
arrived quickly
Richard -
October 9, 2021
Verified Purchase
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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.
Robert - November 15, 2015
👍 3 of 3 people found this instruction helpful
Tool Type
Lawn Mower
Difficulty
Easy
Time
30-60 minutes
Tools Used
Screwdriver, Socket set
Parts Used
Drain oil, remove engine from mower, remove lower half of crankcase and pry out the old seal. Clean up the crankshaft, push the new seal into the lower half of the crankcase, then install the new gasket and bolt everything back together.
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bottom oil seal leaking
Paul - August 20, 2023
Tool Type
Lawn Mower
Difficulty
Medium
Time
15-30 minutes
Tools Used
Screwdriver, llarge pry bars
Parts Used
1 removed spark plug wire for safety
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
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
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Leaking oil from crankcase
Steven - June 10, 2022
Tool Type
Engine
Difficulty
Easy
Time
15-30 minutes
Tools Used
Socket set, Nutdriver
Parts Used
Removed crankcase cover, replaced seal and gasket
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Bent crankshaft
Kevin - July 25, 2019
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 engine from push mower
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!
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!
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very little compression ex. valve leaked
Hans - September 29, 2018
Tool Type
Lawn Mower
Difficulty
Hard
Time
More than 2 hours
Tools Used
Screwdriver, Pliers, Power Drill, Socket set, Wrench Set, Nutdriver
Completely disassembled engine cleaned all parts and repainted
honed the cylinder, regrind both valves
reassembled all parts by changing out all ordered parts.
honed the cylinder, regrind both valves
reassembled all parts by changing out all ordered parts.
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Seal leaking at out put shaft,letting oil drain out and locked the motor up.
joseph - February 2, 2017
Tool Type
Engine
Difficulty
Medium
Time
1-2 hours
Tools Used
Screwdriver, Pliers, Socket set, Wrench Set, Adjustable Wrench
Parts Used
Removed the crank case cover. Replaced the out put shaft seal and case gasket. Flushed the engine out with gunk motor flushing oil. Reset the coil clearance. Started the motor, ran for 1/2 hour, drained the oil and replaced with fresh oil. This repair saved me getting a new power washer that would cost around 400.00 dollars. The hardest part was finding the m/n of the motor as I do not work on these very often.
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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.
Our 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.
