Mower Oil Leak Repair

If you've read the Dirty Shirt Diagnostic page you should already be familiar with the concept that this oil leak is a part of a system and you need to understand just enough about a system to diagnose it. You don't need to be a small-engine wiz to solve this problem; basic understanding is good enough. It's also true that we'll start by focusing on the easiest to accomplish and least expensive option first to see if that fixes the problem – just like is says on the Diagnostic page.

(A) The oil dip stick tube enters the engine block here and seems to be the most logical place to start. There's a lot of oil below this area but there's almost no oil above this area.

Our basic understanding of systems tells us that most engine manufacturers use either a gasket or some sort of rubber component to prevent engine oil from leaking. By taking a very close look at where the dip stick tube enters the engine block (B) we can see a rubber lip that surrounds the dip stick where it enters the block. We'll start problem solving here.

We also know that in order to begin acquiring replacement parts we'll need some specific identification information from the mower. Removing the dipstick tube and gaining access to the rubber component is simple and it's accomplished by removing one bolt (C) and has already been removed in this photo. However, to gather specific engine information the engine cover had to be removed (D) – it's held on by 4 bolts.

The specifications sticker is located under the engine cover and will enable you to be specific when searching for parts or information. Our mower is a Lawn-Boy but the engine is made by Tecumseh – that's an important piece of information and it's right on the label. This multi-branding happens all of the time and it's done for a number of reasons that we won't get into here. The people who carry parts for these machines will need to know they're dealing with a Tecumseh engine and the Lawn-Boy brand will be a secondary piece of information.

Tecumseh does not use a traditional serial number for engine identification; they use an "engine family" identification system (at least for this mower they do). You need to write all of these numbers down and perform some web searches and/or make some phone calls to parts houses.

All of the work performed on the mower within this project was done with a nut driver and a small socket. That's about as easy as it gets and we're solving a significant problem by just looking at the situation and applying some DIY common sense.

Our corner lawn mower shop had a replacement rubber seal for the dip stick tube and sold it to us for $5.65. The dip stick cap has been seeping oil for quite some time so we decided to replace it too. The mower shop didn't have a new cap in stock so our salesman grabbed one off of another mower and gave it to us – no charge.

The large hole in the middle of the photo is where the dip stick tube is normally located. When the tube was removed the rubber seal came out with it. A close up visual inspection of the hole was performed to ensure that no dirt or other foreign matter was preventing an oil proof seal. The hole was wiped down with a rag to make sure it was clean.

The oil-mess had to be cleaned up to make it easier to see if the oil leak problem had been resolved after the repair. Jeff used brake-parts-cleaner sprayed into a rag to do this and carefully wiped the mower down. Brake cleaner cuts through oil and grease, evaporates quickly but it is deadly to rubber seals. If the brake-parts-cleaner comes into contact with rubber seals the seal will perform for a while and then begin to leak.

WD-40 is also a great cleaner and it's friendlier to rubber parts but it evaporates much more slowly. It's worth mentioning that you would never want to apply WD-40 to a bearing or anything that must retain grease to function properly. WD-40 will liquefy grease and cause a bearing to run dry of lubrication. It's a great cleaner precisely because it cuts through grease.