Vibration: a Source of Gremlins, or Maintenance Man Needs Tow

Nut Coined by Spring Lockwasher

Nut Coined by Spring Lockwasher

Surprise: When motor sailing, a smell of diesel was noticed and first ignored and then checked. The bilge was full of diesel fuel!

With the engine stopped the source was not found, but when started up the steel hose from the outlet of the engine fuel filter to the high pressure pump was spewing fuel.

Approximately 50 liters was removed during the subsequent clean-up.

Inspection found the steel line to be fatigued and cracked but not separated and the fuel filter was “loose” and had been vibrating.

Also the cantilevered (engineers abhor a cantilever) fuel filter bracket was held by one nut and washer only; the other was not found.

Hoses: New Rubber & Original Steel

Hoses: New Rubber & Original Steel

The first photo (above) shows the nut that was in position and loose. Vibration over time had coined the hardened steel washer into the nut, further loosening the connection.

The steel line failed as a result of flex due to the vibration.

A diesel shop ordered new metric fittings and made up the new assembly with medium pressure rubber hose.

The second photo (left) shows the new rubber hose and the old steel line now brazed to be saved as a spare.

New hose Installed with new Banjo Fittings

New hose Installed with new Banjo Fittings

The next photo (right) is looking down on the engine with the new hose installed, tested and not leaking.

The last photo (below) is of the fuel filter bracket, now properly secured with two new lockwashers and two new nuts.

The mechanics at the diesel shop have seen similar failures and did not find this happening unusual.

Preventative maintenance would have picked up this developing vibration problem.

Filter Mounting Studs

Filter Mounting Studs

An annual check with a handful of wrenches and a check of all nuts and bolts that hold engine parts in place and/or properly adjusted is good insurance.

The important tip here is that good preventative maintenance would have prevented this mess and a required tow.


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