• Welcome to the Two Wheeled Texans community! Feel free to hang out and lurk as long as you like. However, we would like to encourage you to register so that you can join the community and use the numerous features on the site. After registering, don't forget to post up an introduction!

Purpose of a crush washer?

Joined
Dec 2, 2004
Messages
381
Location
Lakeway, TX
First Name
Claire
I've got a question for you mechanical-minded types. What is the purpose of the crush washer on the oil drain plug? Specifically, why a crush washer and not a regular washer? Is its purpose to notify you to stop tightening the plug, when the washer "crushes"? :confused:

I've been using the same old crushed crush washer for the last couple of oil changes and haven't noticed any related issues, such as leaks...
 
Joined
May 6, 2005
Messages
93
Location
SA
First Name
Dan
Last Name
Chambers
AKA lock washer. They provide a little spring pressure (helps keep the fastner tight) between the mating surface and the nut or bolt. You can use them repeatedly. I have never replaced one unless I lost it.
 
Last edited:
Joined
Mar 3, 2003
Messages
1,361
Location
7600 feet up
Also, being made from softer metal (ie: aluminum or copper), they tend to conform better to the surfaces they are being crushed between and therefor seal better than a hard steel washer would.

I keep using them until they do begin to leak (usually after 3-5 uses), then get a new one at the auto parts store. They usually have a kit full of all different sizes and materials and can get you a new one to match what you got. Usually less than $1.
 
Joined
Jun 3, 2005
Messages
365
Location
Hurst
First Name
Roy
Last Name
Heath
As Cycle stated, Crush washers by design compress when forces are applied to them. Two reasons they are used. (maybe more but im only aware of two). Are. One the washer gives a more uniform seal to the mating surface of the fastener. And two. All fasteners lose some tensile strength and begin to stretch after repeated load and unload situations. With this in mind, the crush washer can aid in good seal after fastener has stretched.
If you were to buy new washer, you should see a diference in the thickness. It is recommended to always change a crush washer everytime fastener has been loosened. (as far as i know)......... But like you, they can be reused.
Crush washers and lock washers are not the same. unless their is some hybrid out there :eek:
This information is just what i can remember off top of my head, and may be off a little. when i get home ill dig through some notes and see how wrong i am

Roy
 
Joined
May 7, 2004
Messages
2,614
Location
Grapevine
On your oil drain they are mainly for making sure it doesn't leak by mashing and conforming to the pan/plug to seal. If you use a normal washer or no washer it's a pretty sure bet it'll seep oil past.

If the washer starts getting too flat and gnarly looking or starts seeping oil around the plug just get another one.
 
Joined
May 6, 2005
Messages
93
Location
SA
First Name
Dan
Last Name
Chambers
cannondale said:
Crush washers and lock washers are not the same. unless their is some hybrid out there :eek:
That's right. I have been reading too many of my old Yamaha Service manuals :). They refer, in some cases, to lock washers as crush washers. In the context Bobcat's using the term you are right.
 

scratch

Inactive Member
Joined
Mar 6, 2003
Messages
4,676
Location
Houston
First Name
Paul
Last Name
Massie
Yep, the crush washer is intended to provide a better seal for the drain plug. I've always just clean and re-used them until they start to leak. Your service manual will provide the amount of torque you should use when tightening the plug, so using a torque wrench is the best way to be sure you have it tightened properly. Too loose and it will leak or worse yet, vibrate out and dump your oil. Too tight and you risk stripping out the soft aluminum that the plug threads into.

Which reminds me - one time I forgot to put the crush washer back on the drain plug after doing an oil change just prior to a group ride, and my Triumph dropped a little oil every time we parked somewhere that day. :headbang:

A few of our TWT members (who shall remain nameless) spotted the drip and couldn't resist ribbing me about my sorry old leaky British bike. :-P But hey, that's what friends are for, right? ;-)
 
Last edited:
Top