What Happens When You Over Tighten a Gasket?

Status
Not open for further replies.
Joined
Jan 14, 2003
Messages
70
Location
California
I've always heard that over tightening a gasket can lead to leaks in the future but I've never been told why this is. Would someone explain to me what happens when a gasket is over tightened?

Does it make a difference if it's a rubber gasket vs metal vs cork? How about if it's two flat surfaces vs one flat surface and one surface with a channel for the flexible gasket?

Thanks!
 
Over tightening squeezes/squishes the gasket outward/inward or even around the holddown bolts and distorts the gasket.
 
Last edited:
In some applications a gasket must expand and contract to absorb movement from differential expansion and contraction.

Rod
 
You would most likely deform whatever is being torqued such as oil pans,valve covers, diff.covers etc. resulting in leaks. I doubt the gasket would seriosly deform where it squishes out but I guess its possible.
 
Last edited:
Originally Posted By: Char Baby
Over tightening squeezes/squishes the gasket outward/inward or even around the holddown bolts and distorts the gasket.


+1
 
A temporary shape change that is self-reversing after the force is removed, so that the object returns to its original shape, is called elastic deformation. In other words, elastic deformation is a change in shape of a material at low stress that is recoverable after the stress is removed.

It's my belief that overtightening a gasket results in plastic deformation, either from the tightening itself or from the subsequent heat cycling of dissimilar materials.

http://www.henniggasket.com/gasket-answers/faqs/understanding-gasket-compression-curves/
 
I installed a rubber like transmission pan gasket without any glue/tacking agent as per the instructions. The gasket was almost 1/8 inch thick and I may have over torqued the bolts. After a month, portions of the gasket between the securing bolts, worked itself sideways out from between the two metal surfaces resulting in a large leak. Now I only use RTV gasket maker.
 
Those folded up cheapo all rubber gaskets are usually junk IMO.

buy the sold separately metal/rubber type if available.
 
It's working with gaskets that a torque wrench becomes a necessity. Without one, you're constantly turning the wrench waiting for that sudden feel of tightness, but it never comes until after you've destroyed the gasket. A perfect example is the marshmallow grommets under the valve cover bolts of a GM 3800. They never feel tight.
 
Status
Not open for further replies.
Back
Top