Why do head gaskets fail?

[nsxtasy]

Just like the topic says. I know that head gaskets can fail, and that such failures can result in the need to replace the engine. I've seen this happen on a 12-year-old car with 150K miles (SO's Civic), and on a 13-year-old car with 50K miles (mom's Lexus). My question is, is this inevitable? Or, is this due to a lack of scheduled maintenance? Or, is there some additional preventive maintenance (i.e. not on the maintenance schedule in the manual) that should be done periodically to prevent such failures (for example, replacing the head gasket?), and if so, what should be done and how often?

TIA

 

[clr1024]

Most head gasket failures I am aware of are because the car overheated and was driven too long at a high temperature. I don't think its something you need to do as preventative maintenance.

 

[otto_joe]

Oh my gosh! Who kidnapped Ken and is now using his account? I thought you knew everything. :tongue:

I don't know everything, but I like to use Google. :smile:

There are some interesting theory's here for MGs:
http://www.mgf.ultimatemg.com/group2/common_problems/HGF_pages/why_do_hgfs.htm
and some more general info here:
http://www.aa1car.com/library/2005/ic010532.htm

I think these make sense:
1. Any over heating
2. Detonation
3. Air trapped in the cooling system

Otto

 

[Big_D]

I Agree...The No 1 cause is overheating the engine. The best thing to do when your engine starts to overheat is to turn on your heater full blast to help discharge some heat. Then pull over and turn off the engine before its too late. My Camry started overheating due to a failed thermostat and I did this in time to save it. I put in a failsafe one that fails open instead of closed.

 

[sahtt]

In some but few cases it just deteriorates like other gaskets do. Usually this is only after something else has occured, usually the engine overheating.

I personally don't like answers, I like reasons. The reason overheating causes your head gasket to fail is because at a given temperature the metals of the engine expand beyond a point designated as "ok" for gaskets etc. to cope with. The head gasket is most directly effected since it often seperates two different kinds of metals, is fairly large, is centered in the hottest part of the engine, and serves many functions.

Once exposed, it deteriorates fairly rapidly. If the overheating is minimal and a compression test verifies a leaking HG, often times if you retorque the head soon enough you can actually solve the problem. Unfortunately this is rarely the case and it isn't until 10k miles later that the car's driveability is obviously effected and any simple solution will no longer fix the problem.