In your opinion whats the main cause of a head gasket to blow

[danf]

After reading so many stories of guy's changing out their head gaskets I was wondering what the main cause could be that makes them fail...Time? Heat?...Lack of oil , antifreeze? What's your take on this subject..Age perhaps...What are your findings? Do they warp?

 

[toytender01]

My vote is for over heating :Egyptian: :Egyptian: :Egyptian:

 

[slabghost]

over time the gasket material begins to deteriorate. Running water only as I sometimes do can hasten failure as will overheating. Metals expand with heat at different rates. The aluminum heads and blocks expand at a different rate than the bolts that hold them together. So age and number of heat cycles has a lot to do with when a head gasket will fail.

 

[54Greybeard]

Yep, overheating will cause metals to expand more than normal, crushing gasket and when cause of overheating is fixed, metal doesn't expand as much so you get a leak. As slabghost said, with the heat cycling involved, the gasket eventually wears out. Thankfully, it appears to be a pretty straight forward job, so much so that if I were to experience an overheat and was planning a trip in the not too distant future I'd probably go ahead and do the gaskets and the timing belts before the trip.

 

[scdmarx]

Age may have something to do with it, but that would be last on my list.

First on my list would be cooling system neglect. Electrolysis is very corrosive and very real. It will irrode away metal and gasket material. Proper coolant is a must, and it needs to be replaced with a fresh charge periodically.
Next on my list would be excessive heat. This might occure for a multitude of reasons, to include cooling system neglect. Imagine, dissimilar metals expanding and contracting at different rates, the number of hot/cold cycles over a few years, then you got 4 year old coolant and the 30 year old radiator cap no longer seals and vents the way it should, resulting in some coolant loss which creates hot spots, the original hoses look ok from the outside but flaking away on the inside clogging up passages like radiator tubes........etc. By the time the bike developes the habit of running a little high on the temp gauge most of the damage is already done. You might get by awhile longer, but the cooling system gets weaker and weaker against hot/cold cycles and electrolysis.
Head gaskets are designed to allow metal to "move around" a bit at different temps. But they can only do so much, as the entire system is designed to operate within certain parameters. Once these parameters are exceeded, all bets are off.

 

[54Greybeard]

GOOD POINT! And that brings up another question.....

 

[dan filipi]

Back when engines were made of all cast iron including the heads a blown head gasket was rare if ever as I remember.
Once makers started using aluminum heads we started hearing about blown head gaskets.
Then they started using aluminum blocks and heads, now we hear about it all the time.

IMO the primary cause of a blown head gasket is different expansion rates of the steel bolts and the aluminum, and gasket "age" has nothing to do with it and neither does the corrosive effect of old coolant. This is secondary.
The coolant would have to make it's way in between the head and block for it to compromise the seal.
The way it would get in between is because of the differing expansion rates causing a looser fit between head and block.
Once the seal is compromised from it's original seal it is past the point of no return, retorqueing head bolts will not stop the deterioration of the seal.
The constant heating and cooling starts the whole process and overheating speeds it up 10 fold.

I have done many valve jobs on cars and every one of them I had the head surfaced to be sure it's flat.
This step should never be skipped because if it is the likelihood of blowing again is increased.

 

[danf]

Do many machine shops resurface the goldwing heads or are there any specialty shops for this, and I am assuming the goldwing heads will warp...??? Has anyone had this procedure done to their goldwing heads here is what I'm asking, oh my bike is fine, I just was curious and wanted to learn more on the subject.. Please do tell your experiences..

 

[dan filipi]

I had the 1200 heads I was working on surfaced.
They both had a low spot in the center.

Any machine shop can surface them but they have to be told these are zero clearance heads.
The procedure is to take off the absolute minimum to get a flat surface which shouldn't need a grind to get there.

 

[54Greybeard]

That's right! When engines were cast iron you didn't hear about head gaskets anywhere near as much as you do now. When I first started working at a Cadillac dealer, there were still a lot of the HT 4100's and it's sisters, the 4.5 and the 4.9 V-8's running around. The 4100's especially had head and intake gasket problems. It had an aluminum block and cast iron heads. The gaskets were graphite inpregnated to help with the scrubbing of the gasket caused by the different expansion rates.

 

[danf]

When removing a old bad gasket from either the heads or the block, What is a common solution used, does one use a plastic scraper? What's the best way or technicque remove it? Perhaps spray it with something first..????? I'm very curious..

 

[dan filipi]

I use a razor blade to get the material off then finish up with green scotchbrite to polish the surface completely clean and smooth.
When installing I spray both sides of the gasket with Copper coat, I feel it provides a better bond for the gasket to stay put and also fills any voids in the metal and gasket itself.
I started using Copper coat after having a Saber Cycle gasket start leaking after a short time.
There are mixed opinions whether it should be used or not, works for me.

This head gasket was from Saber Cycle.

 

[89-300ce]

The 4100's especially had head and intake gasket problems. It had an aluminum block and cast iron heads. The gaskets were graphite inpregnated to help with the scrubbing of the gasket caused by the different expansion rates.

Now that's an odd combination. Any idea why they would have used iron heads on an aluminum block?

Jorg

 

[mcgovern61]

Now that's an odd combination. Any idea why they would have used iron heads on an aluminum block?

Jorg

It was actually common. Ford went through this with their 3.8 liter engine in the original Windstar in 1995. It would blow head gaskets more often than changing the oil! I had a used 95 Windstar that I purchased the extended warranty on and it went through 2 head rebuild and 1 block as a result of blown head gaskets. It was a shame because it was a really good, comfortable easy to drive vehicle otherwise. Good thing I got the warranty......they picked up the tab all the way to 100K miles (when I finally traded it in).

 

[54Greybeard]

think because the block was easier to cast than the heads. This was the 80's and about the only ones that had any experience with casting aluminum here was the marine industry. Mercury Marine actually did the casting for the ZR-1 for Chevy.

 

[n5mdvcolorado52]

Been a Mechanic for 40 Plus years my experience is majority of time engine has been overheated at one point in time.

 

[kevinweston]

with doing my i would said age and anitfreeze.

 

[danf]

I agree heat is the problem, so. The number one problem is excessive heat I think most will agree...So low oil, and a fan switch not working will cause major heat along with low or no antifreeze in the engine will cause problems, maybe a water pump gone south or a stuck thermostat would also cause major heat....Did I miss anything? oh and oil pump bad or low oil pressure...