Blown Head Gasket?? How or Why? on an A series engine

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Blown Head Gasket?? How or Why? on an A series engine

Postby SynthDesign » Sat Feb 11, 2012 9:45 am

So the pics are from my 85 AW11 MR2 with 178k on the original 4A-GE engine. Last March, while driving home, the car stalled. Upon restarting it made a horrible noise, like keys in a garbage disposal. I was able to limp it a few hundred feet to a safe place to be towed with almost no power.

After starting it up for a second when it got home, I was pretty sure I had a broken valve/spring or wrist pin. Same thoughts from a few good Toyota Techs.
I pulled then engine and upon inspection, the head looks great as well as the bottom end. What wasn't so good was the head gasket. There's exchange between #1 and #2 cylinder.
The gasket has been burned away by almost 5mm between the cylinders. So far everyone I showed the gasket or pictures to says that's not supposed to happen. Especially on a naturally aspirated engine. There was also a bit of burn through on #3 to #4 but nothing compared to the 1st.
4age head gasket 1.jpg

4age head gasket 2.jpg


So Thoughts? Sans some rotted seals, everything is within spec and clearance for the engine. It ran great before that and never once overheated or had engine issues.
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Re: Blown Head Gasket?? How or Why? on an A series engine

Postby Petros » Mon Feb 13, 2012 10:04 pm

that is how my headgasket fail when I run regular gas (I have high compression engine, must run premium). I would say it is was from detonation from either wrong timing, or poor qualtiy gasoline, or maybe bad EGR?. Try running premium. You also might try the same mod I recommend on the tercel head gasket to improve cooling around that part of the head. YOu already have coolant holes there, so just make them a bit larger to improve coolant circuation. Make sure you use careful installation procedure or torquing down head.
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Re: Blown Head Gasket?? How or Why? on an A series engine

Postby dlb » Tue Feb 14, 2012 6:54 am

since you guys are on the topic, i have a related question. i had a friend suggest to me after doing the head gasket on my wife's truck to remove the valve cover and re-check the head bolts torque after a few weeks or something. i didn't see any mention of that on any of the guides i looked at so i haven't worried about it yet. is this a good practice though?
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Re: Blown Head Gasket?? How or Why? on an A series engine

Postby Petros » Tue Feb 14, 2012 7:42 pm

It always used to be standard practice on older designed head gaskets that you had to retorque the head bolts after it had been run for a short while. THere used to be a required procedure when you bought a new car that you had to bring it back after 500-600 miles of low speed driving (no full throttle) to have it serviced; the dealer mechanics would change the "break-in" oil and retorque the head, and check all the other fluid levers, look for leaks, etc. And I made the mistake once of not retorquing the head on a 1967 Datsun 1600 convertible sports car (now a classic, but than cheap) after a rebuild. I got to replace the head gasket when it blew out at about 700 miles.

The new head gasket designs do not required it, and sometimes I would do it anyway. But I have not noticed a difference, it is just extra work. If you do it, pull back on the head bolt to break it free about 1/8 of a turn and than go to the required torque in the factory sequence.
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Re: Blown Head Gasket?? How or Why? on an A series engine

Postby andrewrenow » Tue Feb 14, 2012 8:40 pm

Petros wrote:It always used to be standard practice on older designed head gaskets that you had to retorque the head bolts after it had been run for a short while. THere used to be a required procedure when you bought a new car that you had to bring it back after 500-600 miles of low speed driving (no full throttle) to have it serviced; the dealer mechanics would change the "break-in" oil and retorque the head, and check all the other fluid levers, look for leaks, etc. And I made the mistake once of not retorquing the head on a 1967 Datsun 1600 convertible sports car (now a classic, but than cheap) after a rebuild. I got to replace the head gasket when it blew out at about 700 miles.

The new head gasket designs do not required it, and sometimes I would do it anyway. But I have not noticed a difference, it is just extra work. If you do it, pull back on the head bolt to break it free about 1/8 of a turn and than go to the required torque in the factory sequence.

thats good info to know i always wondered the same thing about retorquing the head because my uncle always told me something like that but i would never listen to them because their always drunk hahaha.
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Re: Blown Head Gasket?? How or Why? on an A series engine

Postby toughtercel » Sun Feb 19, 2012 5:26 pm

I just finish replacing 3rd head gasket of my wife Tercel FWD less than a year , wondering if some thing really wrong with me ( as mechanic ) or parts, I bought aftermarket head gasket 3 different company also I check out few other part stores at B.C./ Washington , they all looks thick and soft gasket .
First one , it 83-87 H.Gasket (aftermarket) after complete the work, the heat was higher than normal , fail 8 month later .
then second I order ( aftermarket) H.gasket for 80-82 , they have 3 extra hole for coolant circulation, after complete , it sure improve the reading on coolant gauge and run great but then a month later the coolant spray into cylinder .After I took apart ,the gasket was squash with all marks from gallery port , that why I was wonder if aftermarket H.Gasket is too thick and soft material.
So my last stop at Toyota dealer parts department , paid about $ 34 , this H Gasket is way different quality ,more solid but 3 less holes.
while installing H.Gasket job then I discover my small Torque wrench (ratchet) the reading is out of range , by the time I finish at 40 lbs ,it felt i was very strong guy then I grab the bigger torque wrench , set at low as 10 lb/15lb then till 20 lb the bolt was turning so I discover my smaller torque wrench has false reading . Now it on the road two week since complete , I been checking the coolant , have not change , so far so good .

P.S. YES I had my head check for crack, machine the surface , and check all the head bolt for stretch.
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Re: Blown Head Gasket?? How or Why? on an A series engine

Postby xirdneh » Sun Feb 19, 2012 7:58 pm

i have had the best luck with FEL-PRO head gaskets
not so good luck with other brands

i assume you tightened head bolts in proper order
and two or three graduated steps of tightness

is your torque wrench accurate?
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Re: Blown Head Gasket?? How or Why? on an A series engine

Postby SynthDesign » Sat Feb 25, 2012 10:16 pm

@ Petros.
I'm not fully in agreement with the idea of enlarging the coolant ducting holes to the head. From what I was told by the machine shop that does most of my work, a certain pressure is required to make sure each hole gets enough coolant at a certain pressure. By changing the diameter it changes the pressure and can allow starvation to certain points with other areas seeing excess flow. Am I wrong?

And another Yes to FelPro gaskets. Good stuff!
Last edited by SynthDesign on Sun Feb 26, 2012 9:02 pm, edited 1 time in total.
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Re: Blown Head Gasket?? How or Why? on an A series engine

Postby larry mcgrath » Sun Feb 26, 2012 12:44 am

My two cents worth, most of the problem with these engines is getting an air lock in the head. when you fill the radiator remove the heater hose that points UP (i beleive its closest to driver on firewall the other hose points down)fill with coolant until it starts to run out of the heater pipe,instal heaterhose and fill radiator. this will eliminate an air lock in the head and in the heater core.It works. My 2 cents worth.
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Re: Blown Head Gasket?? How or Why? on an A series engine

Postby Petros » Mon Feb 27, 2012 7:02 pm

yes, Synth, when you alter the holes in the head gasket it will alter where the coolant goes. A larger hole in one location means less coolant circulating in others. There is no reason to suspect that the 4age head has coolant circulation issues, this engine was designed by a totally different (more competent) group than the 3ac/4ac, so unless there is any evidence of uneven cooling that it is best to just leave it alone. trapped air in the head can be a problem, the radiator is lower than the engine in this car, and can cause that problem. Not true in in most cars, but there are a few than this can happen, I have had serious trouble with in cars where the filler is below the head. Trapped air is a serious issue that must be dealt with and might have been your problem.

The 3a engine though has evidence of uneven cooling that is why I altered my head gasket, all the evidence was there that they coolant circulation was bad and not up to snuff. My modified head gasket has proven to be far more durable than a stock 3a head gasket. So I did the proper thing for it. Another reason I want to swap out the 3a engine from my car.
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Re: Blown Head Gasket?? How or Why? on an A series engine

Postby toughtercel » Sun Mar 04, 2012 5:38 pm

If you want extra three hole for better coolant circulating , then you may as well order 1980-82 head gasket , instead , I did use it , I am not sure what the difference .
As the air lock .that common on some cars , while I was working as coolant mechanic in the 80's, we jack the car up front end high or front side up ,then we pour anti-freeze in the rad real slow ,if pour fast then air bubbles will get caught in the system .Same thing adding brake fluid into master cylinder , avoid air bubbles
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