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Head Gasket blown twice

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austin10_4

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Another problem with the Austin!

The head gasket has blown 3 times altogether now, since we have been looking after it.

The first time wasn't much of a shock, as this was an old gasket which had done many miles before.
So, we replaced the gasket making sure we tightened all the nuts in the correct order up to 30lb using a torque wrench. After not many more than 100 miles, we suddenly started noticing a scratching noise turning into a thump followed by a loss of compression between sparks 3/4 as apposed to 1/2 the first time. So, putting this down to bad luck, we proceeded to change the gasket yet again. Today, the mileometer reads 130 miles since we changed and after the inital 100 miles, we retightened the nuts to 30lb. We took the car out about an hour ago, and the same thing happened. The small scratch turned into a loud banging but we managed to get home. once at home, we left the car for a bit and returned to find no compression in the engine, and oil being spat out the exhaust so it must be the gasket again.

Now, seeing as this is the 3rd time its blow, im guessing the cylinder head must need skimming and possibly the block.
Please can anyone advise whether this is the case, or something else needs doing. Also, if skimming is required, how much do you think it is likely to cost?
Thanks Guys.
 
Austin, the best way to tell if either needs skimming is to place a straight edge on the flat surface and try to insert a feeler gauge under it at various points. It has to be a true straightedge to get meaningful readings. Any variance of over .002" is cause to have the surface renewed. Perhaps a local machine shop can perform this for you, as the straightedge is a rather expensive item. The minimum amount of material to be removed will be dictated by the amount of warpage, but rarely is over about .010"~.015".
A friend of mine who races an MGB went through several head gaskets last year, and actually blew a freeze plug out of the block on two occasions. He finally traced it to an uneven block deck. He had it skimmed flat, and has had no further problems.
Jeff
 
Ok a little update. Today i took the head off.

Here's the pictures of the gasket. As is clear from them, the gasket has not fully blown out yet, but was very near. Also, part of the gasket is wedged under exhaust valve, and the gasket is breaking up on the far end between sparks 3/4. This time it blew in 1/2 again. Does anyone else think that by looking at the state of the gasket, after only 100 miles it is in very poor condition with it breaking apart in some places? Maybe i should change my gasket provider? Thoughts??

Blown Gasket
https://img405.imageshack.us/my.php?image=pict0842do9.jpg

Breaking Up
https://img526.imageshack.us/my.php?image=pict0846gt2.jpg

Overview
https://img526.imageshack.us/my.php?image=pict0854yh7.jpg

After removing the gasket today, i noticed 2 things.

My original gasket which did 1000s of miles was made in the UK and the replacements have been from New Zealand.

The original gasket is almost twice as thick as the replacement ones.

Could this point to cheap foreign import gaskets? and not something substanital enough to withstand more than 100 miles?
 
Hard to tell from our vantage point. Is 30lbft the end torque? That sounds rather low. Has your torque wrench ever been calibrated?

Is the cylinder block flat? How about the cylinder head?

What about crankcase ventilation? Is it possible that you have none and are blowing that pressure out wherever it can go?
 
Paul Johnson said:
Hard to tell from our vantage point. Is 30lbft the end torque? That sounds rather low. Has your torque wrench ever been calibrated?

Is the cylinder block flat? How about the cylinder head?

What about crankcase ventilation? Is it possible that you have none and are blowing that pressure out wherever it can go?
Click to expand...

30fl.lb was recommended by the drivers club, but we tend to then put a ring spanner on them and turn them about another half turn. The torque wrench came from a mechanic so im guessing thats ok. The cyclinder block and head is flat as far as i can tell, but ill do some more tests on it later. As for crankcase ventilation, you've lost me there so could you expand on it please?
 
The "folding" evidence at the bolt kinda suggests there's some room for the gasket to 'squirm' with compression/combustion pressures. A machinist's straight-edge and some careful inspection of the head and block are in order. Something has changed shape in there to allow that much distortion.
 
The consensus seems to be that you should check the head and block for flatness before pinning this on some other cause. I agree completely. It could be that the replacement gasket was too thin or otherwise defective but I wouldn't fall into the trap of believing that without making sure the block & head mating surfaces are flat first.

I think the earlier comment about crankcase pressure referred to the possibility of a plugged breather or other vent which would let pressure build up in the crankcase. It's a good thing to check but I think the other things mentioned are far more likely to cause your problem.
 
:bows:
 
Hi Austin 10_4, Call David manners in the UK and see if he has the proper gasket for this engine. You might also talk to Bryan Purvis there too. Cheers---Keoke
 
Has the car overheated in the past?

If so I would recommend you do more than check for true. I would recommend you take it to a competent machine shop that can do a pressure test on it. Possiblity, especially with a cast iron head, that there is a crack around a valve seat.

This would explain repeated gasket failures. When you tighten the bolts, you mention you are using an additional torque to yield type of tightening. If so, better make sure you are using NEW bolts.
 
Thanks for all the help guys, its very much appreciated. Tomorrow i shall take the head to a machinist near us and see if it needs skimming and if it does ill get it done. If it doesnt't then ill get the block checked aswell, but ill go from there. I am also changing my gasket dealer to see what type i get from them. Is it a necessity to change these bolts though? Yes, we did have an overheating problem in the past which is fixed now.
 
Then, again, professionally, I recommend you get the head pressure tested.

Any time bolts are given a torque setting, ft-lbs, etc. Then a degree tightening afterwards(commonly called torque to yield) the bolts are stretched. When they are used more than once the metal stretches inordinately. They should be replaced.
 
RonMacPherson said:
Then, again, professionally, I recommend you get the head pressure tested.

Any time bolts are given a torque setting, ft-lbs, etc. Then a degree tightening afterwards(commonly called torque to yield) the bolts are stretched. When they are used more than once the metal stretches inordinately. They should be replaced.
Click to expand...

Ok, i will get a pressure test done aswell. I will also see what i can do to get some new bolts aswell. Thanks!
 
30 LBS torque seems awfuly low to me for a head. I would think more like 70 to 90, but then i`m no Austin expert. I also think the thickness of the gasket could make a good deal of difference.
I agree with the general consensus about getting the head and block surface checked for trueness {Flat} also have the head pressure tested if possible {any cracks will show themselfs immediately}.
On the torque specs I would deffinately look for the proper specifications {not just take someones word for them} new head Bolts/Studs Nuts and washers {If used} Thouroughly clean each threaded Stud/Bolt hole in the block lightly apply oil to the stud/Bolt threads before inserting them in the block. torque evenly {the proper sequence} I like to use two to three rounds before achiving final torque. {example} The first round I would go 10 then restart and go to 20 then finally to 30
Overheating leads to a strong possibility that the head and/or block is not entirely true. Hopefully they are not too far out as to be skimmed.
Just my .02 cents worth
Kerry
 
AweMan said:
30 LBS torque seems awfuly low to me for a head. I would think more like 70 to 90, but then i`m no Austin expert. I also think the thickness of the gasket could make a good deal of difference.
I agree with the general consensus about getting the head and block surface checked for trueness {Flat} also have the head pressure tested if possible {any cracks will show themselfs immediately}.
On the torque specs I would deffinately look for the proper specifications {not just take someones word for them} new head Bolts/Studs Nuts and washers {If used} Thouroughly clean each threaded Stud/Bolt hole in the block lightly apply oil to the stud/Bolt threads before inserting them in the block. torque evenly {the proper sequence} I like to use two to three rounds before achiving final torque. {example} The first round I would go 10 then restart and go to 20 then finally to 30
Overheating leads to a strong possibility that the head and/or block is not entirely true. Hopefully they are not too far out as to be skimmed.
Just my .02 cents worth
Kerry
Click to expand...

Thankyou- a very useful post. I have asked 3 people about torque including an austin dealer and they all agree 30 lb so ill stick to that. -The head is being checked today and i will most probaly order a new set of studs to go with it. Only ÂŁ30 for 16- Bargain! As for overheating, thats very interestin, as last year, the car was overheating alot and not long after the gasket blew so ill have the block checked aswell. Thanks for everyones help.
 
Though it's a good idea to replace them, I'd not be too worried over the head studs being stretched on an A10: 30 ft/lb torque, and what...15 of 'em? Compression is not too brutal either. The real culprit is likely a warped head. They're comparatively THIN and very prone to warping damage due to overheating. Shape change in the block is less likely but since it's opened up it'd be silly not to check it.
 
Ok, this morning i spoke to a very well trusted company in the Uk called THE AUSTIN TEN MEN and they recommended to torque 35, so thats probaly my first issue. Secondly, they said there are alot of cheap gaskets going around, but they will send a GENUINE austin part, with the austin proof with it, so thats my second problem. Still waiting to hear about the head, but it looks like all these problems are mixed together to spell disaster. Only once i've changed the gasket and done over 200 odd miles will i stop worrying!
 
Quick update for anyone interested /bcforum/images/%%GRAEMLIN_URL%%/smile.gif

New gasket arrived today and has to be twice as thick at least than the others i been receieving. I ordered a new set of studs aswell which turned up and ill replace them just to be on the safe side. The cylinder head is being picked up later and had 1 fowl removed from it, so that could have contributed to the problem.

Thanks again guys you've all been really helpful. /bcforum/images/%%GRAEMLIN_URL%%/thankyousign.gif
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Next, we wanna see the "VROOM!" post! /bcforum/images/%%GRAEMLIN_URL%%/wink.gif
 
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