How an aluminum head is pressure tested for cracks.

The subject head is a 5sfe Toyota DOHC
The procedure will be the same for any head.

First all the old gasket material has to be removed around all the water ports in the head.
Head gasket, thermostat, any ports that flow water.
This procedure is usually done after the head has been checked for warp.



Once that is done the head is placed in the pressure testing fixture.



Next the proper test plate is selected from the stack.



This plate fits this head.

See how it covers all the water ports on the head deck.



Next the clamping bars are placed over the head and tightened down.



any other water ports are blocked of with plates or plugs. One plate has an air fitting so compressed air can fill the water jacket.
On the right end of the head.



Compressed air fills the water jacket, appox 30psi.
Soap water is then sprayed over the head, Looking for bubbles from a crack.

Another side.



Great care is used in the combustion chambers, and all runners, along with the top of the head.
This head was good and showed no signs of cracks for coolant to leak from.

 

Very interesting. Thanks for sharing!

 

Soap water.... I guess you can't have this done with the cams in place?

 

If the cams are below the valve cover rail they can be left in the head. But not many heads are built like that.

One family of heads that the cam can be left in is the Ford Escort SOHC, since the cam runs thu the center of the head.

 

BMW E36 6-cyl, probably not .... ?

 

Is that the older L-6? The Rocker shafts are pressed in from front to back.

If it is the BMW that I am thinking of, then It could be. But I would not want to, for the reason that the cam and rocker shafts would block the view across the top and make it simple to over look a crack across the top of the casting.


It would cost a bit more to have the machine shop R&R the rocker shafts and cam to do the test, But I feel it would be worth the money spent.

 

I have also used a machine that dropped the head into a tub of water to see any air leaks. Both work the same just different ways. I have pressure tested many cylinder heads with that style machine, most agrevating was a flat head v8!!!!

 

tzdevill... the tank style sounds like an Axe brand, there are others that use that design I am sure.

I am not much on that style, beacuse of the upkeep needed, that water reaks in a few days too a week.. even if you add some bleach to it every couple of days, and then too much bleach discolors the alum heads.

 

Ya at that shop we changed the water every week and used some kind of "treatment" they had found.

 

here's my ghetto pressure bench



You slap cylinder head to that, bolt it tight and then measure with leakdown tester

 

muoto... and you test for cracks that way? Or valve seal?

 

valve seal mainly

 

That I can understand then, it would only show a cracked head if it was in the combustion chamber.