If Magnafluxing doesn't work on Al, how do I check for cracks?

I'm picking up a car that is supposed to have "cracked heads". It overheated and ran hot for a while. The heads are Al and I'm not sure if it's blown head gaskets and warped heads OR if they really are cracked. How can I check for cracks?

Now, I know the cracks should be on the intake side of the head where the head bolts go through, but will I see them?

I hate to spend $150 for a shop to tell me they're cracked when I could get another set for $200. Who wants to spend time and money on heads to find out they were a mistake? So, how can I avoid the waste?

You can't magnatize an aluminum head so how do you check it for cracks? A dye?

Still learning,
Ben T.

They use some thing like perma glow or some kind of name like that. It is a dye that you paint all over the aluminium part then clean it off and go over it with a black light and it shows the cracks.

Originally posted by StudyTime
I'm picking up a car that is supposed to have "cracked heads". It overheated and ran hot for a while. The heads are Al and I'm not sure if it's blown head gaskets and warped heads OR if they really are cracked. How can I check for cracks?

Now, I know the cracks should be on the intake side of the head where the head bolts go through, but will I see them?

I hate to spend $150 for a shop to tell me they're cracked when I could get another set for $200. Who wants to spend time and money on heads to find out they were a mistake? So, how can I avoid the waste?

You can't magnatize an aluminum head so how do you check it for cracks? A dye?

Still learning,
Ben T.

You use a process called "zyglo" on aluminum then you could follow up with a sonic check for surface thickness imperfections.

On my heads, they shaved a little bit from them to make sure they were true, then they vaccum tested them on some kind of fixture. I'm not sure of the exact process, but those heads had gotten darned hot and are perfectly fine.

I'm also not sure that aluminum heads can "crack" I think they will just warp... But, my .02 cents is only worth about.00005 cents on that :)

-Shannon