[jermaine]

could any one assist me with this crack issues.Ihave some straddle crane brake fluid coolers to repair that has a crack at the toe of the factory weld it only operates at 8 bars so welded over the crack to seal it from leaking but shortly after my weld cracked in the crown.i ground them out and rewelded them using two stringer beads.i have gotten a few more to repair and noticed one of my previous repairs are in it cracked at the same point and another of my previous repair also cracked at a different factory joint. what could have caused the initial cracks and what is the best way to repair them.looking forward to your feedback.

[coldman]

As we all know, aluminium is "hot short" and is therefore prone to cracking under cooling shrinkage. In this case, you are welding up against a heat exchanger with extended surface area fins that removes heat away from your joint too FAST.
The answer is therefore preheat and also post heat. I can't see the size of the whole unit you are repairing and if it will fit in an oven. Maybe you could preheat and with a propane torch and have someone follow up with the propane torch keeping the finned area hot enough to allow your bead to cool at a more normal pace. You will have to be careful not to burn up the fins too.
Good luck and let us know how you get on.

[Drifta-X]

Coolers like this often crack if they are solid mounted.
They should always be rubber mounted to prevent this occurring.

It is a frequent problem with drift cars as they have rock hard suspention.
Intercoolers, oil coolers, steering fluid coolers etc.

[Otto Nobedder]

The crack should also be "stop-drilled". You've got to find, with certainty, each end of the crack, and drill a hole who's edge "just touches" the absolute end of the crack, else your welding will actually extend the crack, often unseen, and it can come back as soon as the metal cools, or hide until it's under pressure.

You've got to be sure of full penetration, as well, or the crack can come back from the bottom.

You can't trust a band-aid cover pass on something that sees 8 bars of pressure, and vibration.

This advice is "in addition" to the very good advice already posted by coldman and Drifta-X.

Steve S

[jermaine]

Thanks guys, i did the pre heat but no post heating gonna try that.is it possible that the cracks in the factory welds were caused from poor penetration