Crankcase crack repair

[radicalfil]

I have just noticed a crack the the crankcase just below the case stud on the bottom of my motor. It is the 2nd case bolt from the rear. I rebuilt this motor a while ago, but it has only about 7,500-10,000 miles on it. Is it possible to repair/weld this crack while the motor is in the car without causing damage to any of the internals? What might be an worthy alternative to welding it? What will be the most likely scenario if I do nothing?

1972 911T MFI Targa
Phil D.

[RickM]

What is the case made out of?

[radicalfil]

whatever Porsche made 1972 2.4L motors out of. My guess is magnesium ? I'm wondering if JBWeld could be at least a temporary fix

[CliffBrown]

Porsche used a JB Weld type product on several parts of the case as SOP. You could try some on the crack and see if it holds, you've got nothing to lose. I would use a dremel to cut a very shallow V in the crack and dry it out with something like brake cleaner before applying the JB Weld.

[radicalfil]

Is there a preference for surface preperation, smooth or rough, in order to acheive optimal bonding of the JB Weld?

phil

[CliffBrown]

I believe a surface free of oil is the most important issue.

[radicalfil]

I'll give it a go the next time I come up to the mountains where the car is being stored, that is a week or two. Don't have my dremel with me.

Thanks for the help
Phil

[adomakin]

JB roks. my bro had a litle 1 litre mini that we lowered by REMOVING the front cones and lopping $hit loads from the rears. he was ripping it down the lanes when SMACK. he hit a high spot in the road and cracked the gearbox case. the crack was nasty-about 60-80mm long and the oil was running out, not dripping out. we drained the oil, stuck it on its side, ground the crack out with a 4inch cutting blade and then blasted it with more or less a whole can of carb cleaner. let it all dry and then filled it with jb weld. it held out for ever. i think he even gave it another clump (although it wasnt as fierce) and it held up. he sold it a couple of years later.

Andy

[audi2.7t]

Just a note ,try using starting fluid to clean the surface ,it dries instantly with no residue.....and a rough surface is preferable for adhesion of JB and other products...
Sam.

[Randy Webb]

You should drill the end or tip of the crack to keep it from expanding. The problem is how to prevent and shards from getting into the engine....

There is a thread with my name on it showing how this was done in a trans.