is this a bad crack in crankcase?

hcoles · 04-29-2008, 11:14 AM

A continuation of top end rebuild..

After some washing off of 20 years of grease/dirt.. we see this.

Near the bosses that hold the rear engine mount on a 3.2 cab.

We are hoping this has been there for a long time.. maybe just clean very well and cover with JB Weld and continue with the rebuild.. maybe get someone to throw a bead on it.... don't know please help..

Thanks.

Big view of where crack is

a close up view

another attempt at close up view

thanks much for any comments or ideas on what to do now...

Flieger · Flieger's Garage

Looks like a casting mark to me. I have seen several worried owners on the BBS who think they see cracks in transaxles or cases only to find that it is just a little wrinkle from the sand mold.

A low angle shot might help to see if it is actually a fissure into the metal.

SCrescue · SCrescue's Garage

+1 on the casting mark. Surface imperfections resulting from the casting process seem to be fairly common on these cases. Do a search and you'll see that others have questioned similar marks. Doesn't appear to be a crack to me.

Mike...

hcoles · 04-30-2008, 05:33 AM

thanks guys...we were thinking of putting the block in the truck and taking it to the machinist for his opinion...but now maybe not...

Fast Corners · 04-30-2008, 12:14 PM

If the inperfection is raised (which it appears to be) I would say that it is just a casting imperfection. For piece of mind you may want to take a dremmel tool with a sanding drum and sand the raised parts down flush with the rest of the case. If the inperfection disappears then you have your answer.

hcoles · 04-30-2008, 03:51 PM

FC, thanks
One end of the crack seems to have a height offset and then the other end seems to be level at the surface. Maybe the offset casting flaw later caused the crack to form and propigate. Are you saying that all along the crack I should be able to drum sand down a bit and the crack should go away? Pretty much either way we are going to use this case... no bucks to change it. Should we have someone put a bead on top?

boba · 04-30-2008, 04:29 PM

It is hard to tell from the photos. I look at it and seem to see some signs that it is a crack, or could be lighting.

Get some dye penetrant on it and you will know for sure. Then you can plan for a solution if it turns out to be a crack or move on reassured.

Flieger · Flieger's Garage

I don't think a crack that large would pass quality control. If it is that serious of a fissure, it would probably leak oil, be dirty down deep, maybe even flex a little. I think there would be other things apparently wrong other than the crack.

It really looks like a casting mark. If you still are worried, just make some marks with permanent marker or other tough dye to indicate where the line is now. Check it periodically. If it grows, then panic. ;-0

hcoles · 04-30-2008, 07:56 PM

Flieger...good idea. mark it and watch... that boss is under compression I hope...but maybe the bending from the weight of the engine is causing the crack... we have some more time to stare at it... could be I can get a better picture or put some die in it.. I have some Prusian Blue die... should I put that in there and take another picture?

Flieger · Flieger's Garage

sure, you could die it and then sand it lightly as a giude coat to see the low spots/high ridges

Fast Corners · 05-01-2008, 07:22 AM

"Are you saying that all along the crack I should be able to drum sand down a bit and the crack should go away"

hcoles,

I believe that if it is indeed what most people believe it is (a casting inperfection) if you sand down through it you should see no more signs of it. Just take it down flush to the case surface at first. Inspect it (by eye or dye) and then see what you are left with. If it looks like it is disappearing then sand down a little more to see if the rest of the inperfection disappears too. Keep in mind that if the crack is truely a crack it would not propagate from the surface down to the stud as the top surface is in compression.

Stress cracks propagate from stress risers (ie. cut treads) in tension areas. I expect that any crack that is connected with the motor mounting boss will start at the threads that the stud bears on and then proagate up to the surface.

hcoles · 05-01-2008, 08:31 AM

I'm afraid to say.. it looks like a crack... if sanded down will still be a crack there... I'll look again maybe tonight. We might try some sanding and see what happens. Thanks.

Flieger · Flieger's Garage

I am unclear on what progress has been made. Did you do any dying or sanding?

I am confident this is a casting mark. If you sand it flush, it will eliminate the stress riser and help the fatigue strength at the nth degree.

If you dont want to sand, just dye it and keep an eye on it. A crack that large would probably propagate. It shouldn't get any bigger. You'll be fine.

Flieger · Flieger's Garage

And plus, the way the mark is oriented, it looks like the corner would "fall off" if it was a crack. There would still be meat there to hold the engine. Don't go through a lot of trouble over this small detail.

lindemans · 05-03-2008, 12:01 AM

Between the crack and the edge of the case, it looks like there are dents in the metal.
It looks like the case has been hit here.
The place and direction of the crack seem to match these damages from cause & effect perspective....
Do you know the origin of these marks ?

hcoles · 05-03-2008, 05:46 AM

re. "dents" ... I think they are from Dieter on the production line... his job is to knock down any bad looking spots... he sort of waves the grinder over the area and goes to the next crankcase.. I've seen marks like this in a number of places on the crankcase and on mine as well. I don't think they gave Dieter enough time to do too much.

At this point the machinist (Ted R.) says to just leave it alone. So that's what we do... I think it is a crack that has been there for a long time and isn't going anywhere soon. The casting quality is not perfect on these cases IMHO... but good enough where it counts.