Crack in block on a 3306 Cat motor

[imabigdave]

So, I've got a D5B with a 3306 motor. Had it for a few (maybe 10) years, put a few hours on it logging and so on. A few (sadly) years ago, I noticed it leaking oil, and discovered that there was a crack in the back left corner (literally the corner) of the block, where the flywheel housing and the bottom plate that the oil-pan seals to meet. So, after talking to a couple of people, I was told that the best way to deal with it was to clean it up, groove out the crack and then use devcon (like JB-weld) on it both inside (where the flywheel housing seals up against it (I was gonna attach a picture but can't find them on my computer) and outside, and that I'd have no more trouble with it.

So, I did...the crack actually looked like someone had HAD the block out with the flywheel housing off of it, and then put a bolt in about a 1/4 of the way and then tried to lift the block with that bolt... if the seal and the seal edge of the flywheel housing was just a little bit wider it would have sealed it off. Anyway, I used a cutoff wheel on a die grinder to clean out the crack, put a bolt with a bunch of washers on it in the involved bolt hole to hold it in place, mixed up the devcon and put it in, smoothed and sanded the edge on the back of the block and let it sit for whatever the recommended cure time was plus a few days. Put the thing back together, got my neighbor back over with his backhoe to put the motor back in the machine (I'd built a stand for the motor so it was easy to work on) then put all the accessories back on (hyd tank and hoses, hardnose, rops). Started it up and it ran like a raped ape, not leaking oil out of the crack, but it was spilling out the back, because like a MORON I spaced on replacing the rear-main-seal. I don't believe I've ever cussed myself out so much. The service manual had said it was "recommended" to replace the rear seal if you removed the flywheel housing. I'd looked at it and it didn't show any wear, so since when I'd ordered all of my parts, I'd given the number for the FRONT seal, I didn't have one to put in and I was in a hurry to get the machine back together....

Sorry if this is too long....anyway, after an some injuries and watching my body deteriorate, I'd started to rethink the "oh, who needs a college education" thing that had worked so well for me up until then, so I was actually ready to go away to school (I'm pursuing a DVM), so I ran out of time to work on the Cat. Fastforward a couple of years, finally have some time this summer, so I started tearing it apart this winter (no fun task, since I only have an open hay-shed to work in) and then finally got to the point of pulling the motor this summer. I've finally got it all back together with a new rear-main-seal (even splurged on the cat dealer with their handy seal installers to come out and put it in for me) and a freshly rodded out radiator (here's a hint for those playing at home, DON'T leave a radiator open and unattended for months at a time, the critters move in and make nests, and then your engine overheats).

So the rear seal is good, but NOW I've got a little oil seeping at the crack that originally instigated this. I'm NOT gonna pull this motor again until something else major needs to be done to it, so I was thinking of just cleaning the area that's seeping up with some acetone (and getting the paint off, of course) and smearing some devcon on top of it. I'm thinking that with the crack involving a bolt hole (and a couple of people that looked at it were baffled as to how it could have happened except for a mfg. defect) that taking it apart, torquing and untorqing that bolt might have spread it. I'd pondered when I'd had it apart to drill out the threads on the "loose" piece and then drill and tap the block deeper and use a longer bolt in that hole, so that the threading of the bolt wouldn't have the risk of spreading the crack.

My questions is: Is there anything ELSE that I could use to basically just seal that crack from the OUTSIDE? OR, should I just use 90wt oil in the crankase so it can't seep as easily Has anyone else dealt successfully with this kind of problem? Again, sorry about the lengthy back-story, it probably wasn't necessary except to vent my frustrations...I hate fixing something twice, much less THREE times.

 

[IH270A]

Its hard for me to imagine exactly where the crack is , but if you can ge to it to smear
on jb weld or the like .. why not just clean it with a die grinder and weld it up using a
nomacast .. or apollo b welding rod on a low heat setting .... I had a d-4 cat once
that a friend , had let freeze and burst while he was using it for some clearing , and
that is how I fixed it .... to this day another friend of mine owns it , and it still works
just fine ....

 

[imabigdave]

IH270A,

I had thought about welding it, but since there's a gasket RIGHT there between the back edge of the block and the flywheel housing (which forms the back wall of the block), and another between the bottom edge of the block and the bottom plate. I didn't want to take the chance of burning that up or otherwise damaging it with the heat.....I wish I had those pictures.....but I'm almost positive that they're at my "college" home 2 hours away. If this helps, it's not so much of a "crack" as there's a chip out of the back lower corner of the block. I don't even have a scanner here to be able to draw the crack into the picture on the parts book

 

[IH270A]

if it is at least an inch away from those gaskets , you can get some heat sink at a welding supply store ,, then set up an air line with a valve and and a nozzle of some kind , blowing right on the area above the gasket .. should stay prettty cool as long as you use low heat

 

[IH270A]

also .. at the local parts store .. or at least the advance stores here have it .. there is small jar of stuff called thermal weld ,, I think ,, it goes on then as the engine heats up it bonds itself to the metal ....

 

[imabigdave]

yeah, well, the original crack runs clear to the gasket, and my other concern is that if I start welding on it, I'll open up what portion of the devcon IS holding (because it's not leaking as badly as it was originally).....might try that thermal weld, I'll see if anyone's got it here. Thanks for all the input, I appreciate it.

 

[D6c10K]

If there is some vibration movement at the crack I'd be suprised if you can get Devcon type epoxy materials to hold...they'll likely crack too.

You might try roughing up the Devcon and the surrounding area, clean it real good and spread a thick layer of silicone over the top to make a flexible seal....not sure if it will stay, but it won't cost much to try.

Might not work in your case since the crack runs to the edge (if I understand your description), but I've heard of a system to repair cracked blocks that uses a series of screw-in plugs closely spaced along the crack....after the first set of plugs is in you put in another set of plugs between the first ones. The second set overlaps into the first creating a full-length patch. Can't remember the company name, but perhaps someone here knows of it.

 

[BIG D]

one of the problems with this type of repair is cast iron and mainy repair items like previously mentioned expand at differerent rate and dont hold look for a bonding material that takes on the same properites that they are applied too I have used in past moleculear metal also sweating oil from the block with a torch is a necessary to get bonding material to hold another though making a patch shaped the same as the outer surface and use a gasket and lots of silicone and small screws good luck BIG D

 

[IH270A]

Hey !! big d gave me an Idea ... go to your local automotive paint store .. you can get a can of the rhino lining .. like they use in truck beds , it is resistant to oils and is a urethane based material wich is really sticky and clean it with acetone or siumilar and spray the rhino liner on it

 

[Iron Horse]

Without knowing what the area looks like , it's hard to say . If it's an open area you can drill the start of the crack , tap a thread in the hole and screw a mild steel bolt into the hole with Loctite on it . Cut off the bolt and grind flush . Center punch the side of the bolt on the crack side and drill and tap another hole . Repeat the first step untill you get to the other end of the crack . The finished job will look like a series of half moons , this is called stitching and will seal any crack , even in pre combustion chambers .

 

[OCR]

Iron Horse... The Thinker

That's an amazing piece of info you just provided there, Iron Horse.

I've got a picture in my minds eye, just from your descripton... what size bolt
would you normally use?

You could drill all the way through too... if necessay... if there were no interference problems on the inside???

Might not be good to drill through... but if you had to... put some grease on
the bit, just when it's going to go through... should help catch the chips from
falling off inside.

Again... very good info... Thank you.


OCR

 

[RonG]

Here is a company that has this refined and might be a good source of supplies or at least fresh ideas on this stitching if you want to know more about it.Ron G
http://www.locknstitch.com/

 

[D6c10K]

Yea, Locknstitch....that's the one I was trying to describe.

 

[Iron Horse]

I've got a picture in my minds eye, just from your descripton... what size bolt
would you normally use?

OCR

It depends on the crack and if there are pieces missing ie. an open crack . But 1/4-5/16 is about the usual size .