kencombs Posted January 23, 2020 Report Share Posted January 23, 2020 20 minutes ago, Jocko_51_B3B said: Well, I found the problem. There was a fine crack along the top of the block near the #3 and #4 cylinders. Since the intake and exhaust manifolds were not yet installed I first saw evidence of the crack when I pressurizing the cooling system and saw coolant slowly accumulate inside the #3 #4 exhaust passage on the side of the engine. How coolant got into the oil from up there I'm not totally sure. I had previously had all six cylinders re-sleeved because there was some serious pitting in the #6 cylinder wall and because all six were already .060 over . I'm sure the crack occurred during the re-sleeving work although I can't prove it. With hindsight, if I had to do this again I might not re-sleeve all six cylinders, just the badly pitted one. Also, I would have made sure to have a magnetic particle test performed after any re-sleeving work and before putting the engine together. That might have saved me a ton of trouble and a truck load of wasted time. I'm not an expert on re-sleeving one of these engines, but I'm guessing it puts a lot of stress on the block, but what do I know? It is very unlikely that sleeving caused a crack in that area. While sleeves are a pressed fit, it is not a huge interference and those thin cast sleeves are much weaker than the block so would be the failure point if the machinist did mess up in some way. If it is horizontal, and near head bolt holes it could have been caused by bolts being over-torqued at some time. Some cracks can be repaired. Got a pic? maybe someone can make a suggestion. Quote Link to comment Share on other sites More sharing options...
Jocko_51_B3B Posted January 23, 2020 Author Report Share Posted January 23, 2020 Unfortunately I don't have pictures, but the machine shop took the block back and stitched the crack which corrected the leak so far. Time will tell. When I first bought the truck the block was OK - no coolant in the oil (the oil wasn't new either). The problem first showed up after the re-sleeving. When I put the engine together I was very careful to follow the torque specs for the head bolts and to torque them in the correct order. The only other source of stress on the block would have been when I put it back on the frame with a cherry picker by using four head bolts, but I doubt that would crack the block. Quote Link to comment Share on other sites More sharing options...
kencombs Posted January 24, 2020 Report Share Posted January 24, 2020 2 hours ago, Jocko_51_B3B said: Unfortunately I don't have pictures, but the machine shop took the block back and stitched the crack which corrected the leak so far. Time will tell. When I first bought the truck the block was OK - no coolant in the oil (the oil wasn't new either). The problem first showed up after the re-sleeving. When I put the engine together I was very careful to follow the torque specs for the head bolts and to torque them in the correct order. The only other source of stress on the block would have been when I put it back on the frame with a cherry picker by using four head bolts, but I doubt that would crack the block. it is very possible that it was already cracked, but treated with stop leak sometime in the past. Draining, flushing and cleaning removed the magic stuff. Very common back in the day. Quote Link to comment Share on other sites More sharing options...
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