32v_dohc Posted August 30, 2008 Report Share Posted August 30, 2008 I have the engine out of my 99 SLS for head gasket replacement. When I removed the gaskets I found that four of the eight fire rings had a crack at the location where the gasket passes between two cylinders. The crack was on the block side and at the combustion edge where the fire ring just touches the block deck. The longest crack was about 1 inch long and on the cylinder that had coolant intrusion. I inspected the block face and the chamfer at the top of the bore has a sharp edge where the cylinder liner material was displaced upward as the chamfer was made. This creates a full ring around the bore with a protruding sharp edge that you can catch with a fingernail. This edge is in the same radial location as the fire ring cracks. The edge is present and uniform on all eight bores. Has anyone else seen this "feature" on other blocks? Does anyone have an idea about how to address the sharp edge? This appears to be what caused my head gasket failure as all 20 of my bolts loosened with a crack sound and were tight. There also appears little evidence of corrosion except at the gasket itself. My gut feeling is the repair will be less than permanent if I just put it back together without doing something to keep the gasket from being damaged by this sharp edge. Also I tried to take picture but my camera would not focus on the edge of the bore or the crack in the gasket. John Link to comment Share on other sites More sharing options...
Bruce Nunnally Posted August 30, 2008 Report Share Posted August 30, 2008 This sounds like a situation where the Dealer would put a new block in. If you are observing what you believe was a flaw in the original manufacture of the block then other qualities of the block may be flawed as well. You might take it to an engine machine shop that specializes in block preparation and get the block evaluated. Bruce 2023 Cadillac CT4-V Blackwing Follow me on: Twitter Instagram Youtube Link to comment Share on other sites More sharing options...
Cadillac Jim Posted August 30, 2008 Report Share Posted August 30, 2008 You might also consider taking some really good macrophoto pictures of the block edge and the head gastket areas and calling GM Customer Service. At this late date, their stock of parts is nearing stasis and they might just send you a new block free. If you post the photos on photobucket and dislplay them here, it will make an easy way to email the photos should they ask (hint, hint!). -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
32v_dohc Posted August 30, 2008 Author Report Share Posted August 30, 2008 I don't necessarily think the block is defective. The process of machining the chamfer looks like is happened to quickly with too much pressure and too dull a tool. This kicked up a burr and the block was not deburred properly. Since it is uniform on all bores I wondered if it was done purposefully to act as an oring or if the order in which the machining processes were accomplished was incorrect. If this appears on all blocks then it may explain why the gaskets fail. A minor failure in this area will quick corrode the gasket due to combustion gasses and allow coolant into the bolt holes. Then it becomes a race of whether the coolant in the bolt holes loosens the before the crack in the gasket stops being water tight and the engine starts running rough. I am trying to understand what happened so that I need not do this job again. This is a picture of the cracked gasket This is a pick of the sharp area on the bore. The raised area is .010-.015 wide and .002-.005 tall. This is another picture of the raised area. John Link to comment Share on other sites More sharing options...
KHE Posted August 31, 2008 Report Share Posted August 31, 2008 Not sure what the issue is but it sounds like a raised portion on the block deck surface??? If so, you might want to knock it down with a stone. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
joeb Posted August 31, 2008 Report Share Posted August 31, 2008 are you sure that ridge is not just carbon buildup? there is a ridge on top of the cylinders for gasket sealing but i did not see the ridge in your pictures on my motor. try using some gasket removal spray and letting it soak in. Link to comment Share on other sites More sharing options...
32v_dohc Posted August 31, 2008 Author Report Share Posted August 31, 2008 If you look at the third picture at one third from the bottom and one third from the left you will see the area between the eyebrow reliefs in the piston. As you move right across the picture the black line is the chamfer at the top of the bore. It looks black because of the angle of the photo. The photo is not from straight on but angled to catch the glint of the jagged outside edge of the raised metal. The bright dots that have a weld spatter look next to the chamfer are the raised feature I am talking about. It kind of looks like the edge made when you grind something with too much pressure and the edge rolls over instead of being cut. I think the answer is to remove it but it bothers me that all eight bore look exactly like this and all bores are uniform around the circumference. Joeb can you describe the ridge you found at the top of the bores? Thanks John Link to comment Share on other sites More sharing options...
joeb Posted September 2, 2008 Report Share Posted September 2, 2008 i read about this ridge on another caddy website. i never really saw any such ridge on my block. if it does exist, it has to be on top of the cylinder sleeve. have you inspected your block carefully? does the top of the cylinders seem flat? i will see if i can find the thread at the other website that mentions this ridge. Link to comment Share on other sites More sharing options...
32v_dohc Posted September 2, 2008 Author Report Share Posted September 2, 2008 My block appears to have been decked flat at the factory. Then the chamfer was cut pushing metal higher than the deck surface on top of the sleeve. Then the block was finish honed removing any metal that was sticking into the bore. This left a perfect ring of metal above the bore that bites into the fire ring. I would like to see the other thread if you can find it. I also wish the guru was still here so I could ask him about it. Thanks John Link to comment Share on other sites More sharing options...
Ranger Posted September 3, 2008 Report Share Posted September 3, 2008 My block appears to have been decked flat at the factory. Then the chamfer was cut pushing metal higher than the deck surface on top of the sleeve. Then the block was finish honed removing any metal that was sticking into the bore. This left a perfect ring of metal above the bore that bites into the fire ring. I would like to see the other thread if you can find it. I also wish the guru was still here so I could ask him about it. Thanks John Boy, don't we all. AJ is a Caddy tech and posted here a few times. I don't know if he comes back anymore, but I do know that he is at the other Caddy site. Link to comment Share on other sites More sharing options...
Bruce Nunnally Posted September 3, 2008 Report Share Posted September 3, 2008 AJ posted recently; he is in the process of moving and will be offline for a bit. Bruce 2023 Cadillac CT4-V Blackwing Follow me on: Twitter Instagram Youtube Link to comment Share on other sites More sharing options...
Ranger Posted September 4, 2008 Report Share Posted September 4, 2008 Oh yeah. I forgot, he's in the process of moving to Charlotte N.C. Link to comment Share on other sites More sharing options...
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