Crack, or normal casting? |
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Crack, or normal casting? |
74ravenna |
Sep 24 2016, 10:04 AM
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#1
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Member Group: Members Posts: 471 Joined: 19-October 14 From: nh Member No.: 18,032 Region Association: North East States |
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stugray |
Sep 24 2016, 10:08 AM
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#2
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Advanced Member Group: Members Posts: 3,824 Joined: 17-September 09 From: Longmont, CO Member No.: 10,819 Region Association: None |
casting imperfections.
They are covered in them. |
TheCabinetmaker |
Sep 24 2016, 10:08 AM
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#3
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I drive my car everyday Group: Members Posts: 8,299 Joined: 8-May 03 From: Tulsa, Ok. Member No.: 666 |
What is that we are looking at?
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dangrouche |
Sep 24 2016, 05:16 PM
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#4
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dangrouche Group: Members Posts: 550 Joined: 1-May 04 From: San Francisco Bay Area Member No.: 2,012 Region Association: None |
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injunmort |
Sep 24 2016, 05:24 PM
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#5
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Senior Member Group: Members Posts: 1,024 Joined: 12-April 10 From: sugarloaf ny Member No.: 11,604 Region Association: North East States |
is that the cylinder spigot?
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earossi |
Sep 24 2016, 07:15 PM
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#6
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Member Group: Members Posts: 210 Joined: 8-December 11 From: Chicago, Il Member No.: 13,878 Region Association: Upper MidWest |
Appears to be a surface crack in the spigot on a cylinder. The problem with surface cracks is that with temperature cycling, they will usually propagate. The way to deal with any crack is to grind out the crater until the crack vanishes. Surface cracks in castings usually grind out with very little effort. But, if the crack is found to have propagated through most of the thickness of the casting, you may suffer failure of the spigot.
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stugray |
Sep 25 2016, 01:28 AM
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#7
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Advanced Member Group: Members Posts: 3,824 Joined: 17-September 09 From: Longmont, CO Member No.: 10,819 Region Association: None |
Appears to be a surface crack in the spigot on a cylinder. The problem with surface cracks is that with temperature cycling, they will usually propagate. The way to deal with any crack is to grind out the crater until the crack vanishes. Surface cracks in castings usually grind out with very little effort. But, if the crack is found to have propagated through most of the thickness of the casting, you may suffer failure of the spigot. If that was a crack, my engine would have fallen apart already. Mine is covered with them. |
veekry9 |
Sep 25 2016, 02:09 AM
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#8
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OldMember Group: Retired Members Posts: 3,068 Joined: 17-June 13 From: TO Member No.: 16,025 Region Association: Canada |
Shrinkage of diecast surfaces,a subject of depth and much study to this day.
A high volume,water-cooled,steel die casting mold,was used to make the cases. Some light reading: (IMG:style_emoticons/default/biggrin.gif) https://www.google.ca/search?q=shrinkage+of...quIeNvvlNN5M%3A Shot sleeve barrel: https://www.google.ca/search?q=die+casting+...aMOSyoRZqTjM%3A Metallurgy this year: (IMG:style_emoticons/default/smile.gif) https://www.google.ca/webhp?sourceid=chrome...+aluminum+alloy Method to produce castings to fine tolerance and finish,economically,short run: https://www.google.ca/webhp?sourceid=chrome...ing&tbm=vid / Look! There's more:https://www.youtube.com/results?search_quer...+die+cast+metal https://scholar.google.ca/scholar?q=solidif...bJdBe8QgQMIGjAA To answer the question of why it looks like that,and the other why,'draft'. (IMG:style_emoticons/default/smile.gif) / |
74ravenna |
Sep 25 2016, 04:51 AM
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#9
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Member Group: Members Posts: 471 Joined: 19-October 14 From: nh Member No.: 18,032 Region Association: North East States |
Its the top of the engine where the cylinder head meets the case.
I'm going with casting imperfections. This is my first go around with taking one of these apart and i've never seen the engine clean! Thanks all. Steve |
rgalla9146 |
Sep 25 2016, 05:50 AM
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#10
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Advanced Member Group: Members Posts: 4,538 Joined: 23-November 05 From: Paramus NJ Member No.: 5,176 Region Association: None |
Its the top of the engine where the cylinder head meets the case. I'm going with casting imperfections. This is my first go around with taking one of these apart and i've never seen the engine clean! Thanks all. Steve I agree. Those rise from the surface. A crack would be hollow into the surface. Some of the responses are 'interesting' though ! |
earossi |
Sep 25 2016, 06:27 AM
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#11
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Member Group: Members Posts: 210 Joined: 8-December 11 From: Chicago, Il Member No.: 13,878 Region Association: Upper MidWest |
Its the top of the engine where the cylinder head meets the case. I'm going with casting imperfections. This is my first go around with taking one of these apart and i've never seen the engine clean! Thanks all. Steve I agree. Those rise from the surface. A crack would be hollow into the surface. Some of the responses are 'interesting' though ! Good discussion. On my computer I can't see the depth of the crack. If it is simply a shrinkage crack, then it should grind out easily with a Dremel tool. But, if it is a through crack, it's a different story. |
veekry9 |
Sep 25 2016, 06:48 AM
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#12
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OldMember Group: Retired Members Posts: 3,068 Joined: 17-June 13 From: TO Member No.: 16,025 Region Association: Canada |
Not a crack,it's a 'shrink riser'.
The mold of the part is(was),a polished steel surface of <63rms finish,nearly mirror. As the molten metal cools and changes volume,it shrinks,creating stress risers,and ridges. A superficial blemish,and acceptable in it's application,which may appear as a crack,to the untrained eye. https://www.google.ca/webhp?sourceid=chrome...e+for+aluminium (IMG:style_emoticons/default/smile.gif) / |
74ravenna |
Sep 25 2016, 07:03 AM
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#13
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Member Group: Members Posts: 471 Joined: 19-October 14 From: nh Member No.: 18,032 Region Association: North East States |
Not a crack,it's a 'shrink riser'. The mold of the part is(was),a polished steel surface of <63rms finish,nearly mirror. As the molten metal cools and changes volume,it shrinks,creating stress risers,and ridges. A superficial blemish,and acceptable in it's application,which may appear as a crack,to the untrained eye. https://www.google.ca/webhp?sourceid=chrome...e+for+aluminium (IMG:style_emoticons/default/smile.gif) / "which may appear as a crack,to the untrained eye." Exactly the situation here. Thanks all! |
76-914 |
Sep 25 2016, 07:16 AM
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#14
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Repeat Offender & Resident Subaru Antagonist Group: Members Posts: 13,455 Joined: 23-January 09 From: Temecula, CA Member No.: 9,964 Region Association: Southern California |
I think it happens on all Aluminum engines. The Subaru engine has them as well.
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Mikey914 |
Sep 25 2016, 09:47 AM
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#15
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The rubber man Group: Members Posts: 12,624 Joined: 27-December 04 From: Hillsboro, OR Member No.: 3,348 Region Association: None |
Only one way to tell for sure. File the imperfection flush with the surface and put a drop of penetrating dye on it. A casting imperfection will not reappear.
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bretth |
Sep 25 2016, 10:53 AM
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#16
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Senior Member Group: Members Posts: 899 Joined: 23-June 15 From: Central TX Member No.: 18,882 Region Association: Southwest Region |
I read about using a torch to briefly heat up a suspect crack in magnesium, and you will see it open. Not sure if this works on AL alloys or not.
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Mikey914 |
Sep 25 2016, 02:17 PM
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#17
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The rubber man Group: Members Posts: 12,624 Joined: 27-December 04 From: Hillsboro, OR Member No.: 3,348 Region Association: None |
Wouldn't personally use a torch on this, too many things that can go wrong.
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earossi |
Sep 25 2016, 02:38 PM
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#18
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Member Group: Members Posts: 210 Joined: 8-December 11 From: Chicago, Il Member No.: 13,878 Region Association: Upper MidWest |
Hitting magnesium with a torch will ignite it; so, suggest you not do that. Many years ago, VW used to make magnesium engine cases. One of the reasons they went aluminum was the occasional fire due to magnesiums flamability.
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veekry9 |
Sep 25 2016, 09:56 PM
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#19
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OldMember Group: Retired Members Posts: 3,068 Joined: 17-June 13 From: TO Member No.: 16,025 Region Association: Canada |
https://www.youtube.com/watch?v=AiYnDskFxTo Burning metal! (IMG:style_emoticons/default/blink.gif) VW/Porsche made the Type4 engine from aluminum for it's tensile strength,not for it's 'unflammabilty'. (IMG:style_emoticons/default/dry.gif) Heated magnesium castings to fit interference bearings,circa '70s,did not catch fire back then. Intentionally lit hair-thin magnesium and titanium turnings,and without the added heat of the torch,went out. A puddle of molten magnesium can be lit up with an oxygen rich atmospere and added torch heat. So,yeah,the metal can light up,but,it isn't like it will spontaneously combust. Putting a torch to a casting long enough to melt,will result in a puddle of magnesium on the floor. It would be very difficult to ignite a casting such as the VW cases,the wall thickness and mass too great. Welding the material with ox-ac in the past was a difficult job,no doubt,but quite possible tho. https://www.google.ca/search?q=oxygen-acety...gA&dpr=1.75 https://www.google.ca/webhp?sourceid=chrome...er&start=10 https://www.google.ca/webhp?sourceid=chrome...agnesium+solder https://www.google.ca/webhp?sourceid=chrome...ing%20magnesium https://www.google.ca/webhp?sourceid=chrome...sting+magnesium https://www.google.ca/webhp?sourceid=chrome...e+sand+casting+ https://www.google.ca/webhp?sourceid=chrome...s+burning+metal https://www.google.ca/webhp?sourceid=chrome...e%20ingredients The round spots on the die-cast magnesium engine parts: https://www.google.ca/search?q=ejector+pins...RLODYQQ_AUIBigB / |
earossi |
Sep 25 2016, 11:35 PM
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#20
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Member Group: Members Posts: 210 Joined: 8-December 11 From: Chicago, Il Member No.: 13,878 Region Association: Upper MidWest |
https://www.youtube.com/watch?v=AiYnDskFxTo Burning metal! (IMG:style_emoticons/default/blink.gif) VW/Porsche made the Type4 engine from aluminum for it's tensile strength,not for it's 'unflammabilty'. (IMG:style_emoticons/default/dry.gif) Heated magnesium castings to fit interference bearings,circa '70s,did not catch fire back then. Intentionally lit hair-thin magnesium and titanium turnings,and without the added heat of the torch,went out. A puddle of molten magnesium can be lit up with an oxygen rich atmospere and added torch heat. So,yeah,the metal can light up,but,it isn't like it will spontaneously combust. Putting a torch to a casting long enough to melt,will result in a puddle of magnesium on the floor. It would be very difficult to ignite a casting such as the VW cases,the wall thickness and mass too great. Welding the material with ox-ac in the past was a difficult job,no doubt,but quite possible tho. https://www.google.ca/search?q=oxygen-acety...gA&dpr=1.75 https://www.google.ca/webhp?sourceid=chrome...er&start=10 https://www.google.ca/webhp?sourceid=chrome...agnesium+solder https://www.google.ca/webhp?sourceid=chrome...ing%20magnesium https://www.google.ca/webhp?sourceid=chrome...sting+magnesium https://www.google.ca/webhp?sourceid=chrome...e+sand+casting+ https://www.google.ca/webhp?sourceid=chrome...s+burning+metal https://www.google.ca/webhp?sourceid=chrome...e%20ingredients The round spots on the die-cast magnesium engine parts: https://www.google.ca/search?q=ejector+pins...RLODYQQ_AUIBigB / Without this turning ugly, I suggest that you Google "magnesium fires". If you go back to the early days of the Beetle, VW used magnesium for its cases. The magnesium did not "spontaneously combust". Fires usually started from other faults such as fuel leaks or electrical fires. Once the engine saw fire, the magnesium would combust. I saw one burn like that when I was in college back in the 60's. And, water will not extinguish a magnesium fire. You let them burn until they run out of fuel. Or, you can foam the fire, though I never did witness that. And, I believe that VW went to aluminum because it was less expensive than magnesium, and more stable. Not for its combustibility as you pointed out. |
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