Cracked Piston Help
06-19-2009, 09:21 AM
#12
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Join Date: Jun 2009
Location: Utah
Posts: 7
06-19-2009, 11:45 AM
#13
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Join Date: Sep 2008
Location: tn
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During a compression test you are checking all the cylinders and comparing them to each other. If one is lower then the rest then you add oil, if the pressure comes back up then you have bad rings. If the oil does nothing then is is either a hole in the piston or a bad valve. If 2 cylinders right next to each other are low then it is probably a head gasket.
The next step is to do a leak down test. You do this with both valves closed and piston at TDC. During this test you are filling the cylinder with compressed air and listen for leaks. If air comes out of the sparkplug hole next to the cylinder your testing then its a head gasket, if it come out of the dipstick then its a bad ring, if it comes out of the TB then its a bad intake valve, and if it comes out of the exhaust then its a bad exhaust valve.
If you do have a cracked piston it will react like a bad ring during the tests. Cracked pistons are caused by detonation.
The next step is to do a leak down test. You do this with both valves closed and piston at TDC. During this test you are filling the cylinder with compressed air and listen for leaks. If air comes out of the sparkplug hole next to the cylinder your testing then its a head gasket, if it come out of the dipstick then its a bad ring, if it comes out of the TB then its a bad intake valve, and if it comes out of the exhaust then its a bad exhaust valve.
If you do have a cracked piston it will react like a bad ring during the tests. Cracked pistons are caused by detonation.
06-19-2009, 03:46 PM
#16
3rd Gear Member
Join Date: Aug 2008
Location: Oklahoma
Posts: 912
During a compression test you are checking all the cylinders and comparing them to each other. If one is lower then the rest then you add oil, if the pressure comes back up then you have bad rings. If the oil does nothing then is is either a hole in the piston or a bad valve. If 2 cylinders right next to each other are low then it is probably a head gasket.
The next step is to do a leak down test. You do this with both valves closed and piston at TDC. During this test you are filling the cylinder with compressed air and listen for leaks. If air comes out of the sparkplug hole next to the cylinder your testing then its a head gasket, if it come out of the dipstick then its a bad ring, if it comes out of the TB then its a bad intake valve, and if it comes out of the exhaust then its a bad exhaust valve.
If you do have a cracked piston it will react like a bad ring during the tests. Cracked pistons are caused by detonation.
The next step is to do a leak down test. You do this with both valves closed and piston at TDC. During this test you are filling the cylinder with compressed air and listen for leaks. If air comes out of the sparkplug hole next to the cylinder your testing then its a head gasket, if it come out of the dipstick then its a bad ring, if it comes out of the TB then its a bad intake valve, and if it comes out of the exhaust then its a bad exhaust valve.
If you do have a cracked piston it will react like a bad ring during the tests. Cracked pistons are caused by detonation.
Not necessarily, ring lands fail all the time due to cylinder pressures.
06-23-2009, 07:35 PM
#17
Thread Starter
Join Date: Jun 2009
Location: Utah
Posts: 7
Well my car goes in wed to a friends family shop for a compression test. But they quoted us at 400 for a valve and 600 if it's piston swap and any minor work to the block. Is that a relatively good price for that kinda work? Most places quoted me a few hundred more.
06-24-2009, 12:25 AM
#18
3rd Gear Member
Join Date: Jun 2007
Location:
Posts: 516
wow, for the amount of work, to get a piston out, I think that is a hell of a price IMO. They have to test it, make the call, pull the motor, drop the pan, pull the heads, mess with the timing chains, and then put it all back together to spec. Some might do this kind of stuff on a regular basis, but for a newb, that is money well spent.
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