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Discussion Starter · #1 ·
struggling with this. check block and head for flatness and defect. New OE HG installed torque to spec and sequence.


will be pulling head and looking for defects in seal surface around fire rings.
 

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1983 280ZX coupe
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Do a 'leak down test' on all cylinders before removing the head, as this will point to which cylinder or cylinders are leaking into the water jacket. If you don't know what I mean, google 'leak down test'.
 

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1983 280ZX coupe
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No not I'm not talking about a compression test.

Do a 'leak down test' where you apply 100 lb compressed air into each cylinder (at each ones 'top dead center') and thhis test can check each cylinder for 4 things: 1. Whistling sound in the throttle body, means that cylinder has a leaking intake valve. 2. Whistling sound in exhaust pipe means that cylinder has a leaking exhaust valve. 3. Remove oil filler cap and a whistling sound, means that cylinder has leaking or broken ring or rings. 4. Remove radiator cap and seeing bubbles (which your tester is showing), means that cylinder has a leak into the water jacket (my guess it is a leaking head gasket or since your engine runs in maybe a small crack in the head or block into the water jacket). My auto class teacher in high school showed us this, to narrow down which cylinder to look at closer in order to fix a problem.
 

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Discussion Starter · #5 ·
that is what I did used an OEM brand leak down tester, pumped 100 lbs of shop air per the inlet regulator, the output reading was between 95lbs and 97lbs, which is excellent for leak down. could only hear that little bit leaking past the rings (nothing from intake or exhaust).

Update on the chem test coming soon....good news but puzzling news as well.
 

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Discussion Starter · #8 ·
added UV dye as a precursor to some different testing, I was planning to pressurize the system over night and come back to inspect with borescope the cylinders hoping to find coolant. to disburse the dye I ran the engine, while it was chugging along I just figured one more time, and bingo, no more gas... Its a puzzle to me, but if I cant repeat the fail I will take the win. I will do more test next week to see if this was some kind of testing fluke....
 
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