Headgasket and Blackstone Oil Analysis
- Thread starter 97lc_bw
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As mentioned on another thread, I send my samples in and never had any coolant detected and yet my HG was failing and leaking. I'm thinking that alot of coolant has to leak to the oil before it is detected? 
IdahoDoug said:
Was this on the 93, I'd suspect that the 97 with the cracked head would definately came back positive.
turbocruiser said:As mentioned on another thread, I send my samples in and never had any coolant detected and yet my HG was failing and leaking. I'm thinking that alot of coolant has to leak to the oil before it is detected?
With our gaskets failing into the combustion chamber I've always been skeptical about the guarantee of the analysis. Seems feasible that the combustion process burns off the evidence.
Rick,
This was on the 97, which did turn out to be a cracked head releasing coolant directly into the oil, and the sample was taken when the water started dropping precipitously. To me, the water level in the overflow bottle is likely to be the first concrete evidence of a gasket failing. By the time the fire ring is weak enough to allow 12psi water to get past it into the cylinder upon shutdown (thus 'using' coolant), then definitely the much higher psi in the cylinder during operation is pushing combustion gases into the coolant as well.
So:
Watch overflow levels. If they drop, send Blackstone a sample, pull your sparkplugs for a look, check color of oil on dipstick, check underside of oil filler cap for light mud colored deposits,and do bubble test. If it's negative on all counts, put dye in the coolant and get special light and glasses and start looking externally on the block/head seam and everywhere else externally.
Still can't find it?
Rent/buy a radiator pressure tester and adapter for smaller fill necks. Pressurize the cooling system and watch down sparkplug holes as well as continuing to look externally.
DougM
This was on the 97, which did turn out to be a cracked head releasing coolant directly into the oil, and the sample was taken when the water started dropping precipitously. To me, the water level in the overflow bottle is likely to be the first concrete evidence of a gasket failing. By the time the fire ring is weak enough to allow 12psi water to get past it into the cylinder upon shutdown (thus 'using' coolant), then definitely the much higher psi in the cylinder during operation is pushing combustion gases into the coolant as well.
So:
Watch overflow levels. If they drop, send Blackstone a sample, pull your sparkplugs for a look, check color of oil on dipstick, check underside of oil filler cap for light mud colored deposits,and do bubble test. If it's negative on all counts, put dye in the coolant and get special light and glasses and start looking externally on the block/head seam and everywhere else externally.
Still can't find it?
Rent/buy a radiator pressure tester and adapter for smaller fill necks. Pressurize the cooling system and watch down sparkplug holes as well as continuing to look externally.
DougM
