Diagnosis needed, no compression, help pls

1995Tahoe · May 30, 2016

1995 Tahoe, 5.7L TBI
180k miles
"Rebuilt heads" from previous owner

Ran compression test, 8=120, 6=120, 4=110, cyl2 was at 0, needle didn't even flinch when cranking. New plug in 2 was covered with soot. Bad tick from passenger side of engine. Bad power, bad fuel consumption. Oil pressure goes down to almost 0 while driving, but will increase under high RPM. BUT no smoke. strange. what are the chances it's rings? Thanks all.

DallasTahoe · May 30, 2016

1995Tahoe said:
1995 Tahoe, 5.7L TBI
180k miles
"Rebuilt heads" from previous owner

Ran compression test, 8=120, 6=120, 4=110, cyl2 was at 0, needle didn't even flinch when cranking. New plug in 2 was covered with soot. Bad tick from passenger side of engine. Bad power, bad fuel consumption. Oil pressure goes down to almost 0 while driving, but will increase under high RPM. BUT no smoke. strange. what are the chances it's rings? Thanks all.

Sounds familiar, I'm thinkin blown head gasket between cyls 2 & 4 or atleast partially between the two cyls.

Sent from my iPhone using Tapatalk

1995Tahoe · May 30, 2016

DallasTahoe said:
Sounds familiar, I'm thinkin blown head gasket between cyls 2 & 4 or atleast partially between the two cyls.

The heads were just rebuilt from the previous owner tho. You still think it's the head gasket?

DallasTahoe · May 30, 2016

Unless you have a camera to fit in the spark plug hole to see, or maybe pull a valve cover to see if maybe you have a broken valve spring, the only way to really know is to pull the head

Sent from my iPhone using Tapatalk

SunlitComet · May 30, 2016

a blown gasket will not cause a zero oil pressure issue. inspect your valve clearance for that dead cylinder and strongly consider you may need to tear off the top end for more clues.

SunlitComet · May 30, 2016

also if the rings alone caused no compression you would see smoke. and if ring caused zero compression, you can kiss that piston and cylinder hole good bye. pressure issue is either bad bearings, clogged or broken pump or blown lifter but the last is very unlikely.

1995Tahoe · May 31, 2016

DallasTahoe said:
the only way to really know is to pull the head

What would I be looking for?

SunlitComet said:
inspect your valve clearance for that dead cylinder and strongly consider you may need to tear off the top end for more clues.

Inspect valve clearance like if it's hitting the piston?

Like above, what would I be looking for if I were to pull the head?

Thanks.

1995Tahoe · May 31, 2016

Aaand it just backfired on me on the way to work. I was making a somewhat sharp turn, nothing crazy though.

ccapehartusarmyINF.(ret) · Jun 2, 2016

backfireing indicates lean mixture wich points to valve timing

DallasTahoe · Jun 2, 2016

ccapehartusarmyINF.(ret) said:
backfireing indicates lean mixture wich points to valve timing

Backfiring doesn't indicate a lean mixture, it indicates timing

Sent from my iPhone using Tapatalk

Diagnosis needed, no compression, help pls

1995Tahoe

TYF Newbie

DallasTahoe

Full Access Member

1995Tahoe

TYF Newbie

DallasTahoe

Full Access Member

SunlitComet

OBS Jedi-Do Good

SunlitComet

OBS Jedi-Do Good

1995Tahoe

TYF Newbie

1995Tahoe

TYF Newbie

ccapehartusarmyINF.(ret)

Full Access Member

DallasTahoe

Full Access Member

Forum statistics

Latest posts