Intake leak? Head gasket failure?

[Archaic2021]

So my 97 silverado 5.0 vortec is having issues

Misfire on cylinder 2
Plug shows some contamination
Compression is 150lbs on this cylinder 150- 155 on the others.
Truck was low on coolant so added coolant
Gurgling through Heater core
Truck is back low on coolant (Park on grass no leaks detected)

The oil level seems to be high like...pretty good amount over the top dot on the district but does not look milky
Good oil pressure
Doesn't run hot


I am not familiar with these vortecs

Could the intake be leaking???

Or is this more than likely a headgasket issue.

Depending on what I decide to do I would like to build this Truck since my grandad left it to me. Lower it...repaint...and build a mold motor build.


If it's just an intake gasket issue I could replace all that pretty easy. .head gasket I might as well run it until I get a motor ready.

 

[east302]

Could be an intake gasket but could just as easily be a water pump or something else. Pressure test the cooling system and see if you spot the leak.

Is the seam between the intake and block wet at the front or back?

 

[1998_K1500_Sub]

The radiator tanks tend to leak. Mine used coolant at a low rate for many years. Suspected the radiator tank b/c my nose told me so, but could never spot the leak. Eventually it got bad enough that I spotted the residue on the driver's side tank. Replaced the radiator and now it uses zero coolant.

I did also have the intake gasket leak, but it came on fast and made itself noticed on the dipstick. It was fixed pronto.

 

[97Burban57]

Definitely pressure test, i just found a leaky rear heater core hose that only showed up after a pressure test, I was losing 1 inch of coolant per month.

 

[Archaic2021]

Did a pressure test no visible leaks.

Guess it's time to rip the intake off

 

[Pinger]

When my (99 Vortec) inlet gaskets were shot it lost coolant (showed leakage at the front between manifold and block) used oil, never overheated but when shut off warm gurgled behind the dash on passenger side (overflow bottle I assumed but possibly heater core).

 

[Archaic2021]

I hope that's all it is, the truck right now just goes on a 10 minute trip to the gas station and back right now but I need to get it road worthy

 

[Dariusz Salomon]

The radiator tanks tend to leak. Mine used coolant at a low rate for many years. Suspected the radiator tank b/c my nose told me so, but could never spot the leak. Eventually it got bad enough that I spotted the residue on the driver's side tank. Replaced the radiator and now it uses zero coolant.

I did also have the intake gasket leak, but it came on fast and made itself noticed on the dipstick. It was fixed pronto.

X2 on this-mine has been losing coolant for since I bought it and only recently I addressed the issue-it leaks around the colling lines ports-never visible leak-just rcoolant residue. I suspected all gaskets-had a steam from the tail pipe-but then tested for fumes in coolant and that calmed me down. Now I'm addressing the issue-radiator,cooler lines-the lot.