98 vortec. where all can it leak coolant?

[Constantine]

Everyday before I leave for work Im having to check my coolant level.
Has been like this for 3 weeks or so.
Has always had a slow leak.

I pull the radiator cap and I can see down about 3 inches to the water line.
I can't find any obvious external water leaks.
My oil doesn't have any water in it.

I want to make sure I'm not missing something easy or common before I remove the intake and/ or cylinder heads.
I've also had a cylinder #4 misfire associated with the time frame of the leak which is why I say that.
Hoping it's not running the coolant through the cylinder.

I'm going to pull the plugs and inspect, they are newer delco iridiums.
Plugs, wires, cap & rotor were changed about 13,000 miles ago.

 

[SAATR]

Pressurize the system with a cooling system pressure test tool. If the leak is external, it should become obvious very quickly.

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[rosco]

Is your passenger side floor board wet? That's a sign of the heater core. I had been fighting a similar leak for a while on my Sub, scratched my head for 6 months until I found water in the oil. No leak since I changed out the intake gasket.

 

[mistaake]

Intake gaskets? Common problem. Have it/had it on both my 98 Silverado and 96 Yukon with the 5.7L Vortec.

 

[Constantine]

Pressurize the system with a cooling system pressure test tool. If the leak is external, it should become obvious very quickly.

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Ok I will try that out.

 

[Constantine]

No wetness in the heater core area.

Is there a way to diagnose the intake manifold gaskets without pulling the intake?
I'm not seeing external leakage around the intake manifold.
Most everything I've read so far says I'd have water in the oil.
Will they leak without getting water in the oil?

 

[rosco]

I didn't see any visual indicators other than the dipstick. A compression test could rule out a cracked head, or leaking head gasket.

 

[kennythewelder]

A compression test will tell you if you have a head gasket leak, along with telling you what shape the rings (ECT) are in. A radiator pressure test should find any coolant leak in the cooling system unless the coolant is leaking into a cylinder, and being burned off by the combustion process. In that case, when you pull the plugs, one of them will be real clean from having water in the cylinder. Kind of acting like a steam cleaner inside the cylinder as long as the leak is very small, and from what you describe, your is. I had a small leak in my 97 5.7L a few years ago that I couldn't find. With a pressure tester, I found it, but could only see it with a mirror. It was leaking from where the head, block and intake all come together on the drivers side, next to the fire wall. With out a pressure tester, I would have never found the leak. Just running the truck wasn't enough to make the leak show. Like you I would just loose a little antifreeze at a time.

 

[Ckeene]

Having same problem with my 99 k2500 suburban I am hoping it is not the intake

 

[kennythewelder]

I replaced my intake manifold gaskets in about 1 day on mine. It wasn't a hard job. I took pics before I started with my phone, so I could see how things were before I started. There are some good videos on youtube, just type in vortec 5.7L intake.