Coolant loss 5.7 vortec

[HotWheelsBurban]

Yeah my 96 Camaro Z28 has that bleeder screw. Oil looks amazingly clean and it hardly uses any oil at 217k miles. I seen cross hatches in the cylinders with my boroscope still.
Coolant temp stays steady around 195-200. Exhaust looks good and it idles perfect. I'm assuming the bubbles came from either opening that rear heater hose fitting or pumping up the system to 15 psi with the tester. Time will tell.

First time I ran into the cooling system bleeder screw was on my 96 Dodge Intrepid, 3.5 overhead cam V6. That was a great car, wish I still had it. Wasn't too bad to work on either, which was good when you had to do the timing job and water pump ( pump driven by timing belt) every 100K. But these cars have some front end issues that are not diy friendly,and expensive if you have a shop do them. That's what got it in the end .....

 

[Steve A]

Most if not all with the bleeder screw is because the top of the engine is higher than the top of the radiator.
Vortec heads are known to crack, especially if they've been hot (overheated), so don't overlook that possibility.
Hopefully you have it fixed.

 

[Jsiff]

Does yours have the rear heater? The plastic heater control valve and plastic T and Y fittings can get pinholes or tiny cracks in them. Won't seep all the time, but that is a place they're prone to leaking.
I guess if it gets hot enough under the hood, the water in the cooling system could evaporate through the bottle vent hose....never thought about it, but it makes a certain amount of sense.

I'm aware of how stupid this sounds, but I honestly don't know.. I have a 99 Tahoe, but it only has rear AC, no rear heat. Yet I am still experiencing the exact same problem original poster shared... any chance of small, slow, coolant loss w/ rear AC and not rear heat? probably not huh? I'm stumped.

 

[1998_K1500_Sub]

I have a 99 Tahoe, but it only has rear AC, no rear heat. Yet I am still experiencing the exact same problem original poster shared... any chance of small, slow, coolant loss w/ rear AC and not rear heat? probably not huh? I'm stumped.

As I mentioned earlier in this thread, I once had a small coolant leak which I could smell but couldn't find, for years (I don't drive my Suburban often, so...).

Eventually I spotted the leak between the radiator driver's side tank and the aluminum core. My nose told me it was in that area, but for the longest time I could not get a visual on it.

Those pesky worm-drive clamps can lead to leaks too, if you have them anywhere in your system. The rubber hose yields beneath them over time and they in effect become "loose", and a coolant leak can appear.

Some folks have leakage problems at the quick-connect fitting on the intake manifold for the heater hose.

These last two have probably already been mentioned, I didn't review the thread

 

[HotWheelsBurban]

The tanks on the composite radiator are prone to cracking after years of bad roads. BTDT on my Burb. It leaked there a little bit for a year, and then one day it got lots worse. Next day had the radiator replaced. Woulda done it myself but had something else to drive and people needing to get to work.

 

[Jsiff]

The tanks on the composite radiator are prone to cracking after years of bad roads. BTDT on my Burb. It leaked there a little bit for a year, and then one day it got lots worse. Next day had the radiator replaced. Woulda done it myself but had something else to drive and people needing to get to work.

When you state 'tank' - are you referring to the coolant overflow bottle? The plastic bottle?

 

[HotWheelsBurban]

When you state 'tank' - are you referring to the coolant overflow bottle? The plastic bottle?

No, the sides of the radiator itself. Black plastic with fins, and nipples and fittings for the hoses and lines. Also there are gaskets between these and the tank, and these gaskets shrink and leak. Or if the truck has had a front impact, the seal is jarred and that creates a leak even if there's no cracks. BTDT.