Coolant loss 5.7 vortec

[97Burban57]

Hey guys do you notice these 5.7 vortecs burning coolant because of the "open" coolant system? I read you get some evaporation because of the overflow tank having that open down tube.
I have lost maybe 1/2 inch of coolant out of the reservoir in the past month.

Last month i did a new fel pro intake gasket, new radiator cap and have checked around for any leaks but haven't found any. It's a 97 Suburban 5.7 and it runs perfect.

 

[HotWheelsBurban]

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.

 

[1998_K1500_Sub]

Sniff around the radiator for leaks on the tanks (left and right side). They've been known to leak, and on occasion do so sporadically.

My 1998 system is tight, now, and uses / loses no measurable amount of coolant. It has had issues in the past, though. Did I mention the radiator tanks? And of course the intake gasket.

 

[97Burban57]

Yep it has the rear heater!! Im actually slowly in the process of deleting it!! I haven't found any leaks headed back to the rear of the burbon except under the passenger side door one of the connectors gets very slightly damp but never drips.

 

[97Burban57]

Im thinking about getting it pressure tested

 

[HotWheelsBurban]

Sniff around the radiator for leaks on the tanks (left and right side). They've been known to leak, and on occasion do so sporadically.

My 1998 system is tight, now, and uses / loses no measurable amount of coolant. It has had issues in the past, though.

2X on tank cracks! My Burb had one on the driver's side tank, and it would seep a little bit, enough to need to refill the bottle every few days.
I speculate this truck was in a wreck before we got it; the left front fender and driver's door have paint issues, and the windshield washer bottle leaks. That and the radiator damage are related, I think. Also, even minor impact to the front will make the seams between the tanks and core leak. Found this out on my other 99 Burb.

 

[df2x4]

My '97s (the Suburban is a 5.7L) don't lose any, at least not enough that I ever notice it. The only time I've ever seen the level drop in the reservoirs is if there's a leak somewhere.

Has your radiator ever been replaced by chance? Reason I ask is a bunch of the replacement radiators on the market come with a capped orifice under the overflow that's only used on certain trucks. Like this:

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If your truck doesn't use this it stays capped as in the picture, and those rubber caps are prone to degrading and seeping coolant.

HPS makes a nice silicone replacement that won't degrade over time like the standard rubber ones. They're expensive for what they are, though.

www.amazon.com/HPS-Temperature-Reinforced-Silicone-Coolant/dp/B08TJMNXJC

Alternatively if you're OK with buying from China, you can search eBay for "5/8" silicone cap" and find them in many colors for much cheaper.

 

[97Burban57]

Well I rented a pressure tester from autozone. Once I hit 10lbs one of the rear heater core hoses started seeping at a decent rate! Never showed up while driving so I'm glad I rented the pressure tester. Ended up deleting the rear heater core and re routed the hoses to just include the front heater core.
Little paranoid driving to work today and seeing bubbles in the overflow tank but it seems to be getting less as its burping out. I was thinking head gasket for a minute but I hope its just the air burping out!

 

[HotWheelsBurban]

Well I rented a pressure tester from autozone. Once I hit 10lbs one of the rear heater core hoses started seeping at a decent rate! Never showed up while driving so I'm glad I rented the pressure tester. Ended up deleting the rear heater core and re routed the hoses to just include the front heater core.
Little paranoid driving to work today and seeing bubbles in the overflow tank but it seems to be getting less as its burping out. I was thinking head gasket for a minute but I hope its just the air burping out!

Yes that's why the bottle has that open ended hose on it, so any air in the system can work its way out. Some later model vehicles have a bleeder screw on the water outlet/thermostat housing for this purpose. As long as you have a good mix of coolant and water( 50/50) and the oil is not getting cloudy or milky, it's working like it's supposed to, if you have a few bubbles in the bottle.

 

[97Burban57]

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.