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I am building a hot rod and have a new ls3 525hp version. I bought it a few years ago. It's been running a couple years now with no issues. I only drive it in 5 mile loops as I am working out all the bugs in the car. I came home after driving this loop last weekend and as soon as I pulled in the driveway the fan wasn't on and antifreeze starting blowing out of the cap. this engine only has around 150 miles or so on it. As it cooled it also sucked the radiator hoses flat. I have since changed the cap, hoses and thermostat. Started it and ran it down the street some and that now seems to be ok. The issue I'm having now it that when it starts the car is very quiet when running which is not normal. Also when I just drove it it hesitates pretty bad when just cruising doesn't matter what rpm. Under gas it seems to be ok just also seems underpowered. I am at a miss. Anyone have any ideas what may be going on? Thanks in advance
Did you bleed the air out the system when you put the coolant in it? Also the hesitation could be anything man, you need to get more details then that. Is it throwing any codes? Did you I u have it tuned properly? Also you said you been working on this project for 5 years? That's awful long to work the bugs put, are you plugs and wires good? What's your fuel pressure? How old is the fuel I'm the car?
Did you bleed the air out the system when you put the coolant in it? Also the hesitation could be anything man, you need to get more details than k that. Is it throwing any codes? Did you I u have it tuned properly? Also you said you been working on this project for 5 years? That's awful long to work the bugs put, are you plugs and wires good? What's your fuel pressure? How old is the fuel I'm the car?
Ok sorry Yes i believe i have the air out of the system as far as i know, I started it and let it run for 15 minutes with the cap off with the front end of the car jacked up until there wasn't any bubbles coming out. There is no check engine light on, The engine was tuned shortly after i got it running and has ran awesome since. I've had this maybe 4 years, and since have put an addition on my house 2 kids in sports and life so i haven't been constantly working on it. Fuel pressure i will check that's the kind of info i am looking for thanks. The fuel in the car is a week old.
Ok sorry Yes i believe i have the air out of the system as far as i know, I started it and let it run for 15 minutes with the cap off with the front end of the car jacked up until there wasn't any bubbles coming out. There is no check engine light on, The engine was tuned shortly after i got it running and has ran awesome since. I've had this maybe 4 years, and since have put an addition on my house 2 kids in sports and life so i haven't been constantly working on it. Fuel pressure i will check that's the kind of info i am looking for thanks. The fuel in the car is a week old.
that's how I bleed the air out as well so that sounds to be taken care of, yeh I would start with checking fuel pressure, check the fuel filter and pump and also it might not hurt to pull the plugs and see how they look. It could something as simple as a bad plug or maybe the fuel pump is getting weak.
So if you ran the vent line to the same port that typically runs to the radiator overflow the vent will be closed unless the radiator cap releases pressure to the over flow tank.
The vent has to go directly into the radiator, top of the water pump (drilled a tapped for a NPT fitting) or a splice in the upper radiator hose.
So if you ran the vent line to the same port that typically runs to the radiator overflow the vent will be closed unless the radiator cap releases pressure to the over flow tank.
The vent has to go directly into the radiator, top of the water pump (drilled a tapped for a NPT fitting) or a splice in the upper radiator hose.
This is why I asked for a picture. LS engines are hard to bleed. I find that the radiator funnels work pretty well. It still takes a while, but they do eventually work all the air out.
The tell tale sign that there is air in the system is the thermostat doesn't open. To tell of the thermostat is open or not, feel the lower radiator hose. If the upper hose is so hot that you can't touch it but the lower hose is only like warm, that's a sign that the thermostat is still closed. Typically cars will idle around 215 degrees in that situation and once the thermostat opens, the temperature will drop almost instantly, while the lower hose gets a lot hotter in the process.
The way I always do it is disconnect the smaller line that comes from the steam line and wait for a steady stream while the cap is removed and then I close the line off and use an old coolant bottle that I have the bottom cut out and flip it upside down into the radiator and let the air works its way out as the water rises and lowers
This is why I asked for a picture. LS engines are hard to bleed. I find that the radiator funnels work pretty well. It still takes a while, but they do eventually work all the air out.
I always assumed the corner coolant vents on the heads would bleed all the air out since they are up near the highest point
the small hose barb directly below the black radiator cap is for the overflow/expansion tank. The plunger in the cap that’s spring loaded is below that fitting so water can’t freely flow like it needs to for the coolant vents from the heads.
Notice the little small black over flow tank i have beside the turbo, amazon maybe 20$ and it works just fine. It has a small hole in the cap of the can to relief pressure and my overflow line runs to it. Ignore the clocking of the turbo, this was just mock up
Pic of my Wrangler steam line plumbed into the water pump. Has worked well for close to 15 years. The down side to that is if you loose the water pump you can't just get a new one at NAPA with NPT tapped hole.
One other thing I do on the LS thermostat is drill 3 1/8" in the outer flange to get some coolant flow prior to the thermostat opening.
This is definitely a big problem. As others have stated, that is not the correct location for that hose. Get the vents routed properly to the radiator, use a funnel to bleed it, and you will be good to go. I see no reason that a bung can't be added next to the upper radiator hose with the steam line connected to it.
ok so I added the overflow tank and the tee into the top coolant hose for the steam line. I cannot get the air out to have the thermostat open I have the front end of the car up in the air and have squeezed both hoses while the car is warming up and it won't open. does anyone have any other tricks to get the air out?
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ls3 crate engine issue 
