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Old 01-22-2011, 12:16 PM
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Default GM 5.3 question for Marco

Marco,

I read some really interesting articles on Pirate this morning regarding the cooling systems of 5.3 Vortec motors. There was a pretty good discussion about why the Vortec's have steam vent lines and how they should be routed to the cooling system.

Until this morning, I didn't even know I had steam vent lines, why you need them, etc.

I'm curious if you have yours hooked up and how you routed them? From the article it seems you either have to have an after market surge tank or you have to have a steam vent tap into the low pressure side of your radiator.

I have a Northern aluminum cross flow radiator. There is plenty of room on the side of the tank below the filler neck to weld in a bung for the steam vent to tap into. Do you think you could weld an aluminum bung like this into my tank?

For those with V8 conversions that have minor to severe over heating problems, this is a great thread to read because it covers everything from soup to nuts. It was interesting to discover you can increase the cooling of your existing system any where from 4% to 10% just by adding a surge tank to the system. This apparently is because the surge tank removes air that gets into the coolant from turbulation, and we all know air is an insulator and not a conductor, so thats why the cooling improves.
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Old 01-22-2011, 06:17 PM
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The steam vent line on my motor comes off of the fronts of the two heads and is plumbed to go through the throttle body. For the longest time I ran it just plugged and the motor ran at ok temps. The only over heats were due to my electric fans not turning on. without the steam vent line hooked up it was also a giant pain in the ass to get the air bled out of. It'd overheat just idling after a coolant refill and I'd have to shut it down, let it cool, run it again, shut it down, let it cool,ect. Eventually it'd get to where most of the air was bled out.

Anyways, this summer I figured it might be time to install the proper stem vent line, so I bought an upper radiator hose "adapter" that allowed me to tee in the steam vent line to the upper hose. I got it from www.jagsthatrun.com. Now the cooling system bleeds much nicer, but otherwise I really didn't notice any real difference. I guess that a tee into the upper hose is how several gm motors do it so the method is fine.

One thing that people say is that without the steam vent lines, hot spots in the heads can develop and you would never see it on a water temp Gage. I am not totally sure that is true.

Anyways, the upper radiator hose tee is as easy as a click to buy, and only requires a small amount of coolant loss to install so I figure why not use it.

The reason I didn't is because I followed the advice of several folks that said it was not necessary...... As far as the swap goes, the best advice I think I have ever gotten is to run the motor as close to stock as possible and issues should be minimized...... This is one of those things that makes it more like the factory did it.
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Old 01-22-2011, 06:19 PM
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Here's what I run

http://www.jagsthatrun.com/Pages/Par...g_LSI-tee.html
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Old 01-22-2011, 09:44 PM
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Wow, that looks like an easy solution. One question though: On the other thread they made a big deal out of the fact the steam vent need to bleed into the low pressure side of the radiator thus why they installed a bung right below the cap.

Using this adapter where the hose goes into the top of the radiator would put it on the high pressure side. But you say they used things like this on some of the stock LS applications?

My steam vent is hooked into the cooling system down low near the top of the water pump via a T fitting. But they say it should hook where the steam can go to the highest part of the system.
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Old 01-22-2011, 11:09 PM
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Quote:
Originally Posted by Air Randy View Post
Wow, that looks like an easy solution. One question though: On the other thread they made a big deal out of the fact the steam vent need to bleed into the low pressure side of the radiator thus why they installed a bung right below the cap.

Using this adapter where the hose goes into the top of the radiator would put it on the high pressure side. But you say they used things like this on some of the stock LS applications?

My steam vent is hooked into the cooling system down low near the top of the water pump via a T fitting. But they say it should hook where the steam can go to the highest part of the system.

Heat rises. Coolant flows from the coolest end (bottom) of the radiator into the engine and return from the engine goes into the top of the radiator. The whole system will be close to equal pressure but the top hose would allow in flow as steam is compressible while liquid is not.
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Old 01-23-2011, 08:46 AM
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Heat rises. Coolant flows from the coolest end (bottom) of the radiator into the engine and return from the engine goes into the top of the radiator. The whole system will be close to equal pressure but the top hose would allow in flow as steam is compressible while liquid is not.
Understood and agreed. The point of the Pirate article in having you put the fitting right below the radiator cap is by design that is the lowest pressure point in the system. When the hot coolant exits the engine and into the radiator via the top hose, it is at maximum temp plus the head pressure from the water pump. As the water moves across the radiator towards the side with the cap, the friction the water encounters in the tubes coupled with the contraction from cooling causes the pressure to drop. Thus why they discuss a "high" and "low" pressure side.

They want the steam to go into the radiator at this point since it is the "low" pressure point (less chance of it being trapped in the line by high pressure), it should also be the physically highest point in the system, and if the pressure builds and the cap purges, it purges the steam first.

All that said, I suspect it is technically accurate but it does seem to be splitting hairs. I'm going to go with the adapter Marco used to ensure I get more of the air bled out of the system. I suspect that is the reason the Meanie always seems to be borderline on the verge of over heating as there is probably a fair amount of trapped air in the system. The current steam vent line goes sharply downwards to the water pump inlet so it has to be not working at all or it is trapping as lot of air in the system.
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Old 01-23-2011, 02:40 PM
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Quote:
Originally Posted by Air Randy View Post
Wow, that looks like an easy solution. One question though: On the other thread they made a big deal out of the fact the steam vent need to bleed into the low pressure side of the radiator thus why they installed a bung right below the cap.

Using this adapter where the hose goes into the top of the radiator would put it on the high pressure side. But you say they used things like this on some of the stock LS applications?

My steam vent is hooked into the cooling system down low near the top of the water pump via a T fitting. But they say it should hook where the steam can go to the highest part of the system.
Some older corvettes had that Tee like Jags that run sells. It's an OEM part you can look up if you want to go that route, but I can't remember how I found it. I think it was labeled as a heater hose Tee but I am not sure....

Anyways, the Tee fits pretty close to the head tank so I can't imagine there is much of a pressure difference between it (in the upper hose) and the radiator cap.

There may be minute differences in pressure in the system, but for the most part it should all be about the same. I think the key is that the bubbles can flow uphill like you are saying.

One thing that really helped bleed my system was having a big functioning overflow bottle and a good radiator cap. The radiator cap should let air bubble out as the motor gets hot, and let the coolant be sucked back in as it cools. this kinda self bleeds the system once it is close.

Can you hear water rushing in the heater hoses? that's also a sign of air in the system... if there is no air in there the coolant rushing through the hoses should be pretty silent.

What radiator is it running? What thermostat?
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Old 01-23-2011, 02:50 PM
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Ahhh I see. Sorry to try to "school" ya. As you know, most folks don't know the direction coolant flows so the dad in me had to ed-ju-mi-kate! Ya know as we get older we have to feel some self worth any way we can!

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Understood and agreed. The point of the Pirate article in having you put the fitting right below the radiator cap is by design that is the lowest pressure point in the system. When the hot coolant exits the engine and into the radiator via the top hose, it is at maximum temp plus the head pressure from the water pump. As the water moves across the radiator towards the side with the cap, the friction the water encounters in the tubes coupled with the contraction from cooling causes the pressure to drop. Thus why they discuss a "high" and "low" pressure side.

They want the steam to go into the radiator at this point since it is the "low" pressure point (less chance of it being trapped in the line by high pressure), it should also be the physically highest point in the system, and if the pressure builds and the cap purges, it purges the steam first.

All that said, I suspect it is technically accurate but it does seem to be splitting hairs. I'm going to go with the adapter Marco used to ensure I get more of the air bled out of the system. I suspect that is the reason the Meanie always seems to be borderline on the verge of over heating as there is probably a fair amount of trapped air in the system. The current steam vent line goes sharply downwards to the water pump inlet so it has to be not working at all or it is trapping as lot of air in the system.
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Old 01-23-2011, 04:25 PM
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Originally Posted by Uncle Ben View Post
Ahhh I see. Sorry to try to "school" ya. As you know, most folks don't know the direction coolant flows so the dad in me had to ed-ju-mi-kate! Ya know as we get older we have to feel some self worth any way we can!
No problem, I learn more every day from all the various sources
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Old 01-23-2011, 05:03 PM
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if you look down a few posts, there is some good info on steam vent lines here:

http://www.camaros.net/forums/showthread.php?t=168401

Post #9 shows a stock location in a heater hose..... couldn't find a pic of one with a stock connection to the upper rad hose like I said there was.
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Last edited by rover67; 01-23-2011 at 05:31 PM.
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