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Old 01-23-2019, 10:12 AM
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Chevy LS LM7 cooling system question

I need some input on a 2003 Chevy LS LM7 cooling system. Iím putting the finishing touches on a 1948 Rat Rod truck and ran into some problems with the cooling system.
I want to delete the heater core and still run the surge tank. Hereís the kicker, I put the radiator in the back. I have blocked off both the 5/8 & 3/4 small hose fittings on the water pump. I tried to loop these two hose fittings but hot water ran back into the cool side when the thermostat opened. Iím running water until I figure this out.
So hereís my question. Does it make any difference if I hook up my surge tank before the radiator or after the radiator? The surge tank will be in the back as well.
Thanks for any input.

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Old 01-23-2019, 07:15 PM
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LS cooling

There has been lots of talk over on the LSTech site about the heater hoses, loop or not.



As I understand it the serge tank is inside of the closed system which means it could be mounted anywhere. That's different than an overflow tank.



What are you doing with the steam vents?
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Old 01-23-2019, 08:45 PM
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LM7 cooling

Thanks 39 Master. Iíll take your advice and see what LSTech has to say.

As for the steam vents. I only have vents in the front and I drilled and tapped a fitting on the water pump (hot output side) and dumped the steam back into the pump which eventually goes to the radiator in the back.

The surge tank can hold 15psi and thatís where the radiator cap is. The radiator itself does not have a cap, which makes it tough to bleed all the air out, but Iím still working on that.

Thanks for the input.
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Old 01-23-2019, 10:31 PM
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LS cooling

If you can find a higher point to pipe the steam vents to that would be a big help getting rid of the unwanted air.



Because of your unique situation it may be best to use one of the new vacuum systems to fill the cooling system. They say it works real good.
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Old 01-24-2019, 03:27 AM
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I have had a coolant vacuum filler for a long time. It basically uses compressed air to pull about 25 in/hg on the cooling system.if you have a leak in the system, you can't pull enough vacuum so you aren't putting antifreeze into a leaking system. Next you put a hose into a bucket of coolant, and open the valve letting the vacuum pull the coolant in, no air pockets.

I used it on a Porsche with the engine in the rear, and radiator in the front. Worked perfectly. Lots of modern engines need to be refilled this way.

Most engines with the heater core always flowing stock, should have the hose looped to maintain proper coolant flow in the engine.

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Old 01-24-2019, 03:30 AM
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LS Cooling

I saw a video on YouTube about the vacuum system and I liked what I saw. I think a future project will be to make one of these vacuum filling systems. Maybe I better get started on it now!

Thanks
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Old 01-24-2019, 06:17 AM
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I saw a video on YouTube about the vacuum system and I liked what I saw. I think a future project will be to make one of these vacuum filling systems. Maybe I better get started on it now!

Thanks
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Old 01-24-2019, 10:50 AM
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It sounds like you need one.

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