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| My 1988 LFX F40 build. (Page 49/68) |
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Will
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AUG 19, 12:21 PM
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The fun trick of a Fiero cooling system relative to a FWD car's cooling system is that the Fiero has two high points.
I never ran a pressurized surge tank on my Northstar car, BUT I did run a lower pressure cap at the back than the front. I also capped off the overflow nipple at the back. That way when the system warms up and burps air, it burps air from the back first, but when it cools back down, it has to draw coolant from the stock overflow bottle at the front. That way I purged both high points of the system from one bottle.
You can probably do something similar for your system... you just have a surge tank where I have an inline filler neck.
If you keep the system basically as the stock 3.6 system, you'll need to manually bleed the radiator. If you keep the Fiero overflow bottle up front, but try to make yours work like mine, then you'll end up filling the surge tank to the brim, which may not be a great thing.
Actually... you may be able to automatically bleed the radiator by running the vent line from your radiator cap under the car all the way back to your surge tank...
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Daryl M
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AUG 20, 01:26 AM
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| quote | Originally posted by Will:
The fun trick of a Fiero cooling system relative to a FWD car's cooling system is that the Fiero has two high points.
I never ran a pressurized surge tank on my Northstar car, BUT I did run a lower pressure cap at the back than the front. I also capped off the overflow nipple at the back. That way when the system warms up and burps air, it burps air from the back first, but when it cools back down, it has to draw coolant from the stock overflow bottle at the front. That way I purged both high points of the system from one bottle.
You can probably do something similar for your system... you just have a surge tank where I have an inline filler neck.
If you keep the system basically as the stock 3.6 system, you'll need to manually bleed the radiator. If you keep the Fiero overflow bottle up front, but try to make yours work like mine, then you'll end up filling the surge tank to the brim, which may not be a great thing.
Actually... you may be able to automatically bleed the radiator by running the vent line from your radiator cap under the car all the way back to your surge tank... |
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Once the radiator is manually "burped" , will it stay that way or will it have to be redone from time to time?
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Will
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AUG 20, 11:32 AM
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In a perfect world in which you only ever send liquid coolant to the radiator, it should stay that way... but the world isn't perfect and if you don't allow some means of burping the radiator, you're likely to accumulate a gas bubble over time. Try it with a no-vent cap and see what happens, but be prepared to add a vent if that doesn't work well.
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Daryl M
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AUG 21, 09:56 AM
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| quote | Originally posted by Will:
In a perfect world in which you only ever send liquid coolant to the radiator, it should stay that way... but the world isn't perfect and if you don't allow some means of burping the radiator, you're likely to accumulate a gas bubble over time. Try it with a no-vent cap and see what happens, but be prepared to add a vent if that doesn't work well. |
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Thanks again for the info. I think I'll start with a 20 pound cap on the radiator. The cap on the surge tank in the engine compartment has the 20pound cap that was standard with the Impala. I think I will start with that and see how it works. My next question is , should I run an overflow tank on the radiator overflow line, or just dump it on the ground?
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Will
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AUG 21, 12:16 PM
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If it overflows at the radiator, do you want it to pull air or coolant back in as it cools?
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Daryl M
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AUG 21, 09:02 PM
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| quote | Originally posted by Will:
If it overflows at the radiator, do you want it to pull air or coolant back in as it cools? |
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Good point
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Raydar
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AUG 21, 10:27 PM
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I did something similar with my 4.9. I completely removed the overflow from the front. The radiator got a 20 lb cap.
I have a fill adapter at the engine, using a 15(?) lb cap. It has an overflow fitting piped to a reservoir in the engine compartment. (This reservoir is similar to the stock Fiero reservoir, except that it's at the highest point. It is not pressurized.)
Prior to going with this setup, I used to lose a lot of coolant out of the front overflow. (Not really germane to this discussion, but I'm blaming it on the "stop leak" tablets that GM recommends for the 4.9. They tend to deposit grit on the radiator cap sealing surfaces. Not a good thing for a Fiero setup.)
Since this change, I have not experienced a moments difficulty with coolant loss.
I can post a pic if you want, but I'm sure you get the idea.[This message has been edited by Raydar (edited 08-21-2020).]
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Daryl M
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AUG 22, 12:54 PM
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| quote | Originally posted by Will:
If it overflows at the radiator, do you want it to pull air or coolant back in as it cools? |
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After a bit of thought,( I realize that's dangerous) I gotta ask, the Impala didn't have an overflow. Why do I need to add one?
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Will
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AUG 22, 05:41 PM
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| quote | Originally posted by Daryl M:
After a bit of thought,( I realize that's dangerous) I gotta ask, the Impala didn't have an overflow. Why do I need to add one? |
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The Impala only had one high point in the cooling system... the Fiero has two. If I do go with a pressurized surge tank, I'll probably keep it at the back with the stock Fiero overflow at the front.
However...
| quote | Originally posted by Raydar:
I did something similar with my 4.9. I completely removed the overflow from the front. The radiator got a 20 lb cap.
I have a fill adapter at the engine, using a 15(?) lb cap. It has an overflow fitting piped to a reservoir in the engine compartment. (This reservoir is similar to the stock Fiero reservoir, except that it's at the highest point. It is not pressurized.)
Prior to going with this setup, I used to lose a lot of coolant out of the front overflow. (Not really germane to this discussion, but I'm blaming it on the "stop leak" tablets that GM recommends for the 4.9. They tend to deposit grit on the radiator cap sealing surfaces. Not a good thing for a Fiero setup.)
Since this change, I have not experienced a moments difficulty with coolant loss.
I can post a pic if you want, but I'm sure you get the idea.
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...maybe I'm too conservative about that and Raydar's way would work fine for you.
Raydar, do you check the level in the radiator regularly? Did you completely block off the overflow port on the radiator cap?[This message has been edited by Will (edited 08-22-2020).]
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Daryl M
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AUG 22, 06:51 PM
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| quote | Originally posted by Will:
...maybe I'm too conservative about that and Raydar's way would work fine for you.
Raydar, do you check the level in the radiator regularly? Did you completely block off the overflow port on the radiator cap?
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The stock Fiero overflow tank in the front is not an option due to the reverse flow of the LFX, requiring that the new radiator have the return (high hose fitting) on the passenger side. This puts a radiator hose where the overflow tank was. The stock Fiero tank is not a good shape for the driver side, so getting rid of the tank makes a simple solution, if it will work. I could modify the radiator cap to prevent suction of air when contraction happens, by blocking the one way vent on the cap. Using a lower pressure cap (18 psi) on the pressurized Impala surge tank in the engine compartment would make the system very similar to the original Impala, but with an easy way to burp the front high point with the modified cap on the radiator. What do you think?
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