Schitzo

iTrader: (6)

Hi
Id like to use the expansion tank below below(pic 1) because it is the right size and looks great. However, I notice it has an opening on the bottom. Upon further searching, I found that the C5 and C6 corvette (pic 1 & 2) surge tanks also have hoses running in the bottom as well. My question is, where do these hoses go and what are they for. All these three tanks have the top smaller hose from the rad cap which I believe feeds in the coolant.
Thanks
Pic 1


Pic 2


pic 3

Schitzo

iTrader: (6)

anyone?

jewce

That's a pressurized hot bottle, not just an expansion tank. The lower hose goes back to the low pressure side of the system. Heater return, rad return, or low side rad tank will all do. The small line on the top is fed by the steam vents that come off the top of the heads. It's basically an active de-aeration chamber.

rao

iTrader: (18)

+1 it really is just a de-aeration chamber

jewce

But a very important one. 2% air in the system is 8% less heat transfer, but 4% is 38% less. If you are in hot weather (Phoenix, Vegas, etc) or tracking it, it makes a BIG diff in coolant temp. Also allows you to get away with a smaller rad due to the continual de-aeration. All cars should have them, then again I'm a cooling systems engineer. Bean counters hate me.

rao

iTrader: (18)

I wasn't discounting it. My car has a similar system. I decided that I didn't really understand it all too well, but I just duplicated the OEM routing and it works great

Steve VanS

iTrader: (1)

So the large tube on the header tank shown above is hooked up to the heater hose returning to the water pump(?) and the small tube to the radiator cap vent tube. We intend to plumb our system that way. Will this be ok? Fill the cooling system, and the header tank about half-way and cap-off?

Garret & Steve almost done with E30-LS1

Schitzo

iTrader: (6)

Jewce,thanks for the help.
I looked at some corvette pics and it looks like the heater hose returning from the heater core hooks up to one side of the fitting at the bottom of the tank. It then goes to the water pump. (to the opening closer to the front of the engine.)

The tube on top by the cap comes from the top of the radiator just below the cap.
With a T fitting, the tank I have in mind should work. its cheap, looks good, right size and is designed to hold pressure.

jewce

Don't run the rad vent cap to the hot bottle. I will never open anyway if you do the system right. The cap on the top of the hot bottle is a pressure cap already. It's just designed to flow air instead of coolant and servers the same system pressure regualtion that a rad cap does. The upper small hose going to the hot bottle should come from the highest point on the engine (or the most likely place for bubbles to go and hang out) and on the LS engines, the steam tubes are it if your version has them. If not, a fitting on the high side rad tank or the h2o pump in the same passage as the upper rad hose will do as well, just not quite as good as the steam tubes.

There is an orifice in the top fitting on the hot bottle that causes a large and quick pressure expansion as the coolant passes through it. The air bubbles expand to 2 or 3 times their original volume and seperate out, while the coolant stays the same volume (relatively - h20 is compressible just not any significant change for the pressures we are talking about). The air seperates out and sits in the hot bottle until the pressure is enough to push it out of the hot bottle pressure cap.

If you run this with a rad cap, you need to run a rad pressure cap high enough (20-22 psi or even higher) to that it will never actually open. The hot bottle pressure cap (15-18 psi) will regulate the system pressure instead and will be much more accurate since it takes a large volume of air to change the pressure vs very little volume of h2o. Also both caps need to be full pressure caps. The little 1/2" plunger in the bottom center of the cap should be spring loaded to keep it shut - most you go buy off the shelf are, but you can run across some that aren't. IF you use an open cap or partial pressure cap (non-spring loaded plunger), you will never actually build any amount of pressure and can boil over or cavitate your pump very easily.

Andy1

+1 to what jewce writes.
Few understand the significance/benefits of an air separator in the cooling system. It is IMO, hands down the best way to ensure any air flowing through the system is separated out. It's also a resrevoir of additional coolant ready to compensate for coolant that dis displacing the air.

Hey jewce, I ran varoius shifter karts for 20 years. Did all my own engines and pipes; 5 local and regional championships.

Andy1

Steve VanS

iTrader: (1)

Thanks, guys.

I understand the vent hose hook-up, but my question concerns the big hose from the bottom of the header tank down to the heater return port of the water pump. Is this a simple, 3/4" that is T'd into the heater return line, or is there any flow-control type valve in this line?

jewce

No valve. Just a tee. They are available at most autoparts stores in the HELP isle. I'd go with metal though. The cheap plastic ones degrade overtime and if you do ever overheat for any reason, you need to replace the plastic HELP ones. They turn into mush above 240 F when exposed to coolant (actually nylon in general does - they need to be polyphthalamide).

terryr

Ford added a header tank to all the CobraR Mustangs, using a tank from a V6 Probe. The Rad cap was altered to allow water in and out freely, and the expansion hose was rerouted to the probe piece. The big hose was teed into the lower rad hose with a fitting. The probe piece then had a hose back to the expansion tank from its own rad cap.

Thealien

iTrader: (2)

Just the information I was looking for! Thanks

Thealien

iTrader: (2)

any venders make these tanks universal? Aluminum?

serpentnoir

iTrader: (2)

I made my own...

Schitzo

iTrader: (6)

I ended up getting an expansion tank from a 1991 E30. The pressure cap is a 1.4 bar (~20 psi). It also has a provision for a low coolant switch which I had to have. Im using a C5 rad.


The tank in my original post uses a 2 bar cap and I was not comfortable running pressure that high when using the C5 rad.

dtfastbear

I'm a complete neophyte when it comes to cooling systems in general and to the LS1, in particular. I'm putting an LS1 into a miata-based race car and I'm still confused after reading all the good info above.

I've got a Ron Davis radiator that doesn't have a fill cap on it, but rather just a 1/2NPT fitting near the top. I've got a JEGS "surge tank" that has a radiator cap, a vent hose just under the cap, a threaded opening near the top of the tank and a threaded opening on the bottom of the tank.

Here's how I think I'm supposed to plumb this whole system. Excuse my poor drawing skills!



I assume I have to get the height of the surge tank right so that the water level in it will be above the top of the radiator so that it will keep the radiator full.

My real question is - am I doing it right to run the output from the "steam lines" on the LS1 heads to the upper threaded opening on the surge tank?

If I fill the surge tank all the way to the top (so that the "steam line" would be under water) would that cause problems?

Any help/advice is appreciated!

Cheers,

Dean

terryr

If that's all the fittings you have to use then that's how to do it. A factory system would have the main fill connect to the rad down low, or even on the lower rad hose. The upper would connect or tee into the steam fitting.
The idea is to keep water in the bottom of the surge tank and let steam/air into the top, thereby letting air out of the cap and keeping the water.

dtfastbear

I'm happy to get whatever fittings I need to get to do it right.

To be clear about what you're suggesting, Terry, is to connect the hole from the bottom of the surge tank to a T in the bottom radiator hose.

Then connect that hole near the top of the surge tank to the steam fitting, as indicated in my drawing.

Then leave the hole at the top of the radiator labeled 1/2NPT plugged?

And, mount the surge tank such that it's midpoint is level with the top of the radiator or just above so that when the radiator and engine is completely full with water, the water level in the surge tank is below that hole near the top of the surge tank?

Cheers,

Dean