The Stovebolt Site Forums The Shop Area General Truck Talk Coolant overflow reservoir

I just installed the chevrolet coolant overflow tank(got it for my B-day from my folks) I ended up installing it under the ranco valve on the firewall- Pics to come of the install.

The manual says to use a pressure radiator cap with the seal in the upper part of the cap, not on the spring portion- Wouldn't that eliminate the pressure retaining ability of the spring type cap by moving the seal to the lid and not the spring?

I have a 0 lbs cap and a 4 lbs cap- I thought about trying both to see how it performs-

I still need to drill the small pilot hole in my thermostat- That is coming soon when I flush the cooling system in the next few weeks.

Anyhow- Thanks for the info.

with an overflow bottle, you need to have the proper cap for it to work. The seal has to be on the top, the cap acts like a valve to allow fluid to the reservoir. If you dont use the right cap, the fluid will over-flow and never make it to the reservoir.

Use the 4# cap.

All the thermostats I have installed in the past few years have already had the hole drilled in them.

So did some driving today. I used the Olbs cap. Generally when I drive with that cap- Mainly in town- I loose some coolant from evaporation. Not a lot but some(like from 1 inch above tubes to down to tubes)

So With the tank hooked up- Mounted below the ranco valve on the firewall- hose from Rad running along inner/outer fender seam to bottom of tank- then overflow drain line running straight down to ground between chassis and starter.

So with the driving I noticed that the tank got a little warm while system was hot(regular running temp)
The coolant level at the the beginning and end of day was the same.

In the coming days I will have a 250-300 mile highway day and will let you know how it does there. that is generally where I see the highest loss of coolant(extended highway driving(45-50mph, and highway, not interstate)

the loss you see is from expansion and it blows out the overflow. An overflow catch tank is intended to catch that overflow, as well as provide draw-down volume. hence the need for the cap sealed to the top of the rad bung.

Ok- so put some highway(extended driving at 45-50mph) mileage on the set up today.

The tank collected fluid. It did leak from the inlet from radiator to expansion tank barb- but a hose clamp solved that- overall it had a little under half a cup of coolant in it when I pulled the hose- and when removing the radiator cap it was down a little.
So now the next test will be to drive the same general amount- but not pull the hose- and then when the vehicle has returned to cool(dormant) temperature see how much coolant is in the expansion tank.

This is all with the 0 lbs non-spring cap.

You are correct- I have no Life.

But to make me feel better- you are the one reading about it

Just my observation.....my 54 truck, 1960 235, 180 thermostat with a 7 lb cap and coolant just covering the core tubes has never needed coolant added and runs consistantly at the 180 thermostat temp. With the correct cap and plenty of room on top of the core for expansion the radiator should never boil over.

Adding a higher pressure cap with provisions to dump into a coolant recovery cannister and filling the radiator completely could easily put undue pressure on the radiator and also the heater core.

If your cooling system is in good shape and your fan blade located high on the radiator you shouldn't have cooling issues. I genuinely think that you should be able to run the 0 or 4 lb cap with plenty of room above the core for expansion and eliminate the need for an expansion tank. Hope this helps.

Dave

Dave,

Thanks for the info-

I have run both the 4 lbs cap and the 0 lbs cap on the truck pre expansion tank.

With the 4 lbs cap I do not loose coolant- I just like the 0 lbs cap because that is what came on it.
and the expansion tank lets me tinker-

I think with the 0 lbs cap open to atmosphere it causes coolant to evaporate and the positive pressure in the radiator blows the vapor out of the vent tube where it does not return to the radiator.

What I want to see(mainly for purpose of running the 0lbs cap) is if the expansion tank will stop the loss with the 0 lbs cap.

I think it will because by the time the vapor flows through the hose to the expansion tank it has had time to cool, plus the sudden volume orifice change from the small hose(roughly 5/16" ID) to the large cannister cause it to condense.
That way it is not being lost but being allowed to breath and then when the radiator cools the change in pressure in the tank will draw the coolant back into the tank.

I told you I have no life, so fun experimenting like this helps me pass the time, and figure out why they thought of offering the tank in the first place.

The 7lbs cap would be nice for the higher boiling point.

Nice engine by the way- I bet that thing is a rocket.

Here is a pic of the install

[img]http://yelostn78.smugmug.com/Other/1949-Chevy-3600/IMG0099/767901307_Hr8bv-M.jpg[/img]

so far so good. With the 0 lbs cap there is no noticeable loss in coolant on the road, where before there would be some. So I think it is working.