The coolant tank on the passenger fender - does anyone know if it's a stagnant surplus/overflow or does the coolant actively circulate through there?

wondering if I add water wetter to that tank, will it circulate through the system or will it just sit in that tank waiting for a time that the real system needs surplus and draws from there.

 

I would say "yes" running the heater might help with that !!!

 

no heater. race car. no dash, no water in the passenger compartment.

I see some hoses entering the tank, but don't know if they are pressurized/flowing while motor is running or if they are only overflow when the motor get's too hot. my suspicion is that its a stagnant tank that takes overflow or gives excess coolant when needed. if that's the case, pouring water wetter in there will be useless because it won't really ever get out of there.

so the question will be, do I need to drain the radiator enough to empty this tank in order to get water wetter into the main part of the system?

 

Don't know if this helps you ???

 

I would have guessed not, and the picture reinforces my thought. Thinking the connection might passively draw and circulate, but that it's not part of the coolant path. Just throwing my thought out there... maybe way off.

 

Actually coolant circulates through the heater core at all times. There is no heater control valve on C5s.

 

GM has pretty much always done this no? I remember hearing this about my GM car many years ago also...

 

For many years it was common practice for all car manufacturers to have heater control valves attached to the heater hoses under the hood. They were usually either manually (cable) or vacuum servo operated and operated when the mode select lever was moved from either "vent" or "AC" (if the car was equipped with AC) to the "Heat" mode. The valves were either open or closed and not used for temperature modulation and prevented coolant from circulating in or through the heater core.
I don't know when GM (or other companies) made the HVAC design transition to eliminate them. If I were to guess, I'd say somewhere in the 80s, maybe early 90s.

 

Based on absolutely no scientific evidence, I would tend to agree with this. I think that as the engine goes through hot and cold cycles that there would be a passive ebb and flow in and out of the tank. It might take a while but I think it would eventually mix with the circulating fluid.

 

Just for the record, and in an effort to help the OP, since he stated his car does NOT have a heater, I've had the hood open on my fully warmed up C-5, with the engine running, and observer the movement of coolant in the tank.....

 

It does not circulate, per se, but it does flow in and out with system temperature.

Long ago, (1950s?), the expansion tank was on the top of and integrated with the radiator. As the coolant expanded with heat, the air-space above the fluid would get compressed and with sufficient pressure the air and/or coolant would be vented to the outside, usually directed to the ground via a drain tube from under the cap down the side of the radiator. It was essentially an "open" system, once the temperature and pressure reached a steady state.

For the past 40ish years, an external expansion tank has been used to capture the overflow. As the coolant heats up, it expands, pushing coolant out of the radiator, and into the expansion tank. As the fluid cools, (like when you shut the motor down) it contracts, reducing the volume, drawing coolant back into the radiator from the reserve tank. As long as the reserve tank never runs dry, air will always be excluded from the system.

So essentially, when the coolant heats up, some fluid is pushed into the expansion tank. When it cools, some fluid is drawn back into the radiator. It's not really circulating, but the back and forth flow will mix whatever you add to the expansion tank into the full system, eventually. So yes, adding water wetter to the expansion tank will get it into the system - not immediately, but after a few cold starts it will be mixed throughout the system.

 

Thanks for all the input. it's pretty clear that the tank on the passenger fender is not in the flow. coolant pushes in there when the car heats up and recoils back when it cools, but the tank is not in the flow path. so putting water wetter in there is pretty much waste.

looks like I will need to drain the radiator enough to empty the tank on the fender, then add the water wetter, refill the system and burp it. just was not looking for all those steps as I also need to drop my under tray to reach the radiator drain.

thanks for the help

 

If you put water wetter in the tank, it will circulate through the system. First from the expansion and contraction of the water as it warms and cools. Second its a balance thing. Kind of like osmosis or whatever. The concentrate will mix with the other water in the system.

 

If you looped the heater core feed hose directly to the tank, or in other words took out the heater core and connected the hoses together, then it will circulate the water wetter out of the tank no problem. Just put it in the tank and drive it and it will get to the whole system.

 

(but the word you were looking for is diffusion not osmosis)

All the coolant is "connected" per se, so any soluble addition to the overflow tank will form a homogeneous solution in time. Whether or not coolant is being actively pumped through the tank is irrelevant.

Try this thought experiment. You have 2 clear jugs. You connect the jugs with a 1/4" ID length of tubing at the base of each jug. Now fill the jugs with water. Now put a few drops of food coloring into just one of the jugs. By the next morning you'll have 2 jugs with the same color water in them. Why?

 

Magic !!!!

 

What's that from?

 

the world wide web of course !!!!

 

Thuh interwebs??

 

When my engine is running I can see a real rush of coolant (movement) by looking thru the translucent side of expansion tank...