How much Coolant Volume Expansion is Normal??

[DMC5180]

First some details.

1. I'm running the NEW Plastic Header Bottle DMCH sells, this allows me to actively SEE the coolant level.
2. There is an Auto bleeder in the system.
3. New (2 year old) 15 PSI Cap.
4. I run the DM-eng (SMART FAN RELAY) The Fans will continue to run or delay shutdown for 20 seconds after switched signal power has been turned off. ( Otterswitch cycles off, mode switch turned off or Key off when fans are running at the time of shutdown).
5. The engine was stone cold with the coolant level at the MIN COLD coolant mark or about 3/4 empty.
6. I fired it up and let the engine idle warm up (about 800) rpm till the the Fans came ON just shy of the 220 mark.
7. At about the 205-208 point (w/temp rising) the Expansion tank Air volume had been displaced by coolant and starts puking out the overflow.

When the fans came ON the coolant level began to recede just enough to stop the puking. I waited a minute or two to see where the level would settle at. Unfortunately, I had to cut the run short and shut the engine off at 200-205, before the Fans had cycled off normally. The Coolant level at shut-off time was just below puke stage. Immediately following shut down (Fans running 20 seconds) the level rapidly recedes too 3/4 full level, I just checked the Cold level this morning and it is now 1/2" below the MIN COLD line.

I am intentionally leaving out one important detail which I'll tell you later, because I'm interested in what is considered NORMAL coolant level fluctuation with temp variations. FWIW: My Normal at speed driving temps are just above the second mark. ( I run a 192˚ thermostat) At that temp the coolant level will typically be at 1/2 to 3/4 full depending on starting level.

I also realize most folks on here have converted to a none viewable (stainless or aluminum) header bottle which makes it difficult to gauge the operating levels. (1 of the reasons I don't like them)

I await your replies.

Thanks

[LEVY]

Being a 31+ years old vehicle, there is not a exact answer.

There are many things you have to consider like radiator size, type and condition of hoses etc.. I really don't know if you are really looking for answers or if you are testing members knowledge.

LEVY

[DMC3165]

This is what I've been told.......

On a stock car (minus self bleeder) The expansion tank should be between 1/3 and 1/2 when cold. Allowing for the tank to capture the expanding coolant under normal operation. If the tank goes dry or starts spewing uncontrollably then you have a problem elsewhere (ie, head gasket, cracked block).

I'm not familiar with DMCH's new plastic expansion tanks so I'm not sure where the marks on it are. I have the stainless tank so I generally check it to see if it's somewhere around half. When I did my water pump last year I filled the tank about 3/4 full and it eventually settled between the 1/3 and 1/2 range. Since then I haven't had to add any coolant and that was around 8500 miles ago.

Hope this helps.

[DMC5180]

Being a 31+ years old vehicle, there is not a exact answer.

There are many things you have to consider like radiator size, type and condition of hoses etc.. I really don't know if you are really looking for answers or if you are testing members knowledge.

LEVY

This is not a test of members knowledge.

I'm looking for a reasonable answer or general consensus as to what is considered normal thermal expansion in a PROPERLY functioning OE configured Delorean cooling system based on coolant capacity(volume) and typical temperature variations. The age of the car should have nothing to do with it. This system was not designed with an overboard recovery tank like most cars use today. Once it's gone it's gone and does not get sucked back into the system as it cools down.

FWIW: Cooling hoses are in great shape for age (12 years) since complete replacement. Radiator is a heavy duty Brass 3-row. The core is about 1/2 thicker than the OEM 2 row. I would expect to have some increased capacity due to the extra row.

I will agree that variations in the system can effect the results. (what Otterstat is being run and the operating tolerances, Thermostat temp being used, whether you can trust the Temp gauge to be accurate.

[Bitsyncmaster]

My bet is between 1/3 and 1/2 full tank is all you can keep. Don't think I've ever seen one over half full. I guess you could look up the volume change of 2.9 gal of water/antifreeze.

[Jonathan]

I was keeping in mind the stock set-up in calculating the additional volume, and that was primarily just the design coolant volume being 11.0 litres from the Owner's Manual.

To me, it comes out to about 400 ml of extra expansion volume where as the SS coolant reservoir I measured to be approximately 2.0 litres worth of capacity. Hence if you keep the reservoir about half full it "should" be enough to accommodate the extra volume.

Now having said that, your coolant bottle cap doesn't really relieve based on volume as much as it does pressure. That pressure is 15 psig, or about one atmosphere. If your car gets hot because of other reasons such as cooling fans that aren't coming on quite quickly enough, or perhaps they aren't cooling the fluid as well as they should, you might exceed the boiling point of the coolant. Again, 50% coolant has a boiling point of about 225 deg F under atmospheric conditions. The coolant system is not pressurized separately, it only builds pressure "because" it is getting hotter and there is no place for that expansion to go. So it is very dependant on how hot your coolant system gets as to whether it will send fluid/vapour out the overflow. The catch is, as the coolant gets hotter, the pressure goes up and there are two contributors to you running out of space.

On paper a half full coolant reservoir should be lots of room, but the real issue is how high the temperature is getting in that fluid. That of course relates more to other aspects of your cooling system. If your cooling system is running as designed, you'll not need to be concerned with coolant overflowing.

[DMC5180]

This is what I've been told.......

On a stock car (minus self bleeder) The expansion tank should be between 1/3 and 1/2 when cold. Allowing for the tank to capture the expanding coolant under normal operation. If the tank goes dry or starts spewing uncontrollably then you have a problem elsewhere (ie, head gasket, cracked block).

I'm not familiar with DMCH's new plastic expansion tanks so I'm not sure where the marks on it are. I have the stainless tank so I generally check it to see if it's somewhere around half. When I did my water pump last year I filled the tank about 3/4 full and it eventually settled between the 1/3 and 1/2 range. Since then I haven't had to add any coolant and that was around 8500 miles ago.

Hope this helps.


Thanks Chris,

The plastic tank is a reproduction of the original with modern materials and the markings are identical with Original plastic bottle. The bugger with the Stainless or Aluminum is that you can't view the level changes when system is hot, unless you have a Hervey tank with site tube.

[DMC5180]

I was keeping in mind the stock set-up in calculating the additional volume, and that was primarily just the design coolant volume being 11.0 litres from the Owner's Manual.

To me, it comes out to about 400 ml of extra expansion volume where as the SS coolant reservoir I measured to be approximately 2.0 litres worth of capacity. Hence if you keep the reservoir about half full it "should" be enough to accommodate the extra volume.

Now having said that, your coolant bottle cap doesn't really relieve based on volume as much as it does pressure. That pressure is 15 psig, or about one atmosphere. If your car gets hot because of other reasons such as cooling fans that aren't coming on quite quickly enough, or perhaps they aren't cooling the fluid as well as they should, you might exceed the boiling point of the coolant. Again, 50% coolant has a boiling point of about 225 deg F under atmospheric conditions. The coolant system is not pressurized separately, it only builds pressure "because" it is getting hotter and there is no place for that expansion to go. So it is very dependant on how hot your coolant system gets as to whether it will send fluid/vapour out the overflow. The catch is, as the coolant gets hotter, the pressure goes up and there are two contributors to you running out of space.

On paper a half full coolant reservoir should be lots of room, but the real issue is how high the temperature is getting in that fluid. That of course relates more to other aspects of your cooling system. If your cooling system is running as designed, you'll not need to be concerned with coolant overflowing.

Thanks Jonathan that's great info. I don't suppose you could run your formula using 220˚F. I would concur that the volume expansion under Normal Highway driving temps (190-195) is about what your results would indicate.

It's a good point you brought up about the Volume difference of a stainless (Cylinder Flat Ended) tank and the plastic Hemisphere end tank. Are the Diameters of the two tanks the same or is the stainless slightly smaller?

[Rich]

Answering the orig. question:
On our car (tested-good 15psi cap, metal header bottle, on an OEM-style cooling system and components) the coolant level is at or just below 1/2 full when cold.

It stays that way all the time. That is, no venting, leaking or puking anywhere after stabilization.

Stabilization: If we fill the tank >1/2 full then it vents coolant during operation, recovers to the ~1/2 full point cold, then remains the same subsequently.

[Rich]

Regarding the coolant expansion volume details/calcs:
Here is a simple stationary test that could accurately answer the question for a particular car. The test applies to to cars like ours, those not fitted with an unpressurized overflow tank.


1. Start with the system cold.
2. Fit a test-only vent hose to the pressure vent fitting beneath the cap. Place an open container able to handle hot coolant beneath the car. Run the test hose to it, open ended.
3. Fill the header bottle just to the top. No air, no coolant overflow to vent hose. Put the cap on tight.
4. Fire the engine up. Run it through a few cooling fan cycles with A/C off.
5. Shut it down, let then engine soak hot and then cool off. Measure the volume of the expelled coolant in the container.

This accounts for all of the factors (bottle size, expansion of hoses, block, all components, thermal settings). At 15PSI and hot there is no air to compress so all the "extra" coolant due to expansion has to vent.

[Jonathan]

Thanks Jonathan that's great info. I don't suppose you could run your formula using 220˚F. I would concur that the volume expansion under Normal Highway driving temps (190-195) is about what your results would indicate.

It's a good point you brought up about the Volume difference of a stainless (Cylinder Flat Ended) tank and the plastic Hemisphere end tank. Are the Diameters of the two tanks the same or is the stainless slightly smaller?

I work it out to an additional 80 ml to go to 220 degrees F. Meaning, the expansion volume from atmospheric conditions to just about the boiling point is 0.480 litres. Still should be lots of room in the empty half of the coolant reservoir.

I have an old plastic reservoir in a tote somewhere. I'll see if I can dig it out and do some measurements to see what the capacity is.