How much coolant is enough or too much?

[lastdime]

My roadster has been losing coolant with only one leak that I found. That was a small drip from the front of the intake manifold. A re-torque of one bolt solved that issue. However, after driving at temperature for 100 miles or so it was starting to over heat again due to loss of coolant. The gauge didn't indicate a problem, but I could hear it boiling when I turned off the engine.

The first thing I did was to replace the radiator cap, figuring it might be the cause. Using a no leak funnel I refilled and burped the the system. But without a coolant reservoir how can one know when the right amount of coolant has been added. In this case, it was full to the hose cap connector. After taking it out and running 10 miles or so the coolant was leaking out of the overflow tank when I stopped. According to my gauge the temperature was still at the low end of the range (85C-90C). Later I ran it again with the same results. So, the question comes back to correct amount of coolant. Was it overfilled and now self correcting? How can one know if you have the correct level of coolant without a coolant reservoir? When you refill, do you fill it up and wait for it to self regulate through the overflow tank?

I still don't know if my leak problem has been solved with the new cap, but time will tell. In the meantime I'm working on the coolant level problem.

[RoadRacer]

You did what I always do, add a lot and let it self correct, repeat a couple times. ¯\_(ツ)_/¯

[lastdime]

That is what I have done before but wondered if there was a better way.

[Old Timer]

I found (on my 347) if you get an air bubble at the top inside the manifold, the temp sensor does not get
covered with coolant, so you don't always know the water temp.
I pulled the sensor to burp the air out, and that helped get all of the air out.

They make a Airlock Purge Tool if you have $120 extra bucks.
My brother in law uses this at his dealership for new cars that are a pain.
I have not used it on my coupe, but he swears it will work.
https://smile.amazon.com/dp/B0002SRH5G/

[Bob Cowan]

However, after driving at temperature for 100 miles or so it was starting to over heat again due to loss of coolant. The gauge didn't indicate a problem, but I could hear it boiling when I turned off the engine.

> this makes me think you have a bigger problem.

The first thing I did was to replace the radiator cap, figuring it might be the cause. Using a no leak funnel I refilled and burped the system. But without a coolant reservoir how can one know when the right amount of coolant has been added. In this case, it was full to the hose cap connector. After taking it out and running 10 miles or so the coolant was leaking out of the overflow tank when I stopped. According to my gauge the temperature was still at the low end of the range (85C-90C). Later I ran it again with the same results. So, the question comes back to correct amount of coolant. Was it overfilled and now self correcting? How can one know if you have the correct level of coolant without a coolant reservoir? When you refill, do you fill it up and wait for it to self regulate through the overflow tank?

> You don't have a reservoir, but you do have an overflow tank?
> With an overflow tank it should self level. You should see a lot of fluid when it's hot,
> and not much fluid when it's cold.


Use an infrared thermometer to see what your temps really are.

It's kind of sounding like you have a blown head gasket.

First, go to autozone and borrow their coolant test kit. Also, borrow their Engine Combustion Leak Detector kit. You'll know pretty quick if you have a real problem.

[lastdime]

I found (on my 347) if you get an air bubble at the top inside the manifold, the temp sensor does not get
covered with coolant, so you don't always know the water temp.
I pulled the sensor to burp the air out, and that helped get all of the air out.

They make a Airlock Purge Tool if you have $120 extra bucks.
My brother in law uses this at his dealership for new cars that are a pain.
I have not used it on my coupe, but he swears it will work.
https://smile.amazon.com/dp/B0002SRH5G/

Interesting on the temp sensor. I'll have to try that.

[lastdime]

Use an infrared thermometer to see what your temps really are.

It's kind of sounding like you have a blown head gasket.

First, go to autozone and borrow their coolant test kit. Also, borrow their Engine Combustion Leak Detector kit. You'll know pretty quick if you have a real problem.

No, no, can't be a head gasket......but it will probably end up being that. :mad: Thanks for the info on the test kit.

[lastdime]

Use an infrared thermometer to see what your temps really are.

It's kind of sounding like you have a blown head gasket.

First, go to autozone and borrow their coolant test kit. Also, borrow their Engine Combustion Leak Detector kit. You'll know pretty quick if you have a real problem.

Bob, I'm getting really confused with the terminology of "expansion tank", "overflow tank", "puke tank", "recovery tank", etc. Is the standard FFR overflow tank designed to recirculate the coolant back to the radiator or just collect the excess overflow?

[egchewy79]

Expansion tank catches fluid that boils off when engine reaches temp, then vacuum when the fluid cools sucks fluid back into the system. The radiator cap that comes with complete kit is a#20 cap. You'll want to get a #16 cap or else your fluid will run too hot

[BEAR-AvHistory]

Had the same symptoms with the COYOTE & the FFR supplied tank you are. It should return water back to the radiator as it cools. If your FFR tank is the same as mine I just kept loosing coolant & tried two fixes.

First bought a bigger tank of the same style from Summit but still had the same problem. Inside are either two different length tubes or one outlet tacked to the bottom & the other a single tube that comes up inside the tank. Be sure to hook the hot water hose from the radiator to the short one. The way it functions is the hot water fills the tank till it hits the overflow tube the it dumps the coolant onto the street where its lost to the car. Whatever is left in the tank will go back into the engine as it cools. I believe there is a constant loss of coolant with this system.

If you already have the hose attached correctly & it still dumps the coolant get a FORD factory tank or a MOROSO alloy tank plumbed the same as the factory tank for your engine. This is an expansion tank & operates pretty much as a closed system with a stock Mustang pressure cap.

In my case my MOROSO tank duplicates the plastic 2013 Mustang GT. By duplicates I mean it has the same hose attachment points as the factory tank although the shape of the tank itself is different. Have not lost or added any coolant in 4 years through daily driving in Carolina.

As part of the makeover I am doing now have dumped all the old fluid which is a good plan to do every few years.

https://cfc7329ad537523a5de1-b21544d490ba797ec9de9d17e947de3d.ssl.cf1.rackcdn.c om/lrs-8080m_3380.jpg

FORD Part

https://thefactoryfiveforum.com/attachment.php?attachmentid=126382&d=1586814394

[rich grsc]

Expansion tank catches fluid that boils off when engine reaches temp, then vacuum when the fluid cools sucks fluid back into the system. The radiator cap that comes with complete kit is a#20 called. You'll want to get a #16 cap or else your fluid will run too hot
AAh no, that is an overflow, recovery tank or Puke tank. An expansion tank is just as it's name describes, it's a sealed tank plumbed into the coolant system that contains an air space above the coolant. When the coolant becomes hot, it expands compressing and pressurizing the air in the tank, thus expanding into the air space. When the coolant reaches normal temperature and contracts the compressed air returns to normal pressure. You can not compress a liquid, you can air.

[Bob Cowan]

Expansion tank catches fluid that boils off when engine reaches temp, then vacuum when the fluid cools sucks fluid back into the system. The radiator cap that comes with complete kit is a#20 called. You'll want to get a #16 cap or else your fluid will run too hot

Not exactly. The cap has little to do with the operating temp. Water has a boiling temp of 212* at standard pressure and temperature. A higher pressure system will raise the boiling point above 212*. If your engine tends to run hot, then a higher pressure cap will control overheating a little bit.

A coolant reservoir is within the system, often plumbed into the middle of the upper hose. Usually about a qt or so of fluid to help keep the system purged of air.

An overflow tank (AKA: Expansion tank) Is connected to the filler neck and cap assembly by a small hose. When the pressure in the system exceeds the cap rating, the spring compresses and the cap opens, allowing fluid to enter the tank. When it cools off, the vacuum created sucks the water back in to the main part of the system.

I think having both is the best way. But most engines do just fine with the overflow tank.

[NAZ]

There’s quite a bit to learn about automotive cooling systems. There’s a great deal of info on the internet, much of it is dry reading that engineers find interesting and some is a retelling of myths that were first perpetrated back when flatheads ruled and observations were incorrectly attributed to the wrong root cause.

But first we should get grounded on nomenclature – specifically the two types of ancillary tanks found on modern cooling system designs. The expansion tank and the recovery tank. What they do, how they do it, and where they fit into the cooling system is important to understand. Install an expansion tank in the wrong location and you will negate its benefits. Hookup a recovery tank wrong or run the wrong style pressure cap and the tank becomes a simple catch can.
http://blog.cantonracingproducts.com/blog/setting_up_your_cooling_system_expansion_vs_recove ry

And here’s a link to more info you may find interesting:
https://www.hotrod.com/articles/ccrp-0707-high-performance-cooling-system/

There is much more that you will find at the end of your keyboard. But I encourage you to search several sources as there is enough conflicting info to confuse you as old inaccurate info keeps getting recycled.

[Norm B]

last dime, judging by the size of your engine, you're going to need a bigger overflow tank. You are probably blowing the overflow tank full and then it is spilling coolant out its vent when the engine is hot and then sucking it dry and getting air into your system when the engine is cold. This air in the system aggravates your problem the next time you run the engine. This could create the boil over at shutdown but, as Bob said this is one of signs of a blown head gasket.

Here's a couple of pictures of mine, one cold and one hot. I have the Breeze "its not fancy but it works" overflow tank that makes seeing the coolant level easy. This is on a SBF 331. Your big block would be much more.
For those are that interested here's a chart on how coolant mixture and rad cap pressure changes the boiling point of your cooling system.

HTH

Norm

[lastdime]

There’s quite a bit to learn about automotive cooling systems. There’s a great deal of info on the internet, much of it is dry reading that engineers find interesting and some is a retelling of myths that were first perpetrated back when flatheads ruled and observations were incorrectly attributed to the wrong root cause.

But first we should get grounded on nomenclature – specifically the two types of ancillary tanks found on modern cooling system designs. The expansion tank and the recovery tank. What they do, how they do it, and where they fit into the cooling system is important to understand. Install an expansion tank in the wrong location and you will negate its benefits. Hookup a recovery tank wrong or run the wrong style pressure cap and the tank becomes a simple catch can.
http://blog.cantonracingproducts.com/blog/setting_up_your_cooling_system_expansion_vs_recove ry

And here’s a link to more info you may find interesting:
https://www.hotrod.com/articles/ccrp-0707-high-performance-cooling-system/

There is much more that you will find at the end of your keyboard. But I encourage you to search several sources as there is enough conflicting info to confuse you as old inaccurate info keeps getting recycled.

Naz, confusion is the operative word here. The more I read the more confused I get. However, these posts have given me points to investigate and hopefully, eliminate. Thanks

[lastdime]

Not exactly. The cap has little to do with the operating temp. Water has a boiling temp of 212* at standard pressure and temperature. A higher pressure system will raise the boiling point above 212*. If your engine tends to run hot, then a higher pressure cap will control overheating a little bit.

A coolant reservoir is within the system, often plumbed into the middle of the upper hose. Usually about a qt or so of fluid to help keep the system purged of air.

An overflow tank (AKA: Expansion tank) Is connected to the filler neck and cap assembly by a small hose. When the pressure in the system exceeds the cap rating, the spring compresses and the cap opens, allowing fluid to enter the tank. When it cools off, the vacuum created sucks the water back in to the main part of the system.

I think having both is the best way. But most engines do just fine with the overflow tank.

Bob, your post really helped explain things. Now I have a much better idea of where to look and what to analyze. However, I will be doing the head gasket test to see if the big problem exists. Thanks

[lastdime]

last dime, judging by the size of your engine, you're going to need a bigger overflow tank. You are probably blowing the overflow tank full and then it is spilling coolant out its vent when the engine is hot and then sucking it dry and getting air into your system when the engine is cold. This air in the system aggravates your problem the next time you run the engine. This could create the boil over at shutdown but, as Bob said this is one of signs of a blown head gasket.

Here's a couple of pictures of mine, one cold and one hot. I have the Breeze "its not fancy but it works" overflow tank that makes seeing the coolant level easy. This is on a SBF 331. Your big block would be much more.
For those are that interested here's a chart on how coolant mixture and rad cap pressure changes the boiling point of your cooling system.

HTH

Norm

Norm, the size of the tank is a good observation. My guess is that you are right with the big block needing a bigger tank. The FFR supplied overflow tank is most likely designed for a small block engine and mine needs a Big Gulp. Thanks

[lastdime]

AAh no, that is an overflow, recovery tank or Puke tank. An expansion tank is just as it's name describes, it's a sealed tank plumbed into the coolant system that contains an air space above the coolant. When the coolant becomes hot, it expands compressing and pressurizing the air in the tank, thus expanding into the air space. When the coolant reaches normal temperature and contracts the compressed air returns to normal pressure. You can not compress a liquid, you can air.

Thanks for the clarification.

[lastdime]

Had the same symptoms with the COYOTE & the FFR supplied tank you are. It should return water back to the radiator as it cools. If your FFR tank is the same as mine I just kept loosing coolant & tried two fixes.

First bought a bigger tank of the same style from Summit but still had the same problem. Inside are either two different length tubes or one outlet tacked to the bottom & the other a single tube that comes up inside the tank. Be sure to hook the hot water hose from the radiator to the short one. The way it functions is the hot water fills the tank till it hits the overflow tube the it dumps the coolant onto the street where its lost to the car. Whatever is left in the tank will go back into the engine as it cools. I believe there is a constant loss of coolant with this system.

If you already have the hose attached correctly & it still dumps the coolant get a FORD factory tank or a MOROSO alloy tank plumbed the same as the factory tank for your engine. This is an expansion tank & operates pretty much as a closed system with a stock Mustang pressure cap.

In my case my MOROSO tank duplicates the plastic 2013 Mustang GT. By duplicates I mean it has the same hose attachment points as the factory tank although the shape of the tank itself is different. Have not lost or added any coolant in 4 years through daily driving in Carolina.

As part of the makeover I am doing now have dumped all the old fluid which is a good plan to do every few years.

https://cfc7329ad537523a5de1-b21544d490ba797ec9de9d17e947de3d.ssl.cf1.rackcdn.c om/lrs-8080m_3380.jpg

FORD Part

https://thefactoryfiveforum.com/attachment.php?attachmentid=126382&d=1586814394

The size of the coolant tank and correct connection seems to be a common comment as a possible problem. I will definitely check it out. Thanks

[NAZ]

I've seen several posts about the FFR supplied recovery tanks being too small to handle the coolant expansion. When the coolant heats up it expands and on a system without an expansion tank, is forced past the pressure cap to the recovery tank if one is present. When the coolant cools back to ambient temp it contracts and creates a vacuum in the system and a check valve on the pressure cap allows the coolant in the recovery tank to be pulled back into the radiator. If the recovery tank is too small the expanded coolant overfills the tank and a portion of the coolant is discharged onto the ground. When the system cools there is less coolant to draw back into the radiator and the rest of the radiator volume is filled by air being sucked back into the radiator. That makes it look as if you have a leak.

I should note that a recovery tank typically has two hose connections, one that draws from the bottom of the tank and an overflow that will draw from near the top of the tank. The connection that draws from the bottom of the tank is the one that connects to the radiator overflow. Connecting them wrong will prevent the recovery of coolant back to the radiator.

My system is smaller than most at 4.8-gallons and I calculated I needed 30.1-oz of coolant expansion. I run a 32-oz recovery tank and that has worked well. That might give you a ball park idea of what you need. But for a more accurate estimation, this can be calculated.

[lastdime]

Use an infrared thermometer to see what your temps really are.

It's kind of sounding like you have a blown head gasket.

First, go to autozone and borrow their coolant test kit. Also, borrow their Engine Combustion Leak Detector kit. You'll know pretty quick if you have a real problem.

I love the color BLUE! I did the blown head gasket test and the liquid remained a bright blue. What a relief. Now on to the other possibilities.

[GTBradley]

I've seen several posts about the FFR supplied recovery tanks being too small to handle the coolant expansion. When the coolant heats up it expands and on a system without an expansion tank, is forced past the pressure cap to the recovery tank if one is present. When the coolant cools back to ambient temp it contracts and creates a vacuum in the system and a check valve on the pressure cap allows the coolant in the recovery tank to be pulled back into the radiator. If the recovery tank is too small the expanded coolant overfills the tank and a portion of the coolant is discharged onto the ground. When the system cools there is less coolant to draw back into the radiator and the rest of the radiator volume is filled by air being sucked back into the radiator. That makes it look as if you have a leak.

I should note that a recovery tank typically has two hose connections, one that draws from the bottom of the tank and an overflow that will draw from near the top of the tank. The connection that draws from the bottom of the tank is the one that connects to the radiator overflow. Connecting them wrong will prevent the recovery of coolant back to the radiator.

My system is smaller than most at 4.8-gallons and I calculated I needed 30.1-oz of coolant expansion. I run a 32-oz recovery tank and that has worked well. That might give you a ball park idea of what you need. But for a more accurate estimation, this can be calculated.
I’m running with the smaller FFR supplied expansion tank. It’s generally thought of as too small and most use a big Morroso tank, but I wanted to see for myself. So far, I agree with NAZ above. When my engine is hot the tank is near full and when it cools down the expansion is near empty but the filler neck is full. I’ve run in 90 degree temps with no change to the fluid level, so I think I’m good with the smaller tank, but there’s hotter days ahead...

[rich grsc]

An expansion tank / degassing tank.

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[NAZ]

Something to keep in mind is that the ambient temperature when you fill the coolant system will affect how much expansion. If your recovery tank is marginal and you filled your system when it was 90F outside that marginal recovery tank may not be enough capacity if you top off the system when it's 60F. Coolant expands and contracts with heat and if you filled the system in the summer, come winter the coolant will contract and want to draw in more from the recovery tank. If you didn't size the tank to hold enough reserve you could be drawing in air during the colder months. When you check your recovery tank and it's empty what are you going to think? Yup, I got a leak.

The math formula for calculating coolant expansion includes the density of the coolant at initial fill and at max operating temp. Since we are only talking ounces it makes a difference. The take away here is that you really don't want a marginal size recovery tank and it's better to have more than enough than to be short on capacity. You always want to leave some reserve coolant in the recovery tank to prevent sucking air into the system.

On the the hand, when using an expansion tank the same is true. You want to size the tank to handle the temperature extremes.

For those interested in coolant properties and how to do their own calculations, here's a good start: https://www.engineeringtoolbox.com/ethylene-glycol-d_146.html

[BEAR-AvHistory]

Just want to toss in one extra thing on the factory & (burp)alloy tanks used with the COYOTE engines. The engines as located in the car can be a real pain in the butt to clear (burp) of all its air pockets so they don't turn into hot spots. There are quite a few threads on how to do this. That said with the degassing tanks both the engine & radiator will self purge any trapped air through two hoses that connect to the high points of both. The hose to the radiator is directional with a one way restricter valve

https://thefactoryfiveforum.com/attachment.php?attachmentid=131442&d=1594217942

With these style tanks you just fill to the mid-point of the tank run the engine, let it cool the add coolant & repeat till it stabilizes at the level you want in the tank

[lastdime]

Here is what I ended up doing to solve my coolant and overheating problem. Much to the thanks of NAZ and many of your comments.

First the plastic supplied inline neck had warped allowing gases to escape and pressure to never stabilize. I replaced the neck with a cast aluminum one and refit the hoses. Then I added a overflow recovery tank with a little creative fabrication of the mount. Just like Bear said, add fluid when it is cold, run it, check level and repeat if necessary. Now it is set at the right cold-hot level and all is well. So much more confidence in the system now and it is easy to see what my coolant level actually is and not have to guess. Thanks everyone.

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