How much coolant overflow is normal?

[Steve83]

Just cause it has a Motorcraft part # and a Motorcraft box doesn't mean anything anymore. My Ford part # waterpump in a Motorcraft box had a white sticky on the back side of it with the word "CHINA" on it.

Yes, it still means it meets Ford/MC standards just like it always has. And like always: Ford doesn't make most Ford parts - Ford makes vehicles. Ford parts mostly come from independent manufacturers who agree to make them the way Ford specifies, and if they do, Ford allows them to use the Ford/MC trademarks on those parts & their packaging. Even if those manufacturers are in Mexico, Brazil, Portugal, or chy-nah. I'll take an imported Ford/MC part over a non-Ford part any day, and I buy a LOT of mine from eBay & Amazon. But I've gotten chy-neez parts from the dealership.

 

[nvrstuk]

Agreed 100%.

Take brgs for example. We know they are supposed to meet the specs/standards of the manufacturer however, we all have experienced the increased failure rate of these "same bearings" now that the are being manufactured outside of production. Meaning an after production part rather than a part that was produced & used on the original vehicle while it was being produced & sold here..

I went thru a "call & find out why" tirade about 10 yrs ago on rear end brgs. I posted up about this back then. Engineers feom thses companies like Bower, Timken, Koyo all said that the specs are the same but there can be variances ( can't remember all of them) but grease was an issue for sealed brgs. In a nutshell- cheap grease & not enough of it. All of them said to pull the seal & pack it full of high quality grease. These were engineers of these companies. Bit of an eye opener...

 

[ksagis]

This is somewhat nuanced topic on the three different kinds of systems. Three types are no external tank (air gap), recovery tank, or expansion tank (basically providing an air gap but in a separate higher tank than the highest point in coolant system).

Basic physics is coolant expands as it gets hotter and drives a need for more volume. In an air gap system (no tank) the coolant expands and squeezes the air (easy). In a coolant recovery tank system, the liquid expands into the recovery tank and when the engine cools, it “pulls” the coolant back to radiator. In an expansion tank system the coolant expands, goes into the expansion tank, and squeezes the air in the expansion tank (easy).

The advantage of the recovery and expansion tank systems is they minimize the remaining air in the system.

I did some research on density changes of coolant over temperature changes and for a 50/50 system with a 15 psi cap, I came up with about 7% change in volume. For a 16 quart system, thats about 1.1 quarts.

So, for a no tank system it needs about a quart of air to not burp coolant, or the recovery / expansion tanks needs to be the right size (I’m ignoring the growth of hoses)

Getting back to OPs issue, it seems to me that it should only burp some number of times until it created enough air gap. So unless he added coolant, or it got hotter than what worked for the baseline air gap, it shouldn’t continue to burp.

Note that radiator caps have different designs depending if they are meant for a recovery system (those have a feature on bottom seal that lets the radiator suck back fluid as it cools.

The graph is specific gravity vs coolant temperature for a 50/50 blend and shows about 7 percent change from 50 degF to 265 degF.

 

[nvrstuk]

Good stuff there! Thx


When designing mine I read that large HP engines create faster heat/temperature rise & therefore a steam issue can/does occur creating more coolant loss due just to the fact of the engine building more heat faster.

So, I still need a larger reservoir on mine even after all that.

 

[gunnibronco]

This is somewhat nuanced topic on the three different kinds of systems. Three types are no external tank (air gap), recovery tank, or expansion tank (basically providing an air gap but in a separate higher tank than the highest point in coolant system).

Basic physics is coolant expands as it gets hotter and drives a need for more volume. In an air gap system (no tank) the coolant expands and squeezes the air (easy). In a coolant recovery tank system, the liquid expands into the recovery tank and when the engine cools, it “pulls” the coolant back to radiator. In an expansion tank system the coolant expands, goes into the expansion tank, and squeezes the air in the expansion tank (easy).

The advantage of the recovery and expansion tank systems is they minimize the remaining air in the system.

I did some research on density changes of coolant over temperature changes and for a 50/50 system with a 15 psi cap, I came up with about 7% change in volume. For a 16 quart system, thats about 1.1 quarts.

So, for a no tank system it needs about a quart of air to not burp coolant, or the recovery / expansion tanks needs to be the right size (I’m ignoring the growth of hoses)

Getting back to OPs issue, it seems to me that it should only burp some number of times until it created enough air gap. So unless he added coolant, or it got hotter than what worked for the baseline air gap, it shouldn’t continue to burp.

Note that radiator caps have different designs depending if they are meant for a recovery system (those have a feature on bottom seal that lets the radiator suck back fluid as it cools.

The graph is specific gravity vs coolant temperature for a 50/50 blend and shows about 7 percent change from 50 degF to 265 degF.

Thanks, I haven't driven the truck more than a few hundred miles since I got it running last fall. It was much cooler then. I don't remember if I topped the radiator up since then. I might have, plus I'm sure the truck was hotter than it had been last fall. I'll see if I can find a point where it stops losing coolant.

Glad to know the rad caps are different if I add an overflow tank.

Sent from my Pixel 7 using Tapatalk

 

[Broncobowsher]

You can use just about anything for a recovery bottle. A quart or two capacity old gatorade jug or just about anything. Stick that under the hood next to the radiator, maybe a few zip ties. Put the overflow hose in it, preferably at the bottom so it can suck it back up as it cools. May not be pretty, but it will get you by until you get the nice one you really want. I've seen this done more times than I can count at the local drag strip. They require a catch can to pass tech. This is what is done when they fail tech, but want to go racing that night.

 

[BronCowie]

Get one of these and replace that windshield fluid resovoir on the drivers side fender with this; connect your rad overflow tube to it. I did and my coolant puking and engine temperature swings became a distant memory.

 

[Steve83]

...I read that large HP engines create faster heat/temperature rise & therefore a steam issue can/does occur...

Steam is not created by rapid temperature changes - it's created by temperature only, regardless how long it takes to achieve that temp. So if steam is a problem, that only means that the engine is getting hotter than the coolant mixture's boiling point. It has nothing to do with hp.

Yes, any engine producing more hp will get up to temperature sooner than an identical engine at idle. But that doesn't cause coolant to boil (become steam).

Get one of these...

Just FYI: that's a common '87-96 Bronco/F-series (& '97 >8500GVWR, except all years of diesel) tank.

Amazon.com: Ford Genuine Parts Ford Parts - Reservoir - Water (E7TZ-17618-B) : Automotive

Buy Ford Genuine Parts Ford Parts - Reservoir - Water (E7TZ-17618-B): Reservoirs - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

 

[ntsqd]

^^^ one application to look up that part by would be '96 Bronco or F-150. I don't think the engine size will matter for that, but my FSB with that part OEM is a 5.8L.
If you want a really cool, aluminum such assembly that will fit exactly the same as that one then here's an option: https://www.cookcraftmetal.com/product-page/ford-coolant-and-windshield-reservoir

I've never really figured out why, but sometimes filling the radiator full with coolant and then letting it find it's own air gap in the tank doesn't seem to work, it just keeps pushing fluid out until the radiator is really low. I'll speculate that opening the cap when not completely cold can or might be part of the problem.
Leaving an air gap that might be a little less than what the system will ultimately settle at seems to work better.

 

[gunnibronco]

Thanks, I'm going to see what an air gap does, and if it finds it's own level. If that doesn't work, it will get a new stock overflow from a later model. Those are great, and I've seen them used on EFI'd trucks. This truck is getting an OEMish patina resto-mod treatment. I want anything I do to have a stock or period correct feel, and be removable to return to stock if desired some day. It's an 88,000 mile, original paint 72 Explorer Sport (one of only 141 in Candyapple Red).

 

[Steve83]

...'96 Bronco or F-150. I don't think the engine size will matter...

I know my 7.3L uses a different tank, but I think all other engines (probably 7.5L, but I've never had one) use that tank.

 

[gnpenning]

For your own sanity. Take a measuring cup and fill with water. Pour out 2 oz at a time in a solid surface and watch the puddle size after each pour. Most people are surprised at how little fluid it takes to make a large puddle.

 

[DirtDonk]

Haha! That's a great idea!

As I mentioned, my '71 was one of those that, while it found it's own level, did keep getting lower and lower and burped out a tiny bit on most trips.
But the Bronco stayed cool until the coolant got to less than the radiator being half full. Much less in fact.
This lowering of the coolant, rather than taking on some emergency status, took more than six months each time.

I have added recovery tanks to old vehicles since the seventies. More for the pollution aspect though, than from a maintaining the level aspect.
Although that always bothered me a bit too, as said it was never a huge deal.

Paul

 

[gunnibronco]

Haha! That's a great idea!

As I mentioned, my '71 was one of those that, while it found it's own level, did keep getting lower and lower and burped out a tiny bit on most trips.
But the Bronco stayed cool until the coolant got to less than the radiator being half full. Much less in fact.
This lowering of the coolant, rather than taking on some emergency status, took more than six months each time.

I have added recovery tanks to old vehicles since the seventies. More for the pollution aspect though, than from a maintaining the level aspect.
Although that always bothered me a bit too, as said it was never a huge deal.

Paul

This won't see that many miles really, so it's going to take a long time to drain 1/2 the radiator. Plus it gets a lot of attention per mile driven compared to the average daily driven Bronco in their heyday.

For your own sanity. Take a measuring cup and fill with water. Pour out 2 oz at a time in a solid surface and watch the puddle size after each pour. Most people are surprised at how little fluid it takes to make a large puddle.

Very true!