Overflow tank never changes... (1 Viewer)

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midfat

midfat

Joined
Mar 24, 2013
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Just finished my total cooling system overhaul on my '97. New rad, water pump, thermostat, gaskets, PHH, heater valve, hoses, etc. It holds rock solid at 185* on extended freeway driving (per OBDII). Everything seems great. But, there's absolutely no change in the level of the expansion tank from hot to cold. Just curious if this is normal, or an indicator of something else?
 
I've owned my truck for 2 years, in that time I've done a complete coolant flush, (filled with green) had a radiator shop doing a cleaning of my radiator, along with that i replaced the oil in my fan clutch. Since my truck is OBD1 i have to use my Snap On MT2500 to check the running temp, it runs 181 degrees, both in town, and on the freeway. Since doing this maintenance, the coolant level moves about an inch, when it's hot it'll read at the "full" mark on the over flow bottle, when it's cold, it's about an inch below that mark.
 
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Lucky you! LOL!!!
 
4G63 POWER said:
It should be fine, but you didn't say how you burped the cooling system.
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Following the new radiator install, drained black and 20 min garden hose flush at idle, I buttoned everything back up and filled from the radiator neck - while the engine was running. As bubble came through the radiator, I kept topping everything off. Did this for about 20 mins until the bubbles stopped. Checked level again today and it's right in the filler neck of the radiator - right where I'd expect it to be. Am I missing something?
 
As a data point mine is at low when cold but comes up a few inches when hot. When cold again the next morning its back to low. I leave it on the low mark so that it has room for expansion. On my old expansion tank it didn't move much since the plastic lid was cracked and it wasn't good at sucking the fluid back into the radiator as it cooled.

As far as I know I'm not running warmer than usual.
 
The system is simply not building enough pressure to overcome the spring loaded radiator cap. OR the radiator cap is faulty.

When pressure in the radiator/cooling system exceeds a certain psi (whatever your radiator cap is rated for) the coolant will flow into the overflow reservoir until enough pressure is relieved for the seat of the radiator cap to close again. Later when the engine cools...(if cool enough)...fluid will be drawn back into the radiator.

So...either your engine is running nice and cool and NO exchange is happening or needed, OR....your cap is faulty and not opening correctly.
 
Yeah, What Flint and others have said. You're running 185* nice and cool as it should be. Call it good to go.
 
4G63 POWER said:
Oh man, tap water in your cooling system. Big no no. Defeated the point of doing all that work. All the minerals.
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The hose was for the flush. Block and system was drained again following flush. Full system was then refilled with distilled water and 50/50 mix.
 
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midfat said:
Seriously? That's a joke, right? The hose was for the flush. Block and system was drained following flush, again. Full system was refilled with distilled water and 50/50 mix.
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We enjoy a water quality out West the mid/mid-East doesn't.

If given a cup of water from Detroit or a cup from any West coast state, always drink the West coast water.

I've been a welder of all metals, had lead testing to ensure health (including the zinc / zpp test that is a pre-cursor to long term lead issues) - I know a few terms & had a few classes where my daily job made me a instructor for new guys.

Simple answer, we have it good for water out West.
Our drilled wells beat most municipal water if you are a Midwest citizen.

Had a father-in-law (WA resident) who bought his dad(Chicago city? -- was out in the midWest) -a R/O filter for his house. The guy was a water specialist for Whatcom county PUD, knew his isht well enough to be in the salmon fish recovery project.

West coast water is like super unleaded gas, it's why the pot from anywhere W of the Rockies is so prized. If you want to get crazy, yep, WA dope is king due to water.

Don't sweat the water you used, your dope is known too - so I bet the tapwater there is just fine!
 
4G63 POWER said:
Oh man, tap water in your cooling system. Big no no. Defeated the point of doing all that work. All the minerals.
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Nope. Not here. I drink stream water here, and I weld lead as part of my job.
We all know Detroit water is known as the worst of the 50 states.

I wish it were different for you, but it's a known issue. You should all have house filters & R/O setups for the water you drink & use in bath/shower (since your skin absorbs so much).

I agree - your water is good for only flushing -not even for food plant if they absorb the heavy metals. Surely not for cooling systems either for the other trace minerals.
 
midfat said:
Just finished my total cooling system overhaul on my '97. New rad, water pump, thermostat, gaskets, PHH, heater valve, hoses, etc. It holds rock solid at 185* on extended freeway driving (per OBDII). Everything seems great. But, there's absolutely no change in the level of the expansion tank from hot to cold. Just curious if this is normal, or an indicator of something else?
Click to expand...
Did all the same Cooling System Overhaul Pieces and Parts? a couple months ago. My overflow tank doesn't change either...guess we did it right! :D
 
If the coolant level in the radiator expansion tank doesn't start to rise within 10 minutes after starting the engine... or lower a few hours after shutting down the engine, the radiator cap is faulty.

The cooling system will be overpressurized when the engine is running if the cap doesn't bleed pressure which risks blowing a coolant hose or even worse...the head gasket
 
@midfat I agree with @Output Shaft. If your system is 100% full there is no where else for the water to go except into the recovery tank. The density of water decreases as its temp rises. Therefor, the volume of water in your you cooling system will increase slightly.

Your list of new parts did not include an OEM radiator cap. Did you replace the cap?
 
baldilocks said:
@midfat I agree with @Output Shaft. If your system is 100% full there is no where else for the water to go except into the recovery tank. The density of water decreases as its temp rises. Therefor, the volume of water in your you cooling system will increase slightly.

Your list of new parts did not include an OEM radiator cap. Did you replace the cap?
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New OEM radiator cap came with the new OEM 3-core brass radiator. I did hear a little hissing from the new cap when I first filled it, but figured it need a few heat cycles to get itself settled. I still have the original radiator cap, so I'll swap out and see if that effects the overflow level. Excellent suggestion.
 
ewillis said:
Did all the same Cooling System Overhaul Pieces and Parts? a couple months ago. My overflow tank doesn't change either...guess we did it right! :D
Click to expand...

^^^^ We want to be careful NOT to use fluid migration as a diagnostic tool for the condition of your cooling system.

As I alluded to earlier, there are really only two reasons you WOULDN'T have a coolant exchange between the overflow tank and the radiator (assuming the system is full and all air evacuated).

1. The temperature (read pressure) simply is not reaching a point that it overcomes the spring pressure on the radiator cap.

2. The cap is faulty (though faulty radiator caps tend to be 'weak' and not stuck closed).

IF condition #1 is present....this MUST be verified by taking an accurate coolant temperature measurement.

IF condition #2 is present....replace the cap. IF the cap is weak it isn't providing the pressure necessary to prevent the coolant from boiling at a lower temperature than is desireable. IF the cap has somehow failed in a manner such that it can not open (not likely but possible), then excess pressure can occur in the cooling system....resulting in undue stress on certain parts.

Item #1 can easily be determined by taking a reading on the coolant system (I have a ScanGauge and can monitor it all the time). NO harm in having a cool running engine.

Item #2 is best resolved by means of 'prevention' (just replace the darn cap every 2-3 yrs.) and NOT by means of 'diagnosis' (read....you already have problems).
 
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