Coolant reservoir level after complete flush and fill

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I just did a complete coolant flush on our Frontier. Everything went well after I got all the air out of the system. After draining my last flush with distilled water I refilled with a 50/50 mix of Presrone All Vehicle anti freeze.

My question: I filled the radiator up with anti-freeze. I noticed the reservoir was almost full. I did run the engine a while to help purge the air so I assumed it was just hot anti-freeze. After letting it cool I tried suctioning out the excess reservoir fluid to bring it down to the area between Max/Min. Everytime I started suctioning out the excess fluid the level in the radiator that was filled to just below cap level would decrease. Is this the way it should be? As long as the level of the reservoir is correct when cool should you not see coolant at the cap accounting for expansion of the coolant when hot. Did I not let it cool long enough? It had been over an hour. Thanks for your help.
 
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I just did a complete coolant flush on our Frontier. Everything went well after I got all the air out of the system. After draining my last flush with distilled water I refilled with a 50/50 mix of Presrone All Vehicle anti freeze.

My question: I filled the radiator up with anti-freeze. I noticed the reservoir was almost full. I did run the engine a while to help purge the air so I assumed it was just hot anti-freeze. After letting it cool I tried suctioning out the excess reservoir fluid to bring it down to the area between Max/Min. Everytime I started suctioning out the excess fluid the level in the radiator that was filled to just below cap level would decrease. Is this the way it should be? As long as the level of the reservoir is correct when cool should you not see coolant at the cap accounting for expansion of the coolant when hot. Did I not let it cool long enough? It had been over an hour. Thanks for your help.

AFAIK that is perfectly normal behavior. It is normal in a system that uses an expansion tank (not an overfill tank, there is a big difference), it will maintain the correct coolant level. Go by the level in the expansion tank once the radiator is full.
I would suggest using a vacuum fill tool if you have a compressor, even a small one will work fine just takes a little longer.

Edit: let it cool down until the coolant temp is around ambient to the touch.
 
I might be wrong but I see 2 problems. Unless you are draining the system by removing the freeze plugs you are only getting about half the coolant out. The radiator drains but the heater core and block do not. When you flush with distilled water a few times you have pure water in the engine and need to add full strength coolant to the radiator, then warm the engine up till the thermostat opens and run the heater on full for 10 or 15 min. to mix everything, then check the coolant with a hydrometer for strength. On most cars that have a pressurized tank you dont have a seperate radiator cap, if you have a rubber overflow hose from the tank its just an overflow and should not effect the radiator level.

Edit: Try squeezing your upper rad hose a few times and see if the levels rise and fall. It also helps get the air out of the system.
 
I might be wrong but I see 2 problems. Unless you are draining the system by removing the freeze plugs you are only getting about half the coolant out. The radiator drains but the heater core and block do not. When you flush with distilled water a few times you have pure water in the engine and need to add full strength coolant to the radiator, then warm the engine up till the thermostat opens and run the heater on full for 10 or 15 min. to mix everything, then check the coolant with a hydrometer for strength. On most cars that have a pressurized tank you dont have a seperate radiator cap, if you have a rubber overflow hose from the tank its just an overflow and should not effect the radiator level.

Edit: Try squeezing your upper rad hose a few times and see if the levels rise and fall. It also helps get the air out of the system.

This one appears to be a real expansion tank and an integral part of the system. It also uses a pressure cap.

2015 nissan.png

cap.png
 
Beyond the fill level question, the OP is not clear about whether he used concentrate or 50/50 for the refill.
 
This one appears to be a real expansion tank and an integral part of the system. It also uses a pressure cap.

Trav this does look exactly like my reservoir. So as long as the reservoir level is good, and the radiator was filled to the top before suctioning out the excess in the reservoir, I could expect the radiator level to drop and that is normal?

View attachment 27580
View attachment 27581
 
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I might be wrong but I see 2 problems. Unless you are draining the system by removing the freeze plugs you are only getting about half the coolant out. The radiator drains but the heater core and block do not. When you flush with distilled water a few times you have pure water in the engine and need to add full strength coolant to the radiator, then warm the engine up till the thermostat opens and run the heater on full for 10 or 15 min. to mix everything, then check the coolant with a hydrometer for strength. On most cars that have a pressurized tank you dont have a seperate radiator cap, if you have a rubber overflow hose from the tank its just an overflow and should not effect the radiator level.

Edit: Try squeezing your upper rad hose a few times and see if the levels rise and fall. It also helps get the air out of the system.
I did not mess with the freeze plugs. I flushed the engine four times with distilled water. I ran the engine with the heater turned all the way up each flush until the thermostat opened and hot air was coming out of the vents. On each flush the engine was run for at least fifteen minutes after the thermostat opened. I was under the assumption that would get all the old anti-freeze out. Each drain the fluid coming out was lighter and lighter. The last flush had almost no indication of the original coolant. The suggestion to check with a hydrometer is a good one and I will certainly do that.
 

Systems with 2 pressure caps often exhibit strange behavior, what you describe is normal for this type of system. No sweat, its working as it should.
 
No confusion on the mixture. I mixed it myself.

" After draining my last flush with distilled water I refilled with a 50/50 mix of Prestone All Vehicle anti freeze. " It should read " I refilled with coolant concentrate to achieve a 50/50 solution".

Sierra048, the way your OP reads, it seems that you added 50/50 mix to fill the radiator, which would then be further diluted by the plain water left over in the engine block. After a complete flush, I add about 1/2 the total system with concentrated coolant, run the engine, then adjust as indicated by a refractometer.
 
" After draining my last flush with distilled water I refilled with a 50/50 mix of Prestone All Vehicle anti freeze. " It should read " I refilled with coolant concentrate to achieve a 50/50 solution".

Sierra048, the way your OP reads, it seems that you added 50/50 mix to fill the radiator, which would then be further diluted by the plain water left over in the engine block. After a complete flush, I add about 1/2 the total system with concentrated coolant, run the engine, then adjust as indicated by a refractometer.
" After draining my last flush with distilled water I refilled with a 50/50 mix of Prestone All Vehicle anti freeze. " It should read " I refilled with coolant concentrate to achieve a 50/50 solution".

Sierra048, the way your OP reads, it seems that you added 50/50 mix to fill the radiator, which would then be further diluted by the plain water left over in the engine block. After a complete flush, I add about 1/2 the total system with concentrated coolant, run the engine, then adjust as indicated by a refractometer.
My apologies. After sending my reply I realized what you were trying to convey to me. And it makes total sense. I'll be picking up a hydrometer and another gallon of concentrate and make sure the concentration level is correct. Thank you for your help. It's much appreciated.
 
Systems with 2 pressure caps often exhibit strange behavior, what you describe is normal for this type of system. No sweat, its working as it should.
Well it sure is confusing. It doesn't seem logical to me but that's why I asked on here. Thanks Trav.
 
At age 64, confusion becomes so rampant that I often question myself when reading/hearing things. My coworker of 35 years+ plays on this deficiency, LOL.

I once had a defective Prestone needle type hydrometer result in incorrect solution strength.

One of the best toys I ever bought was a coolant refractometer, especially because our John Deere tractor manuals always seem to be incorrect about coolant system size. I also maintain an industrial Kohler generator that has incorrect coolant system sizing.

Anyone have experience with the cheap ones?? https://www.amazon.com/Antifreeze-R...9Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=
 
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I know confusion well. Turning 66 soon. It is frustrating. I just got home from Walmart picking up my anti-freeze concentrate and a Prestone hydrometer. It's all they had. Hoping it will get me in the ballpark.
 
Systems with 2 pressure caps often exhibit strange behavior, what you describe is normal for this type of system. No sweat, its working as it should.

Well Trav, I think I figured out what was confusing me with the coolant level. When I was suctioning out the excess coolant from the reservoir, I hadn't replaced and tightened the radiator cap so all I was doing was draining the radiator while suctioning out the excess coolant. Once I put the cap back on the radiator and tightened it, I could drain the reservoir tank without it lowering the level in the radiator. I tried it while waiting for Ms Sierra048 to make it down to the garage for our trip to Walmart. I will verify once my car cools down. I'm hoping that was it. Didn't mention this before but I had done the same thing to our Xterra we owned before and everything went like clockwork. Identical engine to the Frontier. That's what had me perplexed. My age is catching up to me quickly.
 
The 2 pressure cap systems are relatively rare, the cap on the radiator is only for filling not for hot/cold level adjustment. Once the system is full through that cap it should not be opened again, fill to the top of the radiator and to the bottom line of the tank if one is used, get the engine up to operating temp, make sure the heater is getting hot and shut the engine off.
Let it overnight cool then fill to the lower line if present on the expansion tank.

Check it again after a run, it should new be at the upper mark if present, if it isn't do not open the cap until it is cold then adjust accordingly, it is normal for a air bubble to purge and the level drop slightly for the first few miles.
 
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