Coolant not flowing back into the radiator
#11
07-28-2019, 01:06 PM
I thought the issue was the coolant was not flowing back to the radiator after the engine cools??
Now, have a coolant leak?
The system was pressurized and it holds pressure (while engine is cold?)
The cooling system was tested for exhaust gases
And was found .. no exhaust gas detected
So, if it is leaking then it has to be while the engine is hot
Is the coolant flowing back to the radiator when engine cools?
The water pump does have weep holes
Hard to see but leak would be very small
Now, have a coolant leak?
The system was pressurized and it holds pressure (while engine is cold?)
The cooling system was tested for exhaust gases
And was found .. no exhaust gas detected
So, if it is leaking then it has to be while the engine is hot
Is the coolant flowing back to the radiator when engine cools?
The water pump does have weep holes
Hard to see but leak would be very small
I've learned from experience that sometimes cooling system problems can be elusive.
The problem IS that the engine is not able to suck the (expanded) coolant back from the overflow bottle during cool down.
This can be tested as follows: 1. Start with a FULL radiator and a cold system. Note the (cold) coolant level in the overflow bottle. 2. Start the engine and warm it up completely. 3. Observe the expanded (hot) coolant level in the overflow bottle. 4. Shut down the engine and let it cool completely. 5. Remove the radiator cap and you'll see that the coolant level in the radiator has dropped from FULL, and the coolant level in the overflow bottle remains at the expanded (hot) level.
The reason for this is that the system has sucked air into the radiator instead of sucking (expanded) coolant back from the overflow bottle. This shows that there must be a LEAK somewhere in the cooling system.
Sometimes these leaks are difficult to locate, especially if they are DEEP inside the engine (e.g. head gasket).
#12
07-28-2019, 04:18 PM
-----------------------
I've learned from experience that sometimes cooling system problems can be elusive.
The problem IS that the engine is not able to suck the (expanded) coolant back from the overflow bottle during cool down.
This can be tested as follows: 1. Start with a FULL radiator and a cold system. Note the (cold) coolant level in the overflow bottle. 2. Start the engine and warm it up completely. 3. Observe the expanded (hot) coolant level in the overflow bottle. 4. Shut down the engine and let it cool completely. 5. Remove the radiator cap and you'll see that the coolant level in the radiator has dropped from FULL, and the coolant level in the overflow bottle remains at the expanded (hot) level.
The reason for this is that the system has sucked air into the radiator instead of sucking (expanded) coolant back from the overflow bottle. This shows that there must be a LEAK somewhere in the cooling system.
Sometimes these leaks are difficult to locate, especially if they are DEEP inside the engine (e.g. head gasket).
I've learned from experience that sometimes cooling system problems can be elusive.
The problem IS that the engine is not able to suck the (expanded) coolant back from the overflow bottle during cool down.
This can be tested as follows: 1. Start with a FULL radiator and a cold system. Note the (cold) coolant level in the overflow bottle. 2. Start the engine and warm it up completely. 3. Observe the expanded (hot) coolant level in the overflow bottle. 4. Shut down the engine and let it cool completely. 5. Remove the radiator cap and you'll see that the coolant level in the radiator has dropped from FULL, and the coolant level in the overflow bottle remains at the expanded (hot) level.
The reason for this is that the system has sucked air into the radiator instead of sucking (expanded) coolant back from the overflow bottle. This shows that there must be a LEAK somewhere in the cooling system.
Sometimes these leaks are difficult to locate, especially if they are DEEP inside the engine (e.g. head gasket).
However, system was pressure tested and held pressure.
No exhaust gases were found when tested for in the coolant system.
This kind of test is done with engine running (hot)
This rules out a leak being just anywhere.
It has to be at the neck of the radiator where a pressure cap would by-pass the ordinary cap for the overflow.
The pressure radiator cap is not functioning correctly
It allows hot coolant to flow out but not allowing it to flow back in
And this is also where air is allowed to flow into the system
#13
07-28-2019, 05:32 PM
In that kind of scenario, the leak can be almost anywhere.
However, system was pressure tested and held pressure.
No exhaust gases were found when tested for in the coolant system.
This kind of test is done with engine running (hot)
This rules out a leak being just anywhere.
It has to be at the neck of the radiator where a pressure cap would by-pass the ordinary cap for the overflow.
The pressure radiator cap is not functioning correctly
It allows hot coolant to flow out but not allowing it to flow back in
And this is also where air is allowed to flow into the system
However, system was pressure tested and held pressure.
No exhaust gases were found when tested for in the coolant system.
This kind of test is done with engine running (hot)
This rules out a leak being just anywhere.
It has to be at the neck of the radiator where a pressure cap would by-pass the ordinary cap for the overflow.
The pressure radiator cap is not functioning correctly
It allows hot coolant to flow out but not allowing it to flow back in
And this is also where air is allowed to flow into the system
The "scenario" I described is not unusual for this year, make, model vehicle (7th Gen Honda Civic).
I understand that the subject vehicle passed a cooling system pressure test and exhaust gas test.
I also understand how radiator caps work on these cars. A new OEM radiator cap was the first thing I tried on my Civic with the same symptoms as the subject vehicle. It made no difference.
Jumpmaster357 also tried replacing the radiator cap on his Civic and also had no result.
The cooling system leak on my car was hidden INSIDE the engine, NOT visible from outside the engine.
Last edited by Timothy1959; 07-28-2019 at 05:41 PM.
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