How to Vent Radiator?

B

bluestreakrem

Member
Car
FX35
My upper radiator hose has been leaking at it's connection point to the filler neck on my 2009 for many years. I finally got around to removing the hose, cleaning the corrosion off and replacing the OEM clamp with a better hose clamp. Hopefully that will stop the weeping that has been occurring for years.

My question is how do you vent the radiator of all air after opening the system?
The filler neck is lower than the top of the radiator. Adding fluid to the plastic reservoir does not completely fill the radiator. I saw what I believe could be a radiator vent screw. It is located on the drivers side of the radiator, near the top and facing towards the rear of the vehicle. The driver side engine air cleaner box is located very close to the vent screw on the radiator and it may have to be moved to gain access to the screw.

How do I completely fill the radiator?
 
I use this funnel kit to eliminates the trapped air pocket. I have use this to change out two radiator without any overheating issues due trapped air pockets in the system.
http://www.tooltopia.com/lisle-2468...ZC7aH3n0kYNXXC-3UmrrOjDKS-dryBlx95BoCkVTw_wcB

---------- Post added at 01:57 PM ---------- Previous post was at 01:53 PM ----------

How I use it is to fill the system with it and leave a bout a quarter of the funnel filled with coolant, turn the heater on to high, and then I run the engine until operating temperature. You will see trapped air bubble out into the funnel.
 
bluestreakrem said:
My upper radiator hose has been leaking at it's connection point to the filler neck on my 2009 for many years. I finally got around to removing the hose, cleaning the corrosion off and replacing the OEM clamp with a better hose clamp. Hopefully that will stop the weeping that has been occurring for years.

My question is how do you vent the radiator of all air after opening the system?
The filler neck is lower than the top of the radiator. Adding fluid to the plastic reservoir does not completely fill the radiator. I saw what I believe could be a radiator vent screw. It is located on the drivers side of the radiator, near the top and facing towards the rear of the vehicle. The driver side engine air cleaner box is located very close to the vent screw on the radiator and it may have to be moved to gain access to the screw.

How do I completely fill the radiator?
Click to expand...

Thanks for the link and comments but using that funnel alone will not totally purge the radiator. Just because you maintain a fluid level above the radiator does not mean you will get all the air out. You have to vent all air pockets trapped and my guess is that the screw connection I am talking about is for that purpose. The upper hose return connection on the radiator is lower than the fill neck, therefore and air pocket exists. The screw/vent connection is located very high on the radiator and should allow complete venting if unscrewed. I was hoping to hear from someone that can confirm this.
Is it an O ring sealed device? Will it came out completly if totally unscrewed?
 
Run the car to operating temperature and the water pump start pumping, it will cycle the coolant and the the air pocket will blurb out into the funnel. It works for me. Not sure if the 2nd Gen FX35 also has the air vent plug like the 1st Gen. On the 1st Gen, even with the air vent plug removed while refill, there still air pocket in the system. For some reason, the 1st Gen FX35 is a PIA to rid of the air pocket. By using this funnel, I have not have any air pocket issues that eventually lead to overheating. With the funnel I do see air bubble out into the funnel.
 
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MTXFN
Thanks for posting the video. That vent screw looks exactly the same as what’s on mine. Now I know what to do. The system must be filled when cold, with the vent plug out. That will allow the radiator to be totally filled using a tall funnel as LAFZ35 has suggested. You have to get the fluid height above the radiator vent screw in order for the radiator to be completely purged of air. After the system is cold filled and the reservoir and cap installed, the system will vent itself any remaining air in the block as the fluid expands into the reservoir as it heats up. That purges the vent tube that connects to the reservoir. Then as the system cools off, pure coolant can be drawn back into the engine from the reservoir without any air.

LAFX35
Simply getting the engine up to temp with the filler cap off, will not purge the trapped air from the high pocket in the radiator. There isn't enough system fluid velocity to carry the air in that pocket down to the lower radiator hose and eventually out of the filler neck. That's why the air vent screw is located where it is in the system. It is at the highest accessible point which must be vented to get the air out which will allow the radiator to be fully filled. Just because you observe air bubbles coming out of the funnel and at some point they stop, doesn't mean the system is full. Yes there may be some air pockets below the filler neck elevation which produce the bubbles you see when it warms up. That's the system venting itself because air naturally rises. It's just a matter of physics. Without enough velocity, you can't push air down. High points in the system must be manually vented before start up to get this trapped air out because it will not be forced out by vertue of thermal expansion.
Now that I see how the screw works from the video I know what to expect and do. I wish car manufactures would not build systems that are not self venting. I deal with industrial engines at work and you never see this sort of crap.
 
Good to know there is a vent plug on the 2nd Gen FX35 like on the 1st Gen FX35. It's a PIA to remove air pocket out of 1st Gen FX35. I hope it not the same for the 2nd Gen FX35. From experience, may 1st Gen FX35 run into issues with air pocket in system even with the vent plug remove and filling slowly. A few have to drain and fill a couple times to get rid of the air pocket in the system.
 
The vent screw itself may not always get all the air out either. Lots of people with 350Z's and G35's have had issues with trapped air even using that vent. For some of them it takes a combo of the funnel and the vent and then repeating multiple times. I ended up having to put my front end on ramps once to elevate the radiator to get all the air out. I have no idea why it's so hard on our cars.

On my 335, I can initiate a cycle through a pedal dance where the system vents itself. Water pump is electric which makes that possible; much easier.
 
I used the funnel and bled as much air out of the vent on the heater hose while cold. Then ran the engine with radiator cap on and had to rev the engine a few times to get the coolant flowing. The level in the reservoir went down so I topped it off to the max mark.
Best way to tell if you get the air out is to run the heater and if cold air comes out instead of hot then there is still trapped air.
It took me going for a spirited drive to get all the air out.
Just remember to check the reservoir level for about a week or so.
 
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