Can't Get Air Out of Heater Core / Considering Vacuum Kit

nolift911

Well-known member
Feb 19, 2006
403
0
I think you will find there is no real rhyme or reason or specific method for getting the air out of the system - everything mentioned will work, it just needs to be done over a couple of full warm up and cool down cycles. I had similar issues but after replacing the reservoir and cap with OEM and bled the system over a period of time with full warm up and cool downs it maintained a constant level and the sloshing went away.

One thing that has worked well for me is make sure your coolant reservoir and cap are in good working order, park the truck on a hill, engine facing up hill, heat on full, raise coolant reservoir as high as you can get it, keep cap off until it warms up and you should see some air bubbles burp out. I did this 3 cycles and my sloshing stopped. Another tell tail sign of air in the system is that the coolant level drops significantly overnight with no leaks.

It is true that after a number of cycles and after doing all of the above does not work - your motor is likely being pressurized. Generally that will show itself with a slow drip on the over flow drain. Head gaskets.
 

Dave03S

Well-known member
Jun 22, 2012
62
2
Seattle, Wa
I'll add one other tip, When the engine is stone cold, like overnight cold the next morning before startup, open the bleed screw and top up with coolant through the bleed screw. This still may take two or three mornings to get every bubble out but I've found it to work. Also its a good way to check your system for air at any time as usually bubbles make their way to that high spot. which would be even higher if you did park uphill.
 

coop74

Well-known member
Dec 10, 2015
287
7
Alcoa TN
I bought the vacuum kit. But while i was waiting for it to show up I tightened all of the hose clamps on the system and a day or two later the expansion tank level dropped. I topped it off and the sloshing noise is almost completely gone. I'm going to wait and see what happens before I drain the coolant to do a vacuum fill. Its been almost two weeks of stable operation.

Could you not still pull a slight vacuum on the system with coolant present and just not put enough pressure to lift water/coolant but it should evac air??? I am asking and not positive on that. looking for comments...
 

The Fourth Amigo

Well-known member
Apr 20, 2009
641
2
I started to think it might be a head gasket so I wanted to do a pressure test. Went looking for a tester and couldn't find one locally, so I decided to make my own. It worked well and I found a small pinhole on the manifold outlet pipe behind the fan. The leak was quite small and the fan was blowing the coolant away making it difficult to find.

It held 20 psi for 20 min after I fixed the pipe. Hopefully I won't have any more issues for a while. I still haven't used my new vacuum fill kit, but I'm content to leave it in the box for now.
 

p m

Administrator
Staff member
Apr 19, 2004
15,617
838
58
La Jolla, CA
www.3rj.org
I think you will find there is no real rhyme or reason or specific method for getting the air out of the system
I am coming to realization that this is true with one of my trucks. Every trick I used on the others doesn't work on this one.

nolift911 said:
It is true that after a number of cycles and after doing all of the above does not work - your motor is likely being pressurized. Generally that will show itself with a slow drip on the over flow drain. Head gaskets.
Hope it is not the case - had the sloshing sound for nearly a year (maybe more), yet the engine runs very well, without top radiator hose being rock hard, any loss of coolant, or engine temperatures anywhere near the "worry" zone.