Air bubble in my cooling system.

Waasheem, Yes I do have coolant in the radiator. And I know there is no vacuum. But there trapped air is starting to lessen. I know if there was a leak I would see coolant but there is no sign. I removed the one the spark plug and used a scope to view the piston and it was not clean or shiny which would have indicated that coolant was leaking. No loss of power, water temperature is normal. I do have a coolant reservoir and it's at a normal level. Also just recently replaced the radiator cap. I have been checking every other day just to make sure, and like I said it's slowly starting to clear. I still want to replace the radiator and hoses. It's an 18 year old truck but runs like a champ. I'm just following mileage maintenance(174K miles) as instructed in my Haynes 2005-2009 repair manual.
But thank you for suggestions.

 

Have you ever noticed the radiator hoses collapsed?

Still, I would do a cooling system pressure test with a cooling system pressure tester, and test the new cap.

 

Good call on replacing the radiator. At 200K, I replaced that, plus the water pump, thermostat, and fan clutch as preventive maintenance. The water pump pulley shaft had a little bit of play. Nothing major but glad I replaced it. Try and level the truck when refilling the cooling system. Use wood blocks if you can. I use a coolant funnel kit (

$34 Lisle 24680 Spill-Free Funnel, Standard Adapters, 11 x 7 x 7"es

Lisle 24680) to help burp the system. It has worked well on all the vehicles I maintain that don't have a bleeder valve.

 

I have that same funnel. It works great, you can overfill it a little, squeeze the hoses to help get the air out. I get this weird glop glop glop thing and it kinda shoots coolant up. So I hold the stopper above the hole to help not make a mess.

 

Cap it off and drive it for a few weeks. Then check it and see if the level has gone down in both the reservoir and radiator.

If the level slowly drops over time and you have no external leaks, the headgaskets are leaking

Check it cold in the morning before starting the engine

 

Head gasket!

 

So here we go again. I replaced the radiator in my truck. All seem well, no gurgling or bubbles. But now, the bubbles have returned. So I figured it needs to be burped again. Since it has to refill water into areas that were drained when changing out the radiator, I even changed the hoses. I run the heater to help run the water through the system, you can hear the water run through. But the bubbles seem to come up when I run my AC, I have checked the AC evaporator coil by cleaning it out and wet/dry vac the drain. It did have a lot of crap in it. But still bubbles.

 

Pressure test the cooling system and leak down the test the cylinders (especially 5 and 6)
heater core is always full flow, heat output is controlled by the blend door(s)
AC and heat are air gapped sources

 

Do a leak down test..

 

I have replaced the radiator a few times. It’s not that hard to get the air out of these trucks.


You 100% have a head gasket leak, sorry.

 

No loss of coolant and good temp?

LOL! I think would just turn up the radio a bit.

 

heater core bad?

 

windshield get foggy at odd times? I had a heater core go bad and a steamy windshield was the warning I missed

 

Did you use a newcap or the old one? Cap has three seals. Car hot coolant expands ad creates pressure. Large inner seal with spring (pushes on step inside neck) allows excess coolant to flow to bottle once 15 psi is reached. Stop engine and it cools. Coolant contracts and creates a vacuum. The little seal at the base of the cap opens and pulls coolant from bottle. However, if the top cap seal (seals against the necks outer flange) isn’t sealing well, it pulls in air instead of coolant from the bottle.

 

Thermostat/gasket leak?

 

First thought is head gasket, this is how mine started. None of the traditional signs or tests would were giving me a positive reading that is was the head gasket. Started as water noises in the dash, then missing coolant, then overheating while all the coolant is coming out of the reservoir. I only found it by installing new white spark plugs and then pulling them out 200 miles later to find one was bright pink while the rest were still white.
Hopefully it’s not a head gasket but still figured I’d share my experience with the similar symptoms I had.

If the heater core is bad you will smell it..

 

Oreo Cat
I'm thinking the same thing. Maybe my heater core is bad. I keep getting bubbles in my cooling system, but the truck runs at a normal temp, I replaced the radiator and hoses and when I drive you can hear the gurgling behind the dash. I ordered a heater core bypass kit and hopefully, the core is the problem. I called a local mechanic shop and they asked, if the truck overheats? No. Any miss firing? No. Then it's not the head gaskets. Since the kit will be used to help me troubleshoot the problem, I'm crossing my fingers. I live in Hawaii, so heating is not a problem.

 

Once up to temp, the cooling system pressurizes to 15 psi. Simple physics tell us the only way to get air into that system is by something with a pressure greater than 15 psi. The only thing in proximity to the cooling system with that kind of pressure is the combustion chamber. Sorry, but any other compromised cooling part other than the head gasket pushes coolant out of the system. It doesn’t suck air in. A failing heater core will dump coolant onto the floor of the cab. It will not move air into the coolant. Trust me, if the heater core leaks you will smell it.

mechanic is wrong. You can have a head gasket leak without misfires or over heating. Yes , those can happen, but not universally. Depends upon the size of the gap. Cylinder pressure on the power stroke is around 800 - 1000 psi; coolant pressure is 15 psi. Also surface tension of coolant is much greater than air. Very easy for a small hole to let a lot of air into the system without dumping a lot of coolant into cylinder. You really need to do the diagnostic tests recommended in this thread.

gurgling under the dash is just a symptom of air in the system and doesn’t point to the heater core as the source. You van never bleed all of the air out because it keeps getting introduced on every compression stroke (1000-1500 times per minute) All that air builds up and hides in low spots, like the heater core, giving you the gurgling.

 

lr172
Thanks for the advice. I have calls out to the Machine shop around me. I have to wait until Monday because most of the shops are closed for the weekend.

 

Problem solved!! I finally broke down an had a professional auto shop look at my truck and find out what was causing the problem with air bubbles in the cooling system. I had replaced the radiator and hoses and still had bubbles, so when they repaired my truck, I found out that the thermostat was no good and was causing the top half of the radiator to boil over. Once they did the repair everything is working as normal.
So rule of thumb, when you replace your radiator and hoses, you may as well replace the thermostat too.