Constantly have air in my cooling system

[CyFi6]

I have this ongoing problem that i cannot figure out. Whenever my car cools down and is cold, when i squeeze the upper radiator hose i can feel air in there, and i can put a funnel on the filler and squeeze the air out and add more coolant. But the next time i drive the car and it cools off, its the same deal. The more i keep getting the air out and adding water, the more the overflow fills up the next time the car cools down. Its like the coolant i add is going to the overflow and not going back into the radiator, but rather air going in its place. I have a new radiator cap and i checked to make sure the hose going from the radiator neck to the overflow tank holds pressure.

Basically:
-Air in radiator everytime car cools
-New cap
-Coolant displaced to overflow instead of going back into radiator, air takes its place
-Hose from filler neck to overflow is good with no air leaks
-No coolant leaks

Please help!
Thanks.

 

[jetjock]

The overflow line must be tight all the way to the suction screen or air will be drawn into the system on cool down. A leaky upper seal on the radiator neck or a bad vacuum valve will also cause it. Course, you could have a leak anywhere in the system and air will be drawn in but in that case you'd be losing coolant.

 

[CyFi6]

Yes my cap has a spring loaded vacuum valve and as stated i checked the tube going from the neck to the overflow tank and it is airtight all the way to the bottom of the tank, thats what i dont understand. I will put a pressure tester on the system to make sure i dont have any other leaks anywhere else.

 

[gofastgeorge]

Possibly the first sign of pending head gasket failure.

When the car is cold, remove the radiator cap, and start it.
Now the next step requires a buddy.
Hold the brake hard, and load the engine to about 2000 rpm.
This is easy with an auto, or drag the clutch with a manual.
(do this in reverse, so you don't run over your buddy if you mis-judge the clutch slip)
If there is a constant flow of bubbles coming up, then you most likely are getting combustion gasses leaking past a weak point in the head gasket.

And if it is doing that,
you might as well start planing on replacing the gasket.

 

[DegreE]

Possibly the first sign of pending head gasket failure.

When the car is cold, remove the radiator cap, and start it.
Now the next step requires a buddy.
Hold the brake hard, and load the engine to about 2000 rpm.
This is easy with an auto, or drag the clutch with a manual.
(do this in reverse, so you don't run over your buddy if you mis-judge the clutch slip)
If there is a constant flow of bubbles coming up, then you most likely are getting combustion gasses leaking past a weak point in the head gasket.

And if it is doing that,
you might as well start planing on replacing the gasket.

You can just do it in neutral.





Put the front of the car up on jackstands. (as high as possible)

remove the rad cap,

fill up the rad,

turn heater on full blast,

let engine run in park or neutral,

grab a sandwhich and watch tv for like 30 minutes,

you should see the level in the rad gone down...

if so, refil again and watch tv for another 15 minutes.

if not, you're done.

 

[gofastgeorge]

You can just do it in neutral.

Not quite.
In ther early stages of failure they will only leak under load......

 

[jetjock]

Fascinating....

 

[CyFi6]

Will a simple cooling system presure test show me the same thing? Id prefer that over loading my clutch like that.

 

[cuel]

You can just do it in neutral.





Put the front of the car up on jackstands. (as high as possible)

remove the rad cap,

fill up the rad,

turn heater on full blast,

let engine run in park or neutral,

grab a sandwhich and watch tv for like 30 minutes,

you should see the level in the rad gone down...

if so, refil again and watch tv for another 15 minutes.

if not, you're done.

I really wish people would quit saying that crap. I also wonder how many people have overheated their cars this way...

So, you're saying to let the motor run, and reach operating temperature, with the radiator cap off? You do understand that, without the cap, the coolant/water will boil over? That, as water and coolant warm, they expand? That the coolant and water are gonna get pushed out the top of the radiator? Personally, I never, NEVER, fill a car's cooling system, and walk away. I'm always right there with the car, making sure that it reaches normal operating temperature, isn't leaking any where, and that the fan(s) are working correctly.


The process you just described should be called "Best way to overheat your engine."

Fill the cooling system cold, engine off, and SLOWLY. After you have filled the system, put the cap back on, start the car, and turn the temp. on the climate control to 85. Let it run for a couple minutes, then shut it off, and check your coolant level. Fill as necessary. Stay with the car, and make sure it reaches operating temp. correctly. If your cooling system is working correctly, you'll only have to fill it once. http://cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=CO&P=5

To the OP: Take JJ's advice. I'd have the new cap tested, just to be sure. If all that fails, go get a block test kit. Yes, a cooling system pressure test will show all leaks.

 

[DegreE]

I really wish people would quit saying that crap. I also wonder how many people have overheated their cars this way...

So, you're saying to let the motor run, and reach operating temperature, with the radiator cap off? You do understand that, without the cap, the coolant/water will boil over? That, as water and coolant warm, they expand? That the coolant and water are gonna get pushed out the top of the radiator? Personally, I never, NEVER, fill a car's cooling system, and walk away. I'm always right there with the car, making sure that it reaches normal operating temperature, isn't leaking any where, and that the fan(s) are working correctly.


The process you just described should be called "Best way to overheat your engine."

Fill the cooling system cold, engine off, and SLOWLY. After you have filled the system, put the cap back on, start the car, and turn the temp. on the climate control to 85. Let it run for a couple minutes, then shut it off, and check your coolant level. Fill as necessary. Stay with the car, and make sure it reaches operating temp. correctly. If your cooling system is working correctly, you'll only have to fill it once. http://cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=CO&P=5

To the OP: Take JJ's advice. I'd have the new cap tested, just to be sure. If all that fails, go get a block test kit. Yes, a cooling system pressure test will show all leaks.

orly? This is how I do it when I do cooling system work at my job at Nissan. (Minus the watching tv and sandwich parts)

 

[cuel]

lol. That's still the wrong way. I've been doing mechanic work for quite a few years now myself. Not once have I seen any manufacturer's recommended coolant fill procedure like that. Besides, iirc, most new cars, like what you would deal with at the dealer, aren't filled at the radiator anymore. They have degas bottles, which are only partially filled, and are the highest point in the cooling system. I'd be willing to bet that quite a few of them have at least a bleeder on the t.stat housing as well. Honestly, watch the top level techs where you work. I'll bet they don't fill cooling systems your way. That would be like driving the car without the radiator cap, or with it only on half way. The engine will overheat.

 

[Alan]

I have a question for all of you guys could you put one of the prestone coolant flush kits on the hose going to the heater core and fill the system slowly while the car is sitting at an angle?

 

[jetjock]

Sure you could but no angle is needed. Just leave the flush kit cap off it so the air has a place to escape. Some people fill through the kit and leave the radiator cap off instead. That said those things are not the best way to flush a system and they introduce another failure point.

I'll reiterate what I've said many times before: In 21 years of owning this car I've never had to burp it. Not once. Fill the system slowly and what little air gets in will be purged through the jiggle valve in the thermostat. Or vacuum fill it.

 

[Doward]

Best way I've found to fill the system.

Cold car
Start car
Remove radiator cap
leave off until the thermostat opens ONCE
if you are low, you will see the coolant level drop
fill
put cap on

Don't just let the car run unsupervised. Holy shit bad idea.

That said, pressure testing the system would be a better way of going about things - also, look for any damage to the hose between the overflow tank and the radiator cap area.

 

[jetjock]

^ That'll work although one problem with the method is the T stat may take a very long time to open if it does at all. In fact most Supras I've checked will idle for hours after a cold start without opening it.

 

[CyFi6]

ok so i could not find an adapter for less than 30 bucks for the pressure tester for my radiator so i put that off for now as im not sure if it would tell me a whole lot. I did however purchase a block tester kit and tried for many minuets pumping and the fluid never changed from blue at all. I am still getting a lot of air in my coolant and the overflow is getting full to the brim/spitting coolant out. Help me narrow this down as i have no idea what else to test.

Again:
No external leaks
Passed block tester
No real coolant loss, other than what is being spit out.
Not overheating

 

[iwannadie]

Head gasket failure, letting exhaust gas into the cooling system which is causing the excess pressure and coolant spewing out of the catch can after the motor is off. No leaks anywhere to let coolant or air in/out, other than the exhaust leaking past the blown head gasket.

Just my guess, based on what happened to my car. I had coolant spew out of the over flow bottle after I shut the car off. I also had oil in my coolant, no coolant in my oil, no coolant leaks anywhere but constantly loosing coolant through the catch can. Coolant never hit the ground instead it would spray against my radiator and evap.

As long as your Tstat has a jiggle valve it should let the air escape, no need to do anything else besides top off the catch can....

Then again, Im no expert.

 

[suprarx7nut]

What would cause the overflow to gain coolant upon cooling? I understand how you would get extra coolant in the overflow when hot, but not when cooling. A bad seal somewhere with the overflow tube would cause that.

Are you actually getting coolant into the overflow on cooldown?

 

[gaboonviper85]

What would cause the overflow to gain coolant upon cooling? I understand how you would get extra coolant in the overflow when hot, but not when cooling. A bad seal somewhere with the overflow tube would cause that.

Are you actually getting coolant into the overflow on cooldown?

I think you misunderstood....what he is saying is when it gets hot it pushes water into the overflow....but when it cools its not sucking it back in

 

[suprarx7nut]

Oh, well then it's gotta be something with the overflow piping, right?

How else would coolant not get sucked back when cooling?