Cooling system keeps getting air pockets

TonyD.

Registered User
Just like the title says, and I can't seem to get them out completely. Over the winter, I accidentally left water in the system and it popped out some weak freeze plugs that had actually been leaking for a while. There was a trail underneath both of them where water had been coming out and it stained the block. Ive replaced those freeze plugs, the radiator and hoses, water pump, thermostat, and heater core. I basically have a new cooling system from the ground up. The head gaskets have 6000 miles on them and the intake gaskets have 1000 miles. There's no oil and water mix, or oil in the radiator. The coolant pressure tests good, at 16 psi, it doesn't move for more than a half hour. I've tried bleeding the way I learned and have always done it, I've tried jacking the front end up and bleeding. This method works only for a few days before the air comes back. I don't know what else to look for. Can someone please help me? Thanks
 
Don't forget to check the cap, the hose to the overflow, the overflow itself, and that the overflow tank is full enough.

Keep checking there first.

RwP
 
X2 on new cap and checking the tube to the expansion tank, but why do you think there is still air in the system? If you filled the radiator with the bleed open until coolant spilled out with the engine running, you've done the first part - next part is waiting thru several heat cycles for the cooling system to stabilize.

Resist the urge to pop the cap and check - leave it alone. Confirm the upper radiator hose isn't collapsing when the car cools down over night. Cycle the heater to be sure it's included during at least one heat/drive cycle.

Where is the low level in the expansion tank after the car sits all night? Where is the high level after the car heats up and rides on the fan? Do you have a stock radiator or aftermarket aluminum? What percentage anti-freeze are you running now? Did you add Water Wetter, etc.?
 
X2 on new cap and checking the tube to the expansion tank, but why do you think there is still air in the system? If you filled the radiator with the bleed open until coolant spilled out with the engine running, you've done the first part - next part is waiting thru several heat cycles for the cooling system to stabilize.

Resist the urge to pop the cap and check - leave it alone. Confirm the upper radiator hose isn't collapsing when the car cools down over night. Cycle the heater to be sure it's included during at least one heat/drive cycle.

Where is the low level in the expansion tank after the car sits all night? Where is the high level after the car heats up and rides on the fan? Do you have a stock radiator or aftermarket aluminum? What percentage anti-freeze are you running now? Did you add Water Wetter, etc.?

I got a new cap when I did the radiator. The symptom is that I lose heat after a little while. The car doesn't overheat. I'll check the levels in the coolant tank. The the top hose is the only hose I didn't replace. How do I know if it's bad if it isn't leaking? And for the coolant tank, how would I check if there's a problem with that?
 
I also use 50/50 and I did use water wetter. Would that cause a problem?

No...that sounds good.

The easiest way to check the flow to/from the expansion tank is to remove the tube at the radiator neck and try to blow thru into the tank. You can also remove the tank from the car and see if the hose lets it drain.

As for the upper hose, it could be inspected off the car to be sure it isn't deteriorating inside. But if it is old, it would perhaps be more practical to invest in a new one if the old one is removed.

What do you mean 'loses heat'? You mean the heater? What temp thermostat did you install? Check the hose from the oil cooler/exchanger up to the water pump. I had an issue that turned out to be someone replaced that hose before I got the car and left it crimped so that flow was restricted. They used a short section of straight hose - I found a molded hose (trimmed to length) that fit without folding.
 
No...that sounds good.

The easiest way to check the flow to/from the expansion tank is to remove the tube at the radiator neck and try to blow thru into the tank. You can also remove the tank from the car and see if the hose lets it drain.

As for the upper hose, it could be inspected off the car to be sure it isn't deteriorating inside. But if it is old, it would perhaps be more practical to invest in a new one if the old one is removed.

What do you mean 'loses heat'? You mean the heater? What temp thermostat did you install? Check the hose from the oil cooler/exchanger up to the water pump. I had an issue that turned out to be someone replaced that hose before I got the car and left it crimped so that flow was restricted. They used a short section of straight hose - I found a molded hose (trimmed to length) that fit without folding.

If I'm driving, it'll have perfect heat, then it'll just turn cold. When I open the good and squeeze the top hose, it's hard but doesn't feel like anythings in it. But when I check it after its cool, it's up to the correct level. I'll check the overflow and see what happens. That's the only part I haven't replaced. The thermostat is a 180 I think. It opens right in the middle of norm on the gauge
 
The thermostat is a 180 I think. It opens right in the middle of norm on the gauge

Sorry if I missed it - what year SC is this? Did you retune for that temp stat? If not, you might want to stick with the stock temp stat, instead.
 
Sorry if I missed it - what year SC is this? Did you retune for that temp stat? If not, you might want to stick with the stock temp stat, instead.

It's a 90 sc. To be honest I'm not sure of the temp on the thermostat. I just know it works. I did find a problem looking at everything. The top hose was seeping where the factory clamp was. I went to the parts store and ordered a new hose, and put 2 new clamps on. That stopped the leak. Filled the system with the bleeder open, closed when full, and walla! It has heat. I do have another concern. When I filled the overflow, I filled it to max cold. After I drove it, it started losing heat at idle and at higher rpms close to wot. It did however have heat when I was cruising. When I stopped, I checked the overflow, and it was full to the top and it looks like some when over the top. It stayed cool and didn't overheat
 
I'd leave it alone...don't open the system back up. Drive it for a few days so that all the air can be purged. I'd also try to confirm it has the correct (192?) thermostat in it.

Does the electric fan ever come on?

Good luck.
 
Last edited:
Fans come on but they come on close to the top of norm. Usually it doesn't get that hot if I'm moving. I'll watch the gauge and it drops when the thermostat opens. I'll see what happens. The new hose comes in Saturday so next week there might be an update. Thanks for your help
 
Woke up this morning for work and it started building heat, then it just went cold. It's a 20 minute drive at low speeds. Think my water pump may be on its way out?
 
I agree with dave. i just did the head gaskets on my windstar 3.8. It had the exact same symptons. On another note was the heater core fluxhed. i dont remember readin if it was. if not its worth a shot.
 
Woke up this morning for work and it started building heat, then it just went cold. It's a 20 minute drive at low speeds. Think my water pump may be on its way out?

Did you check the weep hole on the water pump behind the pulley to see if it shows any leakage there at all? If you remove the belt, can you feel any roughness or play in the water pump bearings?
 
Did you check the weep hole on the water pump behind the pulley to see if it shows any leakage there at all? If you remove the belt, can you feel any roughness or play in the water pump bearings?

I'll check the water pump first chance I get today. That would be pretty terrible if it was head gaskets. They don't even have 10k on them
 
I'd think in some cases, the water pump could be sucking air around the seals, but I don't know how to verify outside of replacing the pump and that's not exactly a simple task....easier than replacing the heater core, tho, I think :)
 
Napa sells a test kit that when you use it it will show if combustion gas is present in the radiator. Thet are not cheap. Somewhere around a $100. maybe a local shop would test for you. my van had the same symtons as you describe. i tried flushing the heater core,that was when it did the steam thing. it has mls gaskets and they showed nothing for a leak. number 1 cyl bore looked different. my machinest said the heads had (some bow). just my experiance. I have bout $400 in my van gasket job.
 
Well fellas, I hate to be the bringer of bad news. She popped a head gasket. I changed my oil last week and I didn't notice anything in it. Then again it was black. I pulled my dipstick out after work and my oil is green. So my next question is since they don't make mls gaskets anymore, or at least not available around here, what can I do about putting mls gaskets on it? I read on another forum that people use the 99+ mustang gaskets, but you guys are the specialists
 
Back
Top