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?

[CyFi6]

Thats the problem. I don't know if combustion is forcing air into the system thus pushing coolant out or if its just not getting sucked back in. I checked the piping and its perfectly sealed. I even put a different piece there for a day and no change. But then i also did the block test and had 100% no change in color it stayed perfectly blue.

[gaboonviper85]

I vote for a pressure test myself....that will bring out all the weak spots..

[jetjock]

ok so i could not find an adapter for less than 30 bucks for the pressure tester

Stant #12027. Around 18-20 bux from lots of places. Rock Auto comes to mind or here:

http://tinyurl.com/3kyxfp

The cap adapter is a Stant #12021

[iwannadie]

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

Mine would still bubble out(mostly air not coolant) After I shut the motor off. Coolant would spray out while I drove leaving my radiator soaking wet. Im guessing the exhaust gas just pressurized the cooling system that much. With the motor off the Tstat doesnt just close suddenly so the pressure is still pushing past the radiator cap. Coolant never seemed to suck back in from the overflow bottle either, too much pressure? Id drive loosing coolant and come home park it and look for leaks, never found them.

Again, Im just going from my experience when I had coolant problems and BHG.

Replace the rad cap, Tstat, pressure test. Drain the coolant into a clear container and let it sit over night, check for sludge at the bottom(or remove/clean you overflow bottle, check for sludge in it). Do all the cheap easy stuff first, then go from there I say.

[CyFi6]

UPDATE:

Pressurized the cooling system. 100% held pressure. Pressurized the overflow tube, 100% pressure held. Replaced cap, same problem.

Basically air is getting in, combustion is not getting into the coolant, everything is air tight according to all my tests....what am i left with? The only thing i can think of is something is leaking when the car gets hot, and thats a time when i cannot use the pressure tester. What do you guys reccomend i do? I also used a four gas analyzer just in the radiator opening above the water with the car running and no hydrocarbons showed. I really have run out of ideas!

[GrimJack]

Do us a favor and replace the line that goes to the bottom of the overflow tank, will you? It's only ~6 inches long anyway. I've seen this get crusty and leak, and most people overlook it because it isn't meant to hold pressure anyway.

Problem is, it needs to suck coolant back into the system when you are cooling down. Ever try to use a straw with a split in it? All you get is air.

[CyFi6]

I have visually inspected it and its fine, and I pressurized it to over 10 psi and it held just fine, so I dont see a reason to replace it. I pressurized the whole tube btw, from the radiator nipple to the end of the tube in the overflow, which includes the connections on the overflow lid etc..

[jetjock]

For coolant to be sent to the tank the radiator must start out full enough so there is no room for expansion. If that's the case then as the system cools it *must* draw coolant back in unless there is a leak or the cap is faulty. If the system were airtight the upper radiator hose would collapse. Therefore you have a leak, either in the system or the cap, or too much expansion space in the radiator. Neither you or your cooling system are exempt from the laws of physics you know.

Pressurizing the hose is an indirect check. Instead prove there's no vacuum on it. After shutdown put a short piece of hose with a vacuum gage on the radiator neck nipple. Or pull the overflow tube out of the tank, remove the suction screen, and gage it there.

You can do the same on the radiator itself after it cools enough to remove the cap. Think about how the thing is supposed to work, formulate a hypothesis for why it doesn't, and then formulate a method to directly prove or disprove the hypothesis. If unsuccessful move on to a new one. I'd also go to Auto Zone and buy some coolant dye.

[Nick M]

Fascinating....

Isn't it?


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)

Spoken just like a lube rack employee.

[GrimJack]

For coolant to be sent to the tank the radiator must start out full enough so there is no room for expansion. If that's the case then as the system cools it *must* draw coolant back in unless there is a leak or the cap is faulty. If the system were airtight the upper radiator hose would collapse. Therefore you have a leak, either in the system or the cap, or too much expansion space in the radiator. Neither you or your cooling system are exempt from the laws of physics you know.

Pressurizing the hose is an indirect check. Instead prove there's no vacuum on it. After shutdown put a short piece of hose with a vacuum gage on the radiator neck nipple. Or pull the overflow tube out of the tank, remove the suction screen, and gage it there.

You can do the same on the radiator itself after it cools enough to remove the cap. Think about how the thing is supposed to work, formulate a hypothesis for why it doesn't, and then formulate a method to directly prove or disprove the hypothesis. If unsuccessful move on to a new one. I'd also go to Auto Zone and buy some coolant dye.Scientific method FTW!

[CyFi6]

BHG FTL! So i figured out its a bhg. Cylinders 5 and 6 are just slightly blown. I did a cylinder leakage test and sure enough when i cranked up the pressure around 90PSI the coolant level started rising. I guess the low pressure from the pressure tester wasnt enough to get past the partially sealing gasket, and for some reason the block tester wasnt getting anything. At least now i know what is wrong and i can start on fixing it. It is going to be tough as this is my daily driver but i think i will be able to work something out. Thanks for the help guys.

[supramacist]

Yep. The cool thing is that it should be easier since you didn't blow it
to hell and back. Machine wise.

Start buying all of your parts and get them all collected before you get to the
put it back together phase.

[Nick M]

So you pumped the cooling system to 90 psi, or the leak tester?

You know what else is fascinating? The area that seems to give the most fits, stock control, has the fewest questions in the SME section.

[CyFi6]

I pumped the leakage tester to 90 psi, so the cylinders, not the cooling system, and then saw the level in the filler opening with the radiator cap off rise/bubble

[iwannadie]

...Same as my bhg, right around 5-6.

[supramacist]

6 is known for being a troubled spot.

[CyFi6]

Ok i have a few small questions because this will be my first head gasket job. I looked up all the prices for gaskets and sets and such and toyota is looking for $350 for a full head set. They want $80 for a head gasket only. Now ebay has a full head set for $37. I was planning on buying a composite head gasket from Toyota, buying felpro valve seals from kragen for 45 dollars, EGR cooler gasket from toyota and buying the full gasket set from ebay and tossing the EGR cooler gasket, valve seals, head gasket and valve cover seals. So in the end i will have
Head gasket from toyota
Valve seals from felpro
EGR cooler gasket from toyota
all other small gaskets from EBAY

What do you guys think about my plans? I have heard the ebay small gaskets are pretty decent for what they are. I also had a question for the valve adjustment. Should i bother getting all of them perfectly? I heard the shims are very expencive and not worth replacing all of them just to get it a little closer to where it should be. Just want opinions on this. I will only be replaceing those things listed above, and lapping the valve and having the head machined. I do not want to do the timing belt at this time so i will leave that alone. Thanks a bunch guys.

[AJ'S 88NA]

Ok i have a few small questions because this will be my first head gasket job. I looked up all the prices for gaskets and sets and such and toyota is looking for $350 for a full head set. They want $80 for a head gasket only. Now ebay has a full head set for $37. I was planning on buying a composite head gasket from Toyota, buying felpro valve seals from kragen for 45 dollars, EGR cooler gasket from toyota and buying the full gasket set from ebay and tossing the EGR cooler gasket, valve seals, head gasket and valve cover seals. So in the end i will have
Head gasket from toyota
Valve seals from felpro
EGR cooler gasket from toyota
all other small gaskets from EBAY

What do you guys think about my plans? I have heard the ebay small gaskets are pretty decent for what they are. I also had a question for the valve adjustment. Should i bother getting all of them perfectly? I heard the shims are very expencive and not worth replacing all of them just to get it a little closer to where it should be. Just want opinions on this. I will only be replaceing those things listed above, and lapping the valve and having the head machined. I do not want to do the timing belt at this time so i will leave that alone. Thanks a bunch guys.Why not get the Felpro HG? In fact why not get the whole set from Felpro?

If you're getting a valve job the machine shop should be able to do the valve lash.

Why not the timing belt? Alot easier to do while you have everything apart.

[CyFi6]

With the way i wrote above its a little cheaper than the whole felpro set, and i would rather have a toyota head gasket than a felpro.

[Nick M]

With the way i wrote above its a little cheaper than the whole felpro set, and i would rather have a toyota head gasket than a felpro.

I wouldn't be suprised if the head gasket set for Toyota of North America is made by Fel-Pro. I have seen many OEM gaskets labeled for the manufacturer on one side, and Fel-Pro on the other.

My Fel-Pro looks exactly like an OEM gasket. And they may have just built it that way, and are not building for Toyota.

[flyguyaaron]

K I am having the exact same prob with my 90, has any one figured out what caused this, please tell me it wasnt the head gasket, only 118,000 miles thanks!

[AJ'S 88NA]

K I am having the exact same prob with my 90, has any one figured out what caused this, please tell me it wasnt the head gasket, only 118,000 miles thanks!
Well it was. Do the tests and find out for sure.