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Ugh, they threw it away at the mechanic's shop last week. I didn't think there was any reason to keep it. But why would I want a cap that leaks air? Is the explosion of coolant and air a problem? How would a radiator cap cause that?
You could have the wrong one fitted. They have different pressure ratings, and your one could be letting the engine get way too hot before venting, (or not venting at all), and could also not be allowing coolant back in as a result. It needs to have let the air out first, so that a vacuum can be formed to suck coolant back. That's if it's the right design of cap anyway. The reason the cap holds pressure in, is to raise the boiling point of the coolant, and to let the engine run at its rated temperature.
You could have the wrong one fitted. They have different pressure ratings, and your one could be letting the engine get way too hot before venting, (or not venting at all), and could also not be allowing coolant back in as a result. It needs to have let the air out first, so that a vacuum can be formed to suck coolant back. That's if it's the right design of cap anyway. The reason the cap holds pressure in, is to raise the boiling point of the coolant, and to let the engine run at its rated temperature.
Thanks BECLAZONE for all of your advice so far!
I can buy a new cap from the dealer (as opposed to the one I got at O'Reilly), but will it let the excess air out though through the overflow tank? And if there is still air trapped in the system, it wouldn't draw in coolant from the overflow tank when cooling, right?
Also, will the car eventually overheat if there is an air pocket that cannot be bled out? So far it had been fine on flat surfaces around town. I am thinking of taking it for an extended drive, maybe up some elevations, but I am worried.
I have given up trying to bleed the air out, and I have been advised not to put more money into the car. However, I would still like to use it as a beater to just drive around town, and I may need it to drive farther before getting my new car.
I was thinking heater core as well. Not sure how hard it is to get to on your model but typically they are a massive PITA.
I used to think the same thing? But then I realized, the heater core never comes out of the car unless it bursts and leaves a nice puddle of coolant on your foot wells.
Look at radiator
Identify the heater core hoses detach both (some people are sensitive about spilled coolant. I can tell you that what I describe can be done.)
It's probably brown and nasty. If the engine is warm that MAY work better, but use extreme caution as pressurized hot coolant is damgerous.
Now, get you a hooked-up garden hose. Don't have? when the system is empty.. gallons of water, poured in like you are trying to make a toilet that won't flush flush. A funnel helps.
Run the hose and or pour the water. The stuff that comes out will be like whoa.
Repeat until the water comes out clear and as fast as it came in.
Hook back up, refill and bleed system.
Come back, and thank me. I'll take $50, if you want
Couple of things to note with a head gasket that are dead on with the problem that the OP is having. The headgasket can be damaged on the exhaust side which allows air into the system without allowing coolant into the intake side of the system. You'll puke coolant instead of burn it.
1.) Over-pressurization of the system. If the headgasket is damaged, exhaust pressure will enter the coolant stream and build pressure on the cooling system. There are a couple of indicators that this has happened. You begin having leaks at the thermostat housing, overflow tank, coolant hoses, radiator seams, coolant cap, etc (anywhere there is a seam)... This is a tell-tale sign that the cooling system is having pressure introduced somewhere. If it's leaking past the overflow cap or radiator cap, there is a good chance that the system is building more pressure than the relief spring in the cap is capable of handling so it is doing it's job and releasing the pressure.
2.) Intermittent heat. Most often the heat will stop working when the engine is at a lower rpm (and more frequently at idle) but will sometimes begin to work again while driving at higher rpms.
OP... I get that you got an evaluation from a shop, but my recommendation is to take it to another for a second opinion. I'd bet my next paycheck on the engine having a blown head gasket. While it may be a Toyota, it isn't invincible. It will only get worse with time until you are eventually stranded.
You can build a homemade pressure gauge for very little money and see how much pressure is being introduced into the cooling system out of a piece of hose and a pressure gauge. Find out what the pressure rating is on your cap, hook it up, and see if it surpasses that pressure after driving it for a while. My cap on my F250 was rated for 16 psi. My truck stayed at about 14 psi and seemed normal until a 20 mile trip and it began spiking to 22 psi and puking coolant. A reputable shop then confirmed my suspicions.
I can buy a new cap from the dealer (as opposed to the one I got at O'Reilly), but will it let the excess air out though through the overflow tank? And if there is still air trapped in the system, it wouldn't draw in coolant from the overflow tank when cooling, right?
Also, will the car eventually overheat if there is an air pocket that cannot be bled out? So far it had been fine on flat surfaces around town. I am thinking of taking it for an extended drive, maybe up some elevations, but I am worried.
I have given up trying to bleed the air out, and I have been advised not to put more money into the car. However, I would still like to use it as a beater to just drive around town, and I may need it to drive farther before getting my new car.
It's very nice of you to thank me. Thank you.
It should let the air out, but yes you're right, if the air is still trapped, it won't suck coolant in.
It would depend on where the air pocket is, and it could be hot in just one area, that wouldn't show on the temperature gauge. The thing is, if it's not getting too hot, (that is, it's acting normally), and if it's not stinky hot in the engine compartment, it seems okay to drive. Just keep an eye on the gauges.
I think you're okay to drive it as a beater, etc, but that is entirely up to you.
I've been trying to think of ways around this, but all, are a little unconventional.
I've never seen an air pocket that was that difficult or took that long to bleed. It's getting air into the system so you need to find that problem first. Otherwise you're going to perpetually overheat and bleed air until the motor is done.
Still putting my money on a head gasket. OP... get a second opinion while it's still running.
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