Stevey629

I took the car to a shop that rebuilt my turbos and redid my vacuum lines, and they press. tested my cooling system. No probs. there apparently. I drove the car for like 2 days, and the crap stock temp gauge went all over the place so I replaced the thermostat. Keep in mind, I didnt drop it in water to see if it opened, so maybe this could be the problem. I dont know. Anyways, I couldn't seem to burp the system, because I had to keep adding and adding, and it just spilled right out of the overflow when warm, and mild throttle is applied. Then, I took it to mazda, they did a pressure test, and the same thing...no leaks, but both caps were leaking, is what they said. So I had them replace the caps and burp the system. They gave me the car back, and the car was making gurgling noises that I could hear from inside the car with the doors closed, yet not hear outside by the motor. This gurgling basically got louder and more prominent when the rpms increased, but it became harder to hear due to motor noise. I asked them right there on the spot, because as I tried to drive away, I heard it, so I stopped and asked why the prob. didnt get fixed. They couldn't seem to figure it out. So I drove it home from the dealer, let it cool for a bit and shut the car off. No leaks from the overflow tank, but I could hear air hissing by the AST, and possibly by the filler neck for the thermostat housing. I also noticed a bit of coolant comming through the top of the sticker on the radiator cap, the one with the "ears shapes" on it. Is this normal????
I try to start the car, and the idle drops way down below 1, trying to stall out. So I stop the car, and wait like 5 mins. Then, I clicked the keys to ACC, and its saying I need coolant, but the temp gauge is where its supposed to be. If I dont have any hydrocarbons or apparent leaks in the cooling system, why is it acting like I have coolant seal leaks in the block? My car has been nothin' but a problem since I got it. HELP?

spurvo

Coolant problems are a bitch, huh? The more I read on this forum, the more I think folks considering buying a used RX sould check the cooling system BEFORE doing the compression check!

Gurgling noises are residual air in the system running through the heater core. They just didn't burp it all through. Takes a few days when trying to do the fill it - drive it - cool it - fill it - etc method. The idle drop may have been the fans coming on. Quite a current draw on the alternator when they come on. Anyway, the "air seepage" past the AST and filler neck is just air in the system that still needs to work its way out. It's passing through the cap into the overflow line, and when you shut off, the air is coming back into the AST as that AST to overflow line is fairly long. This is why I do that turkey baster trick. Now that your caps are good, this should just be a series of fillings to work that air out. Unless...

Am I reading correct that you have the stock AST? This is a known to fail part. The failures can be as mild as a cracked nipple for the overflow tank outlet (creating the vacuum leak we've spoken of) to a chipped cap land (the area that seals the cap. This would leak coolant, keep the system from pressurizing which allows it to overheat, and be another vacuum leak source) to splitting along the seam and dumping ALL your coolant ALL over the engine and causing overheat pretty damn near instantly! So if I'm right, REPLACE THE AST NOW! Do this before you try to diagnose any more coolant problems, other than continuing to fill the filler neck and AST as you drive. Do that EVERY time you drive it, before you leave for work, before you drive home, and before you go to bed.

Anyway, the dealer probably doesn't know about the throttle body hose pull trick to burp the system (though you are probably full enough that this won't help much now) and they probably don't know that the AST is a failure prone element, and they probably just did what they know to do with cars that only have 4 to 6 coolant lines maximum. Instead of 14! Don't harsh on 'em too much. They just don't know. Not that I do....

WTF!? Coolant out the sticker? NOT normal. If that REALLY is so, then get yet another cap. Anyway, just burp your system by filling it everytime it cools enough to open a cap. Or do what I did, which was to place a tube from the AST overflow outlet into a water bottle halfway full of coolant, start the engine and let it idle through two fan cycles with the lights on. Many bubbles came out for a while, then just straight hot coolant. Shut it off, leave it for two hours (to fully cool back down) and repeat. No more bubbles in the system. Usr the turkey baster to draw liquid up from the overflow tank, and I was done. Now that was long, huh?

Stevey629

yes. I press on the cap sticker with the ears, the radiator fill cap, and I can feel coolant. My finger is wet after pressing on the sticker. The sticker has two small slits in it, and Im wondering if the cap is supposed to let coolant or air through. ??? I was confused about this. The AST cap also has two slits in the sticker on the top, but I dont feel coolant on the top of this one, as I do with the other one.

Stevey629

another ques, I think my ast is leaking, cuz theres puddles of coolant all around that lip section of it. And I can feel coolant under the cap when its fully screwed down on the AST. Dammit. Time for a new AST which means more money, but at least I will know it'll be reliable. Which is the best one? I was thinkin of going with petits, but I wasn't sure. I just wanna replace the stock location, which I heard the Petit one does do. Oh, and I looked at those AST's, and the caps look like they have some red colored switch on them. Is this to hold the cap on? NE ways, I think Im in need of a new AST, and fast. And I tried burping the system again, and I can still hear coolant bubbles in my heater core, I hate it. Dammit. dammit. OH, and is that radiator cap that I got really not supposed to have any coolant at all leak through? I thought its not supposed to hold pressure, and let air out, so maybe coolant is getting through? Someone explain to me how the caps are supposed to properly function. Im really confused. Gosh. Someone smack me cuz I dont get my coolant system.
Spurvo thx for being supportive and patient every time Ive been posting about my prob with this.

spurvo

Happy to help. Just got my Fluidyne in today. What a bear... drop in MY ***!

OK, there are two types of coolant system caps. One type is a simple seal. If you look at the underside of the cap, there is simply a rivet and a rubber gasket around the outside. This cap sould not vent, and this is the cap that should be on your FILLER NECK, not the AST. All that this cap is supposed to do is create a removable seal for filling. It is NOT there for pressure relief.

The second type of cap is a pressure relief type. This cap will have a shaft that extends maybe 1/2 inch down from the top of the cap, and there should be a disc on the end of that shaft. That disk will have a rubber gasket on it, as will the top of the cap. Finally, there will be a spring between the lower disc and the top of the cap. When the cooling system gets hot, the liquid inside expands and creates positive pressure. At the pressure point that the cap is set to do so, it will allow fluid to flow past that lower rubber disc into the chamber above, and out the overflow tube. This is done by pressing past the spring pressure. Notice that this cap also has a rivet that extends through the lower disc. As the coolant cools down, it shrinks. This creates a negative pressure in the system, and the rivet in the lower disc is pulled down, and coolant comes back into the system to fill the vacuum. The coolant comes from the overflow BTW. All of this occurs on the AST on our cars, though some folks have eliminated their AST, and the pressure relief cap gets moved to the filler neck position, as does the overflow line.

So look at the underside of your caps. Is there as spring and disc on the filler cap? There shouldn't be. If that cap is leaking out the top of it (the rivet is not holding), get another one! The AST cap should have the spring and disc. It should also be rated for 0.9 bar (a metric pressure value that is close to 13 psi), ok?

Next, the cap on the Pettit AST is a manual pressure release type cap. It performs exactly like the typical spring and disc type, and will vent and re-fill the system the way the normal ones do, BUT when you pull up on the red lever, it releases any pressure (or vacuum) that might be in the system. Typically you don't mess with the lever, unless you really need to pull the cap right away. You can release the hot coolant pressure with this type of cap, pull the cap, do what you need, and not get scalded.

The Pettit AST is fine, but look on the forum for one that is similar but has a stronger neck built in. The manufacturer's name starts with an N, but I don't remember the rest (NSI?). Some have reported that the cap neck on their Pettit got weak over time, but the other manufacturer's won't do this. There was a pretty nice post about a month or so back... (I run a Pettit BTW. Works great )

Lastly, I know you are trying to burp your system, but if your AST is leaking around its cap (which is what you describe sounds like to me) you can burp 'till your blue, you're not gonna get the air out. Everytime the engine cools down, it will suck in air, not coolant from the overflow. This is compounded by the leaking rivet from the filler neck cap.

My prescription: Get a new filler neck cap, get a new AST ASAP, then worry about burping your system. If you are going to drive the car before these instructions are obeyed (OBEY ME!! hee hee... can't even get my girlfriend to do that!), turn your running lights and/or headlights on while the car is on. This should kick the fans on earlier than they would otherwise (210F instead of 221F) which will help save you from overheating and REALLY spending a lot of money! With the leaks you describe, the fans most likely will come on every 5 minutes or less with the lights on. And you will hear gurgling when you shutoff, and when you rev it while sitting in the car.. If you can stand to not drive it until the AST shows up, do so!!

That's all from Walden Pond for now... Heewhackity doo doo DOO!! (old Doonsbury reference)

Stevey629

OK! thx for the explaination with the caps, that cleared up a lot of questions I had with that. I just got the caps replaced though, I guess I should ask them for other ones then? Damn. I dont know how coolant is leaking through that sticker on top. And yeah, the one on the ast has a lower disc, but I dont know how to test (make sure its spring loaded) the spring, as the spring itself is not visible...I guess its under the metal sheath that goes from the lower disc to the top of the cap. and yeah, the cap seems to leak sometimes, and sometimes doesn't. I dont wanna take my chances with it. Thx for the medication Doc, Ill see what I can do. SERIOUSLY appreciate this help.

Oh, and another ques. about the coolant system, since u are my new found expert with this and have been undoubtedly the most helpful person with this problem BTW. I dont see how a pressure test holds pressure, even with an ast that bleeds off air to an overflow tank which Im assuming is where the air gets released, and essentially doesn't hold a seal. A pressure test cold shows nothing past the ast so to speak, since that lower disc doesnt open to allow coolant to pass to the overflow until its hot right? But cant u do a pressure test when its hot? In this case, how would u be able to tell where the air is getting in? NE how, this problem concerns me because I'm assuming and hoping that there is just a bad hose or problem in either the ast or overflow tank. THX for the help dr. spurvo, u got a PH.D in the coolant system for this car.

spurvo

Most pressure tests I've seen apply pressure at the place where the pressure relief cap would go, using an apparatus that mimics a cap, but allows up to 30 psi to be applied. It'll work hot or cold that way. If we were to pressure test using the filler cap position, I would expect the AST cap to open at 13 psi. I haven't tested my system yet to see how it responds, though... I'm pretty sure the pressure relief spring on the caps are not temp sensitive, like a T-stat. They just open at the correct pressure, or don't. In fact, most parts stores have a neat little apparatus shaped like the mouth of your filler neck, and they can apply pressure to your cap to see if it holds to spec. There was a post the other month where a guy found three different Stant caps from a local parts store with three different pressure relief points, one was 16 psi to open a 13 psi cap! You might take your caps and get them tested to be sure they are functioning properly... Again, they should operate the same, hot or cold.

No Ph.D. yet, only a B.S. in biochemistry. And I'm actually using my degree! Cooling system not my specialty, just the system I'm most familiar with, and thus most willing to waste forum space with. More than happy to help someone when/where I can. I've gotten sooo much help from this site so far... Can't really figure out how I'd own this car effectively without it!

shred

I went through this hell not too long ago myself. Just dropped in a Koyo (another 'drop in' radiator, my ***). But anyhow, learned a lot about the cooling system (should've most of it was on the ground when taking the radiator out).

After I got the radiator in, when filling the system, it was extremely painless. Matter of fact, I didn't even have to burp the system, it filled itself. I did check the resevoir after getting to running temp and kept the filler cap off while running up to temp, shut it off and checked the level. So from that I would expect that you have some issues that deal with gasses escaping your engine system that you cannot find with a pressure test.

Some schooling on this stuff, when you have the engine running, you pressurize the entire system and on top of that you have heat. The pressure keeps the fluid from turning to gas or boiling over right away. So if you have a small leak that gasses but not liquid can get through, you will burn off some fluid and never see it. Usually you see this happen through the engine on a bad seal. Often times it is that friggen AST which if leaking gasses, will loose fluid and you won't see a thing.

So now to the pressure test, you pump air into a point on the car without the heat, unless you have a good sized hole, you might/might not see the leak. This is just a simulation of heat pressure but not a very good one. Will find big holes but not all of them, especially a bad AST (have experience with this).

Since you replaced your caps (another leading cause of lost fluid and engine failure) do you still have the problem of did it go away?? Please tell me that you bought original caps from the Mazda Dealership!! If you didn't, don't drive your car until you get them replaced with the original Mazda caps.

Another (and hopefully not your problem) possibility is that pressure is being introduced to your cooling system from the engine compression. High pressure in the motor while it is running can force air into the coolant passages and overpressurize the cooling system. Sometimes this is one-way but other times it can destroy your engine by getting into the oil. So check your coolant in your oil (really easy, pull the dipstick, will look like a chocolate shake on the top) or oil in your coolant (open filler cap, will float to the top, there will be some small amounts in there, its normal!! We are looking for oil slicks!). Another good test is to start the motor with the filler cap off and look at it when the motor is running (starting from a cold soak) and see if there are bubbles comming up. There should be no bubbles so if you see some, get it checked out, this is a bad one.

There might be some coolant somewhere but be very careful driving your car with coolant issues. There was a recall on RX7's for the coolant overheating, pooling on the top of the car and then dripping on the exhaust manifold that starts fires. That low coolant alarm is the result of a recall on the 93 TT FD. Between that and other issues that will destroy your motor, better find out what the issue is.

If nothing else, start your car up, let it warm up and then turn the heater on full heat in the defrost position, if you get a film on your windshield, you got a heater core problem. Easy fix, find the lines that goto the heater core through the fire-wall, take them off and connect them to each other. Bypass the heater core.

Whew, hope that is enough. As you can probably tell I have had my share of problems with coolant systems. From Fords to Mazda, its a bitch. I am still having my last coolant problem right now. Friggen engine light comes on when the fans engage, probably voltage. Just what I need, new alternator or fans probably the next to get replaced.

As for me, have a BS in Comptuer Engineering, doesn't help with RX7 though, this sucker is sreaming for a Mass Air Flow Sensor and an updated comptuer controlled boost management unit. This vacume crud is just a horrible mess.

Stevey629

well, I did get the caps from mazda, and for some reason, I feel like they're leaking. Why the HELL would there be dribbles of coolant on the top of the filler neck cap? NE ways, I haven't tried that method with the heater core, but I will lose the ability to heat my car if I do that fix right? But hey, if thats the problem, Ill do that fix until I get the heater core replaced, thx for the tip.

How do u start the car with the cap off? Ive tried this, but the coolant just starts rising right up to the top of the neck, and wants to just flow right out. I took off the filler neck cap, and left the AST cap on. I would like to try this, because I heard that doing this can also get rid of air bubbles in the coolant system faster.

I also replaced the thermostat, and am wondering if I somehow did this wrong. I put the gasket on, faced the "jiggle pin" up, and put the whole spring action mess faced towards the motor, and assumed I did everything right. I did get the original mazda one BTW. Is there a possibility that something there creates air pockets or something?

shred

You can get dribbles form the filler cap, it is designed to pop also but it merely has a rivit. Although I haven't seen one do this, I would almost certainly say that you have too much pressure in your cooling system, and it doesn't look like it is comming from heat (thats if you get the dribble from the cap before the car gets warm).

If you get a partial boil-over from a loss of pressure this can happen also. Your engine gets hot, pressure builds, somewhere the pressure escapes and the engine boils over since the pressure is lower, tons of gas buildup. You should be able to see this somewhere as a mist unless your engine is eating it up.

How much fluid are you loosing and when do you see the moisture on the cap?? Just a little more description an I am sure that someone will either have had the problem already or know how to fix/diagnose it.

What happens when you run the car normally from startup and a full system of coolant.

As for how I did the coolant thing, I just did it. There wasn't enough pressure to push the fluid over. As for the gasses in the coolant, that is what the AST is for. It will capture gasses and microbubbles in the new coolant and let then escape to the overflow tank. Probably one of the best air bleeding systems I have ever seen. Don't ever take that AST off or bypass it, does tons of good stuff for the motor.

Stevey629

just ordered an asi AST. It should be commin soon. Should I replace any of the hoses that comes off the AST while I'm there replacing stuff anyways? maybe the coolant to overflow line and better clamps? I'll do a search on how to install the thing, but I was wondering if I have to drain the coolant and start all over when I put this new AST in. I hope that this AST will solve the problems I'm having. Will that new cap that the AST comes with ever fail? If it does, where do u get new ones?
Oh, and the cap just has tiny amts. of coolant on the top of the cap. Just enough to wet the finger. No puddle or anything visible. Just upon touch, it has coolant on the top.

spurvo

I replaced my AST when I replaced all the hoses, but I would think pulling the coolant would make the job cleaner. ASI was the company I was thinking of. Good for you!!

New hoses are dirt cheap insurance against over heat...

Stevey629

So, since the search function doesn't seem to be working, and robinettes site and a few others just say to remove the AST, putting this one in is pretty painless Im assuming. I just don't feel like buying another jug of coolant and doing this burping thing all over again. Oh well. Such is the life of having this car I guess. I basically dont wanna do this, and find out that the problem is something else. The car seems to be doing better, as I continue to burp air out, but the overflow tank is still having issues, and drippin' coolant right back out. So, is there any way to somehow keep the coolant that I have in right now, and just swap the AST tanks without losing too much fluid? Because I want to test this tank out and make sure the cooling system holds pressure before I go flush it all again. Because if I find out that the problem is still there, then I most likely have to drain, and start over AGAIN. I guess the positive side to this is that I will really know how to flush my damn radiator.