I have a coolant leak thats coming out of the top of the coolant overflow tank below the passanger side headlight. It isnt a crack or hole, but what looks like where a plug would go thats missing and coolant is leaking out. Can't be more big around then a golf tee. Does anyone know what or if anything is supposed to be there and where i can get somthing to stop the leak? Could really use the help.

Thanks guys!

 

There is a vent hole near the top portion of the overflow tank. If there is too much coolant in the system, the excess will get expelled through that hole. However, if you have other coolant issues, pressure can build up and push too much coolant into your overflow tank, thus expelling most of it through the vent hole.

 

Does anyone have a picture of this vent hole... the coolant was low before it started pouring out, bc the buzzer came on prior to the leak... i can see where the coolant is leaking out... is this the only hole in the overflow tank? And is it supposed to be open?

 

Mahjik is right. Start by verifying that your overflow tank is not overfilled. With the car totally cold (i.e., 8-10 hours post shutdown), check your overflow tank dipstick and ensure that the tank is ONLY full up to the "F" mark on the dipstick. If it's WAY past the mark, you'll need to siphon some out of the tank until it only reads on the dipstick up to the "F" mark.

If you've been adding a little to your fill port occasionally every time it appeared LOW, this is likely where your coolant has been going. Anyway, start by getting the overflow tank to the proper level. Then, if the car still consistently appears to be low on coolant, you may have air in the system that needs to be bled out, or another problem with your cooling system.

The vent hole is near the top of the tank and base of your fill tube. It looks like a little rubber grommet O-ring and has an opening about the size of a golf tee.

 

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/coolant-overflow-tank-vent-hole-658716/

 

Thanks guys, the hole is right in front of where the neck of the tank reaches the body. I'm going to go ahead and take out some of the coolant out of the overflow tank, then should i flush out the system?

 

If you don't know when the last time the system was flushed, then yes. I would also go ahead and replace your coolant caps.

 

So by flushing out the system that will take care of the air that needs to be bled out, therefore maybe solving my coolant light comming on every time i drive? I dont see anywhere else where i am leaking coolant. Thanks for the advice guys.

 

Not necessarily. You've only identified where the coolant is coming from, not necessarily 'why' is coming out of there. There are several reason which can cause what you are seeing. Unfortunately, there is no "easy button" for this car so simply flushing the coolant system isn't going to magically fix all coolant related problems.

 

So it's probablly something more then just a leak...

 

If its coming out of that hole, yes.

 

Any idea's??

 

Could be:

1. Coolant caps aren't sealing any more
2. Failed coolant seals

There are several things which can cause this issue, those two are fairly common which is why I suggested above to replace your coolant caps.

 

Coolant cap as in radiator and AST caps?.. Hope its not #2, is there anyway to tell?

 

Replace the caps with new ones, top off your coolant and then see if it happens again. Some people dont see any significant smoke with coolant seal failure, other fds wont stop smoking.

 

Replace them both. They are cheap and should be replaced on regular intervals like other wear items on the car.

 

Well i have a Pettit AST and its relativly new, put it on last year. Should i go ahead and replace that along with the filler neck cap?

 

Yeah your coolant system isn't sucking up the coolant from the overflow bottle after the engine cools down, hence why you keep adding more coolant hence it overflows.

I had similar issues once and I suggest you change the filler neck cap and AST cap and most importantly check all the hoses coming from the AST. Since you said your AST is pretty new, I'm sure there is a leak from one of your hoses.

If the car didn't leak before you put in AST, chances are the problem is there.

 

Ok, i'll give that a try. You think it'll be ok to drive it now, or wait untill i buy a new cap?

 

Your symptoms are THE classic coolant seal failure though as Mahjik and others MANY times above pointed out, bad caps CAN have a similar effect. You mention several posts down from the original how your add coolant light has been coming on, right?
So one assumes you have been adding coolant as required. Yet that coolant is going somewhere, which is out the overflow. Believe me, you ARE losing more than you think whilst you are driving, but it vaporizes so well you don't really see it.
In a properly working system the coolant is supposed to expand into the overflow tank, the volume of the tank is such that as properly filled levels, there is room for expansion WITHOUT going out the overflow hole. If you ever take the tank out and see this hole, you will realize how far up it is from the 'full' mark on the dipstick that sits in the overflow tank.
After you turn you car off and the coolant...cools, the volume decreases and a principle called the thermosiphon effect sucks the expanded coolant out of the overflow tank and back into the engine's cooling system. This is all part of what is called a "closed system".
In a malfunctioning system, a couple of things typical of these cars happens. One is when the coolant seals in the engine are starting to leak, this allows some combustion pressure to go into the cooling system, and it forces coolant out into the overflow tank and so much is forced out it goes out the overflow hole. So you get into this chain of events where you are always adding coolant, as so much is forced out under combustion pressure that there is not enough to draw back into the system.
The second most common thing that happens is when one or both of the caps start to leak. Remember, all it takes is ONE teeny tiny little leak, a microscopic pinhole in a hose or a cap seal, and what happens is the thermosiphon effect is defeated when the engine cools. All that coolant that expanded into the overflow bottle just stays there, and so your car sees an actual decreased coolant level, and the light goes off and you go and fill it up again, and it WILL overflow as it is designed into the overflow tank, which is now too full from before, so it pukes out the hole. This cycle is repeated until you fix ALL your leaks.
You need to get a tester or have the system checked for leak-down. I am SURE you will see this is happening. Then you go from there, you can send a sample of coolant into a lab and have it checked for hydrocarbons, if they are present your engine is definitely on its way out and will require a rebuild.

Both of these issues are very common and have been discussed about...oh, ten thousand times. Coolant woes are THE Achilles' heel of the FD.