it will be boiling in the over flow tank, but it wont over heat. its an s4 and the guage shows 1/3 and the exaust does NOT smell sweet. whats up?

 

Get your cooling system pressure tested.

Or you can take off the filler neck cap, pull the EGI Comp fuse, and have a buddy crank the car over. If you see a constant stream of bubbles, you have a blown coolant seal.

It does sound exactly like a blown coolant seal though

 

but i would smell coolant in the exaust right? it wouldnt push it out

 

Not going to lie, does sound like a coolent Oring problem... Cause the compression in the engine would push coolent into the overflow bottle... not sure though. Is that an aftermarket gauge or stock?
The stock ones are to my knowledge not very acurate... so im replacing ALL of my gauges

 

When mine were blown, I never really noticed a strong coolant scent directly from the exaust. Even with blown coolant seals, the amount of exaust gases is much greater than the coolant... fumes i guess you would call it. I could smell coolant a bit driving around at low speeds though.

 

it was exeptionally low on coolant when i got it, maybe its just because the engine was hot and there wasnt enough coolant in it so it was pushing air around?

 

does that happen all the time? if it does? time for rebuild... its coolant seal. same thing with me. betta save up some money for rebuild.

 

I would assume that a weak seal may allow the exhaust pressure to escape into the coolant system, but it may not be weak enough for the pressurized coolant system to force it's way into the engine past that same weakened seal. At some point the seal will weaken enough to allow passage both ways, and will eventually fail altogether.

That's just a hunch, and for all we know you may have a hose that isn't seated fully, a bad radiator cap/thermostat, bad o-ring on one of the sensors, or one of the many other coolant related problems that seem to spark up on these cars. The only two ways i've seen to make sure is to pressure test the system and hunt for leaks, or find something that will tell you if you have exhaust gases in your coolant. I should be doing the same to my car soon, but i've just been too damn busy with work and life to give it the attention it needs right now.

 

when your motor is not running, the coolant leaks into the motor. When it is running, the compression/combustion pushes the exhaust gases into your coolant.
something like that anyways.
-Ben Martin

 

actualy the Orings can bereplaced without replacing the entire engine... but while your inthere might as well if its old an tired...

Im sure mike could prolly help... ill do anything i can

 

Get the pressure test. If it passes, get a new MAZDA radiator cap.

Before you start to rebuild the engine, try everything else first.

Does the coolant expand into the tank as the engine warms up? Then does it correctly pull back into the radiator when the engine cools? You can have a vacuum leak between the cap and the overflow tube that allows air to be sucked into the radiator when the engine cools. Then some of the coolant stays in the overflow. Next time you run the car the process repeats.. Eventually you are low on coolant. At this point when you run the car, the hot air and steam is bubbling into the tank and the car acts exactly like it has a blown coolant seal, only it doesn't. At this moment, you will be in very great danger of overheating your engine.


I had this exact problem with my 90 Vert N/A. I tested everything, compression, cooling system pressure test. I replaced my rad cap, my tstat with oem. The problem still existed. When the overflow tank got full or when the low coolant buzzer went off, I poured the overflow tank back into the radiator. I found I wasn't losing coolant, just moving it one-way into the overflow tank. I didn't know to test the overflow tube for a leak, so I lived with it like this for months. I then eventually changed the cooling system over to Evans NPG+ and went the nonpressurized route. It works great for me, but I don't recommend it for anyone unless they have thoroughly sorted out the cooling system and are very sure that EVERTYTHING is in perfect operating order.

Good luck.

 

If you don't have the typical white smoke, then it's not the coolant seals like most people here think. If your coolant is bubbling out the over flow tank, you need to replace your radiator cap. Here's the reason. Your radiator cap is suppose to hold X amount of pressure with-in the cooling system. With a faulty cap, it doesn't take much pressure for the coolant to back flow through the cap and back into the over flow tank when the engine gets hot.

This is what was happening to my Fd. I thought it was also the coolant seals but I never had any of the white smoke. I was prepared to do the block weld procedure when I was flushing out the system. Typically when I change my coolant, I remove the upper TB coolant hose and fill the system. Since that's the highest point, it allows all the air to escape making it un-necessary to bleed later. When the coolant is topped up, I will then put my mouth over the filler neck and blow till I see coolant exit out the TB hose. When that happens, I reconnect the hose and top the system off again. I then do the blow test again. Sometimes you will see air bubbles exit the filler neck.

That's my normal bleeding procedure but this time when I was doing the blow test, I could hear air bubbles exiting my overflow tank. I thought strange because I know that I don't have enough mouth pressure to make that happen. In the Fd you have the filler neck (where I blow through) and a separate AST (air separator tank). I then pinched the line exiting the AST and did my blow test again and this time no air was leaving the overflow tank. That's when I realized that the pressure cap on my AST may be faulty or not sealing properly underneath the spring to allow the air/coolant to back flow like that. I then went to Advance Auto to buy a 13psi radiator cap for only $6.50. Now the coolant isn't bubbling out any more.

 

Same exact thing happened to my s4, a new water pump did the trick!

 

From what i've seen it's not a bad idea to replace a lot of the seals after the engine has overheated. While on a good condition motor with low miles, like my 58k original miles, i could get away with just replacing the coolant seals...i don't want to run the chance that the engine had been overheated more than the once i did it and that the side seals and such are fatigued from the extra heat.

 

i just had that problem with mine
temps were fine but overflow tank kept filling up and steaming out

replaced the radiator cap and problem was fixed!
go with that option first!