I have a s4 NA stock. All the coolant would go into the coolant reservoir and that causes the "add coolant" light comes on. I have to take all the coolant out from the reservoir and refill it to the top everyday before and after i go to work. I have already changed the cap but it doesn't fix the problem. I really need some help here please

 

Pressure test coolant system. Fill up rad with engine cold, leave cap off, start car, watch for air bubbles coming out of coolant neck/rad(whichever cap you have off).

 

Im pretty darn sure im not losing any coolant. I do not see bubbles when it was cold start. But it does stall sometimes when it's cold start. Do you think would the thermostat cause the problem?

 

Your looking for bubblesTo see if you have a bad coolant seal. I was having the same problem. It ended up being a leaking seal. Are you having any hot start problems?

 

no hot start problem. I know mileage does not play a big part but the car only has less than 45,000 miles

 

My problem didn't fully show up untill I did my turbo swap. When it was N/A it would do the samething as yours. I started boosting and it got worst. You may be ok for a while. FYI miles won"t tell you if it has run hot or how long.

 

bump, really need some suggestion before winter comes!

 

first off make sure you have a good OEM (MAZDA ONLY) radiator cap. the pressure is getting too high causing it to vent into the overflow bottle.

what is your temp at in the dash gauge when hot?

are you running factory fan clutch or e fan?

 

Sad to say.. Every time I've seen that problem it means a coolant seal is bad.. Which means you need a rebuild and at least one new plate..

 

This problem is not necessarily a coolant seal...people have bad habit of jumping to that conclusion too quickly.

The problem isn't pressure, but vacuum. You have a leak in your system that is allowing air in when the car cools. Normally when the coolant cools it creates vacuum that pulls the coolant back out of the overflow. When you have a leak (that doesn't necessarily leak coolant all the time) the system leaves the coolant in the overflow and draws air from the leak. After a few heat cycles the over flow fills up and you have to refill the system. A bad cap can also cause this. If you pressure test the system you should be able to find the leak. I had a similar problem...turned out to be the second cap on the thermostat housing.

 

I had a similar problem -- coolant goes out, but not back in. Pressure tested, still leaked, tighten hose clamps, still leaked, then put the tester on the thermostat neck, pressure held.

Turns out I had a bad flat filler cap on the S4 thermostat neck. Threw on a spare pressure cap and it solved the problem.

 

I just bought one off ebay for 20 bucks. It looks pretty legit to me but I will defin go get a OEM one.

The temp gauge appears normal as before, about a quarter up the base line.

My whole car is stock beside the mufflers.


So you think the thermostat can cause the problem? Sometime my car would not hold the idle when it first started. And how do you perform a pressure test with the system? sorry about all the questions

 

I notice the pressure escapes whenever I open the cap or take off the bleed plug. There is a hissing sound. And also "add coolant" light would only comes on when im on low speed/stop light/idling. Once I hit the free way or parkway, the buzzer would not go off

 

You can rent a pressure tester from Autozone. It'll come with a bunch of adapters to attach it to either cap position...i would test it on the radiator with the flat cap in place, as I'd bet that's where you're leaking. Or you can just buy two new caps and try that.

 

Do you have any update about your problem? Cause I'm having the exact same symptoms on my FD.
The add coolant buzzer comes on only at low speed or idling, never on the free way.

It is normal that you hear a sound when you slowly remove the cap when the engine is at normal operating temperature. This happens because the system is pressurized. If you remove the cap quickly all the coolant will get out on the floor because the pressure is released rapidly. If you remove it slowly, the pressure will go in the hose to the overflow.

 

Check passenger side hose coming from your firewall going to your rear iron. I had a pinhole leak when I pressure tested it at 15 psi. It was too little I took my time until it finally came out in between the rear iron and tranny. Our forum suspected it was freeze plug but thank goodness it wasn't. To replace the hose is PITA you have to remove the dynamic chamber to give you ample room.

 

how many psi do I wanna see when I do my pressure test?

still the same, picked up an OEM cap. The coolant still all goes into the reservoir. I really don't think is my coolant seals causing the problem. Like I said, Im not losing or burning any coolant, it just all goes into the reservoir after a while of driving. I've been busy lately and I haven't got a chance to do a pressure test.

Pictures would help a LOT!

 

I had the exact same issue after I replaced the heater hose on the drivers side....eventually the buzzer stopped and the car never over heated...but I'm have cold start issue ever since....wonder if its related

 

In the words of Spock, on Star Trek, no matter how undesirable the facts may be, facts remain as the only key to the solution...meaning...coolant does not return to the cooling system because the system is not totally sealed, meaning...it has a leak, not necessarily a coolant leak that you will find, but, the system is pulling air into the system from somewhere when it cools down and is suppose to be pulling coolant back into the radiator. A radiator cap that is not double sealed(cap for a closed colling system) is being used or is no good or there is a leak, even if it is very small or....internal...there is a leak.

 

On my side, I'm not really positive. I don't think anything could cause the overflow to fill continuously during a ride except a bad cap (which we both changed for an oem one) or a bad coolant seal that let the exhaust gas go in the coolant system to push the coolant in the overflow.

I hope this is not the problem but I have been searching for more than one month now for an external leak.

 

mine never overheat nor lose any coolant. thermostat would cause cold start issue. Back to my problem, I really haven't had anytime to work on my car. My last card will be replacing the thermostat and hoses, if that wouldn't fix the problem, we all know whats the next step.....

 

Have you replaced the hose between the filler neck and the overflow bottle? How about the hose attached to the inside of the overflow bottle? Either of these could cause the coolant to not get sucked back in after the engine cools down. Your system should hold 13 psi using the pressure tester.

 

both of you need to bite the bullet, cause you have a bad motor.

why do i always have to be the one to say it?

the system should be totally sealed until about 13psi, a bad water seal will push water out beyond that 13psi threshold and will not draw it back in after cooling. even if the cap happens to be faulty, there would have to also be an issue with a one way check in the reservoir hose. there is no check valve in it but clogs have been known to develop and act as a one way valve. you would then see shrunken coolant hoses as a result due to the vacuum, if not, see above.

 

none of my hoses is replaced but I will do it soon

Yeah, im ready for a rebuild, but I wont jump into that conclusion without any testing. thanks for the info!!