Coolant going into expansion/filler tank

[Phil]

On my FD, I recently did a coolant change (drained from radiator and the block) and put about 7-8 litres back in. I squeezed the hoses and removed the throttle body coolant hose until it all seemed bled and also filled up the expansion/filler tank to the correct level.

This was done a few weeks ago and has been fine since, although I noticed my heaters wern\'t getting very hot at all and so I thought there may be an air lock. Yesterday when I left work the coolant buzzer came on although the temp guage stayed exactly where it always does (just below half). When I got home I checked and there was no coolant in the pressured filler kneck so I managed to get about half a litre in. I also removed the AST cap and the AST was dry so filled up from the filler kneck until the AST was full as well.

I noticed that the dipstick in the unpressurised filler kneck in the inner wing was showing water nearly to the top. (Over the max level)

When I came to leave for work today it did the same thing so I have topped it up again!

There are no bubbles in the coolant running it with the presure cap off and no smoke from the exhaust. That guage reads fine.

Are these symptoms of a malfunctioning/split AST?

[MillSpeed]

Most likely a dodgy AST cap. There\'s loads of threads on this, worth doin a search.

[brew]

phil , i have the exact same symptoms, did the AST cap resolve the problem?

[Rixio]

Check out the coolant thread in technical stickies
http://www.mazdarotaryclub.com/forums/showthread.php?t=30047

Where the water is being lost from...?

Usual suspects...

Filler Cap
AST Cap
AST
Heater Matrix
Split Pipe
Kinked Pipe
Water Seal

[antnicuk]

The cap on the ast is supposed to allow the excess/expanded water to flow from the engine into the ex bottle as the engine gets warm and then allow the engine to suck it back in from the ex bottle as it cools down.

If the pressure cap is not working properly it will push the excess water into the bottle and not be able to suck it back so every time you top it up it just keeps filling the ex bottle.

[brew]

i think i have an airlock in the system, has anybody got a picture of the coolant hose i need to remove.

i\'m on a step learning curve with this RX

[Grizzly]

I did a bit of reading up on this subject.

All this should be done with the Engine cap in place. (The Engine cap is the one with no Spring)

Basicly undow the AST tank from is Mounting and get a Coat hanger and rig it up so its higher than the level of the engine, Now you need to turn the Heater to Hot (with the Ignition on) then fill the AST to about half way.

It may be a good idea to remove the coolant hose on the back side of the Throttles (its between the Bulkhead and Throttles), Then watch for water starting to come through, whist its Coming out replace the hose.

Keep an eye on the AST level and Top the back upto half way if it gets anywhere near empty and start the car, the level drop at first until the System is bled (don\'t let it run dry) then you will notice it will start to climb up the AST when it starts to get bled/warm. When the level reaches between 3/4 and the Top turn off the engine and allow to cool. After an hour or so check the AST level, replace the cap and refit to its Origanal position.

Doing it this way makes the coolant level higher than the highest point of the engine there for its Under more presure to relive air locks.

Its a good idea also to replace both caps (Engine and ast) once a Year. Also check that the Pipe from the AST to the Overflow Bottle (behind the Drivers side headlight) is in good order and holding water, Once the system is Bled try not to take the Engine/AST cap off unless the Buzzer goes off, But keep a close eye on the Level of the Overflow tank.