Help! Coolant caps, what pressure? Leaking coolant!

[FDRZRich]

I have done a search this morning on here for help, but all its done is make me more worried!!

Had service done last Mon, asked to replace radiator cap, as rubber seal had swelled and clearly wasn\'t sealing properly.  

Car had been forcing the top pipe to pop off the AST and chuck coolant out, but only after a run.  Had to fill it when starting, as coolant buzzer was coming on.  Puddle underneath car where AST is too.  Car starts on the button every time, hot or cold, which I think (hope) is a good sign, ie seals not gone on engine! It has about 30k on WGT rebuilt engine, never driven in anger really.  Thought that problem was caused by rad cap leaking.

Which pressure cap should be on the main filler and which on the AST?
The AST had a 0.9 one and a spring, the other didnt have a spring, but don\'t remember pressure.  The replacement one i have now is a 1.3 with a spring, but it was put on the AST and the AST (0.9) one was put on the main filler.  Should they both be sprung?
All was fine on way home. Next day coolant buzzer goes off soon after starting up.  
Noticed caps were wrong way round and have swapped them over. Should I have? Noticed steam coming from left headlight area after shutting down. Middle pipe to AST coming from rad filler had come off, even tho it was clamped!! The pipe coming from the bottom of the AST is also weeping a bit.  It is chucking out about 500ml of coolant, as that is how much it takes to fill it to normal level (about an inch down filler neck, just below the small hole down there).

Car drives fine, boosts fine, starts fine etc, this is really worrying me now tho. :confused: Have to do it nearly every day now..... If the seals had gone it wouldn\'t be chucking it out the ast would it? The place that serviced it also said that the rad could be blocked because the fans were cutting in and out within about 2mins while it was sitting there, indicating that it was getting pretty hot, pretty quick!! Any ideas anyone?

EDIT: PS Car is a standard \'96, not even got a catback on it! Not got PFC so can\'t see exact temp.

[clive]

Hi Rich sorry to hear your having problems,

You should have the 0.9 caps on as this was a Mazda upgrade for all Gen 3\'s years and years ago.

Until you have sorted out your leak from the AST area you will never have the system settle and so you will not know if you have a problem or not.

You mention filling,and l know you have had your car a long time but when filling ignore the AST and just top up as you say one inch down on the engine filler.

If you checking this leak your self have a good look at the pipe that goes from the AST to the tank on the wing as these are prone to chaffing and leaking.

p.s on a system with no leaks and the water seals are starting to go, they develop a water leak from under the O/S /front wing out of the tank overflow hole and not the AST.

Hope this helps

[FDRZRich]

Thanks for saying that about leaking from the hole in the expansion tank if the seals are going, its cheered me up a bit!:rolleyes:

Its just that I\'ve read about exhaust gases in the system causing it to over pressurise, which would explain the leaking.  

The water is definately coming from the connections to the AST, but I will check the pipe going to the expansion tank as well.  

So are you saying that both caps should be 0.9 bar?

I do always fill from the main cap, I never normally take the AST one off.

Does the main filler cap have a spring on it or not? Can I get a normal one from Halfrauds?

[clive]

Take your cap with you and l think you will get one from any  motorist shop as from memory these caps are common to other Jap cars.

Just remembered, THE AST\'s  SPLIT ,doh!

It\'s a common fault where they split around the seam and then the water tracks down onto the pipe joint, so thats probaly your problem.

You have to chuck em in the bin and buy a new one ( around £80 from Mazda l think)

[FDRZRich]

That was the first thing I thought of when this started happening, but I\'ve checked the AST and the thing must have been made pretty well cos its causing the pipes to pop off rather than split the thing!!
The water is coming from the pipes, but I\'ll double check just to be sure!

So...... 0.9 on both, spring on AST, no spring on Main filler? Or what?

[FD3UK]

You only need pressure cap on the AST, cap on thermostat housing is a filling level point and is fitted with a NON presure release cap.

It seems like you have something else amiss as well though, before fearing the worst, check for airlocks or blocked radiator.

Kev

[FDRZRich]

Woohoo! Well after reading your posts and getting myself really worried and depressed, I finally had a day off and time to check out where exactly the leak was coming from!!

After taking out the air box and intercooler flexipipe I could see that it wasn\'t the pipe going to the expansion tank that was leaking. I blew into that hose and could hear bubbles in the expansion tank.  I thought I\'d check the hose coming from the thermostat to the AST, as it had managed to come off the other day.  I pulled it off quite easy, without having to undo the spring clip. Hmmmmmm I thought, looked inside hose, and the connecting past of the AST has snapped off inside it!! It was all starting to crumble away, and there was no way I could get it out, so I cut the hose off, and was able to reconnect it to what was left of the \'spout\' on the AST. I cleaned up all the spilled coolant so it was nice and dry, topped up to replace what had come out.  I have driven it about today and (touch wood) no steam from front left area and no coolant buzzer evertime I start her up!! Come on!! Thank god for that!! I\'m gonna keep a close eye on it, and prob get a new rad as soon as I can afford to, first I\'m gonna get a new AST and hose!!!:D

[clive]

Well done, sounds sorted

[FD3UK]

Well done, glad to here it was only a simple cure.