AST Cap gone?

[ash]

Hi All,

After doing some (well quite a bit) of research on here, im changing my AST cap for a new one rated at 0.9bar, but i was just wondering how if the AST cap fails what would happen?

If it fails does it not control the pressure of the water and tries and find the quickest way out to release the water and that route would be the coolant reservoir and therefore water would spill out the small hole in it?

Just trying to understand - i had a look at the coolant diagram but it didnt show the travel of water from the AST to the Coolant Res.

Thanks all :cheers

[nikp]

If the cap fails it would hold no pressure, and would let coolant out until the pressure has equalized with atmosphere. In other words, yes, you would lose coolant. However, I think your understanding of how the coolant works is a bit wrong anyway - the cap releases the excess pressure into the coolant reservoir anyway - the only difference being a failed cap would not maintain a satisfactory presure.

[ash]

Yesterday i removed my undertray, ran the car to operating temp and waited until water escaped. Coolant level remains the same on dodgy gauge and buzzer did not come on (engine was switched off when coolant was being released).

What seemed to be happening was, when the water got to a certain temp. point it would pour out of the coolant reservoir, and i mean pour. I could hear boiling noises from the res and the AST - any ideas??

So if the cap had failed and could not equalize the pressure would the coolant not continue to flow out the AST until the water had cooled down?

Also, from cold on idle how long until the fans should come on roughly?

[Tiger_kpt]

I\'m having the same problem at the moment with mine.
 
Was fine running standard set-up. Then I recently purchased and fitted the Pettit Racing AST with pressure cap as well as their uprated 22-24lb race pressure cap. I fitted the AST tank and used the uprated race cap.
 
I then begun to experience similar problems... engine fine when running. But when turned off - the coolant system leaks alot of coolant out of the reservoir. And I have to keep topping it up before driving.
 
I first thought that maybe it was down to the race cap, being too highly rated. Excess pressurised air not able to escape and so found an easier route - and created a leak. So switched to the standard Pettit Racing cap. Same thing happens.
 
The water seems to be coming from the front left hand corner of the vehicle. Not sure of it is from the expansion tank or one of the lines to or from this tank. But the water is dripping from that area as it can be seen down the undertray as well as dripping through the rad/oil coolers at that corner.
 
Any ideas as to what this problem could be anyone?

[Lum]

I don\'t mean to scare any of you but i was experiancing exactly the same symtoms as both of you describe. I\'ve not long finished putting the engine back in as i rebuilt it because the coolant problem was down to failure of the water seal on the rear rotor housing:eek:
I changed my AST cap thinking that could be the problem and it sorted it.. for about 2 weeks.
I would defo change the cap. I got mine from a local motor factors it was a universal jap fit cap, rated at 0.9 bar. Only about £4.
Try that and see how you get on, otherwise try searching on here for water seal failure and you\'ll find a few handy test\'s and things to watch out for to try and determine the problem!
Hope this helps :Thumbs-up

[Tiger_kpt]

What are the symtomns of water seal failure? And what are the tests? Can\'t seem to find much in terms of topics on that so if you could give some links to things rather than re-writing that would be great.

I\'m sure that mine can\'t be water seal failure as the engine runs like a dream! - only the loss of the coolant at the moment.

[nikp]

I\'m sure that mine can\'t be water seal failure as the engine runs like a dream! - only the loss of the coolant at the moment.

Water seal failure won\'t affect the perfgormance of your engine that much, so a well running engine is not a good indication

[Tiger_kpt]

Hmmm... that is worrying then. Well... from tomorrow fate is in the hands of Pip at WGT. I\'ll let the Gods decide. lol.

Have to admit... since changing my main coolant pressure cap a few days ago (not AST one), it does seem a little better. Shall see.

[Martiny]

I also dont want to be a scare merchant, but Nik and I had exactly the same symptoms you describe, and it eventually traspired to seal failure.

How about trying the standard AST again? Some aftermarket ASTs dont have a good seating for the cap, then it can behave as above.

[nikp]

You have deffo got water seal failure then Martin?

[ash]

Ok, well my radiator is leaking! So that is at least good news - have put in some BARS which i think has done the job.

New AST cp fitted £5from factors, flushed system and replaced coolant. All seems good now but i do have an electrical question that is puzzling me that i will post in another section.

[davehg]

i would never ever run anything in the water that stopsleaks, it will only cover up a problem that you may have and also block the water cooling ways in your engine causing yet more problems. if its leaking your best to replace it, if not it could cost you more cash later on.