My home made pressure tester plus AST q\'s

[RemarkLima]

Just thought I\'d show you my home made pressure tester, it\'s an old rad cap, drilled to take a bolt in tyre valve... Took quite a bit of effort to get sorted but works a treat

Just stick a foot pump on and you\'re away!!!

It works well, sadly my car is loosing pressure... But god knows where, no visible leaks, certainly not going into the combustion chambers as it started fine after loosing pressure a few times, no white smoke at all... Weird!!!

If the AST isn\'t holding pressure what happens? The only place i could hear a noise was from the AST cap... So not too sure why, I think the next point of call is to put a stock AST back on and see if that helps and see if it holds pressure again. Sound about right?

[ianelvar]

Nice one!! That\'s sweet. Mine made noises from the AST when the cap wasn\'t holding pressure. I\'ve heard seen a few posts about alloy tanks not making a good seal because the part that the cap fits onto has got slightly warped during welding, so putting the stock one on might be a good idea. Failing that, I\'ve had brand new caps that won\'t hold more than 5 psi. Ian at Carls place said he\'d had trouble with brand new Mazda caps that don\'t hold as well.
Any sign of water getting into the combustion chamber?

[RemarkLima]

Hmm, good to know... I\'d like to work out a way to pressure test a cap on it\'s own, somehow attach a value to a length of pipe to attach to an AST and block off all the exits IYSWIM... Next project

I was just about to get a new rad cap but the one I have seems "OK"... But maybe not. Also I share the came concern about the AST, that maybe it\'s just not sealing against the metal lower part properly and so can\'t hold the proper seal...

Any sign of water getting into the combustion chamber?

That\'s the good news, no sign at all, car started 100% on the button, no smoke at all from the exhaust until it started to warm up a little and kick out loads of condensation, but ran really sweet which just wouldn\'t happen at all if I\'d pumped that much water into the combution chambers

[ozzyvelcro]

splash some soapy water around the foot pump hose,connector and gauge just to make sure that it isnt leaking from there, also the cap on those ast\'s are known to be iffy, I would try the stock ast.

Regards Danny

[RobbieRX-7]

You should get the coolant to 80C so the thermostat is open and your testing the radiator and heater matrix in the car. Good idea btw.

[RemarkLima]

Definate concensus for the Mazda AST then

Robbie, are you sure you need the thermostat open for that? The reason I ask is the rad hoses got harder as I pressurised the system so it was definately pressuring the rad, not sure about the heater matrix or the block if that\'s the case... But I thought the thermostat just stopped coolant flowing but the lower hose would still go back into the block and matrix???

[RobbieRX-7]

im not 100% sure what gets blocked off by the stat, but they usually block the rad when cold, then it opens and hot water flows through the rad. If i was doing it, i would get it upto temp then pressure test it, just be carefull removing that cap though lol My stock thermostat opens at about 78c just as a guideline

[Martiny]

But hold on, dont our thermostats have little hole in them?

[Grizzly]

Those sorts of Pressure testers are Good for finding leaks and checking Matrix\'s etc but for dedicated "Water seal" testers you want one of these.http://www.atkinsrotary.com/store/customer/product.php?productid=16858&cat=568&page=1
I think there more for engines out of the cars but they are made to check just the water seals.

BTW Robbie\'s correct the rad isn\'t blocked of so no water can pass through at all, it\'s designed so the Thermostat causes a Masive blockage and the flow of water is diverted back into the engine, if you pressure the system up you must have the cap on the AST as it will push water back that way from the rad.

[RemarkLima]

So, just so I know I\'ve got this the right way round, with the cap on the AST I can pressurise the system to 13psi (as per the pressure cap) and this should pressurise the entire block, matrix, rad, turbo\'s etc? As the pressur goes via the rad, to the AST, through there into the lower hose and into the block and off from there???

I did notice in the FSM they tested the system on the AST cap, rather than the filler cap... And then pumped it up to 20psi, to test for leaks etc...

I\'m sure that should have pushed water into the engine if my water seals had gone, right? I\'ll get it up to 80C as well and try again, at least it\'ll keep me warm this time

[Grizzly]

In a nut shell, your fine putting pressure in at the Engine cap as long as you don\'t exceed the Sprung AST cap rating.

The problem with your type of Tester is its been known to not work with Water groove damage, Basically what happens is you push the Seal back into its seat. Its the pressure from the Engine\'s combustion/rotation that pushes the Seal out of place and causes the problem.

I think if you search for Rixio\'s Overheating thread you will notice his passed a water pressure test with a section missing from the seal groove, thats why i say this sort of Comp tester is better for testing Rad\'s, Matrix\'s etc.

[ianelvar]

Good point from Grizzly. Try starting her up with the tester attached but no pressure in the system. You\'ll be able to see if there\'s a premature buildup once she starts firing.
Good shout on the soapy water as well.
I couldn\'t find my leaks until I started prodding the hoses and started feeling round for any signs of water, then it all started to fall into place. I had a split in one that didn\'t show itself until gently \'persuaded\'
I also had an awful problem with the silver one getting the large hoses to seal properly and had problems with the screw type hose clips that had been installed on the small hoses. They wouldn\'t seal under the screw mech, so I swapped back to OE spring clips and it sealed fine after that.
My money would be on the AST or cap(s) at the moment though.

[Grizzly]

Good point from Grizzly. Try starting her up with the tester attached but no pressure in the system. You\'ll be able to see if there\'s a premature buildup once she starts firing.

Don\'t forget that pressure will build up anyway (heat makes the water expand etc) but what your looking for is Massive pressure increases with min heat increase. Thing is the build up of pressure is so dramatic from Cold that if you take the AST to Expansion bottle (the one under the Drivers wing) pipe off the ast and watch, you will not be able to stop it weeping when the engine is running.

Good point about the Clips, In my opinion jubilee Clips are hopeless, as already suggested i wouldn\'t swap the stock Spring clips if there is no need.

As for the Ast cap, it is possible to tighten it up by bending the tabs (that hold it on the filler) in slightly with some Pliers, this will make it a bit harder to fit but you will get a better seal.

[RemarkLima]

Cheers for the comments guys! All definately helps and the reason I made this is so I can keep doing a few experiments without having to go to a garage each time (or pay far too much for a proper pressure tester).

But unlike Rixio\'s problems, my pipes remain soft until warm, no water is pushed from the expansion tank and no bubbles with the filler cap off... I think it could well be the AST not sealing properly, seems to be a case of just a new plastic one every couple of years eh?

I could hear a very small hissing from the AST cap, but it\'s more of the spring doesn\'t seal the rubber foot too the lower part then it\'ll never work!

[Grizzly]

Yep AST\'s can be a pain in the rear, Try taking the pipe off that goes from the AST to the Overflow tank under the Drivers side arch, then dry it well and run it, see if there is a leak or any moisture build up (you could use your tester for this) if its not dramatic try bending the tabs on the side of the Cap slightly so it\'s tighter on the AST. (Like Pic below)



I have recently seen both the AST playing up (check the mating surface inside the filler is smooth and no Flash marks or over time it causes a low spot in the rubber seal) and the cap (i don\'t know why but i have had really bad luck with caps, in the past few years i\'ve bought 6 and 4 of them did\'nt seal properly from the shop)