My car has gone through two coolant fill necks and a couple of caps and I've gotten to the point where i'm considering making a blockoff plate and putting it in the place of the fill neck. Has anyone tried this, and what were your results? Could there be any negative side effects from this to the system?

 

The fill neck (assuming you are talking about the one on the water pump housing) is also the thermostat holder and connection to the upper rad hose. I can't imagine how you could block it off...

If it is the plastic neck that is cracking, you are probably overtorquing the bolts. Also, you can replace it with the older style metal neck if you swap the water pump housing as well.

 

I meant replacing just the plastic neck and cap with a block off plate.

 

dont block it off. it's made to release pressure and not to just explode.

 

How does it release pressure?

 

Nope, it's just a plain cap. The pressure release cap is on the radiator.

Blocking it off wouldn't be a good idea. It's the highest point in the cooling system, which is why the filler cap's there. Without it you wouldn't be able to bleed all of the air out.

A new filler neck should last for many years. Are you using used ones instead?

 

How much would a dealership charge for an OEM replacement?

 

Actually mazdatrix sells them as well http://www.mazdatrix.com/b8.htm

Items J or K..depending on the year of your car. Between 30-40 bux usd. I have no idea wat the dealer is selling them for...but mazdatrix usually has decent parts prices.

 

dealership is about the same price i had to buy one about a year ago, for my vert


-Shawn