NOT using a presure cap.. harme dmy engine?
 

So what are you using?

The purpose of a pressure cap is to increase the boiling point of the coolant. Now saying that I do not know what would happen if you do not. I would guess it would boil over sooner.

Wait......did I just jack this post?

James

You must use a pressure relief cap or the cooling system will overpressurise and pop something (like one of your 15+yo rubber hoses), possibly resulting in a cooked engine. Get one from Mazda ASAP.

Well now. That makes perfect sense!

James

I believe he is asking about not having a cap at all?

actually, i meant to say that i have been runnign with two pressure caps. one on the filler neck and one on the radiator. the car never got any coolant from teh overflow and it has been runnign like that for 1500 miles i just replaced it with the non pressure cap.. so it should be okey. by the way every single hose including the coolant bypass hoses are new. but teh coolant dissapered in 2-3 days ... how bad did i damage the engine? i added coolant as soon as the coolant light came up.. but what scares me is that by not throwing out teh coolant in teh overflow tank all that hot asscoolant stayed in teh engine 24/7 until it dissapered on its own. could i have prematurly aged the coolant selas>?? or damage the engine at all?

bump

Ok, I think I understand what you are saying. You have two caps. One on the radiator and one on the filler neck.

As long as one of those is a pressure cap you are fine.

James

No, only the one on the radiator should be a pressure cap, because it is connected to the overflow bottle. The cap on the filler neck should just be a plain cap.

If you put a pressure cap there coolant may leak out when the cooling system pressure gets to the cap's relief pressure.

Put a Mazda filler cap on there like it's supposed to have.

i did now. but before could teh engin ebe damaged because the coolant had no place to go?.. well it dissapered soemhow so the coolant was going somewhere right? but how is that possible if it has 2 pressure caps. HAD! since i already bought and installed the non pressure cap

Reread my post.

ok guys after installing the non pressure cap. the car is running great and its getting the coolant from teh overflow tank and giving it away when its hot. so im happy my shit is working. now today when i started the car in the morning it gave off smoke its alil more than a puff but it was whitish kinda grey. doe swhite smoke always mean coolant? it doesnt smoke after that first early morning start im gonna strat it tomorrow and see if it does that.. could it be something with the fuel?

yeah it gave off more smoke today a lil more.. i can't tell if its white or grey.? how can i make sure?