Megaspeed7

Hmmm I've had a bunch of RX-7s and never been this stumped before (not really stumped, just curious what yall think).
I just finished fixing the TII I bought that was wrecked and I have one small problem. The plastic piece on the fill neck out of the water pump cracked. Mine is the TII kind with the nipple coming out of it for the overflow tank and the cap with the spring to bleed off high pressure. Well I went to mazda and ordered a new one (they are aluminum now, oooh) and it came back as the fill cap without the nipple for the overflow tank! The guy told me that I would have to pay some amount to restock so I just kept it, but Can I use this on the car with any sucess? maybe fill the system and then bleed some air off after its hot and it will be ok? Someone please help me figure out how the system will work (or not work) completly closed not using the overflow tank.

Thanks,
Patrick Harris.

rico05

I would not try it. Just go to a junkyard, and find a used one. With out a bleed, how would air bubbles get out???

Megaspeed7

15 year old plastic sucks, they all crack after that many years of thermal stress. I need a NEW one from Mazda, anyone know the part number?

Also about your air bubbles statement:
I explained how to relieve air bubbles by letting the car heat up and then crack open the cap. Once you get to a decent pressure in the system you can then tighten and it won't matter for the rest of the time. also you can remove the bleed screw to do this instead. But the thermal expansion of water is what I am worried about not bubbles. I am worried the pressure might get too high and bust some water seals. Am I Wrong here?

come on guys help me out
Patrick

mguire

I don't think you will break a water seal, the cap will vent to the air when your car heats up and you will loose fluid all the time. You need an over flow container.

But, I you were to use Evans Coolant, you might be able to get away with this since the fluid runs at very low pressures (doesn't really expand).

If your serious about converting to Evans Coolant (many advantages, but more expensive), talk to Rob Golden at Pineapple Racing. (pineappleracing.com)

-Eric

Megaspeed7

The new neck thing came with a sealed cap. Its not like the sprung cap. It fits VERY tight and has no spring in it. I assure you something else will "vent" before this does.

About the Evans coolant. That sounds like a great idea. I have read about it before, and I'm gonna call pineapple and see whats up. Might have a writeup about this later.

I also might use a drillpress and a tap and put my own brass fitting in it tonight and go back to my old sprung cap. It will be some work (very little, but SOME) and I'm sure it would work out fine while lasting a LOT longer than the plastic setup. Thanks for the ideas though and I'd hate to ruin a great peice of aluminum. Keep coming with the ideas though.
Thanks,
Patrick

Megaspeed7

Cooling systems need the pressure to keep from boiling over. I would figure that a sealed cap would help contain the coolant while holding high pressure, this is why I am afraid of blowing something else (pressure might get TOO high like steam engine). And I'm sure this is why cars have overflow tanks and vent caps on them.
Bring in the comments.
Patrick

Megaspeed7

bump it up

NZConvertible

You are right in your thinking. The system is kept under pressure to raise the boiling point. The radiator cap holds this pressure up to 0.9bar (13psi) then vents so the pressure does not go any higher. If the pressure goes too high it WILL find a way out, by splitting or popping of a hose, cracking a radiator tank, etc. The cooling system must have a way to keep pressure at a safe level or it'll just **** itself.

Megaspeed7

I drilled and tapped a 5/16 barb fitting on the new aluminum neck. It works perfect and It will last at least 15 more years! Thanks for talking some damn sense into me. It was hard to tap, but I managed to line it up perfectly.
Thanks,
Patrick

RETed

You got some dumbasses at your dealership...
What you got was an FD filler cap and flange.



-Ted

Felix Wankel

What year did you order it for? It sounds like they gave you an 88 setup, which had the pressure cap and overflow nipple on the radiator.

Also I hope you put the pressure cap on when you put that nipple on

Megaspeed7

I put the pressure cap on. Its beautiful shiny aluminum and brass. Works perfect. I saw the fuzzy *** microfiche, it was for an 87 car. I have the printout right here. But I know all the differences, It was just so damn fuzzy we couldn't tell if it had a nipple on it or not.
Oh well it is working great.
Patrick