It looks like that one but I can not tell what size it is from the picture.  I have found several that were 1.75 inches in diameter. 

My cap is 2.125 in diameter.  In radiator parlance it is an “A” size.  Since this fits a Mazda, I would suspect that this is the small cap??

 

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From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
Sent: Tuesday, July 01, 2014 5:30 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Radiator Cap

 

Like this? B Mazdatrix. B https://www.mazdatrix.com/getprice.asp?partnum=15-2050-KF01

 

 

On Tue, Jul 1, 2014 at 2:55 PM, Bill Bradburry <flyrotary@lancaironline.net> wrote:

Well, not much activity in the last couple of weeks!?

So when I designed my cooling system I installed a fire extinguisher bottle

that I had welded a radiator neck onto. B I put a 21 pound radiator cap on
this bottle. B I keep the bottle about 3/4 full of coolant. B If there should

be an overflow of this bottle and the pressure is exceeded, the coolant

would flow overboard. B AFAIK this has never happened. My coolant pressure

runs around 20 pounds in flight, so I assume that the radiator cap is
burping air to keep the pressure at that level.
I have a tube from the bottom of this fire extinguisher that goes to the

overflow tube in the radiator neck of the radiator. B This radiator neck has
a radiator cap that has no pressure control under it. B This radiator cap

only seals at the top and does not block off the lower seal that is present

in the radiator neck. B I take my coolant pressure from this tube that goes

between the radiator neck and the bottom of the coolant bottle

Recently after I shut the engine off, I noticed that I was loosing coolant

from the area of the radiator cap on the radiator. B The radiator cap is

probably 7-8 years old but I only have about 130 hours running the engine,

100 of which is in flight. B I assumed that the radiator cap was leaking and

so I decided to replace it.

Easy said not so easy done!

I have looked high and low for a radiator cap that does not have the spring

loaded pressure regulator under it. B Most auto parts guys just say HUH?

I didn't write down any part numbers when I bought it and don't even really
know where I got the damn thing.

Does anyone have a similar system and or know where I can get a replacement
radiator cap?

I have considered getting a regular cap and drilling a bunch of holes in the
lower seal but I would prefer not to do that if possible.

Thanks for any help!

Bill B


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