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Thermostat/Filler Neck Housing Cap

Old 01-23-08, 03:43 PM
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Thermostat/Filler Neck Housing Cap

This is pissing me off juuuuust a wee bit..

Mine is leaking. I discovered it while changing my oil today. I took the cap off, cleaned the rubber gasket and re-installed it. Ran the car and didn't see any leaks. Closed the hood, came back a few hours later and there's a bit of coolant under the cap. This just makes me angry...

I looked on Mazdatrix and found the cap I need. It's the 'flat cap'...but they want $20.00 for it NOT including shipping! What in the living hell?

So my question is, where is an alternative place to find one of these things...I dunno...cheap?
Old 01-23-08, 03:51 PM
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well, the cap plays a key role in your coolant system, so i wouldn't look for cheap. . I had the same problem, and I learned that once the car starts getting up to warm temps, the coolant actually expands, creating pressure against everything and anything to do with the cooling system. If your caps bad, then it won't be able to handle this pressure, and leak. I'd look for an OEM replacement. I found one that wasn't stant (the company's name is japan or something like that), and it's an 18 psi OEM part. Works perfect. No leaks, so now i'm on tho the next problem on my list. .lol
Old 01-23-08, 03:59 PM
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I mean, I can afford $20 plus the shipping but if I can find it cheaper (Which I haven't yet) that would be great. I checked Atkins and ebay.
Old 01-23-08, 05:33 PM
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Go to the local auto parts store and get a Stant cap.
Sprung...unsprung...doesn't matter.
I think these "import" Stant caps are like $10 / each.


-Ted
Old 01-23-08, 05:38 PM
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Ted,

My friend bought one of those and he said it leaked still. Something about the spring thing ***** it up or something. Have you used these with no problems?
Old 01-23-08, 05:58 PM
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Funny thing is that I have the same issue. I tried several parts store flat caps and pressure caps with the same result: coolant seepage. Next time I'm at the dealer I'll pick up a "Mazda" cap and see if it changes anything...or maybe just weld up the damn hole and add a fill valve...
Old 01-23-08, 06:01 PM
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just get the oem one , dont skimp around for one that you know it might leak
Old 01-23-08, 06:25 PM
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Originally Posted by Acesanugal
Ted,

My friend bought one of those and he said it leaked still. Something about the spring thing ***** it up or something. Have you used these with no problems?
Yeah, I'm that friend and it leaks a small amount. Nothing that worries me, but I know I need to fix it.

Another option would be to get a series 5 neck, because they dont have the cap... unless they really are plastic like you just told me on the phone Collin. Then, I'm clueless. Maybe just perm. block it off like Aaron said...
Old 01-23-08, 07:13 PM
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I've used the sprung cap on a non-sprung application with no problems.
True, Stant has a bad rep for quality, but I just return them and pick up a new one until the bitch seals.
So, yes, it's not surprising the Stant cap leaked.
Sometimes, the "ears" are not bent correctly, so I just bend up more to get a better seal.

It shouldn't matter if you're using a regular cap or a sprung cap.
The filler thingy is all toleranced the same with or without the bypass fitting.
So, a sprung cap should sit the same whether you have a bypass or not.


-Ted
Old 01-23-08, 07:14 PM
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Thanks, Ted.
Old 01-23-08, 07:14 PM
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Mine leaks because of a tiny hairline crack in the plastic neck, rather than any problem with the neck itself. Some of the seepage problems noted in this thread might, maybe, possibly, be due to a similar crack.?

Ted, one of my favorite things on this site is always the lovely, tastefully dressed young lady in your avatar of the week. I can never decide which one I like best.
Old 01-23-08, 07:16 PM
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Plastic neck? S4 car... Metal. There's actually a crack/break in the rubber gasket on the cap I have.
Old 01-23-08, 07:36 PM
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Originally Posted by buttsjim
Mine leaks because of a tiny hairline crack in the plastic neck, rather than any problem with the neck itself. Some of the seepage problems noted in this thread might, maybe, possibly, be due to a similar crack.?
This is why I use an FD one.
Cast aluminum FTW!


-Ted
Old 09-04-09, 07:54 PM
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yes old thread.

I have the same issue i changed the car and put an 13lbs cap with a spring and that seemed to not work at all! stiff leaks. now i changed it back to a flat cap. bt now im getting seepage where the small sensor on the stock raditor(the pastic topd) as well as alitle on the front radiator cap? any help would be fine i was gonna get another radiator or thermostat...
Old 09-04-09, 08:40 PM
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its an s4 gxl with the plastic/metal stock radiator....
Old 11-16-18, 05:15 PM
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Help?

So im looking for the cap piece that bolts on to the t-stat housing. Mine is cracked, someone had previously jb welded it. Which was dumb on their part, but im having a lack of heat issue, like no heat at all. Just tore my whole dash out to replace heater core. Still no heat so chances are the combination of it being cracked and possibly the t-stat being stuck open are the culprits. BUT.... I cant find it any where, autozone, orielys, advance, car quest and a hand full of foreign and import part stores can't even order it, the mazda dealership retired both the neck and the cap. Soo where can I find one?. I prefer a metal one, atkins has one but it has a nipple on it which mine does not. And its plastic. Help me out

Thanks!!! Zoom zoom

Old 11-16-18, 06:29 PM
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Mazdatrix sells the cap assembly (Radiators, Caps, Water Level Sensor).
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