Header tank cap

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TONYT25T25
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Header tank cap

Post by TONYT25T25 »

Bought the following item from GSF as a spare after reading previous posts.  The part was the listed for my vehicle but does not pass the test shown on you tube where the guy blows through it and it makes a trumpet noise, is there any other form of test or has anybody got any views/experience on this  particular type I bought.
https://www.gsfcarparts.com/174vg0160
The current one fitted albeit a different colour has 2 circular apertures within the cap, I am wondering if this part from GSF does the same function.  Looked on Brickwerks but the image does not show the inside of the cap as a comparison.
 
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Aidan
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Re: Header tank cap

Post by Aidan »

do you have resistance to sucking on the spigot ? it only holds 1 bar of pressure, the quack test is a bit temperamental, obviously these are no longer available genuine and there are duffers about but GSF, JK, heritage, even Brickwerks probably pretty much all the same

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Re: Header tank cap

Post by TONYT25T25 »

Thanks Aidan, if i put the palm of my hand over the cap to make a seal and suck on the spigot it pulls my palm in removing my palm and sucking there is a little resistance but still allows air to be drawn. Blowing on the spigot has the same effect and air can be heard being expelled. 
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Re: Header tank cap

Post by airheadboxer »

Don't know if this is any help.

I got really frustrated when my old cap failed the testing initially and so did the new one until I found this post from CJH that sums up what needs to be considered when testing the cap and why so many seem to "fail"" (including new ones).


Re: Header Tank CapsPost by CJH » 13 Jun 2018, 17:38
Rob - what makes you say that it's no good? Is it that it doesn't quack, and that you can blow and suck through the nozzle? I had a new one that was the same, but I realised that the rubber washer that holds the valve in the cap will only seal when it's screwed down onto the bottle. Without that, I think air can get past the washer, and that's more likely I guess when the washer is older and may have shrunk a bit. So as far as I could tell, the suck/blow/quack test isn't conclusive unless you do it in situ, screwed down tight on the bottle. Goes against the common wisdom I know, but now that you've had yours apart, would you agree that it's only the tightness of that washer in the recess that would prevent air passing, but once screwed down the washer will compress and make a seal?

**End of post**

If you don't have a way of screwing the cap onto something to test, then I've found that by placing your thumbs on the top and placing two fingers from each hand underneath like pincers to hold the black valve disk in place you then perform the suck/blow test. Using this method both my new and old caps passed because the black valve disks were the loose type (this wasn't obvious initially) and this method kept them in place.

 
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TONYT25T25
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Re: Header tank cap

Post by TONYT25T25 »

Thanks for this, I think the test you highlighted relates to the original cap (currently fitted to my vehicle) this replacement one i purchased  only has a centre hole spring loaded (please see image on initial link).
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Re: Header tank cap

Post by TONYT25T25 »

This is the cap purchased from GSF as listed as suitable for my vehicle, as can be seen it only has a centre piece activated by a spring, my current one has two what appear to be valves.  As it did not pass the quack test but as mentioned above the quack test is a bit temperamental.  I am considering the following test.  Finding a suitable container (drinking bottle) filled with water which the new cap can screw tightly onto.  Then running a hose from it into a container full of water.  Squeezing the bottle to simulate pressure to see if water then goes from it into the container, then releasing the pressure by unsqeezing so pressure is released and see if the water is drawn back into the bottle.  Obviously the PSI cannot be tested with this test, so am I wasting my time, and in case have not found a suitable container yet.
Image
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TONYT25T25
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Re: Header tank cap

Post by TONYT25T25 »

Running with the same theme instead of starting a new post, still using existing header tank cap and ran van up to temperature today, engine running good and temperature good.  Engine idling and temperature at midway position/just past when fan kicks in and off.  Question is at what temperature/needle position does coolant flow from the header tank into the top up tank.  Monitored the top up tank but no increase in water level.
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Re: Header tank cap

Post by Mocki »

The coolant only "overflows" into the top up tank when it has expanded enough to push out of the header tank , and then only if there is enough coolant expansion to need to push out past the cap , basically water boils at 100°c unless it’s under pressure , then it boils at a higher temperature, not sure exactly what hat temperature is , but basically if the pipes in the engine bay are hard there should be enough pressure to let the coolant pass the cap 
about 1bar I think 
you are only going to see a tiny amount going into the top up tank, and back as it cools , less than half a litre iirc 
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TONYT25T25
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Re: Header tank cap

Post by TONYT25T25 »

Thanks Steve, left it running for a bit and no amount of coolant passed either way.  But only observed through inspection cover (number plate) will take engine lid off next time and check pressure on piping.  Not having any problems as engine runs and cools fine, just looking and checking to prevent any possible issues.
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TONYT25T25
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Re: Header tank cap

Post by TONYT25T25 »

Need to put this post to bed before I return the cap to GSF as suspected defective.  It is quite easy to both suck and blow through the nozzle of the cap, therefore leading me to believe that coolant can also pass thru to easily and not maintaining the correct pressure in the system, my concern is if that if true then even under a little pressure in the system before it reaches the correct level that coolant will flow from the header tank and overwhelm the top up tank, any advice welcome. image of item I am talking about below.

Image

 
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Re: Header tank cap

Post by Oldiebut goodie »

Did you have it screwed onto the tank when you tried the suck and blow testing?
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TONYT25T25
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Re: Header tank cap

Post by TONYT25T25 »

No I didn't,  I did push an empty bottle up against the rubber seal to simulate it fixed to the tank but it made no difference.
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Re: Header tank cap

Post by TONYT25T25 »

After re reading above responses and prompt by Oldie, I fitted the new cap to the Header Tank attached a bit of hose to it, did the suck and blow test and it worked ok, ie could not suck any coolant out or blow into the tank, so it does need to be on the tank to fully test.  So presume it works ok.
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