Aftermarket Radiator Caps

Breza · Post by **Breza** » Mon Mar 08, 2004 10:27 am

Hi Guys (and Gals)

I was hoping someone technically minded could help me.

Can fitting an aftermarket radiator cap witha higher pressure rating be detremental to our poor beloved FTO's?

The reason I ask is I fitted an Apexi radiator cap for a touch of "Rice" to my FTO when I fitted my Apexi Pod and a week later my Heater Core has dropped the contents of my cooling system in the passenger footwell.

I know the two are probably linked but if I go to the expense of having another core fitted what are the chances of the same thing happening again?

Cheers

Chris
blk_fto

dannyboyau · Post by **dannyboyau** » Mon Mar 08, 2004 11:19 pm

they are linked

if you use after market cap you should make sure the pressure rating is the same

Hellsmurf · Post by **Hellsmurf** » Mon Mar 08, 2004 11:33 pm

Ruchi will probably go into far more detail than me with this

, but here goes:

As far as I know the radiator cap is sorta like a fuse in an electrical system - if the conditions exceed a certain limit (ie a high temperature) then the cap will let off steam and safely bleed off the high pressure. By replacing the radiator cap with an uprated one you have probably made the hoses in the system the weakest point, so one of those would give out before the radiator cap when stressed.

The reason they use the uprated caps in motorsport is because they uprate the whole system, hoses and all, to handle higher pressures.

In short, one of the radiator hoses probably gave out because the system tried to run a too high pressure, as dictated by the radiator cap.

hope this helps.

Hellsmurf · Post by **Hellsmurf** » Mon Mar 08, 2004 11:40 pm

lol having re-read your original post though, all of my last post assumes that the radiator cap has a higher pressure rating than a standard one, and is NOT JUST for rice...

you might have to check with the manufacturer to see what pressure it holds...

if its the same pressure rating as standard, then i really have no idea

ruchi · Post by **ruchi** » Mon Mar 08, 2004 11:59 pm

lol!

you gave a really good answer Hellsmurf, so there's no need for me to go into detail (sigh of relief is heard coming from some

)

In short, the radiator cap is a pressure release valve and works just like a pressure cooker does.

Hellsmurf · Post by **Hellsmurf** » Tue Mar 09, 2004 12:23 am

ok Chris, a quick search turned up this Apexi radiator cap, from Funky Products...

http://www.funkyproduct.co.uk/searchpar ... mit=Search

Assuming its the same one as you have, then it does hold a higher pressure than the original, and this is your problem.

If you want to keep the aftermarket radiator cap, then when you are replacing your radiator hoses (which are what would have originally broken), get the mechanic to fit uprated ones to hold the higher pressure (reading off the Funky Products site, at least 0.13MPa [1.3kg/cm2]).

Replacing the hoses will also give you the chance to add more rice to your underbonnet

, if you buy coloured or stainless steel braided hoses.

HostileSmoker · Post by **HostileSmoker** » Tue Mar 09, 2004 2:09 am

Reading this with great interest as I was about to buy a 'ricey' aftermarket rad cap...

Does anyone know what the standard FTO rad cap's pressure rating is?

Also, I've got the Samco replacement coolant hoses on their way (the 3 main pipes) but are there just these 3 pipes & the heater matrix to consider or anything else as well?

ruchi · Post by **ruchi** » Tue Mar 09, 2004 9:11 am

According to the FTO technical manual, the standard radiator cap has a range of 74-103kPa.

The cap which Hellsmurf found at Funky is 0.13mPa or 130kPa, so its pressure level is around 30% higher

Without going into detail, and without doing all the maths, lets just say that this higher pressure cap would mean that both the pressure and temperature within the cooling system would be much higher.

Interestingly, it would seem that most of the aftermarket "performance" radiator caps are around 130kPa, and none of the websites they are listed on, have any warnings or recommendations about making any other changes to the cooling system. Perhaps the existing system should be able to handle it, or perhaps they expect you've already made changes? I'm not sure about this point, anyone else know?

Breza · Post by **Breza** » Tue Mar 09, 2004 9:30 am

Hi Guys,

Thanks for the info, Yep it's the uprated Apexi cap.

The cooling hoses are fine it's just the heater matrix that shat itself.

But I suspect it was in poor condition in the first instance due to the amount of corrosion that came out on my hand when digging around under the glovebox/centre console. Guess this all comes down to how the car was treeated by the previous owner in the land of the rising sun.

For piece of mind I think I am going to get my new (2nd hand) heater matrix tested to see if it can handle 130kPa before I get it fitted.

Hopefully cooling won't be to much of a problem anymore I am moving back to Tassie in a couple of weeks. No more 41 degree QLD weekends.

Cheers

Chris

GPXXX · Post by **GPXXX** » Tue Mar 09, 2004 12:09 pm

note to self - keep the std radiator caps on my car.