High Pressure Radiator Caps - Opinions?

[-GT-]

My radiator cap is cactus, and before i go shelling out my hard earned i would like to hear a few opinions of my options. I'm considering getting a high pressure TRD one because my car sees fairly regular track days and i am wondering if they are worth it, or if its part bling part hype?

I have a search but haven't raised much in the way of useful discussions or experience. My understanding is that being higher pressure they will allow the system to build to a higher pressure before venting to the overflow, thus raising the boiling point of the coolant and allowing it to continue to work under the more demanding conditions of a hot track day, correct?

Is there any downside to these caps? I'm thinking like the lower temp thermostats that aren't suited to standard engines in normal road conditions because they don't allow the engine to get to designed operating temp?

I don't imagine the extra psi (i'm looking at the 127kPa, any idea what the oem one is rated to?) will cause big problems for hoses clamps etc unless they're already stuffed, i guess i'm more just wondering if they're a worthwhile purchase or if they're just for bling n brag?

[Draven]

worth 10rwkw maaaattteeee!
sincerely, 95% bling and hype, and the 5% of people that find it useful don't need to ask

[-GT-]

Yeah, figured it was a bit like that, only reason i'm considering is because at the last track day it overflowed once or twice, and i need a new one anyway. Its more for piece of mind on the track, but was just wondering if there's anything i'm not aware of.

Guess it will depend on the prices i find too, if toyota are going to try and ream me i might just bling it up. So, apart from risking being labelled a ricer there's nothing else i need to consider?

[Draven]

well personally I wouldn't buy TRD unless I had to, purely because having "TRD" on it immediately increases the price
a good generic rad cap would be my pick

[-GT-]

Cool, thanks, i'll have a shop around.

[CrUZida]

Raising the pressure in the cooling system will put more stress on everything.
You'll increase the chance of blowing a hose, or even the top/bottom tank (especially if they are plastic tanks)

[-GT-]

Yeah, that was about all i could see. But is it that big an increase? The 2 options are 18psi and 21psi, anyone know what the standard ones run? I can't find a reference. I can't imagine it being anything like a 6-8 psi increase, i figured maybe up from 15 or so?

[oldcorollas]

Yeah, that was about all i could see. But is it that big an increase? The 2 options are 18psi and 21psi, anyone know what the standard ones run? I can't find a reference. I can't imagine it being anything like a 6-8 psi increase, i figured maybe up from 15 or so?

yah, typically around 14 or 14.7psi (ie 1 bar)
older cars also use 7psi caps...
where it mighjt be of use is if you have cavitation problems or hotspots in the head causing bubbles to form... it reduces this slightly, but unless you have identified issues that require a higher fluid pressure.. there's not much point really.

why did you get overflow? overflow bottle not big enough? too full? the overflow bottle is an integral part of the sytem, so it also neeeds to be sized correctly (and positioned correctly) to work effectively... perhaps

[-GT-]

Everything is standard, overflow bottle, position etc. The overflow was after long sessions on a reasonably warm day, 10-12+ laps, noticed it had lost coolant out of the overflow overflow (if you know what i mean), checked radiator and it was down so topped it up.

I just figured it got a bit too hot and let off a little steam, but the radiator cap is the original one (ie 16+ yrs old) and it just doesn't seem to be sealing particularly well anymore. If the rubber seal is stuffed is it not holding enough pressure and just venting when it gets hot?

[RONA]

Just replace it with a standard cap, I noticed the corona was losing fluid, on long drives on hot days yet the temp never got above half. I replaced the cap with another genuine (new) toyota item, and it hasn't used coolant since in almost a year.

[oldcorollas]

Everything is standard, overflow bottle, position etc. The overflow was after long sessions on a reasonably warm day, 10-12+ laps, noticed it had lost coolant out of the overflow overflow (if you know what i mean), checked radiator and it was down so topped it up.

well, you have other problems then...

the way the system works is... the engine coolant systen is sealed, and when the fluid expands, and the pressure exceeds the cap pressure, fluid goes into the overflow bottle. that is normal.
upon cooling, when the fluid volume in engine decreases, fluid is sucked back from the overflow bottle by the suction caused.

if you have fluid in your overflow bottle, and it is up above the level of the suction pipe, but you still have air in the radiator, then you have problems. either your cooling system has a leak, and it is sucking in air instead of fluid... or you have leaky HG, allowing gas into the cooling system from the cylinders.

if your overflow bottle fills up and overflows when hot, but is sucked dry upon cooling... there's something seriously wrong.... perhaps....

have fun
Cya, Stewart

[mullett]

Yeah, hi-pressure caps aren't really worth it unless it's a pretty dedicated system. You can call Toyota, and they'll tell you the standard opening pressure (I imagine it's about 13psi). TRD release crap like this because there's easy money in it. And the extra PSI is just something to brag about for the people who buy it. Think of it as yet another shiny part for your engine, like braided-look hose covers. You should be able to get an OEM spec one from Auto One or similar for about $10. It might be worth getting your coolant tested by a shop to make sure your head gasket isn't on the way out (or more sinister), and while you're there do a cooling system flush and put some (GOOD) coolant in. Toyota Red is the best as far as I know, although it IS expensive. The cheap green Tecaloy stuff is junk, so is the SuperCheap crap. I think some of the more up-market tecaloys are OK, check Coventries for the full range.

RM.

[CrUZida]

Stock caps are usually 0.9bar, or 13psi as you said.

[EldarO]

Yeah, hi-pressure caps aren't really worth it unless it's a pretty dedicated system. You can call Toyota, and they'll tell you the standard opening pressure (I imagine it's about 13psi). TRD release crap like this because there's easy money in it. And the extra PSI is just something to brag about for the people who buy it. Think of it as yet another shiny part for your engine, like braided-look hose covers. You should be able to get an OEM spec one from Auto One or similar for about $10. It might be worth getting your coolant tested by a shop to make sure your head gasket isn't on the way out (or more sinister), and while you're there do a cooling system flush and put some (GOOD) coolant in. Toyota Red is the best as far as I know, although it IS expensive. The cheap green Tecaloy stuff is junk, so is the SuperCheap crap. I think some of the more up-market tecaloys are OK, check Coventries for the full range.

RM.

as per standard 7M troubles, my cooling system has been less that flawless...

The tards that redid my head put in some green shit for the coolant, although i have a brand spankers bottle of toyota red conentrate.. i probably should have given them the instruction to use toyota red :/

im kinda confused about how the cap works, i get the part where it builds pressure, compresses the spring, and opens the seal and sends the water to the overflow, however, im not really sure on how it sucks it back in, surely after its sealed, the vaccuum locks the cap more tightly...?

can someone please explain this to me, if you dont mind..?

Eldar.O.

[CrUZida]

Pressure build up, the cap opens, the liquid pours into overflow.
Pressure lowers, the liquid is sucked back in, the cap closes