Does anyone know the source for a 7 psi radiator cap that will fit my thick Koyo radiator (same cap style and size as stock I think)?

I'm not sure if the "standard" caps in online shops made for domestic vehicles will fit so if you know the answer to this question, that might be helpful also.

I'm currently running a Greddy 127 kpa cap, which is ok, but not optimal for running Evans (makes it harder to auto bleed air for example since it has to get really hot before it opens). It doesn't look very easy to get the spring out of there either to run 0 psi. Besides which, Evans recommends a few psi to prevent moisture from getting into the system.

 

I have been looking as well, with no luck. Alberto said he is using an FD RX-7 cap, but I have yet to track one down and see how much pressure they have. Let me know if you find one and where you get it.

 

old bump for any new info?

 

subscribing for this info as well...

 

I looked high and low and then just gave up. I did trace coolant pressure and it takes a surprising short amount of time (like 5 mins) to build 18 psi (running Evans). I figure it doesn't really matter whether I'm running 7 or 18. Fact is that Evans won't ever blow a hose off since it cannot form steam.

EDIT: Unless the hg lifts of course.

 

I was told by Ray @ PFS I have an FD mod'd cap that is essentially a low pressure cap now-I dont believe it started life that way but I could be wrong. Id take pics of it inside and out but I doubt I'll be near my $hitbox anytime soon.

I dunno if this would help or work for you guys still interested.

http://www.thunderracing.com/shop-by...-Caps_614.html

 

ya I saw those 7psi caps but didnt know if they fit our radiators. I guess a better question is what kinda cap do we cross reference with. Could we just cut the spring on the stock cap?

I dunno if I wanna use Evans over just 50/50 yet. I'd have to flush the heater core and maybe the radiator to get rid of any residual water. But that Evans flush is 30$ a gallon, then another 120$ for the NPG+

 

You need to buy the "small" cap. I tried a random 7 psi cap off Amazon and that won't work - designed for domestics.

str8dum1, I think the Evans is worth it. Can't you just dry out your heater core and radiator? Why flush with the new motor going in?

 

Ok guys I run a R35 GT-R cap, they have two rad caps, I did PM Raj the number a long time ago maybe he still has the part number or I can look and see if i still have it.

Anyway the cap that is closest to the engine on the R35 has no spring/no pressure. I had to trim the tabs that hold it to the rad slightly to get it to fit. This may not be required on all rads but the PWR rad I have it was required it took about 2min with a dremel to trim them, very easy.

As Alberto said RX-7 caps also do not have springs but I don't have that part number.


***edit*** i looked back i never PMed Raj the part number!?! But I also remember looking back at my PMs that an FD cap fit my car. If anyone wants I can get a picture it is basically a cap with a rubber ring on the bottom and no spring.

**edit added pics**









I found some R35 pictures it was the cap closest to the engine not the resevior.

 

Good work/find!

 

http://www.courtesyparts.com/kb_sear...7930_7954_7957

$12.83
part # 21430M cap assembly filler.

 

Why does the GTR use no spring on that cap? I could understand on the reservoir tank, but why keep the reservoir tank pressurized and the rest of the cooling system open to it instead of the other way around (the way we all do it)? I presume there is some spring on the reservoir tank to allow the system to hold pressure.

 

ya thats just a filler, like your overflow tank i assume. the reservoir is pressurized. That cap is actually called the radiator cap, compare to the no spring cap filler.

fords and other cars pressurize on the reservoir as well.

 

Is this a 0 pressure cap or just low pressure?

I've running Evans in my Z for 2 years now. For those of you on Evans as well, have you noticed that in the Winter when you turn on the heater that the air is extra hot? In other words, my temp control doesn't really work.

I can set it all the way counter-clockwise (temp off) and it's fine. But the moment I turn it a hair up to warm up my feet the incoming air is really hot.

I suspect because Evans removes more heat from the engine, yet it doesn't get rid of heat as quickly (from itself) as 50/50 my heater core is a lot warmer?

So yes with Evans, the engine does run a bit warmer than water+WaterWetter, or 50/50 mix. But it doesn't boil till about 450F degrees.

 

Zero no spring at all on it, all it does is keep the coolant in your rad.

 

so if Evans requires 7psi, how is this 0psi GTR cap of use?

 

it can use 0-7psi.

realistically on a street car, the stock cap is just fine as well as per Evans.

 

do you guys run no thermostat with your Evans? crunch time to decide if I want to use it or not.

With a new motor, do you guys still flush the radiator and heater core? The radiator should be pretty dry but the heater core might still have stuff since theres no way to really drain it....

 

I run a thermostat and I took an air hose and blew out my heater core. Seemed to work fine.