SgtB

Go to autozone and see if It's a generic size. Shouldn't be more than $10

WarTowels

I had a problem with one of my Mishimoto radiators, the exact same scenario you described happened to me and my S2000. I contacted the seller, who contacted Mishimoto and I had a new cap sent to me within the week for free.

Re-bled again (maybe that was the initial problem but no way to know now) and it was perfectly fine after that.

-Towels

L()veMyS2K

Disclaimer: I am not an expert, and I need the advice of one- also sorry for the length of this.
I have a 2005 Ap2, stock, with 105k miles.
I replaced the Denso with a Mishimoto MMRAD-S2K-00 and supplied 1.3 Bar cap.
Replaced thermostat.
Once I placed the rad in, I poured in distilled water, and ran it to operating temp on level ground.
Drained water from radiator-ensured water was removed completely.
Poured in Honda type 2 coolant in, performed Billman's bleed precedure on level ground.
Everything seemed fine, heat from vents was hot,normal operating temp, no leaks,etc.
Drove the car around, heat stayed hot, operating temp stayed at 7 bars, but when I arrived home, coolant had spewed from cap, leaks no where else apparent.
After much internet searching i chose to use a cooling system tester.
The system checked out well, but cap lost pressure quickly and would not go beyond 13psi.
Contacted Mishimoto, and recieved a new cap, identical to the one i had previous.
Put it on, bleed system again on level ground via Billmans procedure.
Again, everything seemed fine, but alas coolant again spewed from new cap.
So i then realized that i should bleed again, but with nose of car slightly elevated.
Bleed system, and it seemed to have the best results i have had yet.
Heat from vents nearly burned my finger tips, operating temp stayed at 8 bars, and car seemed to run smoothly.
Yet, again i found evidence of leakage the next day.

My two problems are this:
Cap leakage
No apparent change in reservoir levels.

My thoughts:
Perhaps distilled water still in sytem, boiling, and causing this.
Air being introduced into system when at operating temp.
Replace cap with a 1.1 bar.

I want to put a 1.1 bar cap regardless, i have no performance upgrades, and use the car as a daily driver, so there is no reason for me to pressurize the system further.
So, please refer me to a cap that will directly replace the Mishimoto 1.3 bar one with a 1.1 bar cap.
I did go to Autozone, and asked to look at the Stant, 92-96 Prelude, 90-93 Integra, 01-05 Nsx, 88-91 CVX and Civic caps, but none of them seemed to match the Mishi cap, in the aspect of the length of the valve guide spring. The mishimoto was longer then all of these caps. Doesnt the lower seal have to mate with the bottom of the filler neck?

All in all, I am at wits end, and probably over analyzing and over speculating.
I just need some sound, straight forward advice, please.

Thankyou and those who read through this, haha.
-Daniel

CoolGuy094

tl;dr

But if you need to replace a leaky Mishimoto radiator cap, get a Spoon Type-F radiator cap from Go Tuning. Contact them on this site as they are a vendor; great guys and very responsive. Replaced my leaky Mishimoto cap with one and its been great ever since.

http://www.gotuning.com/product_info...roducts_id=547

myhui

Will a Honda OEM cap work?

Mine's leaking too.

boyguan

A oem cap from a different year will work. If you look at our eom cap its vey different than this one. I got one from a older honda civic that will work

My problem is that if you measure the inside lip of the radiator to the top part of the radiator you will see it is like 3/4 of a inch. The mishimoto cap is a tad taller than 3/4 when measured from end of seal to other seal. An oem cap measures a tad less than 3/4.

I am not even sure if the aftermarket cap will seal it against the base allowing pressure to form

Anyone able to chime in?

myhui

I've found that the Mishimoto cap is not air tight. So coolant can flow out into the catch can, but after driving home and parking the car overnight, as the coolant goes back to ambient temperature the catch can's coolant is supposed to be sucked back in to the radiator, and that doesn't happen. With the OEM radiator, that does happen.

boyguan

I had this problem and that's why my car always smells like coolant. I recently changed the cap with a Honda one but like I stated I don't think it creates pressure

myhui

Which Honda cap did you use?

boyguan

An older style civic cap. It's not tall enough which is the problem