March 17, 2025, 05:43:42 PM

Author Topic: Mishimoto radiator leaking from cap  (Read 2937 times)

Offline Born-again 7

Mishimoto radiator leaking from cap
« on: September 22, 2016, 03:44:41 PM »
I need help with my Mishimoto radiator, I hit a tire on the freeway, damaging my old Hinson radiator. So i called on AAA to repair the car. I tried to get a new radiator from Hinson and Samburg, but had no luck. So i got stuck purchasing the Mishimoto radiator. It looks nice and fits well, but it leaks from the radiator cap. The cap on the AST tank is the highest point of the cooling system and seals fine. I have a 20lb radiator cap on the radiator and a 12lb on the AST.

The lower cap on the radiator leaks bad, despite its high 20lb rating. I tried two different high pressure caps on the radiator and they both leaked. My question to you is: does someone sell a radiator cap that does not vent off pressure? Im trying to avoid pulling off my radiator and having the filler neck welded up.
« Last Edit: September 22, 2016, 06:34:08 PM by Born-again 7 »

Offline Exidous

Re: Mishimoto radiator leaking from cap
« Reply #1 on: September 22, 2016, 06:49:52 PM »
Try a stant Lev r cap. Mines 18psi and never leaks. The radiator on the otherhand...
94 BB Sleeved gen IV LS7, MS3ProU with TC, RONIN 8.8 and LT's with custom 3.5"single to VAREX muffler.

Offline Born-again 7

Re: Mishimoto radiator leaking from cap
« Reply #2 on: September 22, 2016, 11:15:33 PM »
I will try the Stant radiator cap. Thanks for the suggestion. ...It sounds like a lot of people are having issues with their mishimoto radiators. maybe we need to jump on Samburgs radiator group buy.
« Last Edit: September 22, 2016, 11:24:54 PM by Born-again 7 »

Offline Exidous

Re: Mishimoto radiator leaking from cap
« Reply #3 on: September 23, 2016, 02:33:43 AM »
You can try to flatten(lap) the sealing surface with some wet/dry sandpaper and a piece of glass. Anything that's really flat.
94 BB Sleeved gen IV LS7, MS3ProU with TC, RONIN 8.8 and LT's with custom 3.5"single to VAREX muffler.

Offline Dvous

Re: Mishimoto radiator leaking from cap
« Reply #4 on: September 24, 2016, 09:08:57 PM »
It's funny I saw this tonight.  I cut off the filler from a brand new mishimoto rad I've got to modify it for a vertical/lower mount setup.  I was looking at the filler tube I cut off tonight and noticed they tried to tig around the inside of it and it looked like they distorted the sealing surface doing that.  Maybe that's your problem too.
'93 fd~black/orange, 5.3l, t56, 7875, HP efi, 4 pt, etc
'63 F250~95' F350 frame, D60, 12valve, zf 5spd, 35's
'51 Willys M38~350/4spd, otherwise all original
'72 FJ40 landcruiser
'03 2500hd duramax~ppe stg 5 trans, efilive tunes, etc, 600hp 1000 ft lbs - daily
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Offline Born-again 7

Re: Mishimoto radiator leaking from cap
« Reply #5 on: September 25, 2016, 04:40:39 PM »
It looks the cap mating surface is slightly distorted, probably from the welding. I just got a phone call from Justin, he's ready to make another batch of radiators. Im just going to wait for Justin's new one to arrive. Thanks for all your help

Offline Exidous

Re: Mishimoto radiator leaking from cap
« Reply #6 on: September 28, 2016, 04:46:59 PM »
If it's just warped sand it down a bit.
94 BB Sleeved gen IV LS7, MS3ProU with TC, RONIN 8.8 and LT's with custom 3.5"single to VAREX muffler.

Offline sunshine

Re: Mishimoto radiator leaking from cap
« Reply #7 on: October 04, 2016, 10:19:57 PM »
do you have any pics of this radiator/setup?
im curious to see how it looks in the engine bay and curious if you fixed the issue?