Jok3r

Baught another sc300 for a project. But I want it to run with no hick ups before modifying.
It's a 94 sc300 2jz ge. Guy says the water pump and radiator are relatively new. I'm guessing it had overheating issues and replaced parts with Chinese crap. Problems weren't fixed and sold it to me cheap.
It runs good on the freeway for an hour easy. But going 30mph-ish uphill it goes to 3/4 up on the temp gauge. (Normally at 1/2). When I pop the hood, there is a small amount of water coming from the large radiator metal cap, (says he replaced it with a cheap one). But it mostly seems like water is coming out of a smaller cap just in front of the main cap. Looks like a line/hose going in front of the radiator and into te he radiator. Should I replace the Chinese delco with a mishimoto? Or will that not solve that line leak??

KahnBB6

iTrader: (5)

The radiators to use in these cars are the Denso #221-3118 OEM replacement radiator, or with a little radiator mount modification a Koyo aluminum Supra MKIV aluminum radiator with an external transmission cooler added. Or a Mishimoto MKIV Supra aftermarket radiator with similar rad mount modification. I can link you to the thread detailing my Koyo radiator installtion showing how to do all of that.

However the easiest drop-in solution will be the Denso #221-3118 OEM replacement radiator. Denso is the original equipment supplier for the SC300. Also you want to check the radiator hoses for suppleness. An OEM Denso radiator cap (from Toyota or Lexus) is what I would use with that radiator. These cars need to have their cooling systems burped properly so all the air bubbles must be gotten out of the system when doing a coolant flush. I recommend Toyota Pink 50/50 coolant.

I am not aware of a "Chinese Delco" radiator option for these cars but if such a part exists no I would not use it. Denso all the way. Or going aftermarket, just Koyo or Mishimoto (MKIV Supra spec radiators that you will have to adapt).

If the radiator does say Denso on it that I would immediately go to troubleshooting the cooling system for air in the system. If it's not that and if the radiator is some off-brand junk I'd replace it with a proper one.

Additionally, and this may seem to be a silly question but... does the radiator still have its factory shroud, including the little removable lower curved section that completes the circular enclosure around the mechanical fan? And does the mechanical fan spin freely with the engine OFF or is there resistance when you try this test?

Jok3r

So the lower half of the curved section of the shroud is missing. The fan spins but has some very slight resistance. The radiator has a cheasy sticker that says " DENSO 41811. 221-3118 MADE IN CHINA" on the top center of it. And the coolant is milky white. I'm most likely gonna replace it with a koyo.
Can you please send the link for your koyo and possible part #. Thank you.

KahnBB6

iTrader: (5)

It’s still a Denso part. As long as it’s the multi-core radiator specified for the early SC300’s it should have been fine. It’s possible there is a defect but Denso stuff almost always holds up.

Koyo makes an OEM style replacement radiator for the MKIV Supra as well as the fully aluminum variant. I chose the latter.

Here’s the DIY thread I made detailing how to install one in an SC300:

https://www.clublexus.com/forums/per...0-5-speed.html

The extra provision in the MKIV TT style radiator shroud is for an additional TT specific electric cooling fan which you would have to find used as a fully assembly. The motors in those are a common Toyota part however and can be serviced if ever needed.

Since the SC300 doesn’t use any additional cooling fan from the factory I wired mine up using a Mishimoto 25A electric fan relay controller with override function.

Technically unless you are experiencing awful summer heat which taxes your A/C system’s efficiency you won’t need it. This only happened to me a handful of times in SoCal. However with any turbocharged JZ engine I feel it’s very worth it to have that auxiliary fan.

In your case it will be optional.

Here’s how I wired up the TT auxiliary fan with my GTE swap:

https://www.clublexus.com/forums/bui...l#post10241327

In the case of an SC300 it may be easiest to allow the Mishimoto coolant temp sensor to handle any tripping of the auxiliary fan for overly hot conditions and simply wire up the override wire to a manual switch in the cabin. How I wired mine was to trigger the extra fan on any time the A/C mag clutch was energized.

The Supra TT uses a somewhat complicated twin relay and sensor-switch system which is great engineering but not so easy to replicate in an SC with the slightly different A/C system that we have. To me the way I did it is just fine. That fan motor is a heavy duty cycle unit that also cross references to certain Prius model years. It is made to handle a lot of use.

Again... this will be optional in your case when going with a Supra TT Koyo radiator.

.......

However before you do all of this I would totally be sure it is that Denso radiator that is at fault. At the very least I think you need a coolant flush.

Additionally and far more glaringly you need to be sure you don’t have any other kind of leak, especially a potential head gasket leak. Rule that out as a possibility anyway.

First thing, flush that coolant totally with Toyota Pink 50/50. And replace the radiator cap with a new OEM one.

Then see if the car still exhibits the same symptoms. And on a morning when the car has been sitting overnight and is totally cold, check under the radiator cap for any milky fluid. There should be none at that point.

Jok3r

Ok I will try to flush the system completely and refill. Got a new oem cap on order. I believe the small cap on front of my rad cap is the trans cooler cap. Has an H on it and is about the size of a dime. It seems to me spewing water aswell. I know the trans itself is toast. No power in first. So maybe it is overheating the whole system.
Thanks for the great info.