Overheating

[cribbj]

The problem with electric fan setups is that people mount the fans directly to the radiator core and eliminate the plenum/duct between the fan & the radiator. Bad, bad design, because the fan is then only pulling air through that part of the radiator core where it's mounted. For a 16" x 31" Supra radiator core which is around 500 sq in, many people put on those tiny 2 x 11" fans from Fluidyne which cover less than 200 sq in of the core, so more than 50% of the core doesn't have any air flow through it, and they wonder why the setup doesn't work.

I'm running a single 16" electric fan with a 500 sq in PWR radiator core in my Supra, and I've had no cooling issues with it (yet) in TX. I left the OEM plenum/duct in place and the 16" electric fan fills that duct nicely and the whole system seems to work as well as the OEM engine driven fan. Plus it works better than the OEM setup at engine idle and creeping along in traffic where I really wanted it to.

David, your 2 x 16" fans cover around 400 sq in, so if your radiator is the same or similar size as the Supra, you're probably losing some efficiency by having those fans mounted directly to the core. You might think hard about spacing them back and installing a double plenum for them to pull through. I still kinda think there are other issues with your setup that you just haven't found yet.

John

 

[Lextreme II]

John,

So i should use a spacer between the radiator and the fan? About 1/2" be better?

 

[turboandrew]

John, what model fan is that? That's probably what I'll have to use on my Supra.

Also, FWIW, not all electric fans are created equal. Many have very low CFM ratings, and some do not rate properly anyway (they rate at virtually no pressure drop, etc). Lex, what model fans are you using? What CFM are they rated at?

 

[SCV8]

There's a corrosion issue with running anything but pure anti-freeze in aluminum engines, so don't look to using water as a solution either way.
The coolant isn't the problem, and if you use pre water, you'll have more problems.
The aluminum just turns to mush.

 

[Zuffen]

When mounting fans in a plenum or shroud you need to leave the back third of the fan blades protruding from the shroud. If you bury the fan in the shroud it will recirculate a percentage of the air.

Essentially you need a shroud that covers the whole of the radiator so it funnels all the air to your fan/s so when they operate they can't get air from anywhere but thru the core of the radiator.

I think part of David's problem is the location of the Turbo as it's adding heat load to the radiator core and restricting the amount of air the fans can draw. They definitely need a shroud. Combine all three problems and you have the answer/solution.

 

[chrisman]

i still think david may be having a head gasket issue under boost--excessive cylinder pressures.., or he could be lifting the head--which i doubt..
it sounds like he is loading the rad with the pressure and heat getting past the head gasket..
either way, straight water ,even under pressure, will boil sooner than the 50/50 mix recomended..
i think there is a way to test the water to see if it has any hydrocarbons or something from combustion in it.. but ive never used the test, so i cant eloborate..

 

[Lextreme II]

LOL... Chrisman... i think u r hitting the right direction.... I do see excessive water in my exhaust. I think perhaps my gaskets are loose.

 

[WDoherty]

Lex, i think it is dangerous to run straight water in the cooling system because it will simply boil. I think anti-freeze also raises the boiling temp. of the mix to prevent boiling, plus straight water is probably corrosive. Toyota Factory Red coolant is some good stuff!

 

[cribbj]

John, what model fan is that? That's probably what I'll have to use on my Supra.

Also, FWIW, not all electric fans are created equal. Many have very low CFM ratings, and some do not rate properly anyway (they rate at virtually no pressure drop, etc). Lex, what model fans are you using? What CFM are they rated at?

Andrew, I have the 16" SPAL. If you go with something like this, make sure you run at least #12 (#10 better) wire for it and a hefty Bosch 40/50 amp relay. This puppy pulls 60a when starting (as recorded by my peak reading Fluke), and 20 amps for normal running. I currently have the circuit fused for 40a with #10 wiring, but may try to lower that to 30a with a slo-blo type fuse.

John