2JZ Radiator Flow?

[sbyder]

Just installed a new alloy radiator and thermo fan into my aristo. The issue is that when i go for a drive, the temp gets up to 105degrees very quickly then will slowly rise from there(the temp sensor is in the top radiator hose). I have bypassed the temp switch for the fan and just got it running on accessories ATM to rule out the switch being at fault.

Which way does the water flow through the radiator? I assumed it went from the radiator top tank into the motor, through the engine, down through the thermostat and back into the bottom of the radiator. Is that right? Or is it the other way around?

I have felt the bottom tank and its stone cold but the top tank is excessively hot. My prime suspect is the thermostat, even though i just checked it and resinstalled it during my flush out with new coolant.

Im gunna rip it out and inspect anyway. In the meantime, any ideas of what else it could be?

Ben

[2jzhilux]

other way round man
hot water comes out top hose

[love ke70]

like ecotech said, cooled water exits bottom tank into block, through motor, through thermostat into top hose, into rad, down rad, into bottom hose etc.

which way is your thermo fan blowing, (put peice of paper in front and see if it sucks in or blows away. it should blow into the engine bay)

[roadsailing]

water flows down a radiator, in the rad at the top and out the bottom.

check that your thermostat is working, easy to do just chuck it in a cut down coke bottle and pour boiling water on it, or heat it up in an old saucpan.

could be a blocked radiator also

[sbyder]

Just pulled the thermostat out, tested it and its working perfectly.
Its a brand new alloy racing radiator, so its not clogged or anything.

It might be that the thermo fan is not strong enough to keep it cool. Its a 16" ebay job, meant to flow 2750 cfm. Heres a pic of the new fan in the shroud and the radiator.



Maybe i should convert back to the twin thermo's i got from a ford corsair...

[2jzhilux]

you want the fans to be sitting on or close as the radiator
where it is there with that fan wont do shit

is there a gap between radiator and fan

[love ke70]

wats it like cruising for 15 minutes? 60km/h if you can do that, or on the highway is prob better for a clear run. does the temp still rise?

[2jzhilux]

also dont know whether you know but when your system is pressurised the boiling point of your coolant is actually raised to about 110 degress c

[sbyder]

had a thought.

If the radiator is really really good, the thermostat would open when the engine gets hot enough (82degrees), then as soon as the cold coolant hits the thermostat, it starts closing again, then opens once its hot again....then closes.. etc...

This is how its meant to work, but i think it might be doing it too quickely.

The thermo is sitting right next to the radiator core, the pic doesnt do it justice. Keep in mind that the bottom of the radiator is VERY COLD, so it must be cooling pretty well. The top tank gets around 105degrees and the bottom is around 30-40 degrees.

I have a blitz cap, so my boiling/overheating point is a lot higher than stock. 115-120 i was told.

The temp would go up whenever i increase rpm. If i went to 4K, then it would increase and stay there until i got boost or increased rpm again.

Well Ive reinstalled the thermostat and now im going for a drive. If it gets hot again, i'll throw the other thermos on and test that.

Ben

[sbyder]

Went for the drive. Got up to 110 and stayed there. Speed up to 70, slowly, and it stayed there. Pulled over, carefully popped the cap and topped up the fluid. Temp when down to 80, then rose to 110 again whislt at idle. Drove home and of course, steam started coming out of the overflow bottle.

Symptoms are: When engine gets hot, radiator gets hot then lets off steam. The bottom of radiator doesnt get hot at all, still very cold to touch.

The causes can only be a few things.

1. Radiator
2. Thermofans
3. Thermostat
4. Water pump

Radiator is brand new, thermostat tested fine and water pump is near new.
I'll swap the thermos over now, and if that doesnt work, i'll take out the thermostat tomorrow and drive without it. Any other ideas?

cheers
Ben

[oldcorollas]

take out thermostat, drill a... 2 or 3mm hole in it so some water can get thru... maybe bigger maybe smaller.. need to experiment.. then put temp sensor after the thermostat.

if the thermostat seals, it will open and close. i've seen it before on gauge..
after drilling hole, the temp climbs a bit sslower on startup, but stays much more steady during operation, as there is always a small flow thru the engine.
if hole is too big, then the motor might stay too cool at highway speed, but if that happens.. get another thermostat and use smaller hole

[sbyder]

thanks for the tip, and even though it may work, im after a reason that its doing this.

[oldcorollas]

what you said. water cools too much as it goes down, then closes thermostat.. takes ages for the water to warm up at the thermostat, and by that time the water in block is boiling...
when the engine is warm and the thermostat is open, there is a nice system where water stays warm.. but when warming up.. or if radiator is just too efficient, then the thermostat will close all the time.

if you have an old thermostat, drill a hole in that, like 4 or 5mm... and just see if there is a difference.. or buy a shit thermostat.. or.. even just get a flate plate, for testing purposes...


you do need to block off the gap between fan and shroud, as the shroud is doing nothing.

edit, if you have the ability, check the temp on the radiator side of the thermostat. that will tell most of the story i think.

edit2: on a K motor, the thermostat is after the head, so it still responds faster.
in your case, it responds to the water out of radiator... which is technically a better way to do it.. but if water is too cold.. thermostat stays shut.. and if it sels or doesn't allow flow... it's not gonna warm up.. so problem is not lack of cooling, but too much cooling

[sbyder]

I agree.

So i recon ive got 2 options, either drill out this thermostat (i have a spare) or buy a low temp thermostat. Maybe 70degrees? Thats if they even have one that low.

Cheers for the help, i knew it was something to do with the radiator being too good.

EDIT: ive seen a few brand names (SARD, SPOON, etc...) stocking 68°C thermostats for other vehicles, so I might try and find one locally, or see if superheap, autobarn or repco has anything suitable.

Thanks again,
Ben

[roadsailing]

i dont think it has anything to do with the radiator being too good, so don't go thinking thats it.

just systematically check everything. if your thermostat isn't working at 80 degrees (or whatever) why would it work at 70 degrees?

i have gone through a lot of issues with my thermostat (was broken and stuck open) and understand that a themrostat isnt an on/off switch, it controlls the temperature of the water.