Help - overheating 1JZ

[Riddler]

Hi all, I've just finished putting a 1jz into my ga70 supra, runs fine for about 30 mins of driving then overheats. I'm running a 2jz water pump and twin thermos. It seems tohave an airlock in it somewhere but we've tried bleeding it a bunch of times and no success.
Any help would be appreciated.

[EldarO]

park up the biggest hill you can find, and check whether you have aleaky heater hoses etc. etc.

alot of people overlook the fact that the 1J is a 15 year old engine, and the pipes you get in the halfcut are probably still original, they're fine in the halfcut, but take them off and mess with them and they crumble.

get a funnel, that seals properly with the top of the rad, park on a hill, turn your heater on full blast, start the car, put the funnel in the radiator, fill it with coolant, and let it run, rev it from time to time, and you'll see bubbles coming out through the water in the funnel.

the funnel HAS to seal properly otherise this doesnt work.

Eldar.O.

[Riddler]

Thanks, but we've already tried that one, looking over it again though, i found the hose behind the back turbo is kinked so I'll fix that and see what happens.
Does anyone know what the 10mm pipe right at the front of the water pump is for?(facing down)

[allencr]

Once its been run for a few minutes with the thermostat open and reved over 2500 rpm, it is very very rare to have any air that hasn't been pushed to the highest point.
How's the radiator?
Was the block flushed out? Sitting there drying out for a while causes
most to have a lot of flakes & sediment & smegma that'll go right to the
tubes & clog'em.
Look at the top of the radiator's core tubes through the radiator cap opening, and I think you'll see that many are closed off.

[EldarO]

Thanks, but we've already tried that one, looking over it again though, i found the hose behind the back turbo is kinked so I'll fix that and see what happens.
Does anyone know what the 10mm pipe right at the front of the water pump is for?(facing down)

the thermo fan hydraulics come out the front, although thats a pipe that has a rubber hose coming off it with a banjo fitting on it that connects to the back of the radiator fan, then a line goes from a connection under that to the hydraulic fan resorvoiur.

sounds like your hydraulic fan isnt running right...

Eldar.O.

[Draven]

since he has twin thermos, sounds like his hydraulic fan isn't running at all

[EldarO]

wow, i should pay attention

buggers me as to what that connection on the front of the pump is, but if it doesnt piss out water when ya cars running, i dont think it has anything to do with your problem!

Eldar.O.

[Whiplash]

do you have your thermos on sucking or blowing? most thermos are designed to suck rather then blow. that might be one problem.
2nd is your thermostat new or working?
3rd check for kinks in the water lines.
4th i know its summer but turn your heater on to open the heater tap whilst running the engine. this will allow water to flow through your heater core and take out any air locks within it
5th try taking half your coolant out and putting in a bucket. then turn the car on and whilst its ideling then start to fill her up slowly. grab teh bottom rad hose and squeeze them vigulously. that will force the water through the channels. keep going till you reach the top. once up top let it idle for while longer and you may see level drop a bit. top up drop squeez top rad hose too. ect. if that dont work and everything is set i have no idea what could be wrong. ive always dont this to radiators and never had a problem. give it a go.

[Soarer_D00D]

1. Get your radiator flow tested
2. Check for blocked thermostat
3. Check the direction the thermofans are spinning
4. Open heater tap, and allow engine to idle with radiator cap off until all bubbles have stopped, then top up with coolant.
5. If all else fails, get a TK test done (Checks for carbon monoxide in the cooling system (read: BHG)) at your local mechanic shop. I'm sure they wont charge much.

[Ribfeast]

Make sure thermostat is around the right way too.
But otherwise as above, especially check blocked radiator and thermos direction. Does it still overheat on freeway, or just town driving?

[lumpy]

Hi all, I've just finished putting a 1jz into my ga70 supra, runs fine for about 30 mins of driving then overheats. I'm running a 2jz water pump and twin thermos. It seems tohave an airlock in it somewhere but we've tried bleeding it a bunch of times and no success.
Any help would be appreciated.

Got the undertray back on?

Checked the radiator for flow?

Sure the thermos are switching on?

[Riddler]

thermos - on and both going the right way
thermostat - new geniune - checked - opens about right temp
radiator was fine with the 1g
doesn't the water flow through the heater constantly on A70s? with the ducting opened when you turn the heater on - what a mate said when reading a Haynes MA70 book.
undertray still off
I've only really been town driving
also we tried bypassing the heater

[thechuckster]

water to the heater is controlled by vacuum operated solenoid (it's not on 100%) and is mounted in the firewall on the passenger side. It's either open or closed and the internal unit mixes hot/cold air to do climate control.

The undertray is useful for proper airflow thru the engine bay - with it off, you will have reduced air flow thru the radiator (hence things will get warmer)

How long did the radiator sit while you were doing the swap? perhaps it has become blocked/gunked up since you last drove it?

dumb question - but thermostat outlet is going connected the top of the radiator?

[wilbo666]

Does anyone know what the 10mm pipe right at the front of the water pump is for?(facing down)

I'm under the impression that some of the JZ non hydro water pumps have a hose connected to the water pump check hole (i.e. water comes out of this hole when the water pump seal fails)...the hose is there so that the water doesn't go onto the alternator and stuff it!

Cheers
Wilbo