1JZ coolant flow issue

[Maverick]

So I just put a jzx90 motor into my cressida and have got it running (barely), however since the body loom plug pinouts are impossible to get I haven`t wired everything up yet and so have no working temp gauge.

The problem I seem to have is the coolant seems like it is not circulating through the radiator (although i`m not 100% sure this is the case) - all hoses are free of blockages, and I replaced the thermostat, but when the engine is running, the coolant doesn`t seem to be running through the radiator, i.e. the top tank gets really hot and the core stays pretty much cold, (the first radiator blew the top tank open after 20 mins of sedate test driving!) I haven`t taken off the water pump (the hydro fan type) yet but it rotates freely and smoothly, and there is no evidence of any corrosion inside any of the alloy engine coolant piping... I`m thinking either the water pump is history, or the headgasket is blown and it`s pressurising the coolant system, however I believe the latter is unlikely as the car is not lacking any power compared to the last couple of 1j cressida`s i`ve owned...

Before I do anything else I will sort the wiring so the temp gauge works, and hopefully do a compression test tomorrow, but In the meantime has anyone ever had a similar issue? anything I could be overlooking?

JT

[slidn_ways]

Sounds like the thermostat might be backwards. And get the radiator reco'ed

[Maverick]

radiator is almost new and flows fine - the thermostat can only go in one way too....

[Draven]

it's not uncommon in 1JZs (well, at least I've heard of it happening) for the fins on the water pump to disintegrate, so externally the pump looks and works fine, but there's nothing left inside to move water.

Once you've double checked the thermostat,I'd be pulling the water pump for sure.

[TRD-12A]

Yaeh i've seen it heaps on the 1j's and on 1uz's aswell the waterpump impeller disintergrates and obviously the water is'nt flowing cause there is nothing there to push it around.

i Know you said it's a new thermostat but just make sure it's not jammed up or something stupid otherwise pull it out leave it out and then check if there is flow if still nothing then pull off the water pump.

[matty12]

check heater hoses for heat aswell,it can be useful when tryin to diagnose a corroded impellor if they are not hot.

[LeeRoy]

Also worth mentioning is that when you open the radiator cap it steams or smokes.

Possibly exhaust in the cooling system or air being cooked and pressurised. Obviously is the water pump is cactus the air won't be able to be pushed out will it?

[Maverick]

Problem fixed - It had a small air leak in one of the heater hoses, car now runs at the right temperature and the hoses don`t pressurize much... yay

thanks for the help people