20v cooling issues

[JustenGT8]

OK the 20v in my clubbie is doing silly things RE cooling and i'm trying to figure out why.

The builder has just used the original inlet/outlet off the back of the head with lines running to the front...no drama there, been done hundreds of times. The heater core pipes have also been looped rather than blocked off.

The problem seems to be the thermostat not opening. At idle you can feel the hot side plumbing from the engine to the rad is up to temp and the thermofans will kick in.... but, the cool side from the rad to the engine (thermo housing) stays cool...no flow cool. The temp gauge is plugged into the thermo housing and almost never gets above 50 deg?

What I think might be happening is all the flow is going thru the heater core bypass so the thermostat doesn't see enough hot coolant to open? The engine hasn't actually overheated and if you give it a decent blatt on the road the temp will start heading past 50 deg but then quickly drops back...i think the thermo might start to open and temps drop back again?

The engine smells hot, so while it's not over heating i suspect its running hotter than it needs to and the thermofans are nearly always on?

OR, i'm overthinking it all and the thermostat has just seized?

Track day this Fri and a bit nervous running it in it's current state. A quick fix would be to just pull the thermpstat i guess? thoughts?

[1JZ-Rolla]

start with thermostat, go from there

Does it have a remote thermostat housing, or has an early bluetop AE86 style water pump & housing been fitted?

[trdee]

Chances are the thermo is seized partially open or something. Also, is the temp sensor in the factory position or some custom thing? When I ran my water to oil cooler on the cold side of the radiator circuit, I found that the temps sat in the 50s all the time, so it could well be that the temp gauge has been put in "Cold side" of the coolant circuit.

Running my 20v with the heater tap fully flowing doesn't affect the engine in the way you describe. Also of note is that even after putting a new thermo in, my 20v doesnt seem to heat the coolant up as much as the old 16v did. If left idling, the thermostat doesnt really ever seem to open. It probably is opening but only by such a small amount that the return hose doesn't feel like it ever gets hot

All vague answers I know... sorry I couldn't be more helpful

[JustenGT8]

Hmm could be Vito but the engine has the hot smell which is one thing that started me investigating.

the temp sender is on the cold side of the thermo, but so is the factory one so it's just in the stock position?

[trdee]

Really? I'll have to have a look at exactly where the temp sender goes on the housing on my motor, but I figured it would have tapped in to the hot side.... From my experiences the cold side of the coolant line is very cold. Learnt it the hard way when I put my water to oil cooler on the cold side of the radiator lines and found my oil temps never went above 55deg even after an hour of driving (that was when i was still running the 16v)

Ima jump on toyodiy and have a look at the coolant routing now...

[JustenGT8]

Here you go



Hmmm multiple sensors but all from the same void once the thermostat is open?

[JustenGT8]

Does that sensor to the cluster interact with the ECU at all? Obviously i have no stock cluster anymore so perhaps i could use that port and ditch that stock sensor?

[trdee]

cant be the same void as you have the heater core in/out lines there. they would fuck with the flow if that was the case. chances are if you pull that housing off you will find they are separate galleries, with all the sensors being on the hot side/bypass

the thermoswitch for the fans is in the right spot as you want it to activate when the cold side goes above 82deg. the aw11 uses a dedicated thermoswitch on the cold side of the radiator

[trdee]

like-a-dis. thank you google images

[JustenGT8]

So, comes in to thermo housing (BTW my thermo switch is on the radiator, hence it's on nearly all the time currently) and enters which port?

I reckon i'll switch the temp sensor to the cluster sensor port and see what happens

[trdee]

i assume it comes in behind the thermo and when the coolant is not up to temp it bypasses back through the heater port where the coolant temp sensors are. otherwise the coolant temp wont be accurate. i can take the water housing off my motor and look at it properly but i dont want to fuck with it again after only just redoing the thermostat let me have a look and see if google can shed some light

[JustenGT8]

Yeah that's cool Vito, don't mess with anything.

I'll reloacte my temp sesnor and should get a clear picture of coolant temps from that.

My bad for assuming former owner had a clue

[trdee]

So is the temp gauge sender in the spot that is marked red in your above pic? Cos if so then yeah, try relocating it to the position marked in blue.

if the back of the motor is not a **** to get to you can try pulling the water housing off your motor to confirm

[JustenGT8]

So is the temp gauge sender in the spot that is marked red in your above pic? Cos if so then yeah, try relocating it to the position marked in blue.

if the back of the motor is not a **** to get to you can try pulling the water housing off your motor to confirm

Yes and i will.

Thanks for the input...helped my aging brain process what it going on

[1JZ-Rolla]

TURDEE is correct, behind that single bolt-on block are two ports into the head coolant galleries, with the gasket sealing between the two. Thermostat and therefore thermofan switch (white sensor) are off one port (cold side feed FROM radiator) and the two sensors for the ECU and gauge cluster are on the hot side. As vito said, these two ports provide teh flowpath for the heater core also (which can simply be blocked off).

Now that you've made it clear your thermo fan switch has been reloated to the (hot side) radiator Justen, I can see why your fans are running too often Damn interwebs/emailz communikashun

[edit] I can't see the images above from work but assume they show the multiple ports in the back of the head