Corolla cooling system issue

[c3n0byt3]

Hey folks,

Been having this issue recently, and need some speculating.
Also posted on another car forum, but no reply yet.

My AE111 160iGLE went for a normal service and the PCV valve was also replaced.
Also some sort of engine flush was done (note this was not a coolant flush).
I get home and coolant is overflowing from the reservoir tank. Happens for a short while, then the level goes down (obviously now lower than before).
Coolant is not boiling.
I've been trying to figure out what's going on.

The temp gauge sits normal throughout a daily drive (45km+45km, 90% highway).
Overflow generally happens in the afternoon when I get home and park.
The fan does not come on, and the coolant starts overflowing.
I can force the fan on (unplug the coolant fan switch), and that helps bring the level down.
Driving with aircon on and heater also helps since it also forces the fan on (well not the heater).
The fan did switch on automatically once, the other morning when I got to work, but it didn't stay on long enough to prevent overflow.
It was a pretty hot morning too I guess.
Both the coolant inlet and outlet pipe are hot to the touch.

I'm leaning towards the coolant fan switch, but my mech thinks it's a blocked radiator.
The radiator is less than a year old (replaced together with headgasket).
I've been reading anything I can find, and it could be the fan switch.
Some say air in system, but for over a month?
Some even say electrical issues with grounding, stopping the fan coming on at the right time.
And yes some say blocked radiator.

I guess it could go either way.
Fan helps stop the overflow.
But temp gauge and the fact that the fan actually can come on could mean that the coolant temperatures are fine, but the radiator cannot cope with normal expansion due to some blockage. Basically the blockage is eliminating one of the cores, resulting in smaller overall volume.

One thing I also noticed is that the radiator cap is 1.1bar.
I think the oem is 0.9bar.
Could this be causing the problem?

 

[berrypi]

go back to OEM cap.

Best check, let car idle and idle... then see if fan comes on. If heater gauge stays constant, and its overflowing - minor issues. If heater gauge starts climbing then its BIG issues.

1. as above, run car till hot and wait till fan kicks in 2 or 3 times, whilst watching gauge and overflow. Fan goes on but gauge climbs (head gaskets on way out, blocked rad).
2. Fan doesnt go on but gauge climbs, obviously, change fan switch.
3. Lastly, could also be water pump.

so in a nutshell, make sure the fan is working. Thats the cheapest and 1st test. If fan DOES work, then look at a blocked RAD or water pump or headgasket issues

 

[Colin62]

Is the water pump working?

 

[silver6933]

Plug in the computer, check if the fans comes on when the ECU closes the relay.

Check water pump and rad cap.

Temp gauge is damped.

Check coolant for traces of exhaust gas.

 

[ponder]

Remove rad cap, start car & blip throttle a few times have someone check to see if water shoots out top of radiator.

 

[c3n0byt3]

Thanks guys.

I think the water pump is working.
I mean, coolant is circulating well.
In my case if it isn't working could the pump be creating too much pressure?

The rad cap is also new.
Although it's 1.1bar, and I heard that OEM is 0.9bar.
That couldn't explain the issue here though. A lower pressure cap would actually release more coolant.
Went to Toyota to try and get a new cap. No stock. And no idea if it's 1.1bar or 0.9bar.

Yeh the fans do come on if the relay is closed.
However I just close it manually by unplugging the sensor switch to test this.
The ECU will close the relay if the sensor picks up a specific temperature.
Maybe the sensor is working, but I've just never gotten up to the required temperature.
Or it's off spec a bit. I just don't know.
So that leaves testing of the sensor. I just need a thermometer to check general coolant temperatures.
The best test would be to remove it and place in water and gradually increase the temperature while measuring resistance.
I don't have those tools.

I will check for headgasket (exhaust gas in coolant), but I highly doubt it.
Headgasket was done less than a year ago.
Yesterday I did run the engine a bit without rad cap. And no water shot out after blipping throttle.
Actually my main aim was to burp the system. A few bubbles did come out eventually, but will see if this helped.

I'm not 100% an expert on these cooling systems, but what I noticed is that with the cap off, as soon as I start the car and let run for a minute, the coolant starts overflowing (now out the main filler hole on top of the radiator since there's no cap on) very slightly. It like sort of trickles. Coolant isn't very hot. I think this is normal since the whole system should be pressurized. But if it's not, that means the expansion is not heat related. So yeh then I guess it could be pump related.

@berrypi: "If heater gauge stays constant, and its overflowing - minor issues." Yes this is basically what's happening, and why I'm so baffled. The heat guage is constantly just below half. Car warms up well, and cools down well. But the coolant is overflowing. So what are the minor issues?

 

[ponder]

I would start wit a rad flush & a new rad cap as those are cheap options. Next step take to someone like silverstone radiators for a test.

Was the replaced rad a genuine part or aftermarket one? Just try and get the correct pressure cap.