Engine Temperature climbing above half way mark

[james250]

With the recent hot weather, i was stuck in stationary traffic and noticed my temperature gauge start to climb above the half way mark. Turning A/C off seems to have stabalised it. I have a fairly new radiator and system was pressure tested to be ok after radiator change. The pressure cap is also new and my thermostat is a few years old and water pump was also changed a few years back. although I don't drive much. I checked coolant level in overflow bottle and it's at the correct level so not low on coolant.

Could thermostat be bad again? I doubt it's the coolant temperature sensor because when i turn AC off it improves. So that will make me think sensor is reading correctly.

Any advice? I'm beginning to think the overheating issue has never fully gone away and keeps coming back specially in hot weathers.

[Las Palmas]

Once in Africa in AlfaSud, the engine temperature got hot, far away from a place to fix anything. Turned up heating, taking heat from engine and put it in cabin and managed to get to a town where the problem could be fixed (bypassed the thermostat). It was a hot tour, with windows open getting circulation of air made it bearable. Hot air, just like a sauna.

[Linas.P]

The temperature going just above the middle, is not an issue, if it really goes towards 3/4 then it would mean big issue. Has the radiator fan kicked in? 

AC should not impact the engine temperature, as John said, only turning on heating could help with cooling. I am wondering whenever A/C condenser could have impact on radiator efficiency, but that is quite unlikely. 

Were all parts fitted OEM? I am just speculating here, but if radiator fitted is aftermarket, maybe it is not up-to standards? 

[Texas]

This IS250 overheating problem turned out to have a peculiar cause, I am not saying it’s your fix but need to explore every Avenue in fault finding.

 

[james250]

So it appears it could be the cooling fan as I can only see the one single fan activating. The fan directly under the overflow bottle doesn't seem to be activating at all. Can anyone kindly check their 250 and see with the AC off, does the fan on the right turn on once engine is hot? I'm referring to the ran on passenger side not driver side

[steve2006]

Have a read through this, there are a couple of fuses for the fans and various relays controlled by the engine ECU.

https://www.clublexus.com/forums/is-2nd-gen-2006-2013/825831-2007-lexus-is-250-awd-radiator-cooling-fan-switch-relay-location.html

[james250]

I had a look at the fuse area. I removed that fuse box cover just below near the Battery and the label printed inside shows that fan fuses should be above the relays but above the relays is the single big fuseable link so it doesn't make sense. My only guess would be that that entire fusable link has the fan fusing embedded into it. I did an active test via techstream to activate the fans and only the one on drivers side activates. I've ordered a second hand complete replacement of the fan unit so will see how that goes.

[Linas.P]

This would make sense that car overheats if fan isn't running. As well check the fusible link carefully, because it is known they blow sometimes and it is real pain to replace. Note as well fan has relay (actually 3 relays), not normal fuse. 

Fan definitely kick in when car is stationary and reaches working temp, it blows for 5-10 minutes and then stops, then repeats it. It is kind of hard to miss because it makes real racket and easy to hear when stationary. Although if you said it does not activate via techstream it will be bad fan or bad wiring, or bad relays. 

[james250]

Fuses are fine. I need to still swap the relays around to see if problem follows. There are two grey colour relays in that rectangular fuse box for fans but for some reason the label on the fusebox says diesel in brackets. So it doesn't make sense. How do you remove these relays?

Also, I've got a second hand fan assembly handy if I need to replace it. But seeing as I'm recently changed my radiator and did a entire coolant flush and change, I really don't want to drain the coolant if I can avoid it. In order to remove the fan unit, I have to remove the big upper radiator hose. Is this house full of coolant? If I was to disconnect that hose will coolant come gushing out? I want to really avoid losing coolant and having to put in new coolant considering how expensive the coolant is and I just recently changed it

[james250]

I've confirmed it is 100% the motor on the fan that's faulty. Fuses and relays are fine. I hooked up a 12v bulb to the connector of the non-working fan and that bulb lights up when fan is supposed to be on. I even tried supplying 12v directly from Battery to the motor to see if it runs but no luck. 

Seeing as the thermostat will be closed when engine is cold, I would think whatever coolant comes out will be just from the top of the radiator. So I could potentially just drain a small amount of fluid from the bottom of the radiator to lower the level and then remove the hose. Will that work?

[Linas.P]

Good investigation. Yes the hose at the top is "full" of coolant, maybe not completely when engine is off, but if you disconnect it there will be spill. I guess if you remove just right amount of coolant from the bottom you can minimise the spill. Yes you need to remove the hose to remove whole assembly, but I reckon it is possible to make assembly just lose enough to remove/replace the fan without needing to remove any hoses. IS250 is just horrible to work on as almost everything requires removal of radiator (and more) for access. And that is already shortcut, because following Lexus manual it would require removal of entire front end and radiator... just to replace the fan. 

I just can remember if motor is held in place by bolts or by rivets.

[james250]

Ok, so an update on this. I managed to change the cooling fan with the second hand unit. I tested the second hand unit first before starting the work by plugging 12v power directly to each motor. The drivers side one was spinning at first but I could see it tries to move. So then I went to move it by hand to see if it spins freely, but it seems a little stiff so I sprayed electrical cleaning spray and rotated it and spun it by hand until it started moving freely then tried again. And it was working well. 

With the fan replacement, I drained just under 1L of coolant from the bottom drain of the radiator while keeping the pressure cap open. After that I was able to disconnect the upper radiator hose which only had a tiny bit of coolant in it that I was able to catch with a cloth. 

After that the fan is relatively easy to take out but the PITA part of it is how tight around the corners it is. So sliding it up becomes an issue. So what I did was removed the entire airbox which gave me too to angle the radiator as I was lifting it out and it's just a matter of fishing it out. When it comes to putting the new fan in, the trick is to put it in an angle starting by putting the airbox side in first otherwise it just won't go down. 

So all done.

One thing is that in the beginning when I was trying to take the fan out and figure out how to, a few times the fan housing scored and bent some fins on the inside of the radiator. Not that many but enough to look like an eyesore but luckily it's inside. I'm assuming bent fins don't cause leaks right? Considering my original OEM radiator had most of the fins bent and it never leaked there. But I think I'm just being a little paranoid