Odd temperature activity, gen7 Celica

ins0mn1ac · 11 Jun 2013 at 14:03

My Dads 51 plate Celica randomly warns it's overheating, then say 2mins down the road the temp will fall by about 50% suddenly and it'll read normal for the duration, earlier we noticed regardless of the sensor temp the fan stayed on with ignition. Now as we got back home the temp reads normal and the fans off.

Would this be the thermostat failing or could it be something more severe? all fluids are perfect and I can 100% say they've not dropped suddenly.

It's a Celica 1.8 vvtli 51plate.

Any advice/help mucho appreciated!

PiKe · 11 Jun 2013 at 14:05

Try a new thermostat first.

p1RATE · 11 Jun 2013 at 15:19

does the fan stay on all the time?

as a matter of course i would replace the thermostat

acemastr · 11 Jun 2013 at 15:30

Thermostat or air lock are my thoughts

Tom_ed1987 · 11 Jun 2013 at 18:14

Does the heater still work while this is happening? Is there any other indiction of it overheating apart from the gauge? Is the coolant level ok? If all that checks out ok test the coolant sensor for the gauge.

Dogbreath · 11 Jun 2013 at 18:36

Most likely thermostat, but check the auxiliary belt is tight to start with. The early engines had plastic impellers on the water pumps as well, though they weren't a common failure point (unlike plenty of other cars).

Zack101 · 11 Jun 2013 at 20:03

Check for an air lock first, it is really common on this model and match's the symptoms you have described. The coolant in the bottle may be the correct level, but there could be air in the system. To get all the air out of you need to get the front end as high as you can, (I mean jacked up really high) then run the engine and the air will bleed out.

The Running Man · 11 Jun 2013 at 21:16

I wouldn't recommend that...oil sump pickup might not like it.

Bleed the system properly and replace the coolant, when was it last changed?

Zack101 · 11 Jun 2013 at 21:22

The Running Man said:
I wouldn't recommend that...oil sump pickup might not like it.

Bleed the system properly and replace the coolant, when was it last changed?

Believe me you will have no problems with oil pick up, this is the only way to do it properly unless you have access to a vacuum filler.

ins0mn1ac · 12 Jun 2013 at 10:39

Catastrophic developments, it's drinking coolant, and once filled it literally drops equally to how it revs and there's no sign of it coming out anywhere. Under car or white smoke :/

Lashout_UK · 12 Jun 2013 at 13:20

ins0mn1ac said:
Catastrophic developments, it's drinking coolant, and once filled it literally drops equally to how it revs and there's no sign of it coming out anywhere. Under car or white smoke :/

Looked in the sump?

ins0mn1ac · 12 Jun 2013 at 13:50

I won't see the car again till tomorrow but I'll have a look! I've told him not to touch it again for now just incase.

ubersonic · 12 Jun 2013 at 14:24

Tell him to take the oil cap off the engine and look if there's mayonnaise in it.

GeX · 12 Jun 2013 at 15:47

I had a car do similar with regards to the temps - it was catastrophic head gasket failure. (there was no white smoke as it overpressurised the cooling system and blew all the coolant out the expansion cap)

p1RATE · 12 Jun 2013 at 16:24

when you say drinking coolant how much is being lost?

most likely HG or possibly a seized water pump. you are going to have to start pulling bits off to investigate anyway.

ins0mn1ac · 12 Jun 2013 at 16:32

Well I popped the bonnet after going back to his house last night and the expansion bottle was nearly empty, topped it up and turned the engine over left it idle and it was fine, any pressure on the accelerator took coolant to the point there was none left, filled again and same happened.

Oil looks super clean from the dipstick and under the cap, no mayo at all, no signs of leaks anywhere all joints on the rad look clean with no moisture.

I can't check anything yet as I'll not see him today but all advice is appreciated! This is starting to look very expensive and he absolutely adores this car its brilliant to drive, shame as he only just added me to his policy yesterday

p1RATE · 12 Jun 2013 at 16:54

That in itself is not too much to worry about, it may have just overheated and puked up coolant.

you are doing the right thing and i wouldnt use the car again until you identify this problem.

When you get in drop all the coolant out and refill ensuring there are no air locks (jacking the car up as mentioned). whilst your doing this its a good opportunity to take the thermostat out and test it. if you warm it up you will see it open and close. this costs next to nothing and will help to rule out an air lock and the thermostat. If this continues i would move onto checking the condition of the water pump and then consider a potential HG, with clean oil and coolant it isn't likely but possible.

ubersonic · 12 Jun 2013 at 16:57

Well if its not going into the engine, and its not leaving the car, is the water in the passenger footwell?

Its the A/C on or off? If its off then you may be losing coolant from the heater matrix behind the dash, try turning the A/C on and see if that helps (on most Toyota's of that era if the A/C is running it will operate a bypass that stops coolant from entering the ventilation systems heating circuit).

ins0mn1ac · 12 Jun 2013 at 17:17

ACs fine heats up/cools down as quick as ever, footwells are dry assuming the matrix is behind the dash!

I'll update after another poke tomorrow.

Zack101 · 12 Jun 2013 at 18:03

It still sounds like you have air in the system. If you can't jack the car up, take the reservoir bottle off (take off the plastic covers and it's held on with 2 bolts) and suspend the bottle as high as the pipes will allow it to go. You need to make it the highest point.

The head gasket is very very unlikely to have gone as it's very rare for them to fail on this engine.

Of course once you have got the air out, you will have to find out where the water has gone to let air in. Probably a small leak somewhere, water pumps are common.