Supra trying to overheat and heater blowing cold

Right I noticed when i parked up at work that my heater still wasn't blowing warm air still very cold, thought maybe its to do with the weather as its not a long trip, but then I noticed the temp gauge heading towards the red (it didn't get there as I turned it off)

I know it could be a few things I.e thermostat, waterpump etc, but has anybody had the same issues might help narrow it down I checked the engine oil which was fine and topped the water up in the expansion tank which was a little low, opened the radiator cap and couldn't see any water, should that be full so I can see water in there aswell, I know it sounds a dumb question but please don't take the piss if I'm being thick lol

Any help is much appreciated thanks

The rad should always be full to just under the overflow pipe but don't use water, its

getting cold now weather wise and if you fill with water it will do two things, freeze up

and cause limescale build up inside the rad etc as well as not helping with corrosion.

Get some premix glycol ethylene, forlife or cool red from Toyota approx £20 for 5 litres, you'll

need 10 litres to fill an empty system.

Halfords also sell a pre mix

How old is the rad cap ? i'd replace that first, have you checked for coolant in the passenger

footwell, also what state is the rad in and coolant hoses, heater matrix feed pipes are prone

to fail when they get old.

To get air in the system usually means you have a leak somewhere or the expansion tank

is too low to let coolant be drawn back into the system or the rad caps failing

I think you should be able to see water in the radiator: it should be brimmed to the rad's neck (be really careful if removing the rad cap when the engine's hot, serious risk of scalding yourself). Possible causes are:

- airlock in the cooling system. This can stop the coolant circulating, meaning the stuff in the engine gets hot whilst the rest of the system stays cold (hence the cold air from the heater). But airlocks don't usually just appear spontaneously, they usually appear when you've drained and refilled the cooling system.

- system very low on coolant. You said it was "a little low", so this seems unlikely.

- blockage in the coolant pipework.

- thermostat stuck closed (not sure if this will prevent the heater from getting warm)

I would go for a little drive, stay within a mile of your house so you can head straight home and turn off when the temperature gauge climbs too high. Feel the coolant hoses carefully to see which ones are hot, warm or cold. That'll tell you where the coolant's been circulating.

Don't really know how old it is it doesent look old mind

I'll top it up but I'm just hoping that the water isn't going somewhere like a leak or head gasket I'll top it up using the halfords premix tomorrow and see if it goes anywhere if it doesent ill drain it and get the stuff from toyota for when I do the vss and other jobs

Oh and I felt the passenger footwell it feels dry so hopefully that's not the problem

I think you should be able to see water in the radiator: it should be brimmed to the rad's neck (be really careful if removing the rad cap when the engine's hot, serious risk of scalding yourself). Possible causes are:

- airlock in the cooling system. This can stop the coolant circulating, meaning the stuff in the engine gets hot whilst the rest of the system stays cold (hence the cold air from the heater). But airlocks don't usually just appear spontaneously, they usually appear when you've drained and refilled the cooling system.

- system very low on coolant. You said it was "a little low", so this seems unlikely.

- blockage in the coolant pipework.

- thermostat stuck closed (not sure if this will prevent the heater from getting warm)

 

I would go for a little drive, stay within a mile of your house so you can head straight home and turn off when the temperature gauge climbs too high. Feel the coolant hoses carefully to see which ones are hot, warm or cold. That'll tell you where the coolant's been circulating.

I'll try that on the way home from work tonite then and see what happens

If its original rad, matrix, hoses then that's where i'd be looking first, head gaskets are pretty good on the mkiv

Run it up on the drive with the rad cap off and see if you can get the heater working, use water for now to find

the leak but drain it asap and re fill with coolant

Sounds like you've lost coolant through a worn out rad cap and now can't get the pressure to fill the heater matrix.

New Rad Cap

New 4Life Red Coolant

as per DNK's advice

Sounds like you've lost coolant through a worn out rad cap and now can't get the pressure to fill the heater matrix.

New Rad Cap

New 4Life Red Coolant

 

as per DNK's advice

I'll check that aswell then what pressure one should I use or just a stock normal cap

I'd recommend a stock rad cap. Keep it stock unless you've got a good reason to do otherwise.

When did you check your coolant last ?

Hopefully it's just lost some water and no damage done

Refill and get all the air out and keep an eye on it

Just topped it up on the way home with just a small water bottle it didn't overheat and the heater blew hot air

I'm gonna order a cap and see if that helps it

100% this is a pressure leak coming from your hose or hose clamps. When water heats it expands and causes pressure and that pressure is leaking and pissing coolant out somewhere. Don't put £20 worth of coolant in till you find the leak. Find the leak fix the problem then put dear stuff in.

I had the same problem and it turned out to be the hose In between the window and the back of the engine in line with the spark plugs right at the back. If it is air tight you don't have to bleed the system on a mkiv supra.