If your car is overheating it can be due to many things

When people hear 7mgte... they immediately think they have a blown head gasket.. this is not always the case

it's a good idea to run through a few other things before you think the worst

overheating generally only happens when stopped in traffic, on the highway the temp comes back down but here's a few things to check anyhow :)

check your water pump
your viscous fan
make sure your thermostat is opening properly (if in doubt, just buy another one they're only $15odd nzd)
make sure your radiator isn't blocked
check for any split hoses
check for any water leaks
your heater core might have air bubbles in it so you need to burp your cooling system (best way i found is jack her up so the radiator is at the highest point... make sure the engine is warm at this point and start her, get the hose or bottles of water and start topping her up... she might bubble a bit while air locks are being cleared, once the bubbles stop cap her up and set her back on the ground)

if none of this has solved your problem get a "TK head check" and check for exhaust gasses in the cooling system... if the blue liquid changes to a greeny colour then it's possible there's exhaust gasses in the water, if it turns yellow there's a definite sign you have exhaust gasses ( i think thats the right colours... it will say so on the instructions anyhow )
if it does confirm exhaust gasses in your water you have absolutely blown your head gasket so get ready to pay out :P

also check your oil, make sure it's not discoloured at all.. milky or chocolate milkshake... if this is the case... you have blown your head gasket or you may have a crack in the block or head... you need to strip her down and get the engine reconditioner to check this for you... usually you can tell by looking at the head gasket.. if the head gasket has definite signs of blowing between galleries usually you don't need to worry bout cracks but you still need to get it all checked.... last thing you want is to buy all the parts, slap her together only to have it happen again

well that's all i have to add for now.... anyone else like to add :)

very good report
must confess most probs seem to derive from one or more of the faults youve given .often then ending up as gasket failure,or worse.
Never trust a new t/stat or gauge when circulation probs exist + new t/stats dont always work .They sometimes need help to open for the first time. ;)

ahhh yes lol, did i forget to mention the thermostat thing... i think sometimes it's a good idea to maybe just drill a 1/4 hole in the top by the little toggle

i figure if it's really really bad and the info isn't up above then they can email me hehe ;)

I ha a gurgling sound in the engine when revving away so I took it to the local shop. I said about needing the system burping and about removing the thermostat and drilling a hole in to ease the problem and they initially agreed.

They split the thermostat housing away and there was no thermostat fitted at all.

They did a HG check and said it was OK. They did not have any thoughts apart from the system needed burping once and for all.

Does anyone have any thoughts.

Thanks

does you car overheat with no thermostat?... i would stick a new one in.. burp it... and make sure your radiator isn't blocked... to hear gurgling in the dash you definitely have air bubbles there somewhere

A little bit more information for you all to ponder. I collected the car this afternoon from the shop and had a really good report on the engine etc. The shop said they had test driven the car and she was still warm so I guess that was true. Within a mile of leaving the car started to overheat and I pulled in and stopped just as the needle touched the red. I just could not get in any sooner because of the road and it would have been suicide to stop.

I had the shop come out and their mechanic let it cool off, topped it up with about 1.75l water from a 2 litre bottle started her fine and drove back.

He took her out for a test drive of 8 miles and she was fine. Got her back to the shop and let her sit with the heater fan off and engine on tickover. The secondary fans came on OK and she behaved as normal.

I have let the shop keep her for a few more days as I want them to do a few cold starts and run ups to see if this happens again.

My own feeling is that they forgot to connect the fan sensor but i was wondering if there was any chance of any damage especially after such a good report on the engine beforehand.

Many thanks to anyone who thinks about this and makes a comment.

I have spent the last few hours really thinking about this.
The car was ready for a new timing belt and had slooshing water noises behind the dash. I sent it into the shop for a new timing belt, water pump check and to check the thermostat and drill a venting hole in the thermostat if needed.
The first thing the shop did was a test on HG reported HG=OK. On that basis they did the belt and thermostat and refilled with new coolant mix. I dont know if they burped the system with the nose raised but I did mention this to them beforehand.

Within a mile of starting (warm start) the temp started to climb too fast and too high and I stopped as soon as was safe.

This all begs the question of how did the air get into the system in the first place so I heard the slooshing sound. Could it have been sucked back from the expansion tank? Is the HG blown even if the shop says otherwise.

Why would the engine overheat. The shop said they had a long test drive prior to me taking it away. I drove steadily for two minutes and nearly cooked it. The danger is that I got it too hot and have destroyed the HG and/or twisted the head. Bloody Hell.

When the car was back at the shop the car showed no signs of overheating and behaved normally.

I am wondering if I should just bite the bullet and put in a new HG. Do I have any arguement with the shop. I have used the car for about 10 days (200 miles since purchase) and not lost any coolant during that time. I really think the HG was OK.

Thats about all I can add for now. Any thoughts would be useful so many thanks in advance.

seems like you're having a bit of fun then hehe

when does it start overheating.... hills... traffic... highway.. which?
does your heater blow hot air?
how fast does the temp go up...
why other than the gauge do you think its overheating... is it bubbling and spewing out water or what?
when you lift the hood... can you smell anything abnormal?
does it feel hot.. when you lift the hood does alot of hot air ram at you?
and you still got the waterfall? drive your car to the nearest steep hill so the radiator is at the highest point... make sure the engine is still cool... turn off... take off radiator cap... start the car... keep topping up the radiator while it's running (with the heater on full blat) and keep doing this till you don't see any bubbles come out... put the cap on and see how she goes

what colour is the oil on your oil cap?
pull out your dipstick... is it normal coloured oil?

lemme know how you get on :)

Thankyou for the reply. At this stage I can only answer a couple of those.
The car has just had an oil change in the shop. The shop were to do a full service but could not get all the parts so asked me to take her away for the weekend and bring her back next week to finish off. Before that the oil was normal and no milkyness.
The heater worked fine and blew hot air.

I noted the overheating in traffic when stood still. Once it started getting hot it was very quick.
At the time I was at an intersection crossing the bottom of a big hill and the traffic was stopped with me right across the downhill. Suicide city.
Once I could stop safely I lifted the hood and could hear steam hissing through in the radiator cap. There was steam in the expansion bottle. The engine did not smell hot but then again it is not caked in old oil and grime.

I have now had another HG tast done and the shop reports all fine. I have had the water pump removed and checked and this is also fine.

I am hoping that the problem was an air lock that blew the coolant out. Why it never came up on the shop test drive I dont know.

Oh well, what a Supra life he he

hi
the worst time for gulping air must be when fitting a stat.Jap motors in general need burped when the stat opens throwing out a bit of water but allowing full water throught system-perfect.A resevoir working on a thermo syphon system cant do much else +aint ideal.
Drilling a hole in the stat may work fine but without a jiggle or complete blocking of thermostat youve surely adversely affected the specific aperating range to one of guesswork.the stat being fitted to obtain maximum engine operating efficiency quickly,encludes a restriction in my mind vital to allow coolant to slow down enough to absorb heat to allow system to work right. Lots of garage probs exist cos the stat didnt open right first time before it was burped ,or
it had an underlying prob not so easy noticed without spending extra time that customers are loath to pay for possibly nothing cos time is money!
With enough information from you im sure folk here can eliminate likely faults ,id try motor again if garage says ok but dont trust the gauge if air may be an issue cos you wont know if it boils. :blink: