Technical Now WHAT!!! OVERHEATING?

[TheCROW]

Guys, everyday on my way to work I face traffic for half an hour....
Always I take a look at my engine temp gauge and it usually stays on the center dot and sometimes a couple of millimeters higher max.
Today, to my surprise I noticed that it went 2 dots higher than the center and as soon as the car started moving again went back down to the center.... and then back up and then back down in matter of minutes....
When I arrived, I kept the engine going and the gauge was at the center dot, I checked under the bonnet: Coolant level was normal and the fan is running..... What could it be? Could it be related to rattling noise I get on warm idle? water pump for example? or maybe not, thermostat?
HEEEEEEEEEEEEEEEEEEEEEEELP!!!

 

[jug]

sounds perfectly normal to me, if you're in stuck in traffic for half an hour then the car really should get hot to the point when the cooling fan turns on, this will then make the temp drop, then the fan turns off so the temp rises again, then the fan turns back on so the temp goes back down, etc etc. this is how the engine maintains the temperature at a safe level. the car is probably getting to a hotter temperature than usual because the seasons are changing. my bravo rarely got much above the min in winter, but it now gets up to half way, i expect it will get even hotter in mid summer, especially when stuck in heavy traffic. for peace of mind you should try to remember the temperature when the cooling fan turns on. if the temp gets hotter than this and the fan doesnt come on then you should worry.

 

[TheCROW]

Thanx for your reply Jug,
Exactly at what temperature should the fan kick in?
And Exactly at what temperature should I begin to worry?
Up to what Temperature is it still safe to drive the car?
What puzzles me is that every day I get stuck in the same amount of traffic and the gauge has never went higher than the center mark.... Why now?

 

[T14086]

I recently monitored a brava & fan was kicking in at 98-99oC & off at around 90oC,obviously expect a certain amount of variation from car to car.

 

[jug]

the fan turns on when the temp is about 2 notches above half way, sometimes a little more. if you get more than three quarters of the way to the red and your fan still hasnt come on then its time to assume your fan isnt working. if the temp gauge gets above three quarters i wouldn't drive my car, or i'd at least pull over to check the water level before driving stright home to do further tests. its hard to say what a dangerous temperature is. when the temperature gets very high you will start to expand and warp the engine. depending on the metals used different parts will warp at different rates, it is common for the head to expand at a faster rate than the bottom end which causes head gasket failure, after that the warping will make the car run very rough as the pistons begin to experience excess friction becuase they no longer have a perfect fit in the cylinders. compression will be lost and the car will feel as though it has lost power. by this point you'd have to be daft if you didnt notice something was wrong. if the car gets so hot that it cuts out it isnt uncommon for the engine to seize in that position as it cools. your engine has left the building

 

[TheCROW]

Thanxalot guys for the replies...
And Jug, I hope I my engine won't experience what you have explained!
Today on my way back from work, the weather was hot and I faced a bit of traffic.... The gauge didn't go higher than the middle dot, in addition to this it drove beautifully.
Let's hope the same for tomorrow morning cos the traffic then is much more. If the gauge goes higher than normal I'll try to tap the dash, maybe the connectors are dodgy.
Will post back tomorrow. Good night all and thanxagain.

 

[TheCROW]

So, today on my way to work, I faced the same traffic as yesterday, same hot weather..... I even turned on the A/C to cold.... Nothing abnormal.
The needle stayed as usual on the center of the temp gauge.....
I'll convince myself that yesterday's incident was a minor issue....
I'll stay on the look out in case it happens again and report back to you guys...
Thanxall.

 

[TheCROW]

Very starange, today also on my way to work, in the usual traffic, the temp gauge went to the dot above the centre dot.... I tapped the dash a couple of times and a couple of seconds later it settled down to the center again slowly....
I was thinking maybe I should change the thermostat to be on the safe side..... Is it responsible for turning on the fan?
In order to change should I bleed the system or is it a simple swap?
Where is it located? My car is a 99 Brava 100SX petrol.

 

[jug]

no the thermostat controls the flow of coolant, when the engine is cold the thermostat stays shut. this is so the engine can warm up more quickly because the cooling system only makes use of the coolant in the engine and not the coolant in the radiator. once the coolant temperature rises the thermostat will open to allow all the coolant to circulate around the cooling system. this is needed to prevent the car from overheating once its warmed up. your thermostat is fine, if it was stuck open the car would take a long time to warm up every morning, if it was stuck shut your car would be overheating a lot on the way to work, you'd know about it if it wasn't working properly.

the fan is switched on when the coolant temperature get hot, this is after the thermostat has opened. the only way a thermostat can prevent the fan from working is if it is stuck shut and the coolant temperature sensor is located on the radiator side on the cooling system. this isnt happening to you trust me. you have a perfectly normal situation in your car. if the temp gauge was only 1 point above the half way mark thats perfectly normal when you're in traffic.

if you do start playing with things like the thermostat you may cause a leak or an air lock. you need to be careful with old rubber pipes and bleeding the system. its safer to leave things alone until there's a problem, dont go causing problems.

 

[TheCROW]

hmmmm ok Jug I'll take your word for it.
Thanx for your reply.
I'll keep monitoring the temp behaviour and will report back in case something happens.
Thanxagain.

 

[Tom444]

My Temp Guage flies all over the place, but a sharp tap on the dash sorts it out no time. Head over to fiatboo.co.uk. They have a tutorial on sorting out the thermostat connection into the dashboard.

 

[Scorg]

My Temp Guage flies all over the place, but a sharp tap on the dash sorts it out no time. Head over to fiatboo.co.uk. They have a tutorial on sorting out the thermostat connection into the dashboard.

Mines is guilty of that one too, I even created a thread on the subject over a year ago as it had me baffled.

Its been mostly welll behaved here the past few months but the other day it decided to jump up and down like nuts until I tapped it a few times.

 

[TheCROW]

Thanks guys
I hope it's just that....

 

[TheCROW]

Guess what?
It happenned again today.... Something is not right Jug.... I tried pounding on the dash and no change.... as soon as the car starts to move slowly, the needle starts to go back to the center slowly..... I feel that the fan is sometimes getting late to kick in and when it does, the temp start to decrease. I could be wrong.... I don't want to blow my head gasket....
Please someone advise, it's making me so uncomfortable.....
What can I do or change to test?
Could it be the fuel pump starting to act funny?
Heeeeeeeeeeeeeeeeeeeeeeeeeeeeeeelp

 

[jug]

hitting the dash is a temporary cure for when the gauge needle moves excessively and erratically, your temp gauge is maintaining a constant reading and only moving slowly so you do not have an electrical problem, your gauge is reading a true temperature, dont hit the dash or you may actually cause the erratic gauge fault.

your fan cant switch on "late sometimes" unless the coolant temp sensor is intermittently faulty, i've never heard of a temp sensor with a fault like that, they fail completely, read inaccurately all the time in the same way, or work perfectly. they are a very basic component that cant really have good days and bad. the electrics concerned could have intermittent faults but that would show with an erratic gauge or an inoperative gauge on occasion.

your only problem is that the car is getting hot, but it isnt a problem, its normal, unless the car cant control and maintain the temperature you have nothing to worry about. since your car is keeping the temp at a safe level it is working perfectly. all cars will have days when they get hotter than usual, there are many reasons why, temperature outside, wind conditions, traffic, length of time engine has been running, the average revs during the journey. on a hot day with no wind stuck in traffic revving your car due to constant start stop driving you should expect your car to get hot. much hotter than a on a cool windy day with less traffic.

i still dont think your car has a problem, you just cant accept climate change can you, summer is coming, try to enjoy it

 

[jug]

just had a brainwave, take the dash apart and bend the temp gauge needle down a few notches. hey presto cooler

 

[TheCROW]

Haha..... I like summer, but I cannot enjoy it while stuck in traffic, biting my nails and just monitoring the temp gauge.... Can you imagine me on the edge of my seat and sweatting like crazy? Just the thought of blowing a head gasket makes me so nervous....... That's why I sold my previous car.

I've had the car for nearly a year and it never acted like that even in the same conditions..... the gauge never went beyond the center, and now it goes just a bit under the red dot.... Is that normal? Is that even safe? Furthermore, the needle motion is not erratic or fast.... So I'm ruling out the electric fault theory.
What now?

 

[OwenS]

Haha..... I like summer, but I cannot enjoy it while stuck in traffic, biting my nails and just monitoring the temp gauge.... Can you imagine me on the edge of my seat and sweatting like crazy? Just the thought of blowing a head gasket makes me so nervous....... That's why I sold my previous car.

I've had the car for nearly a year and it never acted like that even in the same conditions..... the gauge never went beyond the center, and now it goes just a bit under the red dot.... Is that normal? Is that even safe? Furthermore, the needle motion is not erratic or fast.... So I'm ruling out the electric fault theory.
What now?

last week (well the day before brooklands) my fan went, which caused my engine to overheat, but it wasn't changing it just went straight up to max..

if there was a loose connection on your thermostat or in the fan wiring, it may be turning on and off intementently, (sp) which may be causing the tempreature to change so much.

Maybe not the solution you were looking for but it's an idea isn't it ?...

 

[TheCROW]

last week (well the day before brooklands) my fan went, which caused my engine to overheat, but it wasn't changing it just went straight up to max..

if there was a loose connection on your thermostat or in the fan wiring, it may be turning on and off intementently, (sp) which may be causing the tempreature to change so much.

Maybe not the solution you were looking for but it's an idea isn't it ?...

Thanx OXCiD3.... This is exactly what I'm talking about....
What do you think Jug?

 

[jug]

oh i didnt realise it was getting right up to just under the red, that is asking for trouble. you say it drops when the fan kicks in or when you start to move, that is normal, both create air movement over the radiator which allows it to lose heat. it shouldn't really get near the red

OXCiD3 is correct, if your fan isnt working when it should you will overheat, but i think the fan is switched by the coolant temp sensor, the thermostat doesnt have any wires, its just a mechanical valve. the fan's performance is vital and worth checking.

you should do a test with the car staionary and engine running, let it get so hot that the fan starts, note the temperature when it starts, then wait till it switches off, note the temp when it does, repeat the test a few times to make sure the fan always comes on when it should and goes off when it should. there is an expected variation but it should always switch on and switch off at nearly the same temperature. if you find it does not, even only once, you know you have a problem with fan electrics. the temparature should be maintained by the fan so that no matter how long you leave the car running it will maintain a safe temeprature, even if you leave it running for 5 days it shouldnt overheat.

test your fan's performance and let me know what happens.