when you remove the old coolant temp sensor you will lose coolant, even if you swap them round quick, so a top up and bleed is needed.

TheCROW said:

Hey Classix, do you have to bleed the whole cooling system to install the coolant temp sensor?

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This is my plan, because i intend to replace thermostat too. If i replace only coolant temp sensor it would not be necessary to bleed the whole cooling system like jug says.

how do you prevent air from entering or fluid from leaking when the temp sensor is removed? since the temp sensor is surrounded by coolant it must allow a leak when its removed. what stops the fluid from leaking?

if you lose any coolant or let any air in then you need to bleed, although i doubt the rad will need bleeding as the air will rise to the top of the system allowing it to be bled from the hose bleed screws.

OK, so yesterday I went to the car and started the engine, I waited about 5 minutes on idle till the temp gauge was on the center dot, I waited a couple of minutes more and I noticed that the rad fan was still off and the temp gauge stable on the center dot. So I started revving the car a bit and that's when the rad fan kicked in and the temp gauge remained stable.... then after a short time of idling, the fan stopped and the gauge was still stable. (Everything normal I believe right?)
then I loosened the bleed screw located on the back of the engine... It burned my fingers... I waited for a couple of seconds and when I noticed some coolant running from the screw downwards the hose I tightened it back and burned my fingers again
So then I turned off the car and checked the coolant level after cooling off and it was still the same.

Today I faced the same traffic on my way to work and all was normal....
I hope this fixed my problem, but I cannot be sure untill after a while cos my problem only occurred occasionally before, so I'm gonna keep my fingers crossed and hope for the best...
I'll post back in case of new developments

sounds like perfectly normal behavior to me. keep your eye on it and let us know what happens

jug said:

sounds like perfectly normal behavior to me. keep your eye on it and let us know what happens

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I will, thanks Jug.

Some great guys thumb: ) on this forum suggest that one thing you could do is open the windows, turn heat full up and vent at full.

I tried this out after a long drive on motorway. It was a hot day, then I got stuck behind traffic, so I tried that trick out and it worked !

...mind you, glad the traffic eased up as I was getting cooked instead !

I made an interesting discovery recently:
As I was examining the cooling system, I noticed some drops of coolant on the expansion tank. Those drops were leaking out of the joint where the thin upper hose connected to the tank. So I waited for the car to cool off and removed this hose to find out that the plastic joint where the hose connects was cracked and letting out some drops of coolant...Maybe the electrician might have broken it when changing the heater matrix... So I removed it and superglued the little copper joint inside to the plastic and superglued the plastic. then refitted the hose and put a new metal fastener on the hose and tightened it. Still got to test and see the result.
What do you think? Could this little leak be the cause of the symptoms I'm experiencing?

it cant hurt to have it fixed, but i dont think the return hose could leak air into the system unless it caused a major loss of fluid. another reason i like doing things myself is that i'll fix something if it breaks, mechanics wont tell you

Today something weird happened, I'm calling it weird cos it didn't used to happen... Before, at all times the temp gauge would remain stuck on the middle dot no matter what.
Today in traffic I noticed the gauge (I'm becomming obsessed with it!) every 3 or 4 minutes would go up to the dot above the center one and then back slowly to the center after a short while. It did this more than 4 times in a 20 minutes ride in light traffic... Maybe this would seem normal to you: The fan would kick in and the temp would go back down to the center.... But this didn't happen not one time before....
Tomorrow I'm taking the car to a young mechanic who worked for fiat for a couple of years... He'd know how to bleed the air out of it....
I'll post back soon.
Thanxall for bearing with me.

every car ive ever owned or even driven in traffic has done exactly that, apart from my old ax gt, that just stayed in the red because it had no head gasket, but apart from that every car's temp goes up and down between the points of high where the fan kicks in and low when it stops. thats what its supposed to do when its hot. do you expect it to maintain a constant temperature with no movement from the gauge? it cant do that because the fan switches on at a higher temperature than it switches off, this difference gives the control range which a healthly cooling system will maintain the temperature at. surely you must have noticed this on your previous cars?

Hi Jug, yes this behavior is normal and fine by me but I called it weird cos it never did this before.... However yesterday and by pure coincidence I was taking my friend after work to pick up his BMW from his garage... What a surprise I had when I walked into the garage to find it was specialized in Ferraris It had 4 brand new Ferraris being fixed!!! The manager turned out to be specialized in Italian cars and fixing Ferraris, Alfas and Fiats as well as BMWs.... I asked him about my issue and a mechanic checked it and tried to bleed it a bit but he told me that there was absolutely no air lock in it.
So they told me that it was probably the thermostat or the coolant temp sensor, if I book it in they will test both of them and change them if they need to be replaced.
The thing is that yesterday afternoon and today I faced the same heavy traffic and the needle remained at the center of the temp gauge.... Let's hope it stays this way orelse I'll have it bled and change the sensor and thermostat to be on the safe side.
Thanks again and sorry for the long post

Alright, that does it.... I'm sick of the darn temp gauge going above the center and then back down.... This never used to happen before....
I'm going in a couple of hours to change the thermostat at the auto electrician.... Any advice before doing that? The system have to be bled and refilled right?

yes you refill the system and bleed from the lowest bleed screw (radiator) up to the top bleed screw. and then go crazy because it will make no difference. i'm scared to ask, but what are you going to try next?

why not make a video of the temp gauge in action so we can see if it really is moving unusually. if the car isnt overheating on any occasion then it is very unlikely that there is anything wrong. if you like i'll even make a video of my needle moving so we can compare.

This only happens in traffic... Before when I first bought the car, the temp needle used to just be at the center dot all the time no matter what, even in the heaviest traffic...
What is happening now is that in traffic, the needle will go well above the center dot slowly and then will drop down slowly when the car starts moving. Sometimes it goes back down slowly even if the car doesn't move... But what scared me the most is that a couple of times it kept going up slowly untill it nearly reached the red dot and only started to go back down when the car started moving.... So I was thinking that maybe the thermostat is on it's way out and sin't operating accurately anymore... I don't know if it has been changed before.

oh i see, that doesnt sound like normal behaviour, you're right to do something about it. a thermostat change has to be worth a try, maybe its only opening partly? poor circulation could also be the cause, have you given the system a good flush? not just the radiator, the full system, using a hose pipe. you might as well do it at the same time as the thermostat. its amazing how much crap you can get out, its usually brown slimy stuff. i serviced a saxo last year and i could have filled a plastic bag with the slime i got out. it was almost like human poo mixed with water, and it stunk. obviously the car hadnt had a coolant change for years, either that or the owner was using the radiator as a toilet

Ok so I'll go and have the thermostat changed and perhaps even flush the system, I'll see what they recommend...
I'll reply back soon.

Something came up and couldn't go to the garage... I think I'll have to put it off for next week... WORK WORK WORK...
In the meanwhile I'll keep my eye on it and report back in case something happens. I believe that as long as the needle doesn't reach the red dot I'll be OK for the time being.
Thanks guys and Jug for putting up with me in this thread and thanks for all your help :worship:

Ok, sorry guys but I have to revive this thread since I haven't had the time to take the car to the shop.
In the last couple of days, I noticed the car became to everheat more quickly than usual even in lite traffic which didn't used to happen even last week!!!
So It's clear that the problem is getting worse....
I called the Ferrari guy and booked the car for Monday.....
I hope it's not the coolant pump cos I really don't know if it was changed before...

How can I know if the pump is on it's way?

Today evening I just drove for about half mile and my temperature gauge touched the red. I thought its one of those guage senses so I tapped it few times but it refused to come down.

Now as per this thread I checked the following:
I get hot air from the blower.
The fan functions properly at the right time.
The coolant temperature after the drive was 83 deg.C
Then I checked oil dip stick for any trace of water but it was ok.
Then I opened the oil cap and I was surprised to see little oil+water thick creamy mixture stuck inside the oil cap. Now this has started ringing the bells. Am I blowing my head gasket? Though the oil is clean on dipstick and I cannot see any trace of this creamy thing inside the oil chamber.

To test furter, I let the engine completely cool down for couple of hours. Then started the engine and let it idle, within 5 minutes the temp guage touched the red. I checked the coolant temperature, it was 54 deg, I touched the engine it didnt feel really hot. I let it idle for another 5 minutes, then the fan starts, the coolant temperature is 82 at this time. I get hot air from the blower, but the guage doesnt seem to move down. I took it for a very short drive and it drives fine.

Now the puzzle is
Is the car really overheating or the temperature guage is faulty?
Have I blown the head gasket?
Now this has started really worrying me.