Coolent Issues

Newbie Joined: 08 Jan 2006 Posts: 14

Right.. I have replaced the thermostat in the last few days, refilled the system and bled it, im now having the problem that when i drive along the tempreature go's right up to the second notch and then will stay there for a while and suddenly drop really fast, it'll just keep doing this all while moving and the tempreature will often go down when i stop.

i put a genuine renault thermostat in today (other one was from an autofactors) and its still doing the same thing!

does anyone have any ideas what could be wrong as i dont really want to keep driving around with the tempreature allways up and down.

thanks

Site Subscriber Joined: 01 Feb 2005 Posts: 728

I would say an air lock in the coolant hose. Is it a 16V?

If so it's apparently good to refill the coolant with the car on a steep slope so the expansion tank is the highest part of the cooling system and air can escape.

Hope I'm remembering correctly Smile

Newbie Joined: 08 Jan 2006 Posts: 14

I first thought it was an airlock as well but have tryed bleeding it so many times! ive just spoke to a mechanic and he said it sounds as though the sensor that sends the tempreature to the guage is intermitent and suggested replaceing that?

anyone else have any ideas?

any other suggestions on how to bleed the system?

Newbie Joined: 08 Jan 2006 Posts: 14

ok just driven home tonight and popped the bonnet after to check if my coolant level had gone down or anything and ive noticed steam coming out of some where on the passenger front corner of the engine bay somewhere but couldn't quite see where, didn't look like the radiator! :S could this be a leaky headgasket ?

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

the reason it drops quickly is because the thermostat opens!

Air locks, dodgy stat, over active gauge can all be problems.

Steam says theres a bit of a problem sort it out asap.

Newbie Joined: 08 Jan 2006 Posts: 14

well ive tryed 3 different stats so it cant be that, ive bled the system so many times and its obviously been emptyed and refilled when i put the other stats in so is it possible for an airlock to still be in their somewhere? got a mechanic coming to look at it on saturday.

Newbie Joined: 08 Jan 2006 Posts: 14

any ideas? or shall i just book it into a garage and get raped for money?

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

like I said sort out the leak thats causing the steam first!

was that not pretty obvious?

bit like saying its sore to walk will I get new shoes when its caught in a bear trap!

Newbie Joined: 08 Jan 2006 Posts: 14

no, sorry m8. cheers for the help

Level 2 User Joined: 25 Oct 2005 Posts: 55

rite, im still having this problem as well! from a while back! Embarassed

Its defo not thermostat related, as both me and matty have put new ones in.

Im sure its an airlock, rather than any pish a garage/mechanic will tell ya, but i just cant understand it!!!!!

if it were an airlock, then surely the air would eventually find its way to the header tank, and it would seem like a loss of coolant!!!! ive not had this happen yet over the past 400 miles or so!

the temp gauge rises past the 1/2 mark (where it should be) to the 2/3 mark, then drops to 1/3! This doesnt sound like an airlock, but its the only thing i can think of. ive not changed or played about with anything else, and it was fine before! only after i added radweld for a leaky radiator and bled the system did this start happening!

the thermostat is a new one, so wont be sticking, so should always be open after 89deg which occurs quite quickly id have thot.

does parking facing the car downhill really help? that way the header tank will be at the top of the system?

c'mon guys, someone must have a good solution! Idea

Site Subscriber Joined: 29 Dec 2004 Posts: 395

When your filling the system with the bleed screw open on the rad, don't just stop when water starts pouring out.
You will find that bubbles of air will keep coming out for a good few minutes after.

Retroholic Joined: 23 Dec 2005 Posts: 3315

how come mine bleed itself of air locks then i thought they done it automatically? i had no heaters changed fooked stat changed coolant and ran engine, heaters go flat out now nice and warm

Newbie Joined: 08 Jan 2006 Posts: 14

Right, ive had the car looked at today and he is 90% sure its the tempreature sender unit and he said my car is definately not overheating or over pressuriseing and he couldn't find any leaks. Im replaceing the tempreature sender unit on monday so will let you know how it go's stew

Level 2 User Joined: 25 Oct 2005 Posts: 55

where is the temp sender unit? dont have my haynes with me?

Is it the top plug on the stat housing? the brown one IIRC?????

let me know how you get on - not to mention how much it costs!

Newbie Joined: 08 Jan 2006 Posts: 14

yep the brown one, costs about 10pounds from a motor factors. will let you know how it go's

Level 2 User Joined: 25 Oct 2005 Posts: 55

Any news matty?

Level 8 User Joined: 30 Jan 2006 Posts: 270

hi there.
i had the same problem for a few months after refilling my coolant system. although i bleed the system i did not get all the air out and the temperature gauge would be all funny, would do as you descibed.
put the car on a slope and bleed again.

Site Subscriber Joined: 29 Dec 2004 Posts: 395

I can confirm that changing the temp gauge sender/sensor will not solve the problem.
I swapped the one on my other clio and it didnt work.

Bled it again and it still doing the same (but only while driving).

It seems to me, that while driving along with the engine cool, the stat is closed and so the water in the rad is not moving and is getting cooled down by the air.
When the engine heats up enough the stat opens and the cold water in the rad suddenly makes its way round the engine, resulting in the sudden drop on the gauge.
Because the sudden drop, the stat closes and the process begins again.
Problem is, that it shouldnt happen like this and the stat opening and closing should be more gradual.

This may be completely wrong but it's just a theory.

Affiliate Joined: 28 Jan 2005 Posts: 360

OK, does the heater work? ... I mean does it blow warm air that gets hotter as the engine reaches normal operating temp?

Level 2 User Joined: 25 Oct 2005 Posts: 55

yeah mick. heater works ok. there should be no way its the stat as its been changed. im gonna try bleeding at the weekend again, but these crappy reno coolant setups with only one bleed screw are shite for lack of a better word!

it was fine before, and its unlikely that something will just randomly break or stop working imo.

i thot the stat would have fixed it, but no. temp sender dosent sound rite coz temp only fluctuates when driving. when stationary it dont move!

'tis pissing me off now!

Level 2 User Joined: 25 Oct 2005 Posts: 55

Ok, flushed the coolant system again, refilled and took it for a drive. First half of the journey up and down same as usual, second half constant (the way it should be!) The total journey was 100 miles!

I've still got no idea what is wrong! Drove it 2day and its just back to the way it was, up and down again!

90% sure there are no air locks!