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Discussion Starter #1
I renewed the coolant with a little more mix for winter but for some odd reason when im driving at speed the gauge is acting weird.

When i'm driving at speed instead of sticking to around 90' which it should, it's moving steady upto 90 then as soon as I start leveling off and going down a hill it drop's down to about 75' in about a second, then it starts building upto 90' again. How it behave's seems down to the terrain i'm driving over! It's fine when i'm stationary. The thermostat is only a few month old too and it seems to get to 90' when moving with no probs. I can only put this down to an air lock in the system ... I have tried squeezing pipes to release bubbles but no joy so far. :mad:

Has anyone got any further tips on how to fix this? Do I need to drain the whole system?
 

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Does sound very much like an airlock but you seem to have done all the usual things. Have you had the heater on full blast to make sure that the coolant is running through the heater matrix, silly suggestion if you have air con but.......

Failing that I think I would drain the system again and re fill very slowly and carefully.
 

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Discussion Starter #3 (Edited)
The heater definately works pretty well (it's damn cold up here in the NE corner! :lol: ) but i haven't purposefully put it on like that to check.

Will give it a go, I think I will just have to siphon as much out as I can and refill it again while squeezing pipes to release any bubbles. Little frustrating if this doesn't work will give it a bash over the weekend. After doing this should I leave the resovoir cap off for a few minutes to let air out and then tighten?
 

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Jack the front as high as you can, then squeeze the pipes with the expansion vessel cap off, and open any bleeder valves, heater, and so on. If you have her safely up in the air, you could start her up, and see if any bubbles of air rise in the header tank?:):
 

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The heater definately works pretty well (it's damn cold up here in the NE corner! :lol: ) but i haven't purposefully put it on like that to check.

Will give it a go, I think I will just have to siphon as much out as I can and refill it again while squeezing pipes to release any bubbles. Little frustrating if this doesn't work will give it a basj over the weekend. After doing this should I leave the resovoir cap off for a few minutes to let air out and then tighten?
Had this problem with an old Audi and I took off the top hose from the rad and so emptied the reservoir. Then, as you, say refilled it and left the cap off and run the engine, was surprised as a lot more needed to go in than what I had " drained " out. Took about an hour to settle down so that no more coolant was required and I repeated the exercise next day after a good long drive and the problem had gone..... Hope that yours works out as simple, I have a feeling it will.........

Not very warm down here in the flatlands also, more Scotch required to be added to alcohol stream perhaps ! On about the NE corner, went in the radome at Buchan one bright and sunny May morning and an hour later was advised to get out and back to the domestic site before I got snowed in, 4" of snow in about two hours at Easter ! :eek:

Good luck with the coolant.
 

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as far as I am aware, it is normal for the temperature to rise to around 90ºC, then drop down to around 75 as the stat opens. Then it will gradually build up to around 85ºC and stay there.

The coolant should be self bleeding. I would fill it slowly when cold, run the engine at fast idle until the fans come on (it may need more coolant when stat opens) then go for a short drive.

When the engine is cold check the level again and top up if nessesary.

There is a thing about the temperature fluctuations on alfa156.net
 

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Easy to forget to have the heater on "hot" when doing coolant changes....don't ask me how I know....;) :lol:
 

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Easy to forget to have the heater on "hot" when doing coolant changes....don't ask me how I know....;) :lol:
It shouldn't make any difference as the coolant is constantly flowing through the matrix whether the heater is on or not. :thumbs:
 

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Discussion Starter #9
I'm going to give it another go and see if it help's it.

It does not drop down initially until it gets just over the 90'C mark (takes between 5-10 mins driving) which may just be a normal thing but it's when it's varying quite a bit after that that i'm a little concerned. At the end of the day it's not the end of the world like, the car is running prety sweet, but I would like to know how this damn thing is meant to be working..!

On alfa156.net it does say it will drop down when the stat opens though, which means if it's reaching to 90'C then droppng thats normal, but if it's reaching say 80-85 then dropping to 75'C (also seems to be in conjunction with terrain or how much I accelerate) then i'm not so sure it is. Well i'll give it another go on the weekend, if it doesn't make any difference I will just put it down to how it's meant to work! :lol:
 

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my local mechanic had an airlock issue on a celica. he said the trick was to ensure the expansion tank is higher than any part of the engine, he had heating on full and ran the engine at full rev until the fans kicked in whilst taking the tank off the bracket and keeping it high up. (the celica actually had a slot to attach the released tank for the purpose)
 

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That`s correct neillied, position the car so that highest point is the
expansiontank (where the filler cap is), steep uphill or a ramp. Heating on full and rev it a bit up to increase waterflow in the system. Keep it there until there are no bubbels coming up from filler cap. (can take some minutes) Done!
Air always concentrates at the highest point
 
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