Technical Cooling Problem

[oldskoolmk1unoturbo]

I have a problem with my cooling system in my MK1 UT.

basically when the car warms up the header tank starts to over flow, the fan will come on and the coolant level in the header tank drops, but the water temp guage doesnt really drop down and it continues to rise to the point where its too hot. i.e it goes into the red.

I think there is a airlock in the cooling system, but as the system is non bleeding then what should i do?

Mark.

 

[circolo]

Could be an airlock - particularly if you've recently changed the water, or replaced a part in the system. But I used to find getting an airlock in the UT system was difficult to do, and would bubble itself out with normal running.

How old is the Thermostat?

I know they generally sieze open, leading to too low water temperatures, but I guess they could sieze shut, meaning the water overheats.

I've had numerous Fiat's, (Strada's/127's/Punto's/Uno's/etc/etc) all of them suffered with thermostat problems, where the running temps were too low. Except for the 127 1300 GT, which was running too hot (as you describe with your Uno, water would expand out of the tank, and inspite of the rad fan coming on the temp would struggle to stay low), replaced the thermostat on that, and it sorted it.

 

[antsuno2]

Hi matey i have just replaced my thermostat on sunday which as circolo mentioned had stuck open leading to the engine running cool so probably using more fuel as the choke was running on (new thermostat £27 main dealer) realy easy, it bled itself, hopefully its not your headgasket? as that leads to pressure build up, water gushing out of the expansion bottle Ant!

 

[oldskoolmk1unoturbo]

The thermostat was replaced recently so i would have thought that it would ok, I have replaced the head gasket and have had the head skimmed, along with fitting a new water pump so they shouldnt be a problem,

After what you've both said i'm gonna take the thermostat apart and have it always open and see if it still over heats then, if not then i'll buy a new one from local fiat garage.

saying that last night i filled the system right to the top and tightened the cap and squeezed the hose and it seems my header tank cap is leaking so i will replace that first and see if it still does it.

P.S does anyone know where the cylinder block coolant drainage screw is? the picture in the haynes doesnt make it clear where it is

 

[antsuno2]

I didn't know such a drainage plug an the block existed just disconnect the bottom rad hose Ant!

 

[Chas Uno]

If the header tank cap is leaking, that will cause a drop in pressure leading to overheating and leakage of coolant. Fingers crossed a new one will sort it out

Only other thing I could think of is maybe the radiator is old and has reduced efficiency due to furring of the waterways?

 

[alexGS]

OK - I'm really confident on this one, since I had the exact same difficulties the first few times that I refilled my Uno Turbo years ago

... Take the small hose off the end of the radiator (the right end, as you stand looking at the engine bay). There should at this point be water (coolant) coming out of the fitting on the radiator. If not, then gently probe with a piece of stiff wire/tiny screwdriver etc. until water appears. Also check that the small hose (which runs to the front of the expansion tank) is clear.

When this small hose is blocked, there is no apparent problem with the engine running normally. But the small hose is essential for the self-bleeding quality of the Uno Turbo's cooling system which, by the way, is an excellent design when everything is working right. The filler/expansion tank is at the highest point of the system, so as Circolo and antsuno2 said, it's usually hard to get an airlock. But check that the heater is working/open freely as well, as this will also help to get air out of the system.

Cheers,
-Alex

 

[oldskoolmk1unoturbo]

I did check the small pipe from the rad to the expansion tank and its all flowing well so thats not the problem, also my heating is nice and hot so no problems there,

i'm picking up a new header tank cap from my local fiat garage so i hope that fixs the problem.

 

[oldskoolmk1unoturbo]

picked up a new cap from local fiat garage, only cost a fiver ;-)

its done the job and stopped it from leaking but i've noticed there is a leak from underneath the tank where the pipe joins, i'm gonna take out the header tank and sort it tomorrow so hopefully no more problems, i wish! lol

 

[F R O S T Y]

picked up a new cap from local fiat garage, only cost a fiver ;-)

its done the job and stopped it from leaking but i've noticed there is a leak from underneath the tank where the pipe joins, i'm gonna take out the header tank and sort it tomorrow so hopefully no more problems, i wish! lol

Mark Fit an alloy tank instead mate it'll last forever!

F R O $ T Y

 

[oldskoolmk1unoturbo]

i would mate but they aint cheap!

 

[rawill]

Please tell us how you got on.

Re the possibility of furring mentioned in post above.

That can happen, if exhaust gasses are getting into the water and it is driven that away for too long, obviously only with a small headgasket leak which is not enough to cause overheating.

 

[oldskoolmk1unoturbo]

i removed the coolant tank and cut an inch of the end of the hose which attaches to the bottom of the tank, fitted it all back with new metal clips and it seems to have done the trick ;-)

 

[circolo]

Sounds like the problems solved!

Incidentally keep an eye on the coolant expansion tank, from manufacture they had a fault which leads to splitting, which will loose a lot of coolant.

When I had my UT, I went through two (plus the original one when I get the car).