Technical Air in heater

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Technical Air in heater

LeonL

Member
Joined
Apr 19, 2012
Messages
134
Location
Wehe
Hello all,
Quick question. When i torn on the heater in my uno 70 it sounds like there is air in the cooling system and i checked the coolant level and it had dropped. The car doesn't overheat and the heater works fine.
Anyone got a idea what the problem could be?
 

bugsymike

Well-known member
Joined
Jul 2, 2022
Messages
1,475
Location
Torbay
Hello all,
Quick question. When i torn on the heater in my uno 70 it sounds like there is air in the cooling system and i checked the coolant level and it had dropped. The car doesn't overheat and the heater works fine.
Anyone got a idea what the problem could be?
It is possible you have a slight heater matrix leak that allows a little water to escape when hot and a little air to enter as it cools down.
Also it is possible you have a slight head gasket leak, putting gas bubbles in the cooling systen which are then trapped at the highest point, usually the heater top water pipe, even though I note heater is working and no overheating.
I suggest you remove any air in top of heater, fill radiator to correct level when cold and then in a week or so recheck.
If you have a rad tester you can pump a little pressure into the system then carefully slacken the top heater matrix hose to bleed out the air and re secure clip.
It is possible if you don't have a rad tester to do this when engine is warm and I have done it, but be VERY careful not to burn yourself!!!
 

s130

Moderator
Staff member
Joined
Dec 5, 2006
Messages
5,333
Location
Wrexham, North Wales
I'm trying to remember my Uno 70 and Uno SX.

1) There is a bleed tap on/around the top of the radiator the top

2) On one of the hoses that to the heater the is an inline bleed tap

3) The hot / cold control also adjusts a valve on the side of the heater unit. You need to check here for any leaks (was often a common problem) and have the valve fully open when bleeding the system.
 
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