heater blowing cold on idol

swamper

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ok this has now got me stumped and iv ran out of ideas..
iv replaced the water pump and the thermostat....re filled bled the system using the bleed screw and heater fan on
ran it checked it... topped up if necessary.....its not got any leaks and the coolant level remains normal.

now the warm air only comes through the vents when the engine is revved and if left to idol will over heat with cold air coming through the vents and then cooling fan doesn't trigger..
is this an air block?...now this car has just done around a 1000 miles over the last 3 days...if it is an air block the surely this would have shifted with all them miles....?
ideas would be of great help here?
cheers
swamps
 

swamper

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it will be if it doesn't sort its self out.......the cold air coming through the vents is almost instant as the the coolant has just drained away........ im baffled
 

z3cade

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Shouldnt worry, you're got an M now ;)
 

swamper

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you know me mate....it needs to be right..but cant get this one
 

heath

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Well for some reason it sounds like the water isnt circulating when its on tickover. First obvious thing to check is that the drivebelt is ok & not to loose. If thats ok it is quite likely you have an airlock in the system, in the past I have succesfully removed airlocks by removing the radiator cap (when cold) then let the car tickover till its warm so the thermostat opens then hold the revs on at about 2 to 3 thousand for a few minutes to try & force it out but keep your eye on the radiator so the water doesnt start blowing out. There are other ways to remove airlocks such as taking one of the heater hoses off (when its cold) & when the water starts flowing out of the pipe block it with your thumb until the water comes out the other pipe then join them back together. This can sometimes be done without the engine running using an assistant to pour the water in.
 

swamper

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thanks for the reply Heath
the drive belt is fine...iv done the running of the engine and seeing if i can removed the air like that but there isnt anything coming through.
i think i'll try the heater hoses next :-bd
 

Daz3

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could you cut the bottom off a coke bottle, undo the rad cap turn the bottle upside down then fill with coolant. This extra coolant should force the water round the system when started up. It worked on my saxo :D
 

swamper

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but its got an expansion daz....if it was going straight into the radiator then yep...

ok iv manage to get it moved by moving the pipes leading to the matrix...top and bottom of it is the air lock has moved (fingers crossed) and the system seems to run fine now...i left it to idol and heat comes through all the time and the cooling fan kicked in after while.
thanks for the help chaps
 

heath

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Fingers crossed then its sorted, when you say you moved the heater hoses do you mean you just moved them around to try & get the airlock out or did you undo them.
Let us know how it goes :)
 

swamper

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just moved them about Heath.....give them a squeeze flicked to foot well...took about 10 mins then they started to go hot...left it a while tried it again with the car jacked up on one side messed about with it again...all good... idled for ten mins rad fan kicked in....so even if its not fully out were on the right lines...nice one ;)
 
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