. Does this move once the car is started and how do I check the little sensor is working also. If it is all knacked is there a cheap fix? Mark.Air cleaner hot air flap
Air cleaner hot air flap
Whilst checking my Pierberg carb today for a rough start, idle problem, I noticed that the hot air control flap in the air filter assembly was at rest directing cold air in i.e covering the hot air tube . Does this move once the car is started and how do I check the little sensor is working also. If it is all knacked is there a cheap fix? Mark.
. Does this move once the car is started and how do I check the little sensor is working also. If it is all knacked is there a cheap fix? Mark.Correction, it is important. Apologies but this is from memory....
Basically, what happens (or should happen) is that air is sucked from the pipe causing the flap to lift up when you start your engine from cold, thus blocking the cold air intake. Hot air from the exhaust manifold is then allowed into the air cleaner chamber and then into the carb which is supposed to prevent carb icing.
When the air temperature rises (around 68 degrees or something like that), the thermostat in the air filter housing (the rectangular block thing with two pipes going in) cuts off the 'sucking' air and the flap drops down to block the hot air coming in from the exhaust manifold and lets the cold air in.
If this is faulty it can cause cut outs when stopping suddenly and idling problems when starting from cold.
The way to test it is to disconnect the tube that runs from the block to the circular area on top of the flap mechanism and then suck on it to see if the flap rises - if it does then the vacuum is okay.
Then you need to check the thermostat thing which is a bit harder to do - you need to remove the top from the air filter housing and the air filter itself, then rest a long thermometer near to the block with the two pipes running from it. Carefully place the top of the air filter housing so that the thermometer is sticking out and is visible to read. Then start your engine.
If it's cold then the flap should be closed (you may need to remove the end nozzle from the arm to get a better view of the flap)
Keep an eye on the temperature gauge - when it gets to around 68 degrees the flap should slowly start to open (in effect, dropping down). If this does not happen then the thermostat thing is faulty and needs replacing. A cheap fix is to disconnect both tubes and join them together so the warm air intake is always open.
Basically, what happens (or should happen) is that air is sucked from the pipe causing the flap to lift up when you start your engine from cold, thus blocking the cold air intake. Hot air from the exhaust manifold is then allowed into the air cleaner chamber and then into the carb which is supposed to prevent carb icing.
When the air temperature rises (around 68 degrees or something like that), the thermostat in the air filter housing (the rectangular block thing with two pipes going in) cuts off the 'sucking' air and the flap drops down to block the hot air coming in from the exhaust manifold and lets the cold air in.
If this is faulty it can cause cut outs when stopping suddenly and idling problems when starting from cold.
The way to test it is to disconnect the tube that runs from the block to the circular area on top of the flap mechanism and then suck on it to see if the flap rises - if it does then the vacuum is okay.
Then you need to check the thermostat thing which is a bit harder to do - you need to remove the top from the air filter housing and the air filter itself, then rest a long thermometer near to the block with the two pipes running from it. Carefully place the top of the air filter housing so that the thermometer is sticking out and is visible to read. Then start your engine.
If it's cold then the flap should be closed (you may need to remove the end nozzle from the arm to get a better view of the flap)
Keep an eye on the temperature gauge - when it gets to around 68 degrees the flap should slowly start to open (in effect, dropping down). If this does not happen then the thermostat thing is faulty and needs replacing. A cheap fix is to disconnect both tubes and join them together so the warm air intake is always open.