Hi there I have been investigating a creaking noise every time I accelerate coming from the centre vent,

I pulled the vent out and noticed that when I accelerate, gently or hard the vent Closes when I let pressure off the vent opens

is this normal behaviour or do I have a vacuum leak or something ?



regards

 

When you shut off, inlet manifold vacuum is at maximum, so you get vacuum at the servo controlling the flap via the control valve. There is a vacuum reservoir and should be a one-way valve so that the vacuum is maintained when the throttle is opened, and manifold vacuum is minimal.

So the short answer is there appears to be a vacuum leak or the one-way valve isn't working,

 

vacuum lines from engine to interior

 

When this happened to me, it was the one-way valve on the vacuum line. Well, more to the point, the fact that my car LACKED a one-way valve.

 

in USA LHD cars, this check valve is located hanging near the battery, close to the firewall/bulkhead, between the vacuum hose from the engine, and the vacuum hose to the Servo in the interior.

seems like it sticks in the closed position, I've put mine in a pan with warm water until it unsticks and starts working again.

 

Cool thanks guys i located the valve..would it be true to say the opposite would happen if i flipped the one way valve in the opposite direction, i gave this a go and the flap stayed shut ...if it was the valve i would assume i would get the same results

i will hunt try hunting around for a vacuum leak thanks for the guidance will keep you posted when i check it out tomorrow

 

all you need to do is remove and blow through the check valve in the direction of the arrow, if air goes through one way, but not the other, the valve is fine.

 

Hi All,

Well i found the problem turns out there were two lines going back in to the firewall on the passengers side "Left" "Steering wheel on the Right " that had a date with some Battery acid that had leaked from the previous battery

corroded all the way through so cleaned it up with some vinegar and black electrical tape and its done the trick until i can get some replacements

Car idles nicely and no movement int he flap....i love a good win

 

good job! you could cut and splice the bad hose section using plastic "splicers" sold at autoparts stores. I think the hose is 1/8" inside diameter.