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Discussion Starter #1
Hello. I have a stupid question. 2 Months ago my 156 began making a horrible noise. At first I thought it was the clutch thrust bearing. I changed the clutch and no luck. Then I thought it may be a timing belt or balance belt bearing/idler. Changed out the timing belt and balance belt and water pump and the noise is still there. Then by chance i noticed the noise stops when i squeez shut the hose to the PCV. However this also causes the engine to idle rough and idle low. I replaced the PCV ( sometimes called a Vapour Separator Valve) with a second hand one. Noise still there. I read in these forums someone else bought a new PCV and the spring and valve (shuttle) are different to the original so I have ordered a new one. In the mean time I have placed the valve back in the PCV with no spring. This stops the noise and the idle fluctuation problem however I guess it means blowback to the crank is now possible, and also I now have pinging (detonation) under load.
My question is can a vaccuum leak from somewhere else cause the PCV to whistle and idle problems?
I know Gazza82 has made a post somewhere referring to this issue but I cant find it.
Thankyou anyone who can answer this question.
 

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Discussion Starter #2
Hello. I have a stupid question. 2 Months ago my 156 began making a horrible noise. At first I thought it was the clutch thrust bearing. I changed the clutch and no luck. Then I thought it may be a timing belt or balance belt bearing/idler. Changed out the timing belt and balance belt and water pump and the noise is still there. Then by chance i noticed the noise stops when i squeez shut the hose to the PCV. However this also causes the engine to idle rough and idle low. I replaced the PCV ( sometimes called a Vapour Separator Valve) with a second hand one. Noise still there. I read in these forums someone else bought a new PCV and the spring and valve (shuttle) are different to the original so I have ordered a new one. In the mean time I have placed the valve back in the PCV with no spring. This stops the noise and the idle fluctuation problem however I guess it means blowback to the crank is now possible, and also I now have pinging (detonation) under load.
My question is can a vaccuum leak from somewhere else cause the PCV to whistle and idle problems?
I know Gazza82 has made a post somewhere referring to this issue but I cant find it.
Thankyou anyone who can answer this question.
I have installed the new PCV and now thw whistle noise is quieter and less frequent but the poor idle is back with an engine leak, Cant find a vaccuum leak.
 

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Not sure if it's the same as a 147 does the end of the pcv pipe fit to turbo and MAF pipe?
 

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I wonder if you have excessive blow-by pressurising the crankcase more than it should. What happens if you let the pcv hose vent to free air whilst plugging the MAF entry? A compression test may help. Has it done a lot of miles? Burning excessive oil?
 

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Discussion Starter #5
Thanks for your replies. The 156 does not have a turbo and the pcv hose goes from the rocker/camshaft cover to the intake manifold with another hose from the same y piece on the rocker cover to the air intake just before the throttle body ( venturi vaccuum). I think there is exsessive air entering the crankcase through a vaccuum leak but not blow by. Compression test is good so rings are ok. Dip Stick seal is good. Not burning oil. Leaving the pcv hose free to air causes very rough idle or very high idle (2000 revs).
 

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Discussion Starter #6
Problem fixed. Intake manifold was cracked. Changing the manifold with the engine in is a ******* but fixed now. Whistle is gone, mixture is good with no rough idle and no pinging. Fuel economy is good now and power. Only issue is the new manifold has one hose underneath that goes from the manifold near the throttle body and back into the manifold and the old manifold that came out has two.
Thanks for the replies.
PS if you stretch the PCV spring you can stop the whistle noise but this does not fix the problem.
 
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