Engine whines during idle. Taking off oil cap will stop high pitch noise.

[snake0ape]

Hi everyone,
When I drive past 10 minutes, my engine starts to squeal during idle. It is a loud high pitch squeal similar to a fan belt squeal. However it is a constant pitch. It is coming near the front end near the belts. When I remove the oil cap, the engine pressure is relieved and the squealing stops. When I tighten the oil cap , the squeal re-starts. The noise happens during idle and when engine is hot. What can I do to fix this problem?

Also the CEL just turned on indicating a lean condition.

Thanks alot all.

[boomtime]

You should start looking in two places:
Cracked vacuum lines or fittings (pcv).
Power steering pumps and anything driven by the belt.

Do your revs rise or fall when you take the oil cap off?

[old guy]

Remove the oil filler cap with the car at idle. Is there excessive vacuum pulling down on the cap?

[john_gonzo]

Using the old length-of-hose-as-a-stethoscope trick may help you locate the source of the noise.

[diagnosticator]

The make up fresh air supply to the crankcase ventilation system is most likely plugged up, preventing fresh air from entering the crankcase, replacing the volume of crankcase blow-by gasses evacuated through the PCV valve sucked into the intake to be burned. The plugged fresh air supply causes excessive vacuum in the crankcase, resulting in the whistling noise you described with the oil fill cap installed. With the cap removed, the excess vacuum pressure in the crankcase is relieved, so the noise stops.

[snake0ape]

Thanks for replies. To answer the questions above,
Yes, there is a strong suckling force to pull off the oil cap. In idle, when oil cap is removed, the idle drops from 1000rpm to 900rpm.

[old guy]

Thanks for replies. To answer the questions above,
Yes, there is a strong suckling force to pull off the oil cap. In idle, when oil cap is removed, the idle drops from 1000rpm to 900rpm.

Excessive vacuum is often caused by a defective PCV valve. Normally the PCV pulls a metered amount of air. Either you are getting an excess amount of vacuum or your PRV is clogged and not letting purge air into the block.

First remove the vacuum line that connects the PCV to the intake manifold and see if you can blow air through the line. If you can blow any air at all you need to replace the PCV valve. If it checks the air flow then you need to remove and examine and or replace the PRV valve.

[snake0ape]

Can someone tell me how I can find the PCV valve on the B6.

[old guy]

Can someone tell me how I can find the PCV valve on the B6.

The PCV valve is underneath the intake manifold. There are three different versions depending upon the model year. What year is yours?

[diagnosticator]

The PCV meters crankcase blow-by into the intake manifold. If the PCV is blocked, there will be low or no crankcase ventilation function, and the crankcase pressure will be excessive high pressure, not to much vacuum in the crankcase. The only way for to much vacuum pressure to occur in the crankcase, if if the make up air supply from the tip is blocked, due to a plugged tube or hose between the tip and the crankcase pressure regulator valve.

[old guy]

The PCV meters crankcase blow-by into the intake manifold. If the PCV is blocked, there will be low or no crankcase ventilation function, and the crankcase pressure will be excessive high pressure, not to much vacuum in the crankcase. The only way for to much vacuum pressure to occur in the crankcase, if if the make up air supply from the tip is blocked, due to a plugged tube or hose between the tip and the crankcase pressure regulator valve.

Not necessarily true. The PRV is in a normally open condition. As vacuum increases the diaphragm in the PRV pulls down on the intake tube and the only purge air enters through the small metering hole on the side of the tube. The metering hole on the PRV tube pretty much matches the metered air being pulled through the PCV valve.

If the PCV metering valve is defective and pulls an excessive amount of vacuum the PRV can't provide that amount of flow and consequently the block receives an excessive amount of vacuum. That's pretty much the condition that the early 034 billet PCV valves caused and consequently they were causing an additive code at idle. Once 034 scaled back a little on the metering the code complaints went away.

[diagnosticator]

Not necessarily true. The PRV is in a normally open condition. As vacuum increases the diaphragm in the PRV pulls down on the intake tube and the only purge air enters through the small metering hole on the side of the tube. The metering hole on the PRV tube pretty much matches the metered air being pulled through the PCV valve.

If the PCV metering valve is defective and pulls an excessive amount of vacuum the PRV can't provide that amount of flow and consequently the block receives an excessive amount of vacuum. That's pretty much the condition that the early 034 billet PCV valves caused and consequently they were causing an additive code at idle. Once 034 scaled back a little on the metering the code complaints went away.

If the PCV is blocked/plugged, I cannot see any way for the crankcase to be exposed to excessive vacuum pressure, since there is insufficient flow of blow-by gasses from the crankcase. With no or low blow-by flow out of the crankcase, there is nothing to create excessive vacuum in the crankcase. I can't think of any situation where excess vacuum exists in the crankcase unless the fresh make up air flow is blocked, with blow-by flowing out of the crankcase into the intake manifold through the PCV. If the fresh air make up flow is blocked, the crankcase pressure regulator cannot control fresh make up air flow into the crankcase, regardless of the position of the diaphragm in the crankcase pressure regulator valve. If the ventilation plumbing is blocked at one location, it is most likely flow restricted everywhere due to deposit accumulation, including fouling the crankcase pressure regulator valve.

Consequently, the entire crankcase ventilation plumbing must be cleaned out, and the crankcase pressure regulator valve and PCV replaced.

[old guy]

We aren't talking about the same condition. If the PCV is plugged I completely agree with your assessment. I'm referring to an open PCV not a plugged PCV. If the PCV metering disc becomes dislodged it will pull excessive vacuum on the block. It will also allow boost pressure to enter the block under boost conditions.

[snake0ape]

The PCV valve is underneath the intake manifold. There are three different versions depending upon the model year. What year is yours?

I have a 2004 Audi A4 ultrasport. What is the part number I need for three 2004 Pcv valve. I am suspecting Audi does not call it a pcv valve.

[old guy]

Clicky click®

Did you try blowing air through it?

[snake0ape]

Is this the PCV valve that is underneath the intake manifold? (2004 A4). Which accessible tube can I blow into to see if the PCV is bad?

[old guy]

Is this the PCV valve that is underneath the intake manifold? (2004 A4). Which accessible tube can I blow into to see if the PCV is bad?

This hose connects to the PCV valve underneath the intake manifold. You should not be able to blow any air at all through this line. If you can then replace the PCV valve. If you can't then you have a clogged condition as Diagnosticator was describing.

[snake0ape]

Thanks Old guy. I can blow right through the hose. I will need to replace the pcv for sure. Is the best way to replace the pcv valve is by taking off the manifold?

[old guy]

I replaced mine a few months ago without removing the intake manifold so it can be done. Removing the manifold would probably be a lot easier. Fortunately mine is a late 03 model so I have a metal hard pipe connecting the PCV to the PRV on the back of the valve cover. Yours has a plastic line connecting the two. You need to be prepared to replace that connection as well as the elbow that connects the other port of the PCV to the block baffle. Those components tend to break apart when removed.

Here is what you are going to be up against. This picture is from an 04 model. To the right of the PCV is a broken elbow that attaches to the block. To the left of the PCV is the plastic hard pipe connecting to the PRV that may break when you try to remove the old PCV.



Here's an alternative to replacing the plastic pipe if yours breaks: Clicky click®

Good luck!

[snake0ape]

Thanks Old guy. I guess it makes sense to replace the whole breather system. It's 10 years old. I am going to think if I do all this myself or give it to a moonlighting mechanic. This is my only car. So I don't want to be missing a part when the car is apart.

[diagnosticator]

We aren't talking about the same condition. If the PCV is plugged I completely agree with your assessment. I'm referring to an open PCV not a plugged PCV. If the PCV metering disc becomes dislodged it will pull excessive vacuum on the block. It will also allow boost pressure to enter the block under boost conditions.

I agree. This explains the difference between our interpretation here. :)

[snake0ape]

Thanks everyone and especially old guy. I ended up using an alternate silicon hose kit and paid a VW guy to put it in for me. http://store.034motorsport.com/breat...-silicone.html

the car runs great now. I hope this breather kit will last. .

[Lornnn]

Thanks everyone and especially old guy. I ended up using an alternate silicon hose kit and paid a VW guy to put it in for me. http://store.034motorsport.com/breat...-silicone.html

the car runs great now. I hope this breather kit will last. .

Wish we had this option with the 3.0. The entire thing runs about $350 and you need Santa's little helper hands to even get the old one out.