Volkswagen Repair: Question about a Humming Noise., vacuum leaks, cv joints

Question
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Followup To
Question -
I own a 1990 VW Fox. I live in Southern Virginia (where it is quite moist), and have no clue what the maintenance history of this car has been.

I have a question about a humming noise, heard only when I am on the road, at speeds between 25 - 50 mph. After 50 mph, the noise seems to fade away. The hum is not constant, but it seems to repeatedly come and go, fade in and fade out. I do not feel it in my steering wheel, nor does the front end shake. I am thinking it could be a wheel bearing, or a CV joint. What say you?

Also, my car is a beast to start when it is cold. It will not idle for nothing. I have to crank it at least once, if not twice, and hold the gas pedal at least half way to keep it running. Could it be the cold start valve? Could it be the Aux. Air Valve? Please let me know your thoughts.

I have heard that VW engines, especially the older ones, have some engine noise, like a low grade rattling, or valve noise. Is this true, or are they generally quiet?

Thank you for your time, and help.

Noel
Answer -
Noel,

I think you need a bearing, as CV joints make a cracking sound. To check the wheel bearings, sway the car gently to the left and right when you hear the noise, while driving. If it comes and goes, you've got a wheel bearing problem.  The bearing on the right will make noise when you turn left and visa vers.

As for your starting probems, you could be right with all of your guesses, but remember to first rule out any, and all vacuum leaks.  Then check your fuel mixture and idle adjustment.  Often the hoses between the intake and the throttle body leak because of oil saturation.  Pour some water onto the intake manifold by the injectors, if the engine stalls, you'll need new injector seals.

Finally, YES! VW Foxes do make a tapping noise from the lifters, this is normal.  It should go away when you increase the RPM's.  

Good Luck,

Paul

Hello Paul!

I have one question about the humming/vibration sound. I can drive straight as an arrow, and it does it. The sound only seems to appear at the above mentioned speeds. I will try the swaying right/left test to see if it does make a difference in the noise.

As to my starting problems...Well, I think my fuel pump is the possible culprit. It has been making a buzzing noise (rather annoying) off and on lately. Now it seems constant. I will replace it first, and then try the water test. That is such a simple thing to do, and thank goodness I just received my Bentley repair manual. Fixing fuel injectors is totally new to me. I also have a spare Aux. Air Valve handy, and may try replacing it, if the above does not remedy the cold nature of this VW.

The tapping noise becomes sort of a rattle when I rev the engine. I think it might be my alternator. I wonder if rebuilding the alternator is a good idea? It seems to have a some noise to it, and alternators are notorious for having the bushings go bad in them. OR...It could be a tensioner for the timing belt, or a pulley?

I truly do thank you for your helpful ideas, and for you taking the time to answer my questions. Have a great day!

Noel

Answer
Noel,

Careful with the fuel pump... those fuel lines get rusty and brittle.  A dirty fuel filter will cause the pump to get noisey as well.

The rattle at the alternator, could be the bearings... take off the belt and check for any free play.  If it's tight, you may need a timing belt tensioner, they get loud when the bearing start to go.

Good Luck,

Paul