VW Cabriolet Engine Noise

[Scdevon]

If the noise doesn't change with engine speed / load, it isn't likely an internal problem. Years ago, water cooled VW gas engines were known for having relatively harmless wrist pin noises which sound like a woodpecker double knock and are engine load sensitive.

 

[StevieC]

It does change with Engine Speed but not proportionally. Then it also disappears at some RPM's

 

[bustednutz]

OK, Try this. Take off the upper timing belt cover. I had a very strange sound coming from underneath mine years ago. Was a real pain to track down. I took off the cover to inspect. Except when I started it back up with the cover off the noise completely went away. As soon as the cover went back on...it was instantly back. Its just a few screws....give it a try. No idea what the cover had to do with it....but it was the cause.

 

[StevieC]

I will try that...

 

[Audi Junkie]

Those engines typically have excessive lash in the oil pump. Can you recheck oil pressure?

Another knocking noise comes from a vacuum booster pump that is driven off the camshaft. Take out the piston and it stops. No need for the vacuum boost anyway. I just don't remember for shure if the 1.8 has this feature.

 

[StevieC]

The oil pump was replaced 20K KM ago... The old one was done and not keeping up the pressure on the gauge in the cabin. The low oil light would be on solid when coming to a light. Replaced it with a high volume 2.0 pump and has been great ever since.

This car is not equipped with the Vacuum booster pump. This was eliminated on Cabriolets in July of 87 (at least up here) when they went to the electronically controlled mechanical fuel distributor with a "Waste Gate"

 

[Audi Junkie]

Have you considered Auto-Rx?