View original topic: Want to listen to an engine and try to guess what is wrong?!
vanagonforever Sun Jan 25, 2015 2:18 pm

Hi everyone,

My 83.5 Vanagon has developed an unpleasant knocking sound recently. Here is a video I just took of the engine running:

The Vanagon has 235k miles on it. The engine at least had the top end rebuilt at some point in the past by the PO but I'm unsure of precisely when. It could have been as much as 100k ago. This is a tired ride but its always run smoothly during the 8 years that I've owned it.

Anyway, the noise started suddenly and my first thought was an exhaust leak. I can't find a leak though. Since the noise started I changed the oil (adding MMO in the process) since it was time and ran it enough to get the lifters to stop chattering. No impact on the knock though. Today I changed the plugs, wires, distributor cap, and air filter because I heard some misfiring when I let off the gas. That fixed the rumbling noise but did nothing for the knocking. I'm not particularly engine savvy so I'm at a loss of what to do next.

Any thing jumping out at anyone?

seventyfo Sun Jan 25, 2015 2:48 pm

Look for a cracked exhaust header right at the flange where it bolts to the head. They can be tough to see from some angles. I had one that was separated all the way around but could only see it from underneath and up close.

Wellington Sun Jan 25, 2015 3:14 pm

cover the tail pipe with a rag when the engine is running.
Use a helper. Then feel carefully around the exhaust close, not touching it, you should be able to feel the leak. As stated above. likely close to one of the flanges near the head.

Terry Kay Sun Jan 25, 2015 4:07 pm

Time to break out the credit card and treat the Van to a new exhaust system.
Whats wrong?
it's worn out.

Wellington Sun Jan 25, 2015 4:29 pm

"listened" again and "saw" a couple other things....
The vacuum line on the fuel pressure regulator is "sniffing" ambient air, hook it up!! I thin think I recall it goes to the plenum.
AC looks like it hasn't been used in years.....not going to fix it?? Why lug around the compressor, remove it.

o-town Sun Jan 25, 2015 6:14 pm

Like the other responses, I was listening and thinking to myself "I can't hear anything above the sound of that loud exhaust leak!" Still listening for a knocking sound. Fix the exhaust. Heard what sounds like regular valve train noise otherwise, to my relatively inexperienced ears

And second vote on connecting the hose off the fuel pressure regulator.

dhaavers Sun Jan 25, 2015 7:33 pm

Our work here is done, but yours now begins.

Git 'r done!

morymob Mon Jan 26, 2015 7:00 am

In the past rumbling on startup meant worn mains waiting 4 oil to help silence them a bit. Drove my 1st bug this way until i thought it was ready to come apart.

Abscate Mon Jan 26, 2015 7:32 am

Exhaust leak. Do you hear how it changes as you rev up? The flow becomes more efficient at higher flow volume so the noise actually goes down in volume.

If it were major engine damage, it would get louder as you revved.

Track down the cracked, broken, busted, rusty parts and replace.

And rejoice in no engine out this week....

:D :D :D

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