engine tapping ...oh no

[Tobert]

It could be valve adjustment. Mine taps like crazy, especially on lighter weight oils.

[Y33TREKker]

It could be valve adjustment. Mine taps like crazy, especially on lighter weight oils.

I was just throwing out ideas with the electrical snapping idea. I guess I had just assumed that the 3.5L VX motor used hydraulic lifters, but I see from the cd manual that a solid lifter bucket/shim type adjustment is used, so valve adjustment could very well be the cause.

How many miles on the engine? VX valve adjustment intervals are every 60k miles.

[IndianaVX]

just rolled 63000..........

[Ldub]

Check your exhaust system to find the most likely cause of the sheet metal rattling sound...the heat shield(s) are a known culprit.

[Joe_Black]

If you have a Harbor Freight nearby you can pick up a mechanic's stethoscope for about $6 which can help isolate the source of the sound. You can also find them at NAPA and other auto parts houses for a little more.

If the sound is coming from the head then it's likely the hydraulic valve-lash adjusters, which have a published known-issue of sticking from varnish build-up. The typical "fix" is the use of 0W-30 or 5W-30 Mobil-1 which will remove the varnish over a period of time. The adjuster could also be failing (unlikely at your mileage, but possible), which in a worst-case scenario would cause very rough running as the affected valve stuck open.

Ldub's exhaust shield clatter is another valid possibility, and a while back Johnnyapollo had a noise that would only happen while in drive that turned out to be the exhaust making contact with the right side suspension link.

How long have you had your VX and been using Mobil-1?

[psychos2]

If the sound is coming from the head then it's likely the hydraulic valve-lash adjusters, which have a published known-issue of sticking from varnish build-up.

What??? The only way to adjust the valve is with a type of shim that goes on top of the valve stem. We call them lash caps at work. We do not have lifters on the vx. It is a setup were the cam opens the valves. shawn

[Joe_Black]

I know, that's what I thought at first since that's what I'm familiar with as well from my FIAT/Lancia and Kawasaki DOHC experience. Apparently, and this is according to Isuzu service information and not my actual under-hood experience, our engine has hydraulic self-adjusting "lash caps". I'm about to have lunch with a friend who owns and operates a local major repair shop and will have more info then.

UPDATE: Apparently there is a such thing as a self-adjusting hydraulic tappet bucket for direct-impinging OHC and DOHC applications. When home later I'll look in the service manual for more info.