QuestionI have a 1989 Chevrolet G10 Van with a V6 2.6 L engine, 100k miles. I hear a faint intermittant rattling sound when the engine is under load or traveling at highway speeds, over 65 mph. The noise is a metalic 'chatter' type noise. I first thought this might be the water pump, but if so the noise would be heard all of the time, correct? I tried a tank of premium fuel thinking the noise might be due to low fuel octane, but that didn't help. I have taken the van to my mechanics, but they can't seem to hear it, since they don't usually test drive the car at highway speeds. The noise is faint and hard to hear since there is a lot of road and wind noise in the Van at high speeds. Any ideas?
Thanks for the help.
Weems
AnswerHi Weems,
A couple ideas...
Actually, a fan belt related noise, like the water pump could be worse at speed.
But some other possible noises are:
On many vehicles, but more so on vans, they put metal heat deflectors, like between the starter and exhaust manifold, above the cat converters, around the hood shroud etc. Some are just close to stuff, and some occasionally will break their mount brackets, and rattle.
I have seen dipstick tube mount brackets break and rattle the same way.
If it has you convinced that it is inside the engine, the knock sensor could be lazy, and not retarding the timing quickly enough. That is for the low octane type ping, or knock.
I have had catalytic converters rattle inside, as well as the exhaust system shock mounting/isolation rubbers get worn, or bent to where there is metal to metal contact as the engine torques under load, and that noise will transmit like crazy.
Some of those heat shields above, or more-so below the cat converters can get a little piece of gravel trapped that will rattle under just certain conditions. To find them, just kinda tap on them with the side of your fist when they are cool, and the engine is off.
And for the test drive....you drive, and make it do it for them.
Good luck,
Van
