All of a sudden she started making this loud knocking/tapping

shadetree_v70 · Post by **shadetree_v70** » 03 Feb 2018, 17:27

I sure hope this isn’t as bad as it sounds but hopefully you guys can at least help narrow it down. So here I was as, happily changing her thermostat and tracking down some weird coolant leaks (the bungs on the radiator where the hard lines attach needed to be snugged), figures I would drive her around the plug to make sure she was good and burped, and this ticking/tapping sound showed up. No change in power, no codes thrown, no leaking oil or coolant whatsoever.

I burnt valve would be noticeable power wise, but could a lifter go bad and it still runs well? It idles smooth (except for that god awful rattle) but I don’t think it wise to drive it until I know what’s going on. Thanks in advance for any help.

1998 V70 GLT with 332,000 miles

Post by **RickHaleParker** » 03 Feb 2018, 18:08

I was as, happily changing her thermostat

Did you move the fuel rail to get to the thermostat housing?

This is where a Mechanics Stethoscope comes in handy.

Post by **oragex** » 03 Feb 2018, 18:16

That doesn't sound like a valve. I would even stretch it and say it doesn't sound like a rod bearing either. But check the oil to be sure.

Something got caught near the serpentine belt? A lost spanner? I'd check the pulleys

shadetree_v70 · Post by **shadetree_v70** » 03 Feb 2018, 18:31

Oil is topped up and with that many miles I change it religiously. No leaks either, although she uses 1/2 qt about every 6 weeks

Post by **FLXC90** » 03 Feb 2018, 18:32

did the noise start before or after you started driving. You could run a compression check for reassurance

Post by **wizechatmgr** » 03 Feb 2018, 18:33

Do an oil change and make sure your filter hasn't collapsed. I'd also double check oil pressure manually with a gauge. Mine sounds like this for a second or two during cold starts at below freezing temperatures.

shadetree_v70 · Post by **shadetree_v70** » 03 Feb 2018, 18:44

I was driving easy, about 25mph, and the noise started. No sputter, stutter, noises, no loss of power.

Maybe I did drop something down by the serp belt but I hear the noise sort of all over not just on that end.

Post by **oragex** » 03 Feb 2018, 19:59

A visual check of the serpentine belt doesn't show anything? I would also remove the timing belt covers and watch the belt and pulleys running. Personally, I wouldn't drive the car until sorted, a safe approach

It may help to get a 2ft hose and put one end near parts of the engine and listening at the other end. just double care near rotating parts - it may cost an engine

Whatever the outcome, at 330000 miles it had a respectable life

Post by **RickHaleParker** » 03 Feb 2018, 20:52

Another possibility, it does sound somewhat like my 2.9 did when it was crossfiring. Pull the plastic cover off, get it in the dark and watch for crossfire. ... Did the distributor cap get bumped and cracked?

shadetree_v70 · Post by **shadetree_v70** » 04 Feb 2018, 07:54

oragex wrote: ↑03 Feb 2018, 19:59 A visual check of the serpentine belt doesn't show anything? I would also remove the timing belt covers and watch the belt and pulleys running.

No tools or other objects lodged. This is something internal but I can’t tell if it’s upper or lower. Oil is drained for inspection and I’ll probably remove the oil pan to look for metal pieces.