2001 Jimmy valve tapping?

My Jimmy makes a noise like a valve tapping -- almost pounding to get out. It's not that I'm low on oil: I've checked and the level's good. And the noise goes away after the engine gets hot (sometimes quite a few miles after the engine gets hot, but it does go away). It's more pronounced and persistent at colder temperatures. The weather's been real strange here lately -- sometimes very cold, sometimes 20 or more degrees above normal -- so I've had a range of temperatures over which to observe this behavior (we hit 66 earlier in the week, and the noise never made an appearance that day). Any ideas why this could be happening?

Thanks.

Hows the oil pressure, are you loosing any coolant? What kind of tapping do you think you hear, is it deep in the engine, bottom end, or like a lifter tapping noise?

Tapping sounds high, like a lifter. Oil pressure seems a little high to me. Yeah, losing a good bit of coolant (I have the dreaded trashed intake mani gasket, for which I have to save up to have repaired, or hope I get a good tax refund). Overdue for an oil change, anyway, so I'm going to get that done in the next day or two. Will see if that quiets things.

Tapping sounds high, like a lifter. Oil pressure seems a little high to me. Yeah, losing a good bit of coolant (I have the dreaded trashed intake mani gasket, for which I have to save up to have repaired, or hope I get a good tax refund). Overdue for an oil change, anyway, so I'm going to get that done in the next day or two. Will see if that quiets things.

You found your problem. The coolant is getting into the engine and running down the lifter valley to the lifters contaminating them, thats why you get the lound lifter rattle. Any other coolant that is getting in is generally damaging the engine/bearings, etc. Running it like this without the intake gaskets fixed will ruin the engine. My suggestion is either park it until you can get the intake gaskets fixed, or get them fixed ASAP. Running it like this will almost certainly require a rebuild soon, costing a lot more than just gaskets, that is if irreversable damage hasn't already been done. There is a good write-up for gasket replacement on here, in the tech section if you are considering to do them yourself.

I had the same problem with my 2000 Blazer. It finally got to the point that it pecked all the time. The factory lifters installed in these engines are not the best. The piston in the top of the lifter is very thin, a little more than an eighth of an inch, and can cock a little in the bore and leak oil pressure off. There is also a check ball in the side where the oil enters the lifter that can fail and the lifter collapses instead of opening the valve. If your going to replace the intake gasket anyway, that would be the time to change that lifter. For about 12 bucks more you can fix both problems. Good luck.

My '97 Bravada did that every winter. I changed the oil and the problem went away...every winter. I guess the oil must've thickened up with condensation????
Kendall 10W-30 & Delco Oil Filter.

I've kept the oil changed, but even with fresh oil it still pecked at start up on cold mornings, then one day it it didn't stop pecking and got much louder. I poured Marvel Mystery oil in the crankcase and ran it untill it was warmed up then did another oil change, it still hammered. This might have been caused by the dredded intake gasket leaking coolant into the lifter gallery, I'd had to add a little coolant a few times. When I pulled the intake I didn't see where it might have been leaking. I removed the lifter that was pecking ( it wasn't hard to find, you could move the rocker back and forth over an eighth inch) took it apart and cleaned it. Filled it with oil and reassembled it, with little presure the lifter colapsed. Installed a new lifter and the problem was solved.