Oil gauge on a 02 monte carlo ss when the engine is started up the oil gauge goes from L to H & when i idela thje engine it stays on HIGH /

SOURCE: monte carlo 2001 ss 3.8 V6

is the battery good if it is shorted out it will do this or if the charging system is not working

SOURCE: 2000 Monte Carlo SS (89,000 mi)

That slushy brown stuff is signs of a blown head gasket. Have a code scanner hooked up to find out why the light is on, it will probably show coolant temperature sensor. Just out of curiosity, check the pvc valve (if your car has one), and see if it's clogged. If it is replace it, the crank case is not getting ventilated.

SOURCE: install a 02 sensor in a 01 monte carlo ss

For the bank 0 (the engine one) Undo the dogbones holding the engine from rocking and push the car forward until it stops, then set the parking brake. With the car COLD, spray the sensor down with PB Blaster and tap it (TAP, not smack) and wait a bit, then use your O2 removal socket to pop it out. Put the new one in with a tiny bit of copper antisieze and be EXTREMELY careful not to get any on the head, just the threads - less is more here. Reconnect it, and then hld down the brake and take the parking brake off, then slowly release the brake to let the engine rock back. Reconnect the dogbones and you're all set.

For the Bank 1 (post cat), lift 1 side of the car and set it on stands, and chock the other wheels, slide under and look after the cat, before the resonator, on the ubend in the exhaust, unplug the sensor and PB blast it a bunch, then use the appropriate wrench. Install the new one with the above instructions.

SOURCE: What kind of antifreeze/coolant goes

if your doing a full flush(disposing of old fluid)use a NON ethylene mix..better for the planet...

SOURCE: 2001 Monte Carlo SS 92,000

No doubt valve seals,the oil gets burned so you usually can't see it.Normal for GM motors,actually the small amount of oil will help the longevity of the engine.They can be changed in a few hours but I would leave it alone.When they get really bad if the car sits and idles you will see some smoke. The seal is just a small o-ring ,they get brittle and fall off.The shop can use air pressure at the spark plug hole to keep the valve up,compress the valve spring and replace the seal.