1998 Pontiac Montana Overheating

I'm a shade tree mechanic and I don't claim to know everything buy I will give you some options. 1-look at the oil. Drain it and look for a milky color or antifreeze in it. 2nd- Pull the plugs. Look for any sign of one or more of them to look very clean. Almost like it's been steam cleaned. Moisture in the cylinder will cause this.3rd- Buy an economical pressure test kit. Cost is usually about 25.00. This will let you know if one or more cylinders are losing compression around a blown head gasket. 4th- Leave the radatior cap off and let the car warm up to operating temperature. Look inside the neck of the radatior and watch for bubbles. All of these are tell-tell signs of a blown head gasket. I'm not familiar with the issue of removing the water pump. But.... Like I said, I don't know everything. As a side note, try replacing your thermastat and radiator cap. Both are relatively cheap and could also be the problem.

Water Pump is extremely easy to replace. Cost for pump and antifreeze should put you back about $60 or so. Time to change 1/2 to 1 hour. There reason to change the pump is just to eliminate it as the problem. Oil level rising and/or coolant loss other than thru the overflow is typically a head or intake gasket leaking. usually leak internally. If engine runs a little rough on startup and then smooths out, it is probably a head gasket. Both should be replaced. Dealers want about $1600 and up for that. :(

the water pump will cost you 30.00 for a new one. you will need a # 10 wrench or socket to take the pulley bolts out a 3/8 drive ratchet to pull the serpentine belt tensioner toward you to take the belt off. a 5/16 socket to fit the water pump bolts there are 5 of them. if the pump sticks to the housing you will need a screwdriver to pry it off with. it will take you an hour if you drain the coolant or thirty minutes if you just cut it loose as the pump comes out. a trick to loosening the pulley bolts is to loosen them before you take the serpentine belt off.and tighten them up after you put the belt back on. just don't forget to tighten them. look under the oil cap for any white mayonaise looking stuff on it.if it is then intake or head gasket leaking. can you hold your hand 2" from the end of the tailpipe with it idleing?usually running hot is a head gasket and loosing coolant with a fluctuating temp gauge is an intake gasket. the 3.4 motor is known for intake /head gasket trouble. save the paper work if it turns out to be intake or head gaskets as there is a classaction lawsuit against g.m. over the these on 3.4 motors 1996 thru 2004