Good afternoon, This forum is a great source of info. and it seems great people, thank you.

I have a 1998 Oldsmobile 88 with the 3800 Series II Engine, this car has I think close to 25x,xxx miles on it, a lot of those miles were mountain roads in West Virginia. So its been driven hard, and long. I say this mainly for background info. only. Earlier this year, I got tired of the coil packs constantly frying, and picked up an ICM at a junk yard in Brandywine, MD. and installed it correctly, all of my spark plug wires are labeled. That was the last bit of maintenance I had done before the present problem arose.

Skip forward several months, I start hearing a high pitched whine or, shrieking almost, coming from the passenger side of the engine, we've always had coolant issues with this car anyway, and it sounded like a water pump going, before I had a chance to replace it, the shriek/whine stops, and the temp of the engine shoots through the roof. the car ended up dying once or twice because of the high temperature.

I replaced the waterpump, still overheating. Now I know that the thermostat if it heats up to that degree, the bi-metal of the spring can warp, so I replaced the thermostat, its still overheating.

I haven't flushed the coolant system yet, but it seems to be circulating nicely. Could the radiator once again have died?

Also, knowing the age of the car we have not replaced the upper Plenum/intake manifold yet, and after I had replaced the thermostat, and turned the car off, I was hearing what sounded like, fizzing, or air escaping from around the PCV side of the intake manifold. Could the manifold needing to be replaced cause the over heating issues that I'm getting?

Also in the manual, it speaks of ignition timing can cause overheating but on this engine its all handled between three sensors. If one of the sensors is off, could that cause the issue as well?

The car was driven around town last night, and the temperature held steady at 250 deg. F, the 'idiot' overheat light did not come on, and the cooling fans kick on at 212 deg. like they're supposed too, could this be a matter of a pc issue, maybe clean the CTS? I'm also going to bleed the air out of the coolant system today as well, and see if that helps, I'd read that on the 3.4 motors, air can cause overheating as well.

I've told my significant other that you cannot kill these cars. This engine and trans. combination are amazing, if not bulletproof. But I will admit, I'm a little vexed: and since I don't walk with a cane, often, and my patient hasn't crashed 3 times in an episode, I'm still grasping for answers...

Any help would be amazing, thank you.

the only common 3800 issue is the lim gaskets and upper intake cracking,and coolant elbow not holding coolant. i would suggest you replace all at the same time to avoid aggravation and if you do it all at the same time you wont have to worry for quite a while. i also blocked my coolant ports to the plastic intake which seems dumb to me, of coarse you are going to have isssues if hot fluids are going through plastic for years on end.

you can get the new lim gaskets, the dorman upper kit comes with everything else to make it last including the new egr ports, except they dont give you enough orings for some reason. i got everything from rockauto i think for around 120-130
https://www.gmforum.com/mechanical-1...2005-a-304071/

while you have everything apart you should take out the fans and blow the rad/condenser out from the back with a garden hose, they need done every once in a while

When the funds were appropriated, I planned on getting the Dorman kit, and basically replace everything: flush the radiator, o-rings, the works. What I cannot figure out, is why the temp. is registering 70 deg. hotter than it should, and maintaining that temperature. The other thing is, is that there is coolant in the overflow tank, if there was low coolant I would have thought there would have been none in it.

there could be air in the system did you bleed it? is the temp always high or does it just go up fast? you have a scanner that reads temps? does it follow the gauge?

The temperature usually runs about 180-190 deg. I bled air out of the system, and there was quite a bit. My question is should the air flow be constant, or will it eventually taper off?

I bled air out and the temp held steady around 225. The gauge is fairly accurate, I wanted to clean the sensor, but its fairly stuck in, and melted to the block.

180-190 is about normal for a 3800. 225 is a tad too high for sitting(even with a/c on).

If the pump and thermostat have been replaced, I suggest an intensive cooling system flush. Especially if the history of the car is unknown.

i would try cleaning the rad fins from the back too.

I did bleed the system, and I'm losing coolant, not a lot, but slow, its not outside, except where that elbow joint comes out of the engine above the water pump, the rest isn't visible (I know what that means). The temp fluctuates from 190-200. I still need to flush the radiator. All of my friends with hoses either their system is down, or the hose is dry rotted...such is life. What are 'Rad fins'?

Now I need to figure out why the brake pedal travels so far to the floor. Thank you for the help.

radiator fins, just wanted to differentiate between cleaning the inside and the fins outside, which is a common problem. getting pollen and road junk in the condenser and radiator is the biggest problem i run across. i live out in the country and i normally have to clean my wifes 98 every couple years

I hope your engine isn't eating coolant. Do you know when the last time the lower gaskets have been replaced? And next chance you get, look at the top of the black intake plenum and look for 3 date stamps.