Hi I have a 98 olds intrigue with the 3800 series 2. Bought it for pretty cheap and it had some issues: poor idle and cracked radiator/over heating. I bought a new radiator and thermostat and the plastic " heater hose thing that runs to the tensioner" NOTE: THERE IS ONLY ONE PLASTIC HEATER HOSE ON THESE ENGINES "THE TOP ONE" THE BOTTOM ONE IS ALUMINUM AND PART OF THE TENSIONER ASSEMBLY.
Anyways I tried my best to drain all of the old coolant out before installing radiator. Installed new radiator filled it properly and bled it properly. Today on the highway the upper hose just bursted off the radiator. On the way home it did it again so i used two clamps on it. it held but needs bled again.

1.to my point there is a dark mily like substance in my coolant tank. even after cleaning it out and flushing the system. I have also been keeping track of oil consumption and it is not using any.
2. there is a lot of pressure in my system everytime I bleed it. Also steam comes out of the radiator where the cap goes. And all hoses are extremely tight like theyr holding 100 psi.
WHAT IS GOING ON?

Couple questions here.
1. Do you know when any of the intake gaskets have been replaced?

2. Have you felt the whole radiator/upper rad hose to see if its warm/hot? I'm wondering if the thermostat is opening at all and if its not, the pressure build up will go back through the water pump and through the lower rad hose.

yes the upper hose is hot and i have no idea when the gaskets were replaced. I want to make this a good car but i'm getting affraid that its a failed head gasket

it is throwing the p0107 map code and ive changed the sensor and still brings the code up so maybe ur on to something

Hmmm, let the engine cool off, take the radiator cap off, start engine and watch the coolant inside the radiator. You need to watch the coolant from cold to hot so turn the A/C on and the heat off. This should put a sufficient amount of load on the engine to warm it up quicker. If you start to see bubbles coming up through the coolant, then its possible you may have a bad head gasket.

Another test would be to do a cylinder compression check. You should be able to find one at a Autozone, rent/loan or buy.

Sorry, but I highly doubt a bad MAP sensor would have anything to do with the cooling system.

I know the map sensor has nothing to do with the cooling system but u asked if i knew when the intake gaskets had last been changed...thats y i said that. But ill try your sugestions and post my results by the weekend.

i dont think ive ever heard of a 3800 with bad head gaskets. i would think it the manifold was bad and the lower intake manifold gaskets were bad there would be an opportunity for them to mix.

as far as the pressure did you check the rad cap or replace it?

Ok, keep us informed.

If he had had bad intake gaskets, he would be losing coolant and overheating and it wouldn't over pressurize the system. But his symptoms was he blew a rad hose off and its under alot of pressure. With that, it leads me to think head gasket. Though your right, even I don't ever recall seeing a 3800 blowing a head gasket.