Thanks for the replies. Didn't have time to work on the car today but did look at the plastic UIM and top of the LIM. It looked like there might have been some slight seepage around one of the O-rings judging by the brown coolant stains but nothing that would go directly into the LIM. We know the LIM is leaking around the corner on the rear cylinder on the throttle body side and under the throttle body...

Something i don't understand is how, if it is just a problem in the UIM and LIM, how can the coolant get combustion gas in it? It defiantly failed the cumbustion gas test at the radiator filler neck. The blue chemical turned yellow. After being parked on the lower end of the driveway, while driving up the hill to the work area, a 30 to 40 foot trail of water came out the tail pipe.


I can see how the LIM could leak coolant into the cylinders but how could it get into the radiator system?
I know the EGR dumps into the UIM and that there are 2 coolant passages in the UIM for the throttle body. The EGR gas is under some pressure but not enough to force it into the coolant passage especially with the engine running as the EGR gasses would be sucked down into the vacuum of the intake.
So i am confused as to how the mechanics of a UIM or LIM could allow exhaust gasses into the sealed cooling system... (yes its not sealed because it is leaking out under pressure when hot,) But how would it get into the radiator?
The only way i know of, on older engines that is, is to have a bad head gasket, cracked head, or block. it would enter on the compression or combustion stroke...

Thanks
Anna

Your 1997 Park Avenue has a series 2, and is not representative of the 'Series 1' used in this vehicle.

Ok well we got the lower intake off today and couldn't really see a bad place in the gaskets but the pressure test confirmed coolant was leaking out.

The valley under the intake looked pretty clean but there is a slight brownish red tint like the color of the oil had to it. The bottom side of the lower intake also has the same brownish red tent to it. There was no sings of water in the oil when we drained it out of the engine though. There was no signs of water in the valley under the intake.
It is very similar to the color of the coolant though, just not as prominent.

When we looked into the bottom side of the lower intake passages , they were all black with mild black buildup in them. When we looked into the cylinder head intake passages, They all have the same black build up in then except the part of the casting where the intake valves run through, they had a small brownish red area on them except for cylinder #4. Cylinder #4 is the one that had the worst looking spark plug. the plug looked like it had not been firing very good. We looked at the coil packs and #4 has rust on the coil tip so that would explain the difference in #4.

We pulled the exhaust manifold off of the front side cylinder head and all three exhaust ports on the cylinder head as well as the exhaust manifold are black with a slight amount of carbon build up. The exhaust port on #1 on the cylinder head might be just a bit cleaner then 3 and 4 as far as slight carbon build up.

It is my understanding that if you have a bad head gasket that is allowing coolant into the combustion chamber, that the piston and valves will be much cleaner then the others. I don't know if that applies to the exhaust port though.

Thanks
Anna

PS. The exhaust manifold is still fastened to the rear side cylinder as well as to the pipe that runs back under the car. Can the engine be rolled forward once the rear exhaust manifold is disconnected from the pipe going under the car? That would make it much easier to reach the exhaust manifold bolts on the rear cylinder or are those reached from under the car?

Disconnect the down pipe and dog bones and pull it forward to get the back side.

Thanks carfixer007, that worked great and we got the cylinder heads off.

We are far from mechanics but nothing jumped out at us that would indicate a coolant leak into the cylinders. There were no burnt of missing pieces on the gaskets, heads, or block. There was 1 coolant passage stopped up between cylinder 4 and 6.
Piston #2 looked a bit cleaner then all the others but still had some carbon on it. None of them were coated solid in carbon. They all looked like some of the carbon build up may have flaked off.
Will be taking the cylinder heads to the shop tomorrow to have them checked out.

The weakest cylinder #1, there is a issue inside the cylinder wall. You can still see the cross hatching and there is (we guess) normal wear marks down in the lower part of the cylinder wall on the front and rear side but there are some spiral scratches in the upper of the cylinder. The spiral scratches run up and down spiraling similar to the cross hatch marks but deeper. Not knowing much about this, to me they look like they could have been made when the block was originally honed at the factory. Maybe the machining set up was just a little off or something was stuck/chipped on the tool they used to home the cylinder?
The pic with the arrows. the lower scratch with the red arrows can be just barely felt with my fingernail. I read somewhere to try to slide a penny past it. I tried that and it did not hang up on the scratch. You can see in some of the pics that they are spiraling downward to the left and another set spiraling downward to the right.
There are 2 that run parallel to each other with just under an inch between them. I took rough measurements with a depth gauge and those two that are parallel get about a 1/16 of an inch closer together as they spiral downward to the left.
They do not run all around the cylinder. there are none on the upper side. The only one that I can feel is that lower one and that is about 1 inch around.

Anyway
I am going to try to post some pics and see what you guys think...
Thanks
Anna

Ok now that I know how to post pics,,, here is the tube I am talking about. We are talking about the same one I believe... I ordered a 2 set factory paperback GM service manual for this car and can not find a section that shows taking the tube out or an O-ring on it.. I would bet there is and like you said, it is just corroded inside..
What would that part be called and how would I go about finding the proper O-ring? Maybe a dealer would be able to pull it up?
I looked through the manual under Heating, water pump, timing cover, hoses, and no luck...

The welder on bracket that bolts to on to one of the studs on the tensioner mounting bracket, you can not see the mounting end with the mounting hole but it is the bracket welded to the metal tube right by the hose clamp. It is defiantly a heater hose.
Thanks
Anna

Older engine but similar design. It was initially difficult to rotate the pipe off the stud to be able to pull it out of the timing cover.
I got the new o-ring in the timing cover set. No idea what the dimensions might be,

Thanks CorvairGeek. I sprayed some WD where the pipe goes into the timing cover and it came out fairly easy.