This is weird...my 2000 Lesabres coolant level in the overflo tank used to go down an inch when cold and up an inch when hot...now after flushing and doing UIM and LIM gaskes and new tstat it moves very little....I check it at 20 degrees out and its onl dropped down abut 1/4"....why would that be ??

Make sure overflow hose is nice n tight at both ends, cap could be the culprit or small leak in cooling system, or air in system. System needs to be tight and no air so when coolant expands goes into the tank, cools contracts back into the system.

You might want to bleed it one more time.

ive driven it a few hundred miles already.. blead it a few times when the stat was open...solid stream of coolant...temp runs about 197 and goes over 200 if you let it sit and idle with the heater off....it does go down slighty when cold and up when hot...just not as much as before

i just went out and looked again...its still warm but I squeezed the upper rad hose and when I squeeze it I can hear the release in the cap working and the coolant moves in the overflo tank so I know the overflo hose is fine...the stat is drilled too...I know there is no air in the system..

it heats up like normal and temp runs normal for this time of year...just seems like the overflo tank would drop an inch before ??

Have another cap to try, those do go bad.

ok...I just went out and the engine was warm 110 degs...upper rad hose was soft...I opened the rad cap and it was full to the brim so I assume the cap is working and allowing coolant back into the rad....I ran the car at idle with the heater off and got the temp up to where the low speed fans kicked on...

The level in the res was up probably 1/4 to 3/8" from when the car was 110 degs....I dont see ANY leaks anywhere...you can tell when you have a leak and the engine is that hot...you would see steam etc....hoses all dry, coolant elblows all dry and remember im not loosing any coolant it just seems like it went up and down alot more before replacing gaskets and pleneum..

Now I wonder if the fact that the gaskets were starting to fail was that causing more pressure and loss so it seemed like it went lower when cold ??

I made a mark on the res tonight when it was 210 degs...now in the morning it will be in the 20'* so ill see how far it went down....but is there really any issue if the rad is full, its NOT overheating, and im not loosing coolant ???

ok here is what i found today....it was 2 degs out this morning...the level in the overflo ...was down a little more than a 1/2" ...it is a big tank so....but it used to be down much more before the repair and new coolant flush...the upper rad hose was soft...it wasnt empty ( neither was my wifes car ) but it was soft....I removed the cap and the rad is full to the brim and would run out a little...

so the cap seems to be working...if it wasnt letting any out the level would never go up in the tank and it would overheat...it doesnt overheat...

if it wasnt sucking back in...the rad hose would be sucked in and the rad would not be full...

I know the tstat is working because the hose hard as a rock after the temp reaches 195-197 and is soft after it cools down...

So...could it be he has the coolant mixed a little on the heavy side and I may have been on the light side .... again I have run it 150-200 miles since he did the work and it seems fine...am I obsessing over something thats not a problem ??

In my pk ave what I do is leave marks on the outside of reservoir. (magic marker)
After sitting all night mark the low or cold level.
When Hot after driving for 20 min+ mark the hot level.
Then it is much easier and more accurate to compare the reservoir levels.
I generally only check after driving for 20 min + the hot line mark and if it is down then, I may start question something.
Hope This helps.

yea thats what i did..it only changes by little ove 1/2"