cool, might be able to slide this in this week.

Please do not open the system after you've driven around the block. Like the manual and cap say, HOT AND PRESSURIZED!!!

Always open the system when cold. To remove any other air the overflow tank does that job. Tyipcally after refilling and running the car for a day or two the overflow is about 1/4-1/2inch low. Refill to the cold line.

The factory service manuals usually say to open the thermostat and then rev the engine to certain rpms a number of times to move any air from the heater core out. That air would be trapped at the thermostat housing on both of my 3800s because the upper radiator hose goes down from the thermostat toward the radiator. Air would be trapped there unless the flow rate is great enough to push it back into the radiator???
So I recheck with the bleeder screw; cold is fine for checking if you wish.

Let me get something clear.
For this site: when advice is given, the safe methods are given. Personally and individually we may practice other methods. However for the good of all on the site and many that are not normally under the hood, safe is the best information.

Safe procedures being transferred to other members is each members responsiblity.

There is nothing here to debate. Safe is the only advice that should be conveyed openly.

I know you follow per FSM, but there is no need to use RTV on the paper gasket? I did

RTV is a nice sealant that is a PITA to clean off later.

I've been having some tstat batch issues. (same batch, all bad) I've recently gotten good enough to change my t stat in under 5 minutes with the 10 step procedure I listed. That vacuum hose really does the trick.

Thanks for the nice write-up BillBoost37.

I'm getting ready to get a 180* t-stat, but have another question. Without stealing the thread, what is the deal with drilled 180* stats? I keep seeing it in people'* sigs etc., but cannot seem to find a thread specifically discussing it. I admit to only searching for about 15 mins.....

I assume it is done to increase flow, but does it really help and is it useful for non or only slightly modified SE'*?

If it is a good mod, how is it done?

It is specifically to increase flow and usually only done on the SC motors because the SC'* generate much more heat. I doublt it would help you unless you changed heads etc.

I believe it also helps to increase flow while it is closed. Which may increase warm up times slightly.

Are you responding to something I posted?

Let me quote from the 1998 Service Manual from GM for the H bodies, Bonneville, Eighty-Eights, LeSabre. The 1993 service manual is the same IIRC. If needed I can copy it as well.

From Service Manual:
Draining and Filling Cooling System
Draining Procedure
Caution: As long as there is pressure in the cooling system, the temperature can considerably higher than the boiling temperature of the solution in the radiator without causing the solution to boil. Removal of the PRESSURE CAP while the engine is hot and pressure is high will cause the solution to boil instantaeously --possibly with explosive force-- spewing the solution over the engine, fenders and the person removing the CAP.

...

Filling Procedure
1. Refill the cooling system with GM Goodwrench DEX-COOL or Havoline DEX-COOL. To ensure sufficient engine cooling, freezing and corrosion protection, maintain the protection lvel at -37 degrees C. Use a solution that is no more than 70 percent antifreze.
2. Place the heater and A/C control in and A/C mode except MAX and the temperature in the highest setting.
3. Allow the engine to continue idling until the lower radiator to coolant pump hose is hot.
4. Cycle the engine speed up to about 3000 rpm and back to idle five times.

Slowly open the bleed valve on the rear of the thermostat housing for approximately 15 seconds to expel and trapped air in the cooling system.


5. After the air has been expelled, fill the radiator. Install the radiator pressure cap, making sure the arrows on the cap line up with the coolant recovery tube.
6. Allow the engine to cool to outside temperature. Check the coolant level in the reservoir.

End service manual quote. Some trademarked are included in the above quotes.

GM'* instructions are clear to me.
I follow their method. The retention of any air in the DEX-COOL radiator with the movement of the coolant to mix them is a factor in sludging from DEX-COOL that happened with certain models of cars, according to my service manager at the Buick dealership. I am careful to remove all air. Whether you wish to do it cold or following GM'* procedure is up to you.