I believe my V8 5.0L 302 is over cooling. The temp gauge never gets into the normal range and the heater doesn't blow hot air, even after twenty or thirty minutes.

The manual says this likely means that the thermostat is stuck open and it should be changed.

I have never done any work on an automobile (though I have done some on a tractor), but the instructions in the manual (Haynes) seem pretty straightforward. Basically, you drain the coolant to below the thermostat, disconnect the hoses, take apart the doohickey, pull the old thermostat and gasket, install the new ones (in proper order and direction), put everything back together again, refill cooling system and then check it out.

Is this as straightforward as it seems? Can anybody think of any surprises that I may encounter?

Thanks in advance.

 

That's pretty much it. Just don't get any goop on the new thermostat and make sure you put the thermostat in the correct way. There is a difference.

 

And make sure the thermostat is sitting directly in the cavity before you tighten it. You don't want to crack that housing!

 

Dumb question. How do you drain the coolant to below the thermo level? I am attemting this myslef today.

Chris

 

You can open the petcock on the lower part of the radiator or pull the lower hose off the radiator.
I prefer disconnecting both hoses from the radiator, disconnect both small heater hoses from the motor, remove the thermostat and reinstall the thermostat housing (gooseneck) with the upper hose still attached to it.
Take the garden hose and flush the radiator down and up several times.
Flush the heater core both ways several times.
Flush the motor both ways several times.
KEEP FLUSHING UNTIL THE WATER COMES OUT CLEAN ENOUGH TO DRINK!
Install the gooseneck without the thermostat (use old gasket
Hook up all hoses
Fill radiator up with water, start motor and allow it to come up to temp adding water as necessary
Install radiator cap and allow it to run for 15 minutes (occasionally varying engine speed)
Shut off motor, remove cap and immediatly pull bottom hose off radiator without scalding yourself!!!
If the water comes out dirty, repeat flushing procedure.
If clean install new thermostat with sensing element (spring) toward motor, use a bit of sealer on the gasket
Reconnect hoses
Pour in 2 gallons of antifreeze and fill with water to 4" below radiator cap level.
Start motor, switch the heater on high and allow to idle until upper hose becomes warm (this indicates the thermostat is opening) all the while maintaining the 4" down level.
Bring motor up to approx. 1500 RPM and back to idle several times to chase any air out of the system.
While still ideling, fill the radiator to the top with water and install cap.
Fill overflow tank to 1/4 full with 50/50 antifreeze/water mixture.
Hook up your horse trailer full of furniture and head for the outback!
Good luck!
Steve G.

 

Make sure to clean both surfaces good, and use some gasket sealer when you put it back together. Not much to it, but aggravating if it doesn't go back together right.

 

very rarely will radiator fluid squirt like crazy out of the thermostat hjousing I would not drain any fluid as it is not nessessary

 

So, I changed out the thermostat. It took about an hour just to get the thing apart because of old bolts and stuck on hoses.

I switched the thermostat, put it back together and it leaked like a sieve.

I went and bought another gasket and did the process over again. I let it sit overnight before refilling the cooling system and starting the engine. This time, there was an occassional drip from the bottom, about once every 8 seconds. I ran it until it warmed up and then drove it around the neighborhood for about 15 minutes. Problem solved. The temp gauge moves into the normal range and the heat is blowing hot air again. When I got back, I checked to see if it was still leaking. It was still dripping, but not as fast. Later, I drove about two miles and then let the truck sit for a few hours while I was visiting a friend. After I returned home, I looked to see if it was dripping. I think I saw one drip. Then I counted to thirty and saw nothing else. I waited for another minute and didn't see anything. Then I shut the engine off.

QUESTION: Since it was dripping before, should I get another gasket and redo it? Or, since it seems to have stopped dripping or is dripping extremely slowly can I just keep an eye on it for a while and then assume that it's not a big deal?

I think three times would be a charm, so I don't really mind doing it, I just don't want to do it if I don't have to.

Thanks in advance.

 

Are you sure that the housing isn't cracked? If not, there must be some of that old gasket still on one or both contacting surfaces. Clean it and do it again. It'll be worth it.

 

Make sure the upper radiator hose is nice & tight and that it isn't the source of the drip, sometimes it needs just another turn of the screw.