ok I swapped in a new t stat, changed the water pump to a known good 1, flushed the radiator with some flush stuff I had. put it back together an still over heating 250 deg!! maybe radiator cap?? still could be the radiator not throwing that idea out... motor is a 77 318

1. Double check the radiator and make sure there are no blockages.
2. Make sure you have the correct water pump. There is a difference between AC and non AC water pumps.
3. Make sure you have the right size radiator.
4. Check the fan clutch. Wait till it is cold and spin the fan by hand. Then run the car to operating temp (in your case, 210ish) and shut the car off and spin the fan by hand again. It should feel much stiffer. If not replace the fan clutch.

HTH,
Dan...

ok, ya well it had a flex fan on it removed that, put a clutch fan on it, I fired it up in the yard an probably after about 5-10min's idling she was 250 deg ish, IIRC the pump is a non ac pump, radiator is a factory mopar radiator it's a 2-3 core, I ran some of that radiator flush stuff in it thinking maybe hey that might fix it, then I ran the hose through the radiator for a few hour's an throught the motor thinking maybe something is blocked but still the same I will try your idea's an update thanks

Does it have a shroud?

Sometimes if it has an air bubble it will heat fast. Are you sure the air is out? Test without T stat can help burp the air. Agree check of water pump and drive belt is in order.

Heating up that fast at idle wouldn't normally be a radiator problem unless the radiator was completely blocked.

Are you using an aftermarket heat gauge? Mine also registers between 230-250 but when I check block temp with a laser gauge, it's 180. I'd do that before making any more changes.

http://www.amazon.com/Temperature-Infrared-Thermometer-Laser-Sight/dp/B002YE3FS4

Let it warm up.Then shut off and feel the rad at top and bottom.It should be pretty close to the same temp.Try pulling the plugs that screw into the block.Use a 6 point 9/16s to remove them.Most wont even drain because of crud in the block.You have to use a screwdriver to open them.Flush it with the plugs out.SBs I fill the block thru the stat opening and then install the stat.Rocky

Checking with a infrared temp gun is good advise!!Is it blowing coolant out the overflow?If not probably not overheating.
I went through this for two years on and off factory gauge off 30 degrees,cheapo 3 pod aftermarket gauge off 25 degrees with two gauges telling me i'm overheating i thought i was.
Gauges read 230 and 240 and infrared reads 185 at the thermostat housing.
Installed autometer mechanical gauge it reads 195 max in traffic and just changed the gauge because i changed ever thing else twice!!

faulty gauge, wrong sending unit, lower radiator hose collapsing? As stated already...use a temp gun to check. Leave the rad cap off and run it and see if it boils the water out.

Can you pull up the original thread on this for more background info. As said I would confirm the actual temp with a known good gauge or infrared gun what ever it takes. Assuming the initial ain't severely retarded which I doubt it is & with a new stat/pump I'm thinking there's plenty of water flow UNLESS the rad is severely plugged & I doubt the lower hose is sucking shut at idle. sounds more like an airflow problem but you've addressed the fan but might put a shop fan in front just for a check to see if it is an airflow issue & can you feel the air being pulled thru on the front side of the rad?. I would take off the water pump fan belt & the stat housing & the stat & with the coolant at the brim, start the eng from cold & gun it repeatedly for a minute or two max & see if there's bubbles or if the coolant starts to rise which it should not rise in that length of time starting from cold since the water pump is totally diasabled there should be a dead calm with no turbulence unless there's a combustion leak. Keep us posted. #1 confirm the actual temp. EDIT hitting 250 in 5 or 10 minutes tells me there's a severe issue going on

yep fan shroud, installed a new 195 tstat, removed the flex fan it had an installed a clutch fan. today I fired it up, let it run for10-15 min's, felt the radiator an the hoses & they were cold, except the 2 hoses running to the water pump from the intake they were hot.. an yes I did bypass the heater core thinking maybe it was plugged but no change.water was boiling out kind ofby the intake not sure if there was water that was sitting up there or what. but what's temp she should be at 200-210??

do you have an IR temp gun? they're cheap, and can save a lot of guessing. you can point and shoot, getting exact temps from the hoses, heads, intake and even the radiator. several guys have mentioned it, and it's a great investment. i even use mine to look at exhaust temps coming right out of the ports, looking for misfires (colder) or a lean cylinder (hotter). i'd trust a digital IR reading before i'd trust an electric gauge and sending unit.

Eventhough you replaced the WP earlier, I would still of a broken waterpump impeller perhaps.
Unless there's some serious blockage.

Have you checked for the mentioned lower rad.hose collapse?
Is the coilspring still in there?

How hot did you let it get this last time when you said the radiator was cold?

195 stat is kinda high.. try a 180. Also make sure it's not upside down, seen that. the upper hose shouldn't be cool at all once the stat is open.

It's often hard to diagnose symptoms via the internet, but here's 2 questions/suggestions, won't cost you anything but time...

are you using a cast iron water pump?..if so turn the thermostat upside down in the waterneck, flow is reverse...

another suggestion, start the vehicle, put the radiator cap on, but turn it back to the point that it's just engaging the tangs where you have to push it down to release, but still engaged, but loose, run the engine, if it doesn't overheat,...I'd start looking at head gaskets...

So... Gauge read 250 but rubber hoses were cold?

At 250 it should be painful to touch the hoses.

Pull the radiator out of the car. Use a garden hose at full blast, and see if the radiator can flow enough to not back up. If the radiator can flow the 5 gallons per minute that a garden hose can put out, then you have enough flow to heat up the upper radiator hose.

So if your upper hose is not hot when the gauge reads 250, and the radiator is not plugged, then you either have a faulty gauge issue or a thermostat that's not opening.

You can test water pump flow by disconnecting the upper hose at the radiator and removing the thermostat. Water should flow out of the upper hose.