318 overheating
 

I know this has come up before, but maybe there are some new genius' on here that can help me from loosing so much hair so fast. I have a 69 charger with a 318 that won't stay cool. I have:
replaced the thermostat after checking it to make sure it opens at 180 degrees.
drilled a hole in the flange of the thermostat
Replaced the sensor in the block.
removed and cleaned out the radiator
but it still climbs to 270 (thats as high as the stock gauge goes) in about 10 minutes even on the highway. But when I stop its not puking coolent or steaming like I would imagine it would at 270. Could the gauge be bad? It just started doing this this month. The only thing I haven't done is get a shroud. Would a shroud make that much difference? Any help would be awesome. Thanks.

Have you checked to see if you have compression coming in the radiator, I would be looking at the head gaskets.

Have you checked the water pump impeller ? Maybe rusted away or broken

How would I check for compression in the radiator? And I thought the water pump leaks a bit if its broken?

arron -

Basic rule, do the easiest thing first, even if it has a low yield.
Check the gauge first, just borrow or buy an cheap Sun gauge from Advance or any parts store and hook it up to a different port.

An IR thermometer isn't expensive (around $30) and can help finding hit spots and has a lot of other uses.

Archer

Remove the rad cap start the thing up and see if there is a large amount of air in the coolant. Check the coolant and see if its moving.

As far as the water pump goes the impellers rust and has nothing to do with the seal.

well its not the water pump. Just pulled it since I already had the fan off and radiator out. It 's fine. No bubbles in the coolant either. I checked before i pulled the rad to clean it. So I guess Ill put it all back together and see if its the temp gauge.

Still say head gaskets.:)............

Been there done that.........

One change, if it's getting to 270, cracked heads or block very possible.

If it was a head gasket or cracked head wouldn't I get white "steam" from the exhaust and a noticeable loss of coolant? I have had a blown head gasket and a cracked head on another car and it poured white exhaust.

My question would be..... Is it overheating or is the gauge bad? What are you trying to fix? Overheating or electrical issues?

I misread the first post and agree with Bob, I wouldn't trust the old gauge. A simple fix would be an aftermarket gauge. Factory gauge wasn't reliably accurate when new.

Well got it solved. It was a bad gauge. I installed a new temp gauge (in a different port so I could get both reading at the same time) and the stock gauge was pegged at 270 and the new one read 190 with a 180 degree thermostat. On the up side I now have a new thermostat, water pump gasket, temp sending unit, a clean radiator, a flushed engine and now know much more about my cooling system. All's well that ends well! Thanks for you input everyone! On to the next thing, Disk brake conversion.

Good Deal..... You still might look into a fan shroud when you get a chance...
Glad it was a simple fix... :)

Now you have it running properly take some infrared gun temps with engine running of the thermostat housing and rad hoses. Record the information to compare in the future if you have a suspected problem in the future.