Please help me diagnose an overheating 283
 

So— this isn’t in one of my pickups, it’s in my ‘57 Bel Air.
All stock 283 power pack. I’ve had it for a couple years and I knew the radiator leaked so I thought that was why it’d heat up. Last year I had the radiator completely rebuilt but of course Nothing happened last year and I don’t even remember taking it out.
The other day I took it off the battery tender and put a couple gallons of non ethanol in. Fired up easily and after I had my wash buckets ready I decided to take it around the block before cleaning it up. I watched the temp gauge climb and circled the block (a country block so maybe 2) and when I got back home it puked a bunch of antifreeze onto my driveway. After it cooled I put a new 180 thermostat in. Didn’t help. I called the radiator shop that redid it and left a message. Guy called me while I was at work and said I should check the temps at different spots with an infrared thermometer. I did, but of course they were closed by the time I got back and could call them.
A couple minutes warm up and a trip around the block gave me these temps:
Top tank of radiator 160 degrees
Bottom of radiator 125
Water pump 225
Top and bottom radiator hoses were hot to the touch but only showed 160 or so I think because the rubber didn’t heat as quickly as the metal.
I turned on the heat in the car and it was working.
When I turn off the car it “diesels” or runs on.
Outside ambient temp 65
I backed off the timing a bit and didn’t notice a difference either.
My thought is water pump but the heater putting out heat is causing me doubt on that.
Thanks for your help. It’s not one of my pickups but this is the forum I frequent- haven’t found a tri5 group that I fit in..

Re: Please help me diagnose an overheating 283
 

If you just have the stock overflow hose that vents onto the ground then it’s just puking out the excess coolant.
It should level off at a couple inches below the top when you check it cold.
The air space at the top is needed for coolant expansion when up to temp.

Re: Please help me diagnose an overheating 283
 

Your radiator cap my be bad they are rated for a lbs pressure. The cap may be bad so car is running at correct temp and radiator cap is bacd so it releases the cool out the overflow.

Re: Please help me diagnose an overheating 283
 

I always thought a car diesels after shut off because it wants more timing, not backing it off.

Re: Please help me diagnose an overheating 283
 

I don’t think it’s the cap causing it to overheat.

I bought a new water pump and hoses and I’ll see if it’s that. Not sure what else to try.
Thanks again

Re: Please help me diagnose an overheating 283
 

2nd the though on the overflow. The older no overflow tank radiators usually had a bit of air space for thermal expansion. Once they added the tank, you filled the radiator to the top.

Check the sides of the motor block with your temp gun. Also the intake next to the thermostat and the top of the thermostat housing.

Your temps so far make me suspect the water pump but easier to take more readings then pull the pump.


On the after run, usually due to too much idle. Add the timing back and maybe more if it still starts easy hot. Adjust idle mix for best rpm then turn in(lean up) about a 1/4 turn. Also possible there is a vacuum leak that a PO 'fixed' by advancing the idle adjustment.

Re: Please help me diagnose an overheating 283
 

If it is puking coolant it’s coming out at the cap. If it is not overheating the cap is bad. It’s designed to hold pressure at a lbs of spring load Good lucky

Re: Please help me diagnose an overheating 283
 

It was overheating before the radiator was rebuilt and they supplied a new 10# cap with it at that time.
Thanks again

Re: Please help me diagnose an overheating 283
 

What’s the coolant level in the rad when the motor is cold?
Do you fill it right to the top?

Re: Please help me diagnose an overheating 283
 

So the radiator is puking coolant at 160 degrees? That's not over-heating it's just expansion. I would add an expansion tank. I had to do that on my 70 Impala to keep all the coolant in the cooling system.

Re: Please help me diagnose an overheating 283
 

10 lb cap is to low imho....replace with a 16 lb and see what that does.
Had a similar prob with all new components turned out the 16 lb and puke tank solved it.

Re: Please help me diagnose an overheating 283
 

Be sure to let us know how you sole the problem. I am not sure exactly what is wrong at this point. Is it overheating or just puking water. I didn’t know a 10 lb existed Be sure to change it out

Re: Please help me diagnose an overheating 283
 

Thanks Paul- I will update the posting once I get it solved. I have a message in to the shop that rebuilt the radiator as well as a new pump and hose awaiting my next day off from work. Also, a mild acid to flush the block with.
It’s definitely overheating not just overfilled. Temp gauge pegs, it runs on after shutting off and any water that hits the intake or water pump will sizzle violently and boil away. She’s hot.
It’ll be Wednesday night or Thursday before I can work on it again.
Thanks for your suggestions— Greg

Re: Please help me diagnose an overheating 283
 

No mention of the type of cooling fan. It my be the problem if yor have a clutch fan it is is not working. Be sure your is working and you have a good fan shroud t funnel the air through the radiator

Re: Please help me diagnose an overheating 283
 

Maybe when you pull the water pump off you'll find the impeller off or broken. It happened to me once.

Re: Please help me diagnose an overheating 283
 

New pump, hoses and thermostat and it’s running nice and cool. Just below half on the gauge. Let it idle a while and then drove it for the same lap around the area and back - didn’t boil or hiss.
I don’t see anything wrong with the old pump but that seems to be what it was.

Thanks again folks- Greg

Re: Please help me diagnose an overheating 283
 

Good deal that it's fixed. Did you pop the back cover off the pump?

Re: Please help me diagnose an overheating 283
 

I did and I hammered the shaft end so I could see the impeller. Looks ok to me? No broken fins or anything obvious like that.
I let it sit overnight with descaler in the block and flushed it well. The tip hose was pretty soft but not collapsed. Thinking the pump was the worst but several little things piled up to make put it over the top.

Re: Please help me diagnose an overheating 283
 

I know it might sound goofy, but on a Sunday or weekend, find a warehouse somewhere that has 'ramps' to where you can come in from the side and get that nose pointed up as much as you can. Pop the hood, and the radiator cap and see if you can "burp" any air pockets.
Another thing is that although some people have the original engine, it's NEVER been flushed correctly, and after 50-60yrs, there's a lot of rust and crap down between the cylinders in the block. And that insulates the bottom of the cylinders.

There's a bunch of better flushes out there now. SO doesn't take a really long time to get all that crap out. Even if you can get those two pipe plugs out of the middle bottom of the Chevy blocks. And a bent piece of coat hanger to dig around while the water is being forced through.

And with all these 'import' Thermostats, a couple 1/8" holes drilled around the skirts can't hurt. That way you always have some kind of water flowing around. Even if it sticks shut. (..funny how they never seem to stick OPEN!)

Re: Please help me diagnose an overheating 283
 

What Rocko said about the crap between the cylinders is so true. I actually pulled my old 283 to put it on a stand in the driveway, then I pulled the freeze plugs and flushed the block thru the holes with one of these https://www.homedepot.com/p/Gilmour-...E&gclsrc=aw.ds I turned it upside down and did it some more and I made a huge rusty powdery puddle of nastiness. Gunk just came rolling out of those freeze plug openings. It all went well. I drained the oil first course, pulled the carb and distributor and sealed those holes with plastic bags and flashing tape and just blasted the water jacket until the water finally ran clean.