Car is a 1975 with a 225. I was having overheating problems and the top hose wasn't getting hot so I replaced the thermostat. No change.

The top tank of the radiator was hot but the core wasn't so I replaced the radiator. (and by the way they are hard to find these days). Still no change.

And I keep blowing out the thermostat gasket!

This is a car that sat for a long time and I brought it back to life. It runs and drives but sits most of the time these days.

Now I am thinking maybe the water pump impeller is corroded away. I pulled the fan belt and the water pump spins with no resistance. (But arguably I don't have a feel for how much resistance it should have.) I've replaced many water pumps on slants over the years but always because the bearing was worn or leaking.

Before I throw more parts at it, does it sound like a water pump?

Also who makes good water pumps for slants these days? Is the Gates on Rockauto any good?

Thanks!

I made my thermostat gasket from an old motorcycle inner tube..............

No problems, and it's reusable........

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

I bought a flowkooler one for my /6 engine project.
I've used them on 318s before. Dunno if it's worth it or not but it hasn't hurt anything yet. Summit or Jeg's has their own version (house brand) too at least for the V8s.
Have you pulled the block drain plug and at least looked at if it's full of rust there? I've had them not flow anything out that drain before when plug was pulled. If block is full of sediment it will hold the heat in.
I also bought a new cast iron thermostat neck from ebay, new in box old TRW stock. I have a couple of stock aluminum ones that are all pitted up.

Remove the thermostat, refill radiator and start it up with radiator cap off. Make sure the head is higher in the front than the back so air will easily escape. Look for flowing coolant in top radiator tank. Coolant flows from head to radiator. If no flow, than replace the water pump, you have replaced everything else.

Volaredon had a good idea to check for rust build up in the lower block. A cooling system flush would be a good idea as well. Drain the coolant disconnect the lower and top radiator hoses where the radiator is new, and flush the block and head. Also disconnect the heater core hoses and flush the core out being careful not to over pressure it with full house water pressure or you will be in for a real treat replacing the core.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

I like to run water + a product called "iron out" this stuff was originally made for radiators as found in a boiler heat system in a building. I had some old Prestone flush kits (it was powder based) that contained teh same stuff as "iron out" is. drain, put straight water in, add a cup or so of Iron out, run til warm (at least) let sit, run to circulate again, drain, repeat til it comes out clean, then a final flush with straight water.

It can easily be the lower radiator hose collapsing when hot, if it's old. That hose is on the vacuum side of the water pump.

i wonder how well evaporust or molasses would do to clear a rusty jacket. drain, rinse, fill with evaporust and then top up with water and let it set. flush again after.

How long you got? If molasses would work it would definitely be slow. I dunno about evaporust.
What might that do to the water pump seal?

If the top hose on radiator is getting hot, you have some flow to the radiator. Pull the cap and you should see the water flowing to the radiator.

What did your fluid look like when you changed the radiator?

Unusual that you have enough pressure to blow the thermostat gasket and it is not damaging other stuff? Is it pushing fluid out the overflow on the radiator when it blows the gaskets?

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6