installed new lower temp 180 degree thermostat. flushed radiator, and performed "paper test". Passed paper test fine. held sheet of paper stuck up to grill idiling. still runs hot at any speed over 55mph. I have spare radiator lying around going to swap it in because +1 cores over current one.

 

Before you go thru installing that other radiator have it flow tested at a radiator shop.
It could be just as bad flow wise as what you have in the truck now.

Little FYI: I had (still have) a car that runs hot to the point you can hear the coolant boiling when you shut it down when it gest too hot.

When I first got the car it had mudd for coolant - no lie!
I flushed it many times over the years I had the car on the road. Other than the first flushing it was always clean.

Turning the heater on full hot / fast fan would hold off the temp a little but would still over heat.
Adding a fan shroud, they never made one for this car/motor as the fan is only about 2" from radiator, did help a lot but still ran hot/boil over just a little later.

I replaced the radiator 2 times, water pump, heater core, all hoses over the years to keep it cool all with little help.
I can also tell you this motor, a v8 BTW, has rusted out many of the casting plugs (freeze plugs) in the block and 1 in the head.

I never got this fixed but in putting in temp rubber casting plugs I found a lot of mudd sitting at the bottom of the block cooling passages and no flushing would remove this.
My thinking is between the mudd in the bottom and maybe plugged passages between block & head is why it runs hot. Only way to fix this is to pull the motor, take it apart and have it hot tanked to clean it out.

A buddy had this same thing happen to a JY motor and when he hot tanked & rebuilt the motor all was good.

So it could be mudd in the passages and only way to clean it out is a hot tank & rebuild.
Dave ----

 

Yes had mudbin radiator, flushed a little out, most has caked its guts. im trying to sell the truck. im not going to yank the engine and rebuild it. becausebits running hot. rins strong, less then 90,000 on rebuild already.

 

plus i only have the straight six.

 

My motor only had 64K on it and ran the same and why I did not want to pull/rebuild. That and pulling the motor in this car it a PITA = small body car with a v8.

I don't think the type of motor means that much.


I do feel your pain, my car sits in the garage waiting for its turn to be fixed or sold, 75 factory v8 AMC Gremlin and no they did not catch fire if hit in the rear that was the Ford pinto.
Dave ----

 

Sold the '88 truck last Saturday.to a nice enough guy in the army. Was going to take it back to his parents farm in NM where it can live out its days. Now I just have to get the body panels back onto my '83 and get it sold too. How much is a fair price to ask? I've got about $1000 in parts on it.