Thanks for all of the help. I always get some good advice when I need it.

I think I found the problem. As some of you have sugested I believe the radiator is pretty clogged up.

I warmed up the motor, even drove it around a little. I let the temp climb pretty high a couple of times. It probably ran for at least 20 min before I cut it off.

I, carefully, felt around on the radiator in front of the fan and it was cool to the touch. I kept feeling around and the only hot spot I could find was right next to the radiator inlet (top), which was very hot. 3/4 of the Radiator was cool to the touch.

I think at above about 2500rpm the waterpump is cavitating and not moving any coolant causing rapid overheating. When it drops below 2000 or so circulation resumes cooling the engine.

Assuming I am correct. What is the best way to clean the radiator? If I have to take it to a radiator shop I want to at least put somthing in to clean the rest of the system before I install a clean radiator.

SeaFoam?

BTW my radiator is plastic with aluminum fins.

 

Use the Prestone flush that is designed to be left in the system & ran for a day before flushing. Less caustic/ damaging to metal, dissolves scale to a size that flushes easily, & becomes chemically inert once it binds w/ scale. If you had an extreme overheat, replace thermostat regardless. Suggest a 180F. Stay away from "Mr. Gasket" thermostats!

 

actually for the prestone flush kit it recommends to run it for a few hundred miles in there and mix the flush solvent with enough water to make the radiator to be full. i used this in my car before i replaced the head gaskets and after i did the job as well and i got to say i was not very impressed with it (just my opinion, not saying its not worth a try) because of the dexcool in my radiatior and it never being serviced till i bought it (and now sold it) it ate away everything and left it completely gunked up. i would also say that something sounds like it is up with your thermostat and maybe your radiator cap too. try belleding the cooling system again after replacing the thermostat and after you put the flush kit in (if you choose to do so).

 

Muratic acid...take the radiator out and lay it flat...fill it with the acid after you full flush it with water and pour it all out...the acid will eat the Lime and Silicate..

once its clogged it might not be salvageable....

 

Where might I procure Muratic Acid?

Due to the sevarity of the blockage I figure i will need somthing strong.

I would not be able to drive a hundred miles to allow the Prestone Flush Kit to work.

 

id definatly just shop around local junk yards for a new rad

 

This might sound stupid, but would it not be easier and better in the end to replace the radiator? If the one you have now is so clogged up that the coolant is not even flowing, there is reason to believe that the muriatic acid or other flush kit wont work either since they cannot flow through the clogged radiator to clean it. I cannot see how you could drive a hundred miles with a clogged radiator. You'll surely overheat the motor and possibly do a lot more harm than good..

BTW, I mentioned before in another thread that a friend had horrible overheating problems in a Mustang with 5.0 due to coolant losses because of improper sealing between the intake and the heads (after engine rebuild with new heads, decked block, intake, etc, etc.) he went through hell changing everything from radiator to heater core and every sensor cap, fan, belt, hose and sending unit in between. AFAIK, he never actually fixed it completely, but he did get the coolant losses down to a manageable level...

 

then if you have the 200 bucks go for the brand spankin new not clogged radiator that has never been used. just my afterthought since you cannot run 100 miles with it

 

I'd remove the thermostat and check flow before I bought a new radiator.

 

I will definitly tripple check this before I replace the radiator.