My 94 Ram Van with stock 318 runs hot when I tow the boat uphill. It used to be just fine in any condition on the very hottest days even while running the AC. It's got 145k miles on it with new water pump and anti-freeze, also new hoses and runs just fine. I had the radiator out and cleaned at a radiator shop about 20k miles ago. Where do I start?

 

Replace the radiator.

 

So how good are the replacements? I am hearing some are plastic and others are aluminum. Anything made of real metal is really expensive (over 400 bucks).

 

The core has to be metal, it's the tanks that are plastic. The material the tanks are made of has no bearing on the ability of the radiator to cool.

Check here for your radiator. They're about half of most auto parts stores, and it arrives in 24-48 hours on your doorstep. Once I actually had it show up 4 hours after I ordered it.
http://www.radiatorexpress.com/

 

I'll look into it. Thanks Alloro.

 

With radiators available you have :
-Copper/brass. copper core brass tanks( OEM)
-Copper core plastic tanks
-Aluminum core aluminum tanks
-Aluminum core, plastic tanks.

I went with an all Aluminum Silla from APW for 172$ hoping it can handle my salt air environment better than the 4 copper/brass units I went through in the previous 9 years.

 

Aluminum transfers heat better than copper or brass. So as odd as it might sound, an aluminum radiator is better.

 

Copper is actually a significantly better conductor of heat than aluminum.

However in a copper/brass radiator, the copper fins are soldered to the brass tubes with lead which is a poor conductor of heat.

Since aluminum tubes on radiators can be 1 1/4 inches wide versus 5/8 inch wide for brass, aluminum radiators can have much higher tube to fin contact area allowing for better transfer of heat and wider tubes also carry more coolant exposing more metal to hot coolant.

Copper/brass radiators are easier to fix, but aluminum is cheaper these days.

The copper brass radiator makers concerned with the massive rise in aluminum radiators, developed a process called cuprobrazing which removes the lead (PB) from the fin tube connection, and these radiators probably have the best cooling ability, but the process is $$$ so the product is $$$$.

The copper/brass versus aluminum radiator debate is hotly contested all over the web.

I changed too many variables at once to say which cools better on my Van, but I've never overheated with either, and am just happy to not have plastic tanks.

 

So now I'm thinking my old metal radiator's core value will be worth nearly as much as a new radiator. In reality any radiator I buy now will probably outlast the van. Thank you all for your postings... I'll get on it this weekend!

 

I think the worry concerning plastic tanks is largely unfounded. German cars like VW and Audi have been using aluminum radiators with plastic tanks for 30+ years without any major usability or longevity issues.

They even had (still have?) coolant specially formulated for those cars which also protected the aluminum engine blocks and heads, also used for decades.