What to do if heat has gotten your Goat
Story Chris Petris
Images Stephanie Petris
We saw this 1970 Pontiac GTO at a local car show. The restoration was looking great except for the underhood area. Don’t get me wrong — the underhood area was in decent shape — it just needed some detailing.
After some discussion, the owner mentioned that he had a few issues that were plaguing the GTO. Plenty of work was required to make it drivable from its apparent drag race days. He explained that with just one summer under the GTO’s belt, overheating prevented the use of its air conditioning. Our full-service GM shop has handled plenty of these overheating issues in the past.
First order of business would be to check out the cooling system. General Motors made four versions of the A-body mid-size car of the ’70s. Buick, Chevrolet, Oldsmobile and Pontiac all had different engine configurations with specific cooling system requirements. Many different engine/transmission combinations were also available for each specific A-body version.
Nineteen seventy was the beginning of lower horsepower numbers and emission systems. Many things were changing besides our exhaust emissions worries; options were becoming commonplace. Large cubic inch engines with A/C pushed cooling systems beyond their breaking point. Engine coolant fans were controlled by thermostatic fan clutches. The fan clutches would cycle in the fan blade as heat blasted against the thermostatic coil.
Radiator cooling fans worked poorly at best compared to our electric cooling fans used today. Radiators of the ’60s and ’70s were constructed of copper, brass and lead. As engine cooling loads increased, radiator configurations were changed. Overall radiator size was increased and rows of tubes added. The typical radiator was two rows of half-inch tubes. Three and ultimately four rows of the half-inch tubes were used to help cool high-horsepower engines. The additional rows of tubes added more coolant capacity.
Many times, the four rows of tubes did not help cooling and, in some cases it hindered air flow. The decreased air flow could actually raise engine coolant temperatures. In those days, we got concerned at coolant temperatures above 160 degrees, while 200-plus is commonplace today. During our testing the GTO’s 400ci engine, rated at 350hp, was running 210 degrees at idle with the A/C off. When the A/C was switched on the temperature kept rising. We had to carefully inspect the entire cooling system before we considered the next step.
The radiator appeared to be an original four-row copper unit with a few minor leaks. Lead solder was used to fuse the copper tanks to the core. Over time, impurities in the lead allow corrosion to form and literally hundreds of minute leaks are occurring all along the tank solder joints. The core itself had scale and mineral build-up over many of the tubes.
Should we send the decades old radiator out for service or replace it? One major drawback to sending out the radiator today is finding someone that can properly repair it. Back in the day, we would send the radiator to the local radiator shop. The craftsman would remove one tank, then force a cleaning rod through each tube. This was a positive way to clean each and every tube. If the tubes survived, you could be assured the radiator would be fine for quite a while. The real art was cleaning the core and tank properly to solder those old joints once again. Today the majority of radiators are aluminum with plastic composite tanks that are crimped onto the core. Many shops use a chemical solution to soak the aluminum core in for cleaning.
The owner really did not want to repair the questionable radiator so the hunt was on for a new replacement. There were a couple of options out there, copper replacement or aluminum? We knew the aluminum radiator would cool better and shave off a few pounds, but it would also very noticeable.
Be Cool had just introduced their OE Series replacement aluminum radiator. This was perfect! The radiator looked like the original while providing extra cooling capacity and the die-formed cross-flow aluminum tanks mimicked the originals in every way. The only telltale sign there was something different was the perfectly welded tank to core seams. Since we were replacing the radiator with a correct looking replacement it made sense to replace all the hoses. We decided to replace radiator, heater hoses and clamps with factory OE look pieces.
While we waited for the radiator and other pieces to arrive, there were some other cooling system concerns. Remember we said the GTO had a prior life as a drag racer? The drag race info is good to know because most cars that spend their time at the strip rarely have coolant in the cooling system. Serious racers are constantly draining the water between each run down the strip. The use of water means corrosion/rust and eventually sediment forms. There is no way to avoid sediment in an open cooling system, meaning a radiator that has expansion space (air) below the radiator fill cap. The air that is above the coolant causes corrosion and tiny particles of sediment are formed.
In 1974, GM introduced the closed coolant recovery system. A coolant recovery reservoir was used to keep the radiator filled to the top. In theory, the cooling system never had air in the system. This would help alleviate the inherent corrosion as long as the system was working properly, pushing coolant into the recovery reservoir as the engine heated up. During the cool down phase, coolant is drawn back from the recovery tank into the radiator keeping it topped off.
We were relatively certain that we would find plenty of sediment in our cooling system from its prior life. The first order of business would be to drain the coolant out of the radiator. What we found looked OK except for the layer of rusty sediment that filled the bottom of our drain pan. No matter what radiator is chosen, it makes no sense to flush compromised coolant from the engine block into the new core.
We are aware that there are miraculous coolant service machines that drain, flush and fill the cooling system with simply hooking up a few hoses. Move a few levers and the miracle machine does all the hard work for you. Here is the problem, as we stated earlier: sediment builds up and you can not agitate the sediment to disperse it throughout the coolant for draining. No machine will do that by simply connecting to the heater hoses.
Manually removing the block drains is the only way to get the sediment where it lies deep within the block. The solution is to remove the block drain on each side and let the coolant flow. Once the block has drained of coolant and sediment, we can flush the system. While we’re flushing the system, the heater core will get the garden hose connected to one side and let fresh water flush the core.
We had a few other areas to check, as Pontiac engines use a separator plate between the water pump and engine front cover that can corrode. There are also a couple of O-rings that seal the cover and water pump that might be suspect. We removed the water pump and plate for inspection. This proved to be a smart move because the plate was in rough shape and the pump impellers were in fair condition.
With the water pump out of the way and the block drains removed, the engine block was flushed of any remaining sediment. The radiator is only as good as the system using it. If the water pump has reduced flow, so will the radiator. All too often, the replaced component is blamed for poor performance when the supporting pieces are to blame. We were ready for the new BeCool radiator now that the system was clean.
We set the OE black finish radiator in position using the supplied rubber mounting saddles without any issues. All the OE radiator hoses and mounting pieces fit easily. Once everything was connected, we filled the system with BeCoolant. We waited for the engine to warm up then capped off the coolant with the BeCool supplied OEM factory look radiator cap.
There are a couple of other things to watch for concerning engine overheating. Our fuels of today are lead-free and have a lower octane rating, increasing engine cylinder temperatures. Improper base and advance ignition timing affects engine performance and heat. Fuel mixture also plays a role in engine temperature as lean fuel equals higher temps.
We checked and set ignition timing and adjusted the carburetor accordingly for our testing. The GTO was a different animal as it sat and idled, the temperature needle sat at 195 degrees with our 180 degree thermostat installed. When the A/C was turned on, the temp never rose above 200 degrees. When we wrapped up the GTO, it was off to the car show. Not one of the judges spotted the BeCool aluminum radiator. They all thought that we had the traditional copper radiator in place. The BeCool OE radiator was put to the test over our hottest recorded summer ever and performed better than expected. We are very proud to say that our BeCool radiator and coolant is made in the U.S.A. You do not hear that often and it sure sounds great to me!
BeCool had also just introduced BeCoolant and when we decided on this radiator, naturally we gave it a try. BeCoolant has a 300,000 mile or seven year life span that protects down to 26 degrees below zero. The cooling system’s boiling point rises to 267 degrees at 15 pounds of system pressure with BeCoolant. Their earth-friendly biodegradable propylene glycol formula also has self-sealing capabilities to seal minute leaks. Of course, BeCoolant protects our new aluminum radiator and all other cooling system components. Using BeCoolant also doubles our new BeCool radiator’s warranty.
1 An obvious sign we had radiator leaks from the coolant stains on the A/C condenser. While the radiator is out it is a good idea to blow out the debris built up in the A/C condenser fins.
2 The coolant is draining out of the passenger side engine block drain. This is where sediment will come out. Sometimes you have to dig the sediment out to get coolant flowing. The driver side block drain is directly behind the motor mount. Unfortunately our plug was so tight we had to remove the starter to access it. All GM V-8 engines have a drain on each side. Both plugs must be removed to completely drain the system.
3 The die-cast radiator tanks are done very nicely and certainly look like OE pieces. The black finish is durable, adding to the stealth look. Nice touch: the brass radiator drain petcock comes with the radiator assembly.
4 The radiator is slipped into the factory shroud before lowering it into place. The engine cooling fan blade was removed to ease installation. We certainly do not want to gouge up our new radiator core because of a tight fit.
5 Most of the A-body GM cars have this rubber saddle radiator mounting configuration. The rubber saddle has to be slipped between the radiator core support and shroud. This is important stuff — do not let the radiator tank rub against the core support.
6 Our half-inch fitting line wrench is used to tighten the transmission cooler line into the radiator side tank. BeCool offers a heavy duty transmission cooler if you desire to upgrade your cooler when changing the radiator.12Now that looks good BeCool supplied OEM style radiator cap with an OE engine cooling system warning label. The BeCool radiator fit just like the OE piece in all aspects.
7 Coating the inside of all the cooling system hoses prevents thermal expansion leaks. We apply a light coating of Permatex aviation sealer to the connection area. This also prevents corrosion from occurring.
8 Most people do not like these OE style clamps. They work better than the typical band clamp with their 360 degree clamping load. The main complaint is how to release pressure once they have been tightened. Push down on the center screw and the band clamp will release easily.
9 In an effort to make the underhood area look factory correct we opted for the GM stamped radiator hoses.
10 New cooling system hoses throughout the heater hoses are the OE style ribbed ones. We also used the factory correct hose clamps here.