Reply To: coolant in a 12

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I took my ’33 836 out for a 25 mile run, mostly at 45-55mph. It’s HOT here today, around 90*+ and sunny, so the roadway airtemps are over 100*.

The engine temps only climbed above the 1/2-way mark on the gauge when running 55 with a slight tailwind.. this is a vast improvement over the overheating I was experiencing at Rochester Mn. I’d like to load up the car and pull some long hills to see how much hotter it will get, the halfway point on the temp gauge is a laser-thermometer measured 155-160*. When the gauge is at the top, the water is at 210*. Right now I was unable to get much above 1/2 way.

So the one or two tablespoons of rust flakes that blew out with the reverse flushing seems to have been the culprit.

The method I used to reverse flush the radiator is quite simple. Remove the upper radiator hose from the engine outlet fitting, leaving it attached to the top radiator inlet pipe. Extend the radiator hose with a long length of PVC pipe and elbows if needed, Glue the elbows if used, and put the open end in a trash can. A clean trashcan if you want to inspect what is flushed out. A 5-gallon pail will work, but the engine holds at least this amount of water, so you will overflow the bucket with each flush of the cooling system.

Then hook up a blow-gun to your air hose/air compressor, and wrap a rag around the end of the blow gun, making a golf-ball sized ‘plug/adapter’ on the end of the gun.. insert this rag plug and blow gun into the water outlet where you disconnected the upper radiator hose. Push firmly st seal the rag to the pipe.

With the cooling system full of water, fill the engine with compressed air through the water outlet, this huge bubble of air will force the water down through the head, the water jacket, through the water pump, into and through the bottom tank of the radiator, forcing the water backwards through the radiator and pushing all the crud sitting in the top tank and covering the radiator tubes out the upper hose and into the trash can.. Refill the cooling system and repeat several times.

You must have a sealed radiator cap installed. And V-12 engines will need the other upper radiator hose to be removed, and the outlet covered with either duct tape or heavy plastic tape, then the radiator hose reinstalled.. You want to introduce the compressed air into a sealed engine cooling system with the only outlet the top radiator hose. I didn’t bother capping or sealing the overflow tube, it’s rate of leakage with this flushing system is negligable.

V-12 owners, don’t forget to remove the tape sealing the water outlet on the other head before starting the engine !!

Greg L