Packard Forum Index » Pre-War (1899-1942)

Yes, absolutely, you need to shut off that heater feed in the summer months, as it short-circuits hot coolant back into the motor.

It takes very little in the way of rust flakes to restrict the coolant flow through a clean radiator. It's common for old cars to have rust scale deposits in the engine block and heads, and while flushing will get rid of most loose rust, once the car is running, additional flakes of rust and debris will often come loose and lodge in the tops of the radiator tubes. In such cases, the radiator acts much like a filter. Back-flushing the radiator will usually remove most debris if it hasn't been there long, and re-flushing the block may get additional debris out of it.

Dupont sold an oxalic acid product for many years, and it may still be available. For any cleaner to be effective, a cooling system needs to be free of oily deposits. If you use any system cleaner in an old car, watch carefully for new leaks at freeze plugs and any steel piping, and don't forget to keep an eye on the heater core.

I was discussing this cooling issue with an owner of a 37 roadster who was having the same problem and he said by replacing the original 4 blade fan that came on the engine with a 5 blade fan it helped with the cooling noticeably.
I believe he got the 5 blade fan from an old Buick.

I used the thermocure product on my car after I pulled the waterjacket and scraped, wire brushed and vacuumed as much scale out of it as I could. I think it worked very nicely, as I've never had an overheating issue. I don't think you'll be disappointed.

Worth noting that much of the cooling that occurs when your car is stopped is actually air-cooling from the fan. That's why you don't have a shroud; it was a different design philosophy.

A good amount is also convective cooling in the crankcase ventilation system, though aside from a mouse house, that's hard to restrict.

I had a similar problem with my 1940 110 6 cylinder. I called the Evapo-rust help line and they assured me that it would not hurt the engine as the only thing that it destroys is rust. I drained and flushed the engine several times then: pulled the thermostat housing from the top of the head and poured in the Evapo-Rust into the opening right up to 1/4' from the top of the head. I allowed it to sit for six weeks.I flushed and filled again and added 50/50 Prestone and DISTILLED water.That seamed to do the trick. No more overheating on flat ground but it overheated after pulling a long grade. Last winter I pulled the front clip and had the rad. cleaned, flow and pressure tested,installed a new manufactured water pump and replaced the water distribution tube that was plugged at cylinders 5 and 6. I did alot more work than that on it s(see my post 1940 rebuild) My problem was solved. I did not start the engine with the chemicals in place so I don't know if circulation would have helped clearing the water distributiion tube. I am sure that the water pump was not working to full capacity. I have since driven it over 1,000 miles with no trouble.
Jim