I have read so many accounts of overheating problems with flatheads that I almost feel foolish asking a question about it, but I have not seen this exact problem discussed so here goes . The stock 53 8RT engine in my 47 1 ton starts , idles, and drives great and always in within normal temperature except sometimes when I shut it off. Then it boils over quite suddenly steaming up the engine bay and spilling a few cups of coolant onto the driveway. Most of the time it does not do this and just acts like any other normal engine. I put in new thermostats, new pump belts tightened as recommended and it still happens sometimes. The fan assembly is rebuilt and working correctly as far as I can tell. There does not seem to be any leaks in the pumps , or antifreeze in the oil. Is this just part of the flathead mystique? If so is it hurting anything ? Suggestions would be greatly appreciated.

Thanks,

Neil

Neil

 

Is the radiator dirty, plugged or restricted? A common problem is dirt getting in the radiator, restricting the air flow. A few minutes with an air compressor can remedy that problem. If your radiator is plugged or restricted internally, you could take it to a radiator shop and have it cleaned with acid, or if needed, re-cored. (Remember that just because water will flow through doesnt mean that your radiator is not restricted) You could try taking the thermostats out completely as an experiment. That would rule them out. Does your truck have a heater? A plugged heater core can cause problems too. If it has one, you can by-pass the heater by connecting the two hoses together under the hood, again, just as an experiment. A common problem with the flat head is that the block is prone to cracking when they over heat.

 

I do not have a heater but I will try thoroughly cleaning the radiator for a start. ( it looks perfectly clean on the outside but who knows? )

Thank you very much,

Neil

 

Correct me if I'm wrong, but I read your post as it runs at normal temp, but blows water out after you shut it down. If that is correct, you may just be overfilling it.

It is normal for the water to get hotter and expand after it is shut off, and with a "0" pressure system, there is nothing to keep the expanding fluid from overflowing, so the level should be kept low in the top tank.

 

Yes , it is normal when running. I have seen some recommendations for a low pressure 5 lbs or less radiator cap. Is that a good idea and would it help to retain the coolant?

Thanks,

Neil

 

I would recommend a pressurized cap. What causes the cracks in the blocks is steam. Steam accures when the water boils. Pressurizing the system will raise the boiling point of the water, however I am not sure how much pressure the radiators will take as the large top presents a weak spot.

 

Not sure if your radiator filler neck will accept a pressure cap or not. If it does a 3-5 lb cap will help, and another simple fix is an overflow bottle, I prefer Capt. Morgan Private Stock, it's a pretty bottle