Flathead Overheating

[Anonymous]

Drove my 49 Merc for the first time after frame off restoration today.  It has 255 original flathead engine that was rebuilt in it.  After driving it for about 5 miles I noticed smoke coming from under the hood.  I pulled over and it was overheating badly.  There did not appear to be any leaks.  After cooling down I added about a gallon of water.  I drive it another ten miles or so and it was overheating again.  The engine was totally rebuilt with new waterpumps.  Does anyone have any ideas?

[Virgil & Sue Klein]

Are you sure you had the cooling system full of coolant before you took off for the first 5 miles.  Needing a gallon of water on a fresh overhaul after 5 miles would indicate that.  Just filling the radiator with water may not fill the entire cooling system but letting the engine warm up until the thermostats open and being sure there is circulation will make sure.  The other issue, I looked up your previous post, is that your rebuilder has swapped the head gaskets side to side.  It would not be the first time that has happened (I speak from experience here).  Although the gaskets look the same they are not exactly mirrors of each other.  If you are not losing water on the ground then it has to be going either into the pan or out the exhaust neither of which is a good option.  Hope you find the problem soon.

[Anonymous]

I think all of the water was coming after I took the radiator cap off.  There was water and anti-freeze all over the hood underside.  I know the rebuilder didnt get the thermostates installed correctly and it was leaking alot.  I know that when I filled it after it over heated I did it with the engine running and made sure it was full.  The block was cracked and had to be welded.  Thanks,

[Roy & Brenda Lange]

Clint and Namcy:

My basis for this is form my 53’Merc:….As to the water all over the engine bay…if you have a overflow tube going down the side of the radiator, it probably stops shy of the lower sheet metal. Take a piece of tubing and put it on the bottom over flow tube down through the metal pan…that way the water will flow on to the ground. The fan is picking up the water now and spraying it all over the engine bay….this will keep the engine bay clean but not fix the proublem.

If as Virgil and Sue said the head gaskets are swapped then the only option is to pull the heads and correct it…..not a big project if you have a torque wrench…..you can do it in a day.

I would guess that you have an air pocket in the block, so it is not cooling. When you fill up the radiator leave it low to allow for expansion of the fluid and the air to come to the top and then let it idle in the drive way and watch for the air bubbles. When they stop, torn off the motor and  fill up the radiator – leave about 1 1/2 ”  to the top to allwo for expansion.  One last thing…have you checked the radiator cap…the 53’s needed a 4 lb cap….it should say on the top of the cap. I am in the membership book if you want to call….Roy and Brenda Lange , Confier Colorado. God luck.

 

 

[Roy & Brenda Lange]

Clint and Nancy: My basis for this is from my 53’Merc:….As to the water all over the engine bay…if you have an overflow tube going down the side of the radiator, it probably stops shy of the lower sheet metal. Take a piece of tubing and put it on the bottom over flow tube down through the metal pan…that way the water will flow on to the ground. The fan is picking up the water now and spraying it all over the engine bay….this will keep the engine bay clean but not fix the problem. If as Virgil and Sue said the head gaskets are swapped then the only option is to pull the heads and correct it…..not a big project if you have a torque wrench…..you can do it in a day. I would guess that you have an air pocket in the block, so it is not cooling. When you fill up the radiator leave it low to allow for expansion of the fluid and the air to come to the top and then let it idle in the drive way and watch for the air bubbles. When they stop, turn off the motor and fill up the radiator – leave about 1 1/2 ” from the top to allow for expansion.  One last thing…have you checked the radiator cap…the 53’s needed a 4 lb cap….it should say on the top of the cap. I am in the membership book if you want to call….Roy and Brenda Lange, Conifer Colorado. Good luck.    

[Roy & Brenda Lange]

Clint:

Let me know what you find out regarding the overheating issue.

Thank you,

Roy

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