I have just purchased a restored '50 F1 pickup with the 239 v8 engine. The restorer restored the bed, body, interior. Also replaced all the engine wiring, ignition, carb, etc. but left the internal engine as he found it. It's running good for me except that I am have an engine over heating problem after driving a few miles. My first step was to replace the thermostats on both sides...did not help. Now I'm wondering if I have a non-fuctioning water pump on one side or the other? Is it possible that even though my water pump pully shafts are turning (I can that they are), that I could still have an impellor that is not turning?

 

Do you have any bubbles in the radiator while it's running. If so could be a bad head gasket. I had a problem with my Flathead 6 overheating awhile back, it turned out to be trapped air in the block from when I changed the heater hoses. A radiator shop can troubleshoot your cooling system problem if all else fails.

Rod

 

I'd be suspect of the radiator. It may be clogged with rust and corrosion. How long will it idle before overheats? If it idles without overheating but heats up on the road, then the water may not be circulating properly.

Vern

 

If you suspect a bad head gasket as mentioned, be careful taking the head bolts off, use an impact wrench that can give even torque. A ratchet or wrench with a cheater bar risks breaking off a head bolt, and there's a crapload of them on the flathead v8 to get off. Check the timing also, it can cause one to heat up as well. If it idles hot but cools down when driving on the highway the timing may be too slow and needs advanced. But thoroughly flushing out the coolant system and refilling with distilled water and antifreeze would be a good first chore since you just got it. And check the fins on the radiator core, if a lot of them are crushed over you aren't getting air through those parts of the radiator. And last but not least check the belt tension on the water pump belt. It should only have about an inch or so of deflection if you push on it, if there's more, you might see it turning pulleys at idle, but if you drive it at higher rpms it might be slipping. As you can tell, there's several possibilities that can cause overheating, and odds are you'll try a few different ones before finding the culprit.

Scott

 

Thanks for the info and possible causes of my problem. I'm headed toward getting the radiator checked out as the next best step....then will see where that takes me. When I drained the radiator in order to install the new themostats, it drained freely and quickly from the drain plug so I assumed there was no blockage there....maybe that doesn't indicate for sure that both lower outlets are OK?

Ron

 

Thanks for the info and possible causes of my problem. I'm headed toward getting the radiator checked out as the next best step....then will see where that takes me. When I drained the radiator in order to install the new themostats, it drained freely and quickly from the drain plug so I assumed there was no blockage there....maybe that doesn't indicate for sure that both lower outlets are OK?

Ron

 

after all of the above you may have a cracked block.common on flatheads.

 

If you find the radiator has gunk caked in there, you can guess the block will too. You may need to resort to mechanically scraping the junk out of it with anything that will reach down inside. Hopefully you will not need to go to the extreme of tearing down your motor.

 

Hello,
Been there done that. In 1995 I purchased a 50 Coupe 90% restored with a fresh flathead. I got her home and it would overheat going around the block. I replaced the head gaskets, had the radaitor recored, installed new thermostats,and still the car ran hot. It would loose water by blowing it out the overflow. It would idle all day long without getting hot but take it on the road and it would get hot as a firecracker. I had a cracked cylinder. It was from a bore through into an imperfect cast or more than likely water had sat in the block for years pitting the cylinder and causing a hair line crack to appear when the engine was bored. The crack was too small to allow oil to get in the cooling system so the coolant did not look like chocolate milk. When that engine got under a load the crack would allow combustion gases to escape into the the water jacket over pressurizing the system and blowing the water out the overflow as I drove down the road. I happened to have a good block that was the same overbore so I changed blocks.
I hope your problem is not as severe as mine was. Try this first to diagnose the problem. ONE, With the engine cold open the radiator cap and smell it. What do you smell? Antifreeze good, Gasoline or exhaust bad. TWO, with the cap off crank the truck. AT IDLE see if any bubbles are evident in the coolant. Please be careful. Now have a friend rev the engine. Please stay several feet away from the open cap but close enough you can observe whats happening. If water blows out the top when the engine is revved you have a problem. The water may rise and spill out a little from the t-stats opening wich is normal but if it blows out you will know it. Mine shot water up a couple of feet wetting the underside of the hood. Its bad if this happens. This is combustion gases inside the coolant system caused by hopefully a blown head gasket wich is common or worse much worse a cracked block. THREE, with the engine warm shut it off ,now feel each head or t-stat housing. Does one side feel hotter than the other? If one side is hotter, that is more than likely the side that is blown or the water pump is not functioning on that side.You can burn up one side on a flathead if that side's pump in not working. If you have straight duals the side thats steaming out the tail pipe is the problem. If it did not blow water but one side overheats replace the pump. I would replace both. Remember to support the engine because the pump is also the motor mount. Do not forget the last bolt that is inside the bottom inlet. If you did not blow water and can tell no difference in temperature from side to side try rodding or recoreing the radiator. Install cooler thermostates or big washers with 1/2 inch holes like the oldtimers did. With the repaired radiator in I would fill the engine with the thermostats off. I would get the water level to just below the T-stat housing install them then fill the radiator to about 2 inches below the cap. More than this will just be bubbled out. Filling like this makes certain no air packets are below the thermostats to air lock the cooling system. FOUR, Another way to locate the affected side is to pull the sparkplugs. Plugs that look washed indicate a coolant leak in that cylinder. You can even try retorgueing the heads. If you are lucky this may clear up the problem. When replacing the head gaskets look at the old gaskets. They will tell you where the leaks are. A stain from the cylinder to a water jacket is a tell tale sign. Look at the valves some may be burnt. Look for cracks around the valve seats. A valve seat to water jacket crack is bad. It can be fixed but it is an expensive repair. And it cannot be done in the truck or even assembled for that matter. A crack between the center head bolt to cylinder can be ignored as long as the crack does not run down the cylinder. Check the heads for trueness. An old time trick was to take a straight edge and lay it across the head and look for gaps. An old school way to true a head is to take a file while holding it flat across the head at an angle file and brighten the metal evenly. This trues the head some what. A severly warped head or block must be milled down or decked by a machine shop. Hopefully you won't haft to get this deep into your engine to correct it's ails. One thing I would suggest is getting a 3 gauge set a mechaninal oil and two temperature gauges. Oil in the center left and right head on each side. Mooneyes would look era and be a nice addition bolted to the underside of the dash. Brass tees can be bought to run the gauges and your factory stuff too.
Good Luck,
Travis

 

I also had overheating problems with the original flathead V8 in my '51, I even had the radiator cleaned out, installed new pumps, new thermostates, etc, and it still overheated as soon as I started driving it. Luckily, my block wasn't cracked, the problem was the corrosion and scale buildup inside that 50 year old motor was so bad in the water jackets, there was absolutely no heat transfer between the block and the coolant. It was the original motor, never rebuilt, with 40k on it. I'm having it rebuilt, it should be done next week, but then again my machinist has been saying "next week" for about 2 months know...haha.

I hear a lot of stories about flatheads running hot, especially if A/C is added, so I took this resto-mod one step further, I had a guy out of Glendive, MT mod my radiator. He just put a complete new (and much, much bigger) core in between the factory upper and lower tanks. It's only about 1 inch thicker, but the flow and capacity is increased big time. He said there is no way I could make this thing overheat with that radiator in it. Just a suggestion. This cost me $500, a little pricey.

F-one, I like that idea of using one temp gauge for each bank.

Gary

 

I had a lengthy discussion with Flathead Jack in California some time ago about the same problem. He nailed the fix as: improper ignition timing.

It was one of those overlooked culprits that fixed the problem. Operating the vehicle, and the changing advance curve made the problem appear only when the car was driven.

 

So would that mean the ignition that was too retarded? (no pun intended..)

 

That's what Flathead Jack's write-up in his catalog says. People think that it idles hot but at highway speeds the "fresh air" helps cool it back down, but in reality it's the timing advancing helping the ignition to catch up and get back in time with the motor.

scott

 

great thread!
My v8 239 heats up when idleling or not. The temp climbs way up, then backs down to below half on the gauge, then back up to hot, etc.

I have 160 thermostats in.. what do you think is causing it?

Also, who has electric fan behind the radiator, who makes them, do they work good?
Thanks

 

Reading these comments makes me wonder if the old Flathead engines are really the way to go on a daily driver these days. If it wasen't for all the pending smog regulations decending upon the old car hobby in this state. I would throw in the towel and go with a crate engine.