I have a mystery. Hoping one of you flathead experts will show me the light. 1951 f1 239 v8. engine runs great, using no oil, 75-80psi on all cylinders. Loses 1 gallon of water or coolant for every 65-70 miles of highway driving. No vapor from exhaust, no leaks external, no radiator overflow, no water in oil, no smell of exhaust in radiator. Can drive truck around short distances 5-10 miles with no loss of coolant. Checking engine temps with one of these new temp guns the hotest it has been is 213 degrees on heads right below spark plugs. Radiator is consistent 20-25 degree drop from top to bottom. I am running new 180 degree thermostats. Temp gauge is always up around the H but truck never smells or runs like it is too hot. Ran a pressure check on each cylinder @ tdc using air pressure at spark plug hole. With 100 psi on each cylinder one at a time got no bubbles in radiator. I know I can only lose water so many ways. Any Ideas or things I can check? Thanks, Rob
If you are losing/adding 1 gallon every 65-70 miles of driving to bring it up to its original level, the original level you are trying to acheive may be too much. They have a tendency to determine their own level of required water/coolant. Run it without adding the gallon, but be sure and monitor it's temperature. Disclaimer: I am by no means an "expert", although I have had several Flatheads.
I agree! mine will spit out overflow if I fill it, untill it is down to a level that it seems to be happy with. Still runs same temp. I am using stock radiator and 180 therms. There seems to be alot of expansion in these.
My 48 F1 likes the coolant just above the core tubes. That's about 2" below the neck. Same story as the guys above. This truck has been a daily driver since 2001 and has seen a lot of road time.
You didnt say what speed range you were operating you engine at. If you are running your flathead at todays road speed 55-70 most likely you are spinning the engine faster than it was designed for. Most flat heads like to run 45-58 with the gearing that is supplied with the vehicle. If you have a low set of gears and the engine spins at a higher RPM the most likely scenario is that the water pumps are pumping additional water to the radiator that it cannot easily flow.When you stop and check the water it appears to be low or lost. This back log of water fills the top tank and exits the overflow port especially if this is a stock radiator with the over flow tube contained in the tank area. If the over flow tube is at the seat base of the cap then a 4 lb or 7 lb cap may cure the burping issue.. The easiest check is to fill the radiator like you normally do about 1/2" below the neck and take your car for a slow ride not over 40 mph. Recheck the water level it should be about the same. Now take your ride out on the 4 lane and run it about 60 for the same time and recheck the water level, if its down you know you are just loosing water out the over flow and that is due to the higher rpm and a leak out the overflow not a problem with the engine.
Thanks for the replys. I am driving between 50 and 55 mph.3.92 gear ratio.The temp is higher at highway speed. Seems to cool down a bit on the slower back roads. I have tried not adding the water back... it just goes through more water until it starts steaming out the overflow, vapor only. that time I added nearly 2 gallons. I have not tried pulling the oil plug but there is no gain in level and no milky oil. I park on concrete and have seen no overflow liquid after a drive. Thanks for the ideas, Rob
Dick, I will try the road test you described when I get home. I was thinking about adding a catch can to the overflow just to be certain I was not losing water there going down the road. Rob
It may only be able to maintan a coolant level that is on the same height of the engine....meaning the distance from top of engine itself, up to the overflow outlet level on radiator,may be where it is capable of maintaing coolant...
Put a catch can on the overflow, get it hot and then run it in neutral at your cruising rpm and watch the catch can. Arguably, the engine won;t experience the same load as when driving, but you can at least tell if your water pumps are overspeeding and overfilling the top of the rad. I'm assuming you're running straight water in your system, what's the pressure of your cap, stock cap? Flatman
If everything else fails, take the heads off ( simple to do on a flathead) and check carefully for cracks between the cylinders and the valves....examine the head gaskets carefully too.
Thanks guys, I am running a 4 lb radiator cap. Yes, nearly straight water. Any Idea what the cylinder head temp should be or maybe how hot is too hot? I wouldn't think 215 would be very hot with about 180 at top of radiator. I was concerned about the water pumps. I heard the impeller vanes would rust away. I have no idea how old they are. Still doesn't explain the water loss though. Rob
If you know someone that has a combustion gas tester for the cooling system, drive by and have a test. It may help making your decision about head removal. Dave.
sorry to say but i think she is cracked between the valves . Check the plug burn . the cracks are very hard to see , use a sharp jack knife and you will feel it . been there done that .
Dave, yes I need to do that. I can't smell anything and there is no bubbles in the radiator while hot but it would prove once and for all. John, All the plugs look fine and really close to the same. If I have a crack wouldn't water be in the cylinder after killing the engine? Thanks, Rob
I'd have the heads off..... Easy to do,.... and then you'll KNOW. Flatmotors were known for head gasket failure, and it wouldn't take much to run thru your coolant supply. If you find some pistons with super clean tops,...you'll know which cyls. are being "watered". Let us know what you find. 4TTRUK
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