Flathead cooling advice wanted

[MN Stumpjumper]

I took my stock '50 2 door on a 400 mile round trip last weekend. I just got the car. On the 1st leg, the coolant puked out the overflow tube when I would deccelerate hard. It never got over 210 on the gauge.
I refilled it for the second leg and it got worse. I was running about 2600 rpm, everytime I let off it would push the coolant out the overflow.
I started running about 2000 rpm and it seemed to stop puking.
When I got home I pulled the hoses off the thermostat housings,no thermostats. I plan to put stats in, should this "fix" the problem? Thanks.

[JWL]

I doubt if adding thermostats will correct the root problem. I am wondering how you decided the problem occurs during deceleration?

The first thing I would check is the sealing of the radiator cap. If the temp does not exceed 210 there should not be puking. There are dozens of other potential causes for puking caused by overheating. These range from improper ignition timing, to inadequate radiator air or water flow, to combustion gas leakage, to dragging brakes, etc. etc. etc. I think you will have to more thoroughly examine and describe the problem before a definitive response can be offered.

[Terry,OH]

With the stock systems, over filling the radiator can be another factor that leads to overflow. If you keep the coolant level just above the upper part of the core, the level should be good.

[wga]

Is this a stock motor? Let's assume it is. Check to see if you have exhaust gas in the coolant. Go to some independent shop in your area and ask if they would use the exhaust gas probe to check for exhaust gas. If you get readings of CO2 in 15 - 20 PPM or so range, you could have a bad head gasket, at worst a crack in the block. A good reading is 4-5 PPM If this test passes - then look for the usual problems - but let us know if it is stock, modified, etc. Could be as simple as the timing is set incorrect. Get some thermostats installed, 160's and get back to us.

[krackerjack1951]

my 2 cents worth are overfilling the radiator..wrong or bad cap..if you fill the radiator full,the water heats up and expands and out it goes till it finds the happy point about 4 inches down..if you have the short neck cap,it will not seal..get yourself an overflow container just to catch the coolant in case you dont want the mess again,lower water level and get the right cap..it takes a few years to learn these problem cures.
i am running a flattie merc for a good many years,still makes me smile!

[MN Stumpjumper]

Sponsored Links (Register now to hide all advertisements)

It is a stock motor, I know it pukes on decell. because the overflow tube is broken off and when it pukes I can smell it,and it eventully blow out of the hood.
It has a 7lb. cap , I'm not sure if it seals in the neck(I'll check). I suspected a compression leak also, I'll try pressure on the system to see if I can detect any signs of coolant in the cyls. Thanks for the feedback Guys!

[Planojc]

Most of the time a compression leak will make bubbles in the coolant with engine running. I run a 4lb cap on my 51 and use a Skip Haney 3lb pressure valve on the overflow tube.

[38 coupe]

I highly recommend an overflow jug. In my experience the flatheads run cooler if the radiator is kept full. The only way to keep them that way is an overflow jug.

[krackerjack1951]

i just had an afterthought...have you cked your belts,,they could be slipping @2600,,back off the throttle @2000 and problem ceases?? when belts get a load and are worn slick and hot they expand,,loosness and slipping could occur.. just one more clue! do you have a stock fan,i think ford had a 3 blade stock fan?? if more blades than 3 just might be working the 4,5,6 or 7 blade fan assys???

[Max]

The FIRST thing I do with an overheating flathead is to remove the radiator and have it cleaned. This means removal of top and bottom tanks. When refitting I ALWAYS place socks in the return hoses to stop crud from getting into the radiator. You can fiddle around forever to try to cure your overheating woes but if the radiator is partially blocked, you will never have sucess.
The cure for overheating is a process of elimination, and you cant eliminate any problems if the radiator is full of shit.

[Straightpipes]

I would put a good quality mechanical temp guage in it. I wouls ensure that the timing is set properly which causes most overheating problems.

[FlatheadTed]

Dito

Originally Posted by Max

The FIRST thing I do with an overheating flathead is to remove the radiator and have it cleaned. This means removal of top and bottom tanks. When refitting I ALWAYS place socks in the return hoses to stop crud from getting into the radiator. You can fiddle around forever to try to cure your overheating woes but if the radiator is partially blocked, you will never have sucess.
The cure for overheating is a process of elimination, and you cant eliminate any problems if the radiator is full of shit.

[MN Stumpjumper]

I had a little time today to look at the cap, it is the wrong one. I measured the fill neck and the cap is NOT sealing at the bottom of the neck. What is the correct cap for this car? (4lb.-7lb.) I have not checked the timing.
The P.O. said he had the radiator rodded and cleaned. I will get some stats in there and find a cap that seals the neck. I also will repair the overflow tube and install an overflow tank. These thing might take me some time, I'll repost the results when I get these items fixed. Thanks again for all the ideas!

[MN Stumpjumper]

Belts are tight,and it has a 3 blade fan.

[FlatheadTed]

The overflow Jug does add 1or two ibs back pressure in the cooling systom ,that helps to keep it in .

Originally Posted by 38 coupe

I highly recommend an overflow jug. In my experience the flatheads run cooler if the radiator is kept full. The only way to keep them that way is an overflow jug.

[ajohn]

My 1936 Oldsmobile with a stock straight eight engine was doing the same thing as your car.I put an entire box of granulated Cascade dishwasher soap in the radiator as I do in all my cars that overheat.The temperature dropped from 212 to 160 in one running of about five miles.This will not always work but it is cheap and is the only way I have ever found to clean the system without major work.It might work for you.

[40 Deluxe]

Check the vacuum diaphragm on that wondrous-whizzy distributor that Ford bestowed upon you. If the diaphragm is blown or disconnected, you will have NO spark advance; thus an overheating problem. Hook up a timing light and watch the marks as you rev the engine. If the timing is the same at say 2,000 RPM as it is at idle, there's a problem. Also check for plugged vacuum passages in the carb, possible wrong gaskets, or bad spark valve (that round thingy with all the holes that screws into the carb base). This system worked OK new but has given a lot of people a lot of headaches since.

[MN Stumpjumper]

Finally getting around to updating you on my overheating problem. I found an original radiator cap to replace the "new one" which didn't seal the lower surface in the radiator neck.
I installed thermostats in the heads.
I have idled , driven hard, and normal. NO overheating issues at all.
Thanks to everyone who responded with advice.

[G.M.]

Planojc you don't want Skips valve on a radiator with a pressure cap. If your radiator released water before Skips valve was installed and the valve cured the problem your pressure cap was to short and not seating down on the bottom seat like Stumps up above. If the pressure cap seats or you have Skips valve you can fill the radiator up to the filler neck and the engine will run cooler and not lose coolant. Henry didn't make a 22 quart radiator to put 18 quarts in it. 2 quarts low is about 12% low. G.M.