I thought I found the problem with the flattie in my panel truck overheating but I am still having one.

A little background:

Last year I started chasing the overheating problem. Whenever I started the truck the stock dash gauge would peg out to "H" in a matter of a few minutes. I replaced the driver's side water pump at the beginning of last summer because it leaked. Between last summer and last fall I flushed the engine once with a commercial flush kit once and twice using water and air to agitate the gunk that was inside the block. All three times I was able to get a lot of black water out. It still over heated. I pulled the radiator and replaced it with three core radiator from a '46 big truck. Before I could do it thought I had to switch top tanks because the hose tubes were too big on the '46. When I did the tank switch I found the original radiator was glogged with rust and other gunk, the '46's tank looked very clean. The truck still overheated, at least according to the dash gauge. It got too late in the season so I packed the truck away in storage.

Fast forward to last Thursday, Spring was in the air so middle aged man's fancy turns toward old trucks and I get the truck out of storage. I checked the radiator and it was low so I topped it off. There was also moisture on the ground. When I got it back up to the house I noticed a dozen or more pin hole spewing anti-freeze. I change the radiator again for a three core out of a '52 F-6. Re-torque the head bolts, most needed another 10 ft/lbs of torquing. I also installed an aftermarket mechanical temperature sensor and gauge. I fill the radiator and find good size leak but it plugged up with a bottle of stop leak.

I started the truck, the radiator stopped leaking. The stock temp gauge pegged over "H" in about three minutes but the mechanical gauge just sat on the beginning temp of 130º for at least five minutes, I started to wonder if the gauge was defective but it started to slowly climb and finally reached about 160-165º and stayed there. I shut the truck off after about fifteen minutes of idling. I thought I had fixed my problem, which might not have been a problem, just a bad gauge.

I left the panel sit and cool all the way down and then started it and left it idle for about 15 minutes or so again. The radiator doesn't leak, my cheap fix is working. My stock gauge flies up pass "H" in a few minutes but the mechanical gauge still crawls slowly up to about 165º while idling. I took it down the road and the mechanical gauge actually dropped a bit while cruising. Stopped at a neighbor's house and the truck choked off. I tried to restart it but it didn't want to start. The radiator was dumping water out the overflow tube and the oil fill was steaming. At first it turned over slowly but then spun faster but still didn't want to start. Left it sit for about five minutes and it started. I drove it about three miles to the gas station, turned it off, pumped in a few gallons of liquid gold, was puking more water via the overflow tube. Wouldn't start, luckly a couple of guys gave me a push and it started with minimal push. Got back home still puking water.

Could this be a bad radiator cap? I have an old cap on it. Would the system over heat if the cap allowed water to escape at too low of a level? If the mechanical gauge is reading 165º I would assume the system is not really overheating but something is making it puke water. I might have filled the radiator too high too, about an inch or so from the top of the fill neck.

Again, the mechanical gauge never went above 180º except right after I turned it off, I think it went up to just above 200º. I would expect this to happen after the system stops circulating.

I have the stock temp sensors still installed in their original locations. I installed the aftermarket sensor, which is a gas one, not an electrical, in the second port on the passenger's side.



This is the first flat V8 I have ever driven, my pride and joy, the '49 F-2 has a flat 6 and I never had any major problems with it. It just takes a beating and keeps on ticking.

 

My friend, I am not real familiar with the flat heads either. But, it does sound to me like the cap is not holding the right pressure . It may be by passing water to the over flow. If your mechanical guage reads 180, then I would say it is not an overheating problem , but just a weak radiator cap. And your temperature will always go up just afftyer shutting it off. You are right on that.I am sure some one more expereienced than me on flatheads can tell you what pressure the cap should be. I knopw on my truck (289 ), it was overheating . I foubnd that the cap was an 8 lb cap. I replaced it with a 16 lb. No more p[roblems.

 

Have you had a pressure & flow tested rad on the truck?
How are the belts on the pumps, good shape & tight?
System operating pressure at 3.5 - 4.5 lbs?
Is your tongue sticking out the left or right side of the mouth?

 

Bob

You could be overheating on the left bank.
Each side of the flathead has a completely seperate cooling system only connected in the radiator.
I think the stock temp senders are a different type sender for each side. The guage normally reads from the left sender and shows the temp of the left bank. The right sender only reads if that side reaches too high of temp and then it overrides the other sender and sends the guage to hot similar to what a sender for a light does.
Possibly the original guage/sender is reading the left bank which is running hot and the guage you added is reading the right bank which is running normal.
I hope this makes some sense.
An infrared thermometer would be a great asset in trouble shooting this. You could shoot a temp off each head near the thermostats and see what is going on.

Richard

 

The sensor in the right bank is just a switch, and it sounds like it is bad. You could confirm like Richard says by putting a mech gauge on the left. In 60 degree weather, it takes at least 10 minutes for mine to get to about 140 or 150, so if your stock gauge is getting there sooner, it is the first thing I'd suspect.

It also sounds like you have a lot of air in your engine. Try adding it slowly while running and warm to get to proper level (which is not to the top of the filler neck, it's about an inch below.

A bad cap won't cause overheating or change temperature, it will just leak off pressure and fluid too soon.

 

Dick, no I haven't had a pressure test of the system. I haven't been able to drive it far enough to get it someplay to have it checked. The pump on the driver's side is new, the original was froze, I freed it up but it was noisy and leaked. The passenger's side seems to work fine.

Richard and Ross, I'll flip the mechanical sensor to the driver's side to check the temp. I wish I had access to a lazer thermo tester I could look for hot spots in the engine.

Richard, I figured the sides of the engine were completely separated when I flushed the engine last year. I only had water coming the side I had the hoses hooked up to.

Ross, what is the best way to fill the engine with coolant. Should I drain it until no more comes out and then fill about half way, start the truck and then slowly poor in the rest? Is there a way to burp the engine to ensure there isn't any air pockets?

These darn flatties are a pain. If they didn't sound so cool and make everyone all nostalgic I would rather go with a flat six.

 

Hi Bob,

I'd flip the mechanical gauge over to the other side to test if it is over heating.

The first few times you run the engine to operating temp after filling it and refilling it, it's gonna blow off some of the excess expanded coolant until it's finds it's hot full level. Without a recovery tank to catch that and allow it to suck back into the radiator as it cools, the cooled off radiator is going to appear to be a little low on coolant. That's normal.

I have a really stupid question....Are you still using a stock 6 Volt electrical system (with the 6 volt gauge)?

 

bob mine did this for quite a while . it was and every once in a while still driving me crazy . the ol' girl will be fine then do the same goofy stuff yours is doing . i flushed mine many times , got the air outta the system , even done a run right you pos indian dance , and had an exorcism done . it just popped the seem on the radiator again and with a 4 lb cap on it , prior to popping the seem it would heat up pdq and run hot . pop the cap it'll run all day with no issues , and just puke some of the coolant . i tried running a leak down , with negative results ,and have come to the conclusion it's just a finiky ol pain in the posterior . i'm gonna replace the pumps and some other stuff as soon as my new means of transport becomes available , { the 53 is parked thereafter for much needed tlc }and hopefully i can find my cooling issue . so i will be watching your thread here with hopes of gaining some dain insight to mine .

 

1949/53 239 Flathead V8 ~ Cars & Trucks use the same units.

8A-10884 .. Water Temperature Indicator Sender-6 Volt ~ Stamped: 224 ~ Use with 4 lb pressure cap.

8A-10990 .. Excessive Engine Temperature Sender-6 Volt ~ Stamped: 217 ~ Use with 4 lb. pressure cap.

EDIT: FTE sponsor GREEN SALES has (6) 8A-10990's & (8) 8A-10884's = 800-543-4959

 

Bob

You should be able to bleed the air from the block as you fill it by loosening and letting it out the temp sender fittings. That and the thermostat housings are the highest point in the cooling system in the engine.

Once the thermostats open all air should be gone. Trapped air will cause the thermostats not to work poroperly the first time though.

Richard

 

When it comes to coolent problems. the infra-red temp gun is the
1st tool I reach for in my toolbox. Well worth the investment in the long run. With it and a cooling system schematic ,I can quickly pinpoint abnormalties. Hope it's nothing serious.Good Luck!

 

Dan,

On nifty modification I have heard is to use the filling neck from a Volare, but I suppose there are others, to take advantage of the overflow system. My neighbor was talking about doing it to his '52 F-1. I don't know if he did it, I'll have to stop by and ask.

Yes, the system is still 6 volt.

Richard,

With the advice of MTflat I drilled a 1/8" hole in the flange of each of the thermostats so they should allow the air to escape. As for the temp sending units I didn't drain the coolant before removing the plug in the port I install the mecanical temp sensor. As I removed it the coolant flowed out and I could hear noise in the radiator. I do this again on both sides and see what happens.

 

Try switching the temperature switch before swapping the mech gauge to the left. There is a schematic in this old thread:

https://www.ford-trucks.com/forums/5...der-units.html

I was wrong, it's in the LEFT head, unless someone switched them.

 

Hi, don't know a whole lot about the flatheads,"yet" but have you removed your spark plugs to see and discolorment? I chased a problem a few years ago and found my head was leaking into my combustion chamber. No smoke out the tailpipe or anything. Frustrating I know, well keep us posted and good luck.

 

I wa just wondering about the voltage with the gauge, but if it's 6V then it should be ok. I saw a guy at Del Mar last month who had mounted a flathead oil filter canister as a recovery tank for his radiator. He put a fitting in th ebottom hole and connected that to th eradiator overflow. Then, he plugged all th eother holes except the top one, which got another fitting to a hose running overboard. Just a thought.