Flathead Cadillac Overheating, Can't figure it out. Any Ideas?

[auburnseeker]

I have a 1948 Cadillac Series 62 with the original flathead Cadillac engine. Supposably turnkey when I bought it. I even Checked it out and listened to it run. It was raining when I looked at it so I decided not to take it for a test drive. ( Never buy a car in the Rain)

After buying it and Getting it home. I checked everything over. Let it run for 15 minutes or so then took it for a short test drive. After about a 3-4 mile run at 55 MPH ( I took it slower at first) It began getting warm. I decided to turn around and head back to the shop. It started boiling over just as I pulled back in the shop. I shut it down. I moved it a few minutes later( still hot) and it started right up. I drained the radiator and found no Thermostat. ( It must have overheated for the past owner as well which he conveniently neglected to mention. I pulled the Radiator and thuroughly cleaned it. I drained and flushed the block and all the heaters. Then put all new hoses on it. Put a new 160 Thermostat in it. Left it with just water and ran it. Same problem. I got engine flush and ran that through it. Then Removed the hoses and ran water through everything until the water flowed clear with the bottom radiator hose off. Excellent flow in the radiator and left side of the block. Not quite as good on the right. Put it all back together and same problem. I even checked the engine with a pin point digital Heat gun in several locations at a temperature of 175 and everything was within 5 degrees. No hot spots. I Pulled the water pump and it looks like new with no damage to the impellor. I even backflushed through the waterpump hole. I did a Compression check as well and have 100 lbs on every cylinder. What should I do next? Any ideas would be welcome. Thanks in adavnce, Randy :confused:

[auburnseeker]

I forgot to mention I also pulled the thermostat back out and punched the center out then reinstalled it. Still no difference. The engine will cool slightly when going down a real long hill. It takes about 25 minutes at idle to heat all the way to the boiling point. You can't seem to get the temperature to drop at all when standing still even with the engine at say 1500 or so Rpms. It just consistantly slowly goes up and doesn't come down. No bubbles in the radiator or steam /white smoke from the tail pipe. Seems to have plenty of power and pickup on the highway.

[PONTIAC1953]

hi, could the radiator have too small of a core ?, is the waterpump fan belt tight enough ?, one more idea, does your lower radiator hose have a metal spring inside ?, if not, when running the suction of the water pump will partly or completely colapse the hose. charles coker, 1953 pontiac tech advisor.

[Restorer32]

Check the timing.

[Ivan Saxton]

There might be a clue to this in the wartime Cadillac V8s. These were used , paired, with Hydromatics, in the Light M5 tanks derived from the Light M3 and M3A1 Stuarts. Also, out here, they were mounted experimentally in the Australian Cruiser tank that was derived form the Lee, Grant, and Sherman, but with a much lower silhouette and a transmission made by Oliver rather than Chrysler or Baldwin Locomotive. These had been intended for ungeared R985 radial Pratt & Whitneys, but when the shipment of these was blocked they tried a triple flathead Cadillac installation. Now apparently some of those Cadillacs were intended for marine use with plenty of cooling water and no radiator. When people used these in cars or trucks from war surplus, they overheated badly. My friend Henry Formby managed to snare one of these to replace the Ford V8 in his vintage car recovery unit. I didn't see exactly what he did because I was at university, nut I understand that he had to enlarge water holes in the head , and/or head gasket. I recall also they originally used those miniscule 10mm spark plugs. That could be worth checking if all else fails.

[Dave Henderson]

Although water comes out of the bottom of the radiator clean, could there still be a flow problem? A shade tree garage rule of thumb is that it should flow out at the bottom as fast as it can be put in at the top. A trip to a good radiator shop for a professional examination might be in order. Another possibility would be a head gasket leak. A sniff test of the crankcase fumes with an exhaust analyzer might diagnose this.

I don't know if overheating is a common problem with flathead Cadillacs in particular, but I do recal a friend having the same problem with a '41 back in the late '50's, and it turned out to be the radiator.

[Dave Henderson]

OOPs, I should have said to test the radiator for exhaust fumes with a sniffer, not the crankcase.

[Rick Hoover]

One of the first things I would check is to see if you have the correct radiator cap on it and that the rubber seal is good. Cadillac has a deep or high fill neck and in many cases folks install a short reach cap on them. Measure the neck depth and then height on the reach of the radiator cap. Off the top of my head, it should also have a 7 lb. cap on there. If the cap is to short, get the correct cap. Another thing I would check is to re-drain the radiator with having anti-freeze in it first. Once drained, look inside the filler neck and see if you have any antifreeze laying in the core tubes. If any antifreeze is laying there, those are the core tubes that are blocked. You won't be able to see them all, but you can pretty much average it out how much blockage you do have with what you are seeing in the neck. And I also agree with checking the timing.

[Restorer32]

We did a '47 Caddy, rebuilt engine, recored rad etc. Always had a tendency to overheat until we checked the timing and advanced the spark a bit. Made all the difference in the world. A retarded spark exposes more of the cylinder wall to the heat of combustion and can make a big difference re overheating.

[auburnseeker]

I appreciate the responses. The radiator does flow out the bottom as fast as I can fill it and that's with a high pressure hose on full action. I did examine all the cores I can see and 2 have blockage that even rodding(I was able to get a control cable from an air vent down them will not loosen) I can actually see about 75 percent of the cores through the thermostat hole in the back of the top radiator tank. Even with those 2 the radiator cores not flowing it still flows very fast and actually sucks the water out like a good clean drain when it is just about empty. In my area the work I did on the radiator surpasses what any of the local shops will do. Every time I have taken stuff to them to fix I have to redo it myself. All they do is a quick boil and bad paint job.

I did check the radiator cap size out early in the game. It is running the correct RC1 7 pound cap. The rubber is still intact and seals but I may replce it just as a matter of course to eliminate one other factor. I did not run the engine number to see if it is the original cars engine.

I will check the timing. Who knows. The only other thing I can think of is the guy I bought it from said he thought his brother did a valve job. Maybe he put one of the head gaskets on wrong and plugged a water hole. (I have new head gaskets already coming) Again thanks for all the ideas. I'll get it back together and do a little more diagnostic.

[Guest ragtoprocketbri]

Hi randy,just read about your problem and just had to respond,in the 70s my father had the exact same car and the exact same problem as you have,he done everything to that car to try to stop it overheating-he even put in a new crate motor(army surplus from a tank)and it still overheated exactly as you described-at this stage he had already checked the rad for flow and he thought it was fine-but as the problem was driving him insane he decided to put the rad into a local radiator repair shop-the outcome when they took the rad tanks off was 90 percent of the tubes were blocked solid-after a rad overhaul-problem solved!hope this is of some help-best regards BRIAN

[Ivan Saxton]

In overview of the above there seem to be several things to check and do.

Possibly the best way to check correct spark timing is (after assureing yourself that the advance mechanism in the distributer is fuctional and in good condition, and does not retard with increasing revs because someone put the reverse parts in), to set the timing according to the instructions of Tom Reese using a vacuum gauge.This was in Antique Automobile 20-30 years ago.

Then flow-check the radiator and the engine individually, with a set volume of water connected in a header, using a stop watch. Check the open gap of the thermostat, and jack open a discarded one the same gap so the flow time is what you would have with a hot engine approximately.

Do I understand correctly that it is your car that has a war surplus engine in it, or just another like it? I am afraid I cannot ask Henry Formby what he did with his new engine in the jail-bar Ford. I recall he did speak of drilling some water holes to a larger size, and it was fairly obvious what he had to do. It is probably smart to do a compression test (if you have not done so already) before lifting a head. It is a shame to have trouble because these were such a powerful smooth, and quiet motor. From memory also these had early hydraulic valve lifters, and you might have funny problems if these are not right.

[auburnseeker]

I did mess with the timing today. My manual says to just set timing at the IGN line on the damper. Which I did do. It was actually advanced the way it was. Factory setting seemed to retard it some. Does anyone have anything better for a number to set it at. Shouldn't it be a few degress off?

I did take my vacuum advance off and check that. It is working and not seized, I also checked my engine numbers and the engine is matching numbers so it is what came in the car new, Not a surplus tank engine. I still have to advance the timing ahead more than the factory setting and see if that makes a difference. I did check to see if it was automatically advancing when the engine is revved and it does. I do appreciate all the ideas. I'm willing to try just about anything at this point. Oh still overheating. Thanks again, Randy

[Dave Henderson]

If trouble persists after all efforts, and you still don't want to go the radiator shop route, here is a do-it-yourself rodding technique that worked for me on a '73 Plymouth Scamp, without removing the top tank. Get a length of 1/16" welding rod and a drill with a slightly larger bit. Drill a hole in the top of the tank. It's brass and can easily be soldered up afterwards. You will find that by inserting the rod through the hole at slight angles you can access and rod out more than just one tube, and as you go along you will be able to figure the best place for additional holes. In my case, it wasn't necessary to drill more than a surprizingly few holes. Carefully work the rod until it hits bottom. You may find some tubes solidly blocked, in which case it's best to leave well enough alone. Then thoroughly flush, countersink the holes slightly, and apply solder sparingly, so as to not let it drip through. Afterward it can be smoothed and painted.

[Curti]

Do the post war Cadillac's have water distribution tubes running the length of the block? If the tubes are missing or plugged it will cause overheating.

If this is not the case and all above suggestions are exhausted, pull the rad and have a new core installed.

[Ivan Saxton]

A few more ideas and possibilities are worth following. You should measure the engine water outlet temperature as accurately as possible when it is at its maximum. Then you need to determine how hot the water is through the radiator. Those hand-held temperature sensing devices are pretty affordable now, though I confess I haven't bought one for myself yet. In spite of Polonius'advice to his son in Hamlet, (Neither borrower nor a lender be, for loan oft loses both itself and friend, and borrowing dulls the edge of husbandry"), I do have a friend from whom I am welcome to borrow one with respect. With one of these you can scan the radiator, and plot the temperature gradients which will tell you exactly what is happening. If the radiator is cool to touch when the engine is boiling, that points to a conductivity/radiation problem or partial blockage.

If you have to clean out the radiator thoroughly, there are a couple of ways you can do this beyond the obvious. Twenty or thirty years ago there was an article in Auburn Cord Duesenberg Newsletter about the use of stainless steel rubbish filter traps to do this. These were apparently a buyable item in USA then. You have to use two of them, inserted in the hoses between engine and radiator. To clean everything out, you reverse the direction of flow through the radiator by improvised hose plumbing. You have to clean the filter traps very regularly, maybe daily for a start, as they collect the rubbish from the top of the engine and the top of the radiator. If I recall correctly, the author wrote that he knew of people who had cleaned the radiators of big antique teens Pierce Arrow and Locomobile, just by driving them around.

One of my friends has a couple of pre 1914 Italas, and you would hesitate to strip one of those radiators to clean it. The radiator of the 1914 eventually became so bad that Bill was forced to do something about it. He wrapped he radiator with old bags to retain the heat as well as possible. He set a drum of sodium hydroxide and water over a wood fire so the boiling NaOH solution fed into the bottom of the radiator, and the outflow with rubbish was collected in another drum. He had to keep replenishing the heating pot. Probably after a day of this no more gunk came out the top. That was the quick part. It was much slower to seal all the pin-hole leaks in the tubes of the honeycomb core that the rubbish had sealed from leaking. Bill opened and cleaned all these carefully with a Dremel, and neatly resealed with pointed 1/8"filler rod heated by a gas torch.

The radiator has not leake, and the car has not overheated in over twenty years since.

I devised a couple of refinements of this when David Dryden had trouble with leakage around the bottom of tubes in a new T Ford 1909 radiator that he bought from California or somewhere. I fitted a long small diameter stainless-steel tube in the nozzle of a small grit blasting gun. With a fiddle, I managed to get glass beads to feed through it, and used a narrow, bent strip of 22Gauge sheet to bounce the grit into the joint where you could not see. I have a small propane gas torch which has a half inch round soldering tip in a special attachment. I ran an 1/8th drill through the centre of that, to hold 18th diameter copper filler rod with the ends dressed and bent so it was possible to solder everything even if you could not see what you were doing. There was a little grubscrew to lock the tips.

Please forgive me if I have mis-spelled anything. I am a bit too tired to correct

typograhical errors this late at night.

[sambarn]

If the radiator has been restored, could it be over painted and decreasing cooling capacity due to to sheer thickness of the paint??

[auburnseeker]

I think I may have things almost figured out now. I did notice it cooled best when I had the thermostat in it. Not just the gutted one but the 160 degree one. I actually think the water is flowing through the system (radiator too fast) I have heard of this before. I put the 160 back in and it ran cooler. It got very warm but didn't overheat. I ran it for almost 50 minutes at the shop at idle almost the entire time. I did notice the radiator temperature to be cooler now at the bottom than it was before. I even got daring and drove it about 12 continuous miles today. 55 miles an hour almost all the time up a one mile long hill and although it did run about 200 or so at the hottest point it didn't boil over. I'm running only water at the moment so I know it didn't break 210. I think the next step is to restrict the water flow a little more with another stat and see if I can get it into a more favorable range. I did advance the timing as well but it's now where it was to begin with. I do appreciate the help and advice. It gave me alot of things to rule out. Hopefully I'm on the down hill side of the problem, Randy