Cadillac flathead V8 overheating in a tank

[Guest opfor2nd]

I am a US Civilian contractor (US Army retired) working in Germany. I have been doing volunteer work to restore an M24 Chaffee tank that is on the post here in Hohenfels. Last August it was put into maintenance for the left side V8 overheating (They are Cadillac flathead model 44T24's). The Germans working for the US Army maintenance facility here checked the thermostats and radiator hoses, Flushed the cooling system and then cross-attached the gauges to confirm that the left gauge ran normal with the right engine to rule out the gauge being the problem. They finally reported to me that it is not really overheating but has a bad sending unit. They based this on their observation that the gauge went to 240 degrees too quickly to be accurately reading the temperature. They also told me they used an infrared gun on it and it is normal. I spent the last 9 months or so tearing apart the interior, cleaning, repainting and reinstalling all the parts and repainting the exterior, but did nothing further with the engine & drive train since it was already in good running order other than the overheat. I did not find a sending unit yet, but that turns out to not be the problem anyway.

Today I was driving the around the motorpool it is usually kept in to warm up the drive train (it does not move smoothly when it has been sitting for awhile). After about 15 minutes the left side temp guage was reading over 200 but I had been assured this is a false report. I parked it for about 3 hours and then drove it about 2.5 miles out to the airfield where it will be on public display for the fest on post this weekend. There was some confusion about where exactly to park it, my MP escort went the wrong way and I had to idle for about 5 minutes waiting for them to come back. As I pulled out again the guy riding in the turret said there was a puddle of anti-freeze behind me. I had only 300-400 yards left to go, so I continued on to my destination. I was almost there when smoke started coming from the left side of the the engine compartment and I shut the left engine down immediately. Antifreeze had spurted out the top and was all over the back deck. The left side of the engine compartment was obviously far hotter than the right. Alot of antifreeze ended up on the ground under the tank. I gave it some time to cool off, then started up only the right engine and drove the last 50 yards to park the tank on only the left one. It was a fairly hot day for Germany (about 80f). The right engine never got hotter than 140f the whole time. I have to drive it about 400 yards to its display point tomorrow and Sunday, but it will start out cold and I can do this on only the right engine. Any ideas on where to start with getting the overheat problem taken care of?

[edinmass]

Hi, be sure to check the engine timing as severely retarded timing will cause it to overheat. Remember the engines should turn in opposite directions if my memory serves me right. (The M-5 twin engine tanks do.) Also, be sure it has the correct water pump as the impeller could also be wrong. Let us know how you make out. Ed

[Guest opfor2nd]

Thanks for the info, I was able to move the tank around today on the right engine only. I have also been advised locally to remove the thermostat completely, since the tank will not be used in cold weather and there is no heater. Is there any outward or obvious indication that the timing is off? Also, it might take me some time to find a timing light over here.

[Owen_Dyneto]

You can do an adequately accurate job of timing the ignition without a timing light, just as it was done in the years before timing lights became common. Rotate the engine in it's proper direction of rotation until piston #1 is coming up on the compression stroke (check with the plug out and your finger over the spark plug hole). Stop the rotation at the correct timing mark (if you overshoot, don't back up, go around again). Then just put a test light across the points and adjust the distributor rotation until the points are just breaking. You'll be within a degree or two.