What else can I do to deal with overheating engine?

My 1950 Chieftain has been running and driving well with no issues for years. Two weeks ago suddenly temp started to increase to 200 F and a bit higher (never to 220, never boiling). I check the radiator first and found leaks all over. Removed the radiator and found it in pitiful shape, with numerous leaks and most tubes plugged in after years of corrosion and dirt (sorry, never did a radiator maintainance in 5 years I owned the car). Had the radiator re-cored with a new panel with 3 tubes, flushed the entire system, checked the 160 F thermostat and it seems OK. Initially had concerns with the head gasket but after checking again with the help of a mechanic it seems all right. Put everything back, hoses are good and tight and engine runs and drives perfectly, good power, etc.

The problem is that the engine temp remains stable at 180 F while driving but about a minute after stopping and idling it starts increasing steadily. I waited about 5 minutes and it went up to 205 F so I stopped it. I did not try to test how high temp will go because of concerns of causing more damage. I started driving again and temp quickly returned to 180 and remains there until next stop. There are no leaks anymore. Radiator cap works well at 4 lbs.

So, with with background, these are my questions trying to figure out what to do next:

1) I found the engine block drain in the rear of the engine, driver's side, completely blocked. Tried hard to remove any debris with wires and pressure and have no water flow there and don't know how to clear it. Can this blocked water passage explain this overheating?

2) The engine temp sensor,a new one installed 3 years ago, is very close to this engine block drain. Is it possible that most of the block is getting adequate cooling but the rear cylinder next to the temp sensor is not getting enough coolant because of this drain that is plugged in?

3) Car is in a HOT location in South America with Summer starting this week, daily temps to 110 F. Which is the best thermostat for this engine? 268 ci original L-Head. Did not have any similar issues in prior Summers.

I certainly will appreciate any advice. My mechanic suggested to replace the head gasket but before going that route I want to exhaust the other simpler options. Thanks a lot for your help ! Manuel

Manuel,

Cooling systems all share the same requirements: Flow, created by the water pump and controlled by the thermostat. Heat exchange provided by the radiator. Airflow provided by the cooling fan.

I recommend that you invest in an infrared no contact temp gun, just point an shoot. Bring the engine up to temperature and monitor the temp going into the radiator versus temp at outlet to the engine. Chart it all the way to 200*F every 20 to 30 seconds. Post your results.

Once the stat opens the return temp will start warming up. If the return temp gets less than 10* of the radiator inlet temp it would indicate the radiator is not cooling. If this happens, place a strong fan or leaf blower in front of the radiator and see if temperatures come back down. If they do come down you need more airflow from the fan.

If the return temp stays well below the radiator inlet temperature, that would indicate a coolant flow problem which could be thermostat or water pump, thermostat being most likely.

If simply raising engine rpm while sitting still will cool it off, it could be either fan or water pump. It will be difficult to troubleshoot without testing with a "temp gun".

As for the draincock, it is pipe thread, simply unscrew it and clear the hole and draincock. You could also remove the temp sending unit but that is delicate, don't risk tearing it up or breaking it if it doesn't want to come out.

Again, the radiator return temperature is key to troubleshooting. A properly operating system will have a minimum of 12-15* drop in temp across the radiator. If it is a huge drop after thermostat fully opens, you aren't flowing coolant.

Please post your findings. ......... TexasJohn

If it were my car I would remove all the core plugs and physically remove all the crud in the block. New core plugs, new hoses and check that the water pump seal is sealing.

If the block drain plug isn't running then your block is likely half full of rust and crud. There is every possibility that your coolant distribution tube is corroded away as well.

Following what TexasJohn55 says with the temp gun would confirm what I suspect. Once you get it clean use a 50/50 mixture of water and antifreeze and change it every two or three years and you will never have a problem again.

I had a similiar problem with my 1947 pontiac streamliner. i cleaned all the core plugs and water flow was good but raidiator kept boiling over at idling speeds,

not while running. In india we do not need the thermostat . i found the problem was the airflow cowl above the radiator which guides the airflow thru the

radiator was removed. i fitted it back and the problem was solved.

Thanks. Very helpful tips. I will get a temp gun and do the measurements as recommended (great idea to have one, will be helpful for other things as well). This weekend will also remove the water pump and see what its condition is. The block drain plug not working troubles me and suspect there is a lot of crud in the block as suggested. I hesitate removing the core plugs, just because it is a lot of work and only have one afternoon a week to work on it, not to mention my limited mechanical abilities. It is one of those jobs that you wish don't have to do but you know will be needed. Will see what happens. I will post more after I follow some of the recommendations. It may be 2-3 weeks until I can get the temp gun from the US. The airflow cowl around the radiator is in place, so this is not a factor in my car.

To follow on my overheating problem:

1) I am waiting for the temperature reading gun to arrive

2) Meantime, removed the thermostat. It opens at about 190-200 F and it closes very rapidly with just a bit of drop in temperature. I will place a replacement I have that is a 160 F stat and see if that improves.

3) Put a "radiator and block cleaner" available locally in the radiator and drove for about 30 minutes. It may have helped a bit because now the block drain in the rear of the block, driver's side, is producing a few drops of water, 1 drop per second to be precise, of clear water. I probed the tube with a thin screwdriver without putting any pressure and all I feel is a thick metal wall at about 1.5 inches deep from the opening with no sign of any communication to the rest of the water system. Can somebody post a diagram of this coolant drain system? In which direction should I try to poke to open up any hardened corrosion material likely present inside? I am worry about damaging the cylinder wall.

Thanks and look forward for your comments !

Manuel

Unscrew the drain cock from the block to clean it.

TexasJohn55: That is what I did and reported back in my post. However, when removing the drain cock I get almost nothing, only got 1 drop of coolant per second. I tried hard with wire and a small screwdriver to remove any debris in the drain cock but nothing comes out, only a few drops of clear water. That is the reason I asked if it is safe to poke the inside of the drain cock tube with a metal probe and in which direction does the water tubing go. I feel a metal wall when probing inside the drain cock tube and I am concerned damaging the cylinder wall. I am also learning how to remove the core plugs as suggested by Tinindian and that will be next job if no improvement. Hope to get more tips from this forum. Thank you all for your answers.

Manuel

hi manuel, you might try removing the radiator cap, remove the block drain valve, and shoot compress air into the block where you removed the drain valve, you should get a improvement in the water flow out the drain hole. that won't solve any other problems.