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IT'S ALIVE!!! And overheats..I think

Started by jbento, July 08, 2009, 10:40:57 AM

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jbento

July 4th 2009

After 7 years worth of work, and for the first time in over 30 years, the engine runs!  Many thanks to all who got us this far!

But now, I think she is overheating a bit.  I have good oil pressure, but I am not sure if water is circulating through the radiator.  Other issue include:

1) When rebuilding the engine, I did not replace the temperature sending unit.  I removed it and it didn't look like something needed replacing (didn't look like there was any electronics or anything else on it to go bad).  The temp gauge was rebuilt so it is probably fine.  Right now it goes pretty quick to max temp.
2) When I had the radiator rebuilt, I dont think they replaced the thermostat. 

So what is the best way to "test" the radiatior and assure it is functioning?  And is there anything else I should check to make sure either I am not really overheating or eliminate the overheating issue?

Thanks!
Joe Bento
CLC# 20081
1940 Cadillac Series 72

Guidematic


Joe,

Purchase an infra red temperature sensor. These are really handy in diagnosing this sort of thing. They are like a small gun that uses a red pointer to where you wish to take a temperature reading, and the display will tell you what the temperature is at that point.

You can tell it the thermostat is opening, and at what temperature, and you can locate any hot spots in the engine, and see just what the actual temperature is at the temperature sensor to check for its' accuracy.

They are available at most tool supply stores, and I have even seen them at places like Home Depot.

Mike
1970 Fleetwood Brougham 68169
1985 Eldorado Coupe 6EL57
1988 Eldorado Biarritz 6EL57
1990 Brougham d'Elegance 6DW69
1994 Fleetwood Brougham 6DW69

Bill Ingler #7799

Congrats Joe on getting the 40 running- now the fun begins. When you say max out do you mean just the needle is on hot or is the radiator boiling over? Here are  a couple of items to check. The temp sending unit should be screwed in the head without any sealant which causes false readings. Metal to metal. Are the shutters fully open? I think depending on what thermostat you have in the radiator, the shutters should start opening about 165 and be fully open at 185. I would go down to my local NAPA and invest in a infrared temp gun and then take different readings around the radiator which should give you an idea of how the radiator is functioning. Remember the hottest park of the engine is where the temp sending unit is located. A cheap way to check your instrument gage against what is happening in at least the top part of your radiator is get a meat thermometer and stick it in the top of the radiator. That way you can find out about what temp equals a 1/4 , 1/2 or full max out needle on the dash temp gage. Also make sure you have a spring inside the lower radiator hose which prevents the action of the water pump from cavitating that hose and cutting down on circulation. Since it is a 40 then you should have a A/C  3 radiator cap which is a 7# cap. Just because the sender cap appears OK doesn`t mean it will work. Finding out what temps you are getting around the engine and radiator will be your biggest help in finding out if the sender unit is the problem.

Whit Otis, 1188

One other quick thought - if you did a complete rebuild and bored the block and put in new pistons and rings, it is likely the engine may run hotter than normal during initial break in.  I had this on my 40-75, and while it didn't boil over, it ran pretty hot for the first thousand or so miles.  Since then it has been perfect.
Whit
Whit Otis -
1941 6219D Custom
1941 6219D
1940 7533F
1986 Mercedes Benz 560 SEL
1999 Bentley Arnage
2019 XT5
Drawing of AP Sloan Custom by Terry Wenger