56 engine temp ok or not?

[Hillbillycat]

My temp gauge always used to stay a tad under the 1/4 mark.
This year it´s a tad over. Makes me worry for I have read over and over these should stay UNDER the 1/4 mark on the 56s. Water pump adn thermostat is two or three years old, ALL hoses the same.

Went and grabbed my IR thermometer and took some readings after a nice 10 mile ride in and around city this afternoon:

Top of radiator core: 204°F
Thermostat housing: 204°F
Carb base: 279°F
Crossover: 340°F
Exhaust manifold closest to firewall: 450°F
Carb bowl 170°F

All readings taken with hood open, trans in P and on curb idle.


Background:
Carb got reset by shop to lowest emmisions with a meter at the tailpipes after I had blown both mufflers last summer. I had previously messed with the carb setting and ignition timing and that´s when the mufflers went kabooom.

Input is welcome 

[Lexi]

Hello Hillbillycat here is a tech tip which I believe came from one of the 1956 Cadillac Round Table programmed learning publications from GM that year. That was based on new cars using then available gasoline with a properly tuned engine and a fully operational temperature gage.

I had my engine rebuilt in 2018 and installed for use in 2019. All cooling systems either rebuilt or serviced. I installed a mechanical gage and my car has never ran cooler. With a 180 degree Farenheit thermostat, so far this year the car runs at 180 or just slightly higher. I seem to recall on real scorchers (90 - 100 degrees ambient temperature), the mechanical gauge may have peaked at 200 - 205 F. Think I did an earlier post on this and will try to find and post a link. I seem to recall some members reporting that on extremely hot days with the AC on (a driver Cadillac with not rebuilt equipment), you might hit even 220 F. My car did on ocassion years ago, but that was before all of my rebuilding. It does not soar to that temperature anymore.

That said, 1956 was known to be a problem year for 1956 Cadillac and cooling issues. Member Art Gardner once told me in a phone conversation that the heat from a '56 Cadillac with the hood open can (quote); "Melt your face off". Still laughing over that one, but more or less true, especially if there is a lot of original untouched equipment on the car. In 1956 Cadillac raised the Idle speed upward and there was a secret warranty for owners of cars with AC who complained of overheating. They were provided with a replacement 6 bladed fan to replace the 4 bladed OEM fan, IF THEY COMPLAINED, says the memo that details this. There was a new part number assigned that never made it to the Master Parts List. Timing. This "stop gap" measure resulted in a slightly bigger 6 bladed fan, but it was replaced with a slightly larger fan (with a different part number), in 1957. Same fan for 1958 I recall. I have what I believe is a rare original one time warranty fan which I upgraded to a 1958 fan as it would draw a little more air which is what we want. Slightly wider vanes and I believe that it sat slightly closer to the radiator which is good. Not sure if other year fans (with increased number of blades), would still fit.

Hope some of this helps. Clay/Lexi

Edit 1: Prior to my engine/under the hood rebuild, I recall that my factory installed gage would normally reach the vertical position as shown in the illustration below. It eventually climbed higher when the radiator developed a leak. That was to be expected. All since fixed. I believe that my original temperature indicator worked correctly.  The mechanical gage I installed after the engine rebuild I first tested and it was extremely accurate and operates properly.

Edit 2:  Remember that Cadillac used the same Harrison radiator from 1949 to 1956. Hope memory is correct. They continued to up horsepower etc., but little was done to upgrade cooling. I seem to recall that the water pump inlet or outlet (or both?) diameters changed I presume to increase flow, but still using the same radiator from the late 1940s. I believe earlier water pumps, at least 1955, will fit, but with a more restricted coolant flow might impact engine cooling.

Edit 3:  Plan to take "Lexi" out probably this weekend. Will IR "gun" my engine temperature and compare to yours.

[Hillbillycat]

Hi Lexi,

thanks for your answer and the soothing cartoon :-)

Mine´s got the 6 bladed fan, also. Not sure if from 57-58 model or a warranty fan.
So I´m safe, I think.

[James Landi]

So impressed with Clay/Lexi's research and knowledgeability, but I feel a  need to add this cautionary note, as follows: I daily commuted with a SDV with trunk, factory installed a/c in early 70's .  Absolutely loved the car, tolerated the 90 miles a day commute, and even suffered through the (OPEC embrago) huge jump in gas prices and twice weekly search for gasoline. Had to get a valve job as the original exhaust valves developed leaks -- my mechanic told me to stay away from unleaded gas  "these engines run hot, you need the lead"   A year or two after the valve job, I'm sitting at a light, the a/c is blasting and the heat gauge is on the move toward the middle... when the light changed to green, the engine was obviously running on fewer cylinders... a compression test confirmed my worst fears--- I can't recall if my Car had a six bladed or standard four, but it did have the original radiator, and more than likely needed a thorough servicing or a replacement.  I've owned old Cadillacs all of my life and drive a lot.  Having an absolutely descaled radiator, a well  flushed engine, and even a coolant filter is cheap insurance.  I've taken to adding a pint of Marvel Oil to a tank of gas, and on one of my 70's cars, the Marvel oil made the difference between a hard starting engine during hot days and one that started as normal. James

[Chopper1942]

Just a thought.  If your radiator is original or is in need of boiling out, you might talk to a very good radiator shop about upgrading your core: more rows of tube and especially more fins per inch. They usually use the same tanks so only a sharp eyed observer will notice that the radiator is upgraded.  Before you replace or do radiator work, flush the cooling system a couple of times to get as much scale as possible out of the engine. This means pulling out the block drain plugs, not just draining the radiator.  A coolant flush machine really only exchanges some of the fluid.  Do it the old fashion way by draining the block and radiator, installing water and a good cooling system cleaner, running the engine for at least the recommended time, drain and flush with water.  If it requires a neutralizer, install the neutralizer and water.  Run the engine as instructed.  Then flush out the radiator and block with water, install the block drain plugs and tighten the radiator petcock. Drive the car, then drain the block and radiator, flush with water, and then fill with a 50/50 of coolant. 

If you don't drive in cold weather, you might think about blocking off the crossover with metal shims.  This will help with hot weather driving issues, vapor lock, hard starting, etc.

[Lexi]

Went and grabbed my IR thermometer and took some readings after a nice 10 mile ride in and around city this afternoon:

Top of radiator core: 204°F
Thermostat housing: 204°F
Carb base: 279°F
Crossover: 340°F
Exhaust manifold closest to firewall: 450°F
Carb bowl 170°F

All readings taken with hood open, trans in P and on curb idle.

Input is welcome 

Hillbillycat I took Lexi out on the road today. I also took 2 rounds of temperature checks for you. After driving 13 miles at an average top speed of 40 mph, with an outide temperature of 75 degrees F, hood open and car idling in park, (about 600 rpm), I took a number of IR gun temperature measurements. See chart below, with the first entry being your temp readings for easy comparison, in black. All converted to Farenheit. Lexi's temperature readings are in red. I then took a second round of temp checks at 57 miles, which yielded slightly higher results. 2nd set car had done 20 miles of highway driving and also the ambient outside temperature had increased to 79 degrees:

Top of Rad:     Your reading:     204      Lexi readings: 161 13 miles 165 57 miles
Therm hous:   Your reading:     204      Lexi readings: 170 13 miles 187 57 miles
Carb base :     Your reading:     279      Lexi readings: 181 13 miles 210 57 miles
Crossover :     Your reading:     342      Lexi readings: 302 13 miles 318 57 miles
Ex manifo :     Your reading:     450      Lexi readings: 455 13 miles 473 57 miles
Carb bowl :     Your reading:    170      Lexi readings: 129 13 miles 152 57 miles
Low Rad h :     Yours nil      :     000      Lexi readings: 145 13 miles 165 57 miles

Note: I took one additional measurement as noted above, "lower rad hose". During the first round of readings my mechanical temperature gage inside the car read approximately 183 F. Car is equipped with a 180 F thermostat. Second round it was at about 190 F, but it was hotter now outside and car had done about 10 - 20 miles of highway driving reaching top speeds of 72 and 75 mph.

I noted that there was at times a lot of temperature flucuation especially with the theremostat housing readings and  also the exhaust manifolds. Readings are an average of both exhaust manifolds. The carb base readings were taken from the carb's front left side, forward mounting stud and the cast iron base. The bowl measurements were taken from both sides and there was some flucuation there. Lots of stuff in the way.

Perhaps the most revealing temperature differentials are those of the carburetor bowls. 41 degrees Farenheit difference in the first reading. With the exception of the exhaust manifolds, all your readings are hotter. I screwed up the exhaust manifold as I measured both where you took one reading. I averaged my 2, but one was cooler but can't remember now which one it was.

Someone with more knowledge than me hopefully will comment on these results. Of note is that my car is running using an original Cadillac (rebuilt) 365 V8. Only non stock items are Pertronix in the distributor and a 6 bladed radiator fan from a 1958 Cadillac. Car has AC, (which was not turned on). Spark plugs not AC44, but would have to look up if you are interested in what I got installed. My car also does NOT have it's heat riser valve. All systems rebuilt or refurbished and running on what I believe is (hopefully) ethanol free Esso premium fuel which I think is fresh octane 91. No pinging. Carb adjusted to run slightly rich and has been rebuilt about a year or so ago. Think vacuum at intake manifold if I remember from last year or so when last checked was about 21 inches of mercury.

I'm no expert but the additional heat associated especially with your carburetor is probably not desireable. Anyone with comments? Should either of us be concerned with any of these results?

Clay/Lexi

[J. Gomez]

Sorry late on posting was out of town and I hate using my phone for replies, fat fingers and small keyboard does not work on my side. 

@Lexi

Clay,

I would speculate your #'s are within the normal operating range. Also, If I'm not mistaken you have the intake exhaust x-over blocked so your reading are below if those were open.

@Hillbillycat

Martin,

Your readings are a bit of a concern as you stated "My temp gauge always used to stay a tad under the 1/4 mark.", I did not see on the replies above if you have/had the correct temp sender when you took the reading before and after.

If your rad core reads 204°F your temp gauge should be just on the center mark (or a tad below), so that is an indication the temp sender may be the wrong one.   

I had one install on my car which I failed to validate beforehand and running the engine at idle for several minutes the gauge stay just at the ¼ mark that trigger my "idiot light"    to check it while on the engine. Lucky I had to drain the antifreeze to remove and install a new freeze plug so it was not painful to install the correct one.

[Lexi]

Clay,

I would speculate your #'s are within the normal operating range. Also, If I'm not mistaken you have the intake exhaust x-over blocked so your reading are below if those were open.

Jose thank you. Great to hear from you buddy. Hope all is well with you. In answer to your comment, "no" my intake cross over is not blocked off. I also do not use an insulator block. Assuming Hillbillycat's carb set up is OEM, I am concerned about those high temps, in particular those concerning his carb and related area. Wonder if he experiences vapour lock? Clay/Lexi

[J. Gomez]

Jose thank you. Great to hear from you buddy.

Clay,

Doing well my friend still kicking, hope you are back to be 100% or at least 99.99%..! 

In answer to your comment, "no" my intake cross over is not blocked off. I also do not use an insulator block. Assuming Hillbillycat's carb set up is OEM, I am concerned about those high temps, in particular those concerning his carb and related area. Wonder if he experiences vapour lock? Clay/Lexi

Well that's what happened when I try to use my left over brain cell to recall storage memories.   

Agree those temps he posted are a bit on the "HOT" side. 

[Lexi]

Still on this side of the sod my friend, which is good. Was quite ill last year and some remnants hanging on. Now I know how our Caddies "feel". LOL. Clay/Lexi

[Hillbillycat]

Hi guys, thanks for your input.
Carb setup is OEM. Was rebuilt by mine a few years back with Daytona parts. Crossover is open. No heat riser.
Hg is lower...around 16 I think, maybe even lower. No vac leaks. I credit this to the later production cam with lower vacuum reading.

Temp sender I don´t know. Could be a wrong one.

Vapor lock I once experienced on the Autobahn two years ago speeding up a grade. Aux pump turned on cured this within a second.

Could it be that my dull knock when engine is hot (see other post last year) is a sign for slight overheating?
I seriously consider to have the engine rebuilt this winter due to the knock I didn´t find the issue.
Maybe I should descale the original radiator and flush the engine first......?

WHY didn´t I do so in the first place when I replaced the water pump and the radiator was out anyway? I know why -  I was afraid that it might have had tiny pinholes that the descaling would open up.

Descale or new core?
We have a good shop nearby that does excellent work.

[Chopper1942]

You did't state what thermostat you have in the car.  If it is a 180 degree, you should not be running that hot at the top of the radiator.  Check the temp of the lower hose. It should be at least 30 degrees lower that the top hose.  Make sure that the hood and radiator are sealed to the radiator support.  this will ensure that the fan is pulling all the air it can through the radiator.
Again, if this is not a cold weather car, I would block off the exhaust crossover.  This will lower the carb bowl temp and improve warm weather driving.  Only drawback is it will be a little cold blooded wntil it gets some temp in the engine.

[Hillbillycat]

Honestly I can´t remember what thermostat it is.
I can re-check the lower hose of course.

[Hillbillycat]

Well, after the shop did a cooling system flush including the drain plugs at the block the temp gauge is down now. They said the plugs poured coffee.....
Thanks for your input.

[Cadillac Jack 82]

I'm glad this post popped up today as I was worried that my temp gauge was indicating my 390 was running hotter than normal.   Now I see that its functioning as it should.

[Hillbillycat]

My gauge did show that it WAS running too hot. The whole cooling system (block included!!!!) needed a thorough flush. So I advise you to do the same. Your temp and gauge should drop back to normal afterwards.
Please make sure to drain and flush the block.

[Chopper1942]

Something to remember is if you have a 180° thermostat installed, that is the temperature the thermostat starts to open. Back in the day, in a galaxy far, far, away, the GM Jedi master requested that new or old thermostats tested be, not always OK installed before. We had a porcelin thermostat tester in which we would place the thermostat and monitor the temp of the water when the thermostat just started  to open and then when it was fully open. If they didn't meet the specs, which I don't exactly remember (keep forgetting my Prevogen). Seems like it was 5°-10°.

Before you start flushing the cooling system, blow out all the fins in the radiator and condenser, (if wquipped). Make sure there is no debris between the condenser and radiator.

I would recommend that you flush your cooling system. This is the way I do it. With the engine cold.
1.  Drain the radiator and remove the block drain plugs.
2.  With a garden hose run water through the block and radiator until it comes out fairly clear.
3.  Reinstall the block plugs and close the radiator drain valve.
4.  Fill the engine with water and add the cooling system cleaner. I like to use one that has a flush agent and a
    neutralizer.
5.  Start the engine and bring to normal operating temperature. At least as long or longer than instructed.
6.  Drain the block and radiator.
7.  Flush with water until clear.
8.  If the flush has a neutralizer, fill the engine with water and add the neutralizer. Run the engine for some
    time.
9.  Drain the neutralizer and flush with water.
10. Remove both heater hoses and back flush the heater core with a garden hose. Run the water through both hoses
    until it is clear.
11. Remove the upper and lower radiator hoses from the engine and reinstall the radiator cap. Install the garden
    hose in the lower hose and run the water through the radiator until the water is clear.
12. Pressure test the radiator cap. If it doesn't meet specs, replace it. Remember every # increases the boiling
    point of water by 3°. Therefore, a 10# cap raises the boiling point by 30° to 242°.
13. Install a 50/50 mix of coolant and distilled water.
14. Install a mechanical temp gauge to be sure of the engine temp.

If you still have overheating issues or it runs hot(220°-230°), Install seals along side the radiator and the radiator support. Also, a seal between the hood and radiator support. This will maximize the air flow throush the radiator. If there is a fan shroud that fits your radiator and you do not have one installed, put on on. It will greatly improve cooling.

If this vehicle is not driven in cold weather, I would install an intake gasket set that has the exhaust crossover ports blocked. This will greatly increase the driveability when at normal operating temperature and decrease the fuel bowl and carb base temps. Helps with "vapor lock". The downside is you will have some driveability issues when cold and the choke will stay on longer.

If you drive the car in the winter or when cold outside, forget about blocking the crossover. Make sure the heat riser works.

[bcroe]

I fixed the cooling on my first V8s with a 6 or
7 blade fan and shroud, and a new radiator with
at least one more set of tubes deep than the
original.  The temp gauge acted like it was anchored
at the thermostat rating.  An overflow bottle with
matching cap meant I never lost any coolant.
Bruce Roe

[Chopper1942]

bcroe, you did it the best way. That extra row of tube is a great help. The other thing is building the radiator with more fins to the inch to dissipate the heat better.