48 cadillac cooling system

[cadillac60]

I can drive my 48 for miles without the temp going above the centre mark on the gauge. If I leave the car warming up in the garage say for 10 min it get very hot & overflows out of the radiator overflow hose.  Any thoughts on this or is it somewhat normal?

Bruce W

[49 Convertible]

Well my first thought would be than when driving the air ciculates through the radiator with the help of the fan.  When sitting and idling there is very little air circulation through the radiator.  So what you experienced is common

[Bill Ingler #7799]

Hi Bruce: When in the garage and you say very hot- where is the needle on the temp gage? Has the engine and radiator had a good flush lately ? At idle in the garage you are not getting much flow of coolant through the engine and radiator as you do driving so a flush might help. You also could have some plugged tubes in the radiator. I would think that you might start with a flush of the engine and radiator. I keep my level of coolant in my 47 at the lowest part of the top tank, just above the top of the tubes. This allows for expansion so you don`t loose coolant out the over flow as the coolant warms up. With a 48, I think you should be running a R/C 7 cap which is a 9lb cap giving you another 18 or so degrees before the coolant starts to boil. Another good clue to a possible partly plugged radiator is what happens when you stop at a traffic light on a hot day? Does the temp gage start to rise and how fast? A slow rise is normal but a rapid rise to say the H on the gage tells you the cooling system needs help   Bill

[cadillac60]

Thank you for your reply's .  I will be road testing it to see if everything is normal at stop signs etc & get back on the forum. Would a stuck thermostat cause this kind of problem?

Bruce W

[Martin Michaels]

If your thermostat will not open you will over heat.

[Jeff Rosansky CLC #28373]

Has the fan been off?  Is it on backwards?
Also, the faster the car is running, the faster the engine is turning.  If you have a water pump issue, it may move enough water when turning say 3000rpm but may not be moving enough volume at 600 rpm.
Jeff

[Brett Baird]

Overheating at highway speeds = restricted coolant flow.  Overheating at slow speeds (stop & go) = restricted air flow.

[Bill Ingler #7799]

One area that sometimes is overlooked is the absence of a lower engine pan just behind and below the radiator, above and just forward of the tie rods. The pan is attached with 4 bolts threaded into the lower rail of the frame. Picture is below. It was explained to me the reason for this pan was to prevent air that passes through the radiator from going down and under the engine. With the pan in place, the air passes through the radiator, over the engine, which in turn helps the air to carry heat from the engine. My 41 as well as the 47 were both missing this pan when I bought the cars. There was at one time a man from around Akron Ohio who was making these pans. Not knowing what nomenclature Cadillac used to describe this pan in the Master Parts book, I can`t find a pan listed so not sure in what years it was used.
Another small item that might help draw more air through the radiator is to use a 5 bladed fan. The 67 and 75 series used a 5 bladed fan which was standard on those cars. The 75 and 67 series Cadillacs were most often used as a taxi and driving was slow with stop and start city traffic. I put a 5 bladed fan on both my 41-60s as well as my 47-62 convert.   Bill

[gary griffin]

Your point about 67 and 75 being used as taxis was interesting Bill.  In 1958 and 1959 I was stationed at Fort Ord California and there were Cadillac taxis operating as sort of shuttle buses. For 25 cents you could ride to any location on the large post, just wave one down and hop in with 6 or 7 other guys. The jump seats were well used. I asked a driver once why they used Cadillacs and he told me they ran forever and carried a good payload. At least 5 in the back with jump seats and 2 in the front plus the driver. We were all young and lean back then and did not mind crowding in to get to the PX or a movie.

[Steve Passmore]

Has the fan been off?  Is it on backwards?
Jeff

This would make no difference. I cant answer for the fans on later cars but turning the fan on a flathead does nothing, the blades stay in the same plane.  The only way you would  see a change of air direction would be for the fan to be turning in an anti clockwise direction.

I'm leaning towards Bills guess in that your overfilling the rad.  On most of my cars one cannot see the water level because of the baffle.  I fill my rads so I can just see the water and on the first drive out theres no problem, but when I stop and turn the engine off it bubbles and throws a few pints on the road.       I never top it back up and theres never another episode. All my cars do this if I cant see the top of the tubes as Bill suggests.    My guess is Bruce when it does this in your garage you automatically top it back up? so don't.

[Dan LeBlanc]

Follow up from 49er:

Fellas, these filters allow you to look right inside you engine. I've ran them for two years and the work great.
     They tell you instantly if your pump is working and circulating coolant properly. Trap any debris.   You can take them out and empty and gunk anytime.
    If you leave any break away gunk there, over a little time the water passes through under pressure breaks it up into fine particles. What's then in your rad you open the drain valve for a minute a couple times a summer and out the settled fine sediment comes. Here after the initial backflush in two years its really clean and the engine stays cool. No problems.  Art

[gary griffin]

I like Art and Dan's comments about the Ganno filters, I may try them.  Remember that every filter is an obstruction to flow. Flow is caused by pressure differential and impedance of flow can be measured with a pressure gauge before and after the filter which is not realistically possible here but if a filter is installed I like the visual model of these better than the solid ones which look better.  If you install one and have a overheating problem in the future clean the filter immediately. Also clean it when you change anti freeze.


I also like my little digital infrared thermometer which shows the temperature of whatever you point it at.  A scan of the radiator for cool spots and then a scan of the engine for the hot spots will show you where the water circulation problems are.

I went to a seminar put on by another car club and an expert was present with demonstrations and a great lecture. 

Corrosion in our cars is cooling system is because of the electrical  differences of the dissimilar materials and anti freeze acts to neutralize the corrosion and should be replaced regularly.

The cooling system is neglected more than any other system in our cars yet it is so important.  This is the last place to economize and do careful research when you replace your cooling system components.  Buy for quality rather than price and spend a little more for a better radiator.

[cadillac60]

I can't believe the flow of information on this cooling problem.  Thank you all very much.  I did two things that seem to clear up the problem.

#1  At the bottom of the filler neck I ran a white chalk mark  around the seat & then put my cap on tight & found when I took the cap off none of the chalk was noticeable on the bottom of the pressure cap. I inserted an O ring on the seat at the bottom of the neck of  & re tested the cap test & it appears now I have a proper seal.

#2  I installed a new thermostat on the chance it was not opening.

I test drove the car for about 5 miles up and down hills in traffic & the temp gauge stayed steady in the middle. When I drove it in the garage & turned the car off not a drop of water spilled.

This certainly was a lot easier than I thought-- glad I didn't have to yank out the rad.

Thanks again for all the info.

Bruce W

[DennisK]

Overheating at highway speeds = restricted coolant flow.  Overheating at slow speeds (stop & go) = restricted air flow.

I agree