VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 1940 Chevrolet overheating probem

I have a 40 Chevy with a new radiator and thermostate that over heats as soon as I hit a stop light! I have flushed out the engine and still it over heats when ever it idles for 4-5 minutes. As long as I am driving it runs about 160 degres.

Does anyone have any suggestions for me?

AS always, that for your help.

Is the engine new/rebuilt? Old problem or new problem?

Answers to those questions will help us suggest remedies.

Gerry,
What do you consider overheating? If the needle climbs to 180 or so its normal.
I assume that you installed a 160 Deg. thermostat.

The most likely cause is air leaking past the seal on the water pump shaft. When running at speed the pump produces some pressure in the engine which is reduced to near zero when idling. The reduction in pressure expands the size of the air bubbles forcing coolant out the overflow. Low level of coolant results in overheating. Another factor is the amount of heat generated when running at speed that is not immediately removed. That heat causes a rise in coolant temperature when circulation of coolant and also air through the radiator core are reduced. Marginal cooling capacity (radiator condition) can also be major contributors.

We had a fellow on the Six Cylinder Tour with a 40 that was having a heat problem. He was advised to install a 41 radiator. He did and problem solved. I understand it bolts right in with no modifications.

There were two radiators for 1940. The Master And Special DeLuxe. The radiators for these models had 4 cooling fins per inch (horizintal fins, not tubes)....the Master 85 had 5 per inch as did the 1941's. The 1937-1940 cars with the 3.73 axle ratio had a larger fan blade and the extra cooling fins for better cooling. The engine works harder on hills and with loads with the 3.73 gears. All 1941's had the 5 fin and the 1941 core will fit a 1940, as the demensions are the same. Under normal conditions and at 80 degrees a 1940 Special DeLuxe with the 4 fin core should have no problem overheating. In general the 1937-40 cars did tend to run hotter and many improvements were made in 1941.
On a 80 deg. day or warmer my 1939, which has a 160 Deg. thermostat, will run at 160 usually but such things as low speed and wind direction at higher speeds will cause it to go to 180 or so. On a 90 Deg. day 190 Deg. is not unusual. Years back the core was replaced with a new one (for a Master 85) and the block was replaced about 25 years ago with a new one. The head cracked and was replaced with a new one a few years back. Prior to that it was beginning to run a little warmer. The cooling system never really leaked any amount but the head was cracked on two cylinders (between the int. and ex. valves. The engine also missed for a bit after sitting unused all winter, but would clear out. Thats what led me to believe the head was cracked.
If the head has not been of the engine for many years it would be a good move to remove it, inspect it for cracks, and clean out the piles of rust in the head water passages.

I have seen a fiberglass shroud on ebay that fits in front of the radiator and directs all of the outside air into the radiator. has anyone tried this aftermarket fix? Would it be beneficial for touring or being in a parade.

dtm

A couple of weeks ago, doing my once every two or three months walk through a salvage yard I spotted an old 216 with a 6 blade fan on it. I bought the fan, installed it on the 52 and will use if for parade duty. It is a little noisy at 50 or so. Takes about 10 minutes to change. My 52 has always had a heating problem on hot days when in parades or just sitting at long time traffic lights. Had it on this Memorial day parade but it was in the 40s an draining so there was no real test.

My 40 Master 85 was overheating the same way. During an engine
overhaul Ifound out why. They had vatted the block at the shop
and the block appeared clean. The goop down in the bottom of the water jackets was so thick and solid that I had to take a wire and scrape it out while flushing with dishwasher detergent
and a hose. After three hours of scraping, soaking, and rinsing
nothing else would come out. The radiator also had to be rodded
and boiled out. That water pump grease mixed with other contaminants was impervious to anything but scraping. The car
runs at mid gage now. I might mention that I had tried radiator
flush and never got any of that stuff out. Good Luck!

Rog40- You might want to consider using a Gano filter in the upper radiator hose. You won`t believe how much gunk wil be trapped and kept from clogging water jackets and radiators.

Just type in GANO, and their web site will come up/

hoppy

Rog40
Found the same problem with the block in my '39. Although the engine did not overheat when I replaced the block due to a crack I opened the left water jacket and found the rust was as least three inches deep.

Rog:
I second your thoughts! Every few weeks it seems someone writes in to say their 60 or 70 year old vehicle is overheating. Frequent contributors to this site offer the usual responses about flushing the cooling system, checking the position of the baffle plate (early cars), air leaking past the water pump packing, running with/without a thermostat, etc., etc. While these are valid responses I tend to think our mindset really applies to newer cars. For the truly older cars we need to keep in mind that they didn't use rust inhibitors in the early days and they are not usually daily drivers. Many of the problem engines sat unused for years or decades, often exposed to the atmosphere. So, rust that formed becomes caked in the system and is usually not affected by simple flushing. I know, I tried the usual remedies to no avail. The only fix was to pull the engine, remove the head, pressure wash the caked on rusty nuggets and slime and install a NOS radiator. Problem solved!

Very well said. At least the head should be removed and the side "freeze" plugs as well as the drain cock on the 216-235 engines.

All these notes are encouraging me to do what I knew all the time. I need to get as much of the rust and junk out of the block before I even try to run the "37 coupe. The car has not been run for 6 or 7 years.

I'm not planning to rework the engine right now I won't have the block out to be cleaned. I am creating some adapters so I can connect the garden hose to the block and head and flush it. And I definitely will not put the heater into the cooling circuit until I have changed the coolant at least a couple of times.

Rusty

My father in-law came over for his 75th birthday yesterday and told me that before I take the radiator in to have it rebuilt I should find some Sal Soda and put that in the radiator, run the car for 40 miles then flush the engine.

I had never heard of Sal Soda but after an internet search it is carbonate of soda (soda ash to you trona people). He claims it worked back in the day. Any thoughts?

Brian

Sal Soda and Draino (drain cleaner) were both common radiator cleaners years ago. They will disolve any loose rust in the system but if the water jackets are filled with packed rust it will do no good. I'm a few months older than your in-law (not that it proves anything).

Sal Soda or Sodium Carbonate will not take out rust and most other crud. It does saponify hydrocarbons. That is it cleans out oil and grease by making it soluble or suspended in water. If you suspect oil or grease, old water pump lubricant, soluble oil or other similar contaminant then Sal Soda is worth the effort. However if you suspect rust or hard water deposits and acid is the best. I use dilute muratic acid first, then rinse, then baking soda (sodium bicarbonate) to neutralize any remaining acid. Sal Soda is be a good option for neutralization. It produces a high enough pH to passivate steel or iron giving at least a temporary rust protection. Be extremely careful using either acid or Sal Soda as they will burn your skin, eat your eyes and destroy aluminum.

Rusty,
I hope your garden hose adapter works for you. As Gene said the best way is to remove the core/freeze plugs to access the deep recesses of the block. If you're not up to removing the engine, I would suggest that you can leave the engine in the car but remove the head. Remove the side core plug (I don't think you can get to the rear with the engine in the car) and use a high pressure washer to clean out the water jacket. Then turn the pressure washer on the head as well. It will make a mess of biblical proportions, but cleanliness is next to godliness!

Keep us posted on your progress, ok?

There are two larger 1 5/8" plugs on the side of a 1937 engine. That along with removeing the complete drain cock will give fair access. A good piece of coat hanger wire will help.

Our vintage Chevrolets occasionally have overheating problems. It was an ongoing problem with Big Red, my 1941 Chevrolet, that was been getting worse over a period of time. I initially planned on pulling the radiator and having it re-cored. I decided to reverse flush the radiator/block. I was looking through some of the many repair manuals for Chevrolets in my collection and found a procedure on this. Basically this is what I did...

* Drain the coolant
* Remove thermostat
* Add prestone cleaner and water
* Run for 10 - 15 minutes
* Let engine cool
* Drain cleaner/water mixture
* Reverse flush radiator until clear
* Reverse flush water jackets until clear
* Replace 160 thermostat and gasket
* Add 50/50 coolant/water mix
* Test system

I rigged a flushing gun using a high pressure sprayer that has a water and air hose connection. This worked extremely well and you wouldn't believe how much crud and gunk came out of the radiator. The water jackets were not as bad, but I'm sure they are much cleaner now. I let the radiator/block fill with water and cranked the air for short blasts. Continue until the water comes out clean with no rust or discoloration.
I've been driving in the 90+ degree weather since doing this and the difference is like night and day.
I plan on writing up a procedure on this for the website as I know many other classic car owners have similar problems.
Hope this helps...
Paul
Paul's '41 Chevy Web Site
http://www.1941chevrolet.com
Dedicated to Classic Car Enthusiasts Worldwide
Vintage Chevrolet Club of America # 29765

If there is a lot of crud in the block even air assisted reverse flush wont shift it all. While it is a lot of work remove the freeze plugs, thermostat and water pump and spray the high pressure "gernie" washer through all openings.
Tony