Reproduction Parts for 1916-1964 Chevrolet Passenger Cars & 1918-1987 Chevrolet & GMC Trucks


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My original 36,000 mile straight 6 '40 Chevy is causing me frustrations concerning how hot it's running. I'm up in the fairly cool air in Colorado and when I bought it I couldn't get home without it overheating four times a.k.a. spitting out radiator fluid and the temperature gage pegged. I Tore in to it and discovered there is no thermostat but yet I talked to a radiator specialists and he assured me that was probably my problem. I have the factory type rad cap which is only around 4 pounds of pressure, install the hundred 180° thermostat while I did a bit better still got hot every time. read a repair manual and said they came with 142 and 162° thermostats, so I got 160° one and it seems to do no better than the 180 ie., it'll run without overheating if I do I drive around for a while then come to a standstill for about two minutes it'll spit out again and the needle goes in the red! Grrrr

At one point I started the car with the hose off and the thermostat out to see if the water pump was pushing water and it was so not at a great pace/rate. Is there a known problem for this? Anybody have any ideas to offer?

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Quote
I have the factory type rad cap which is only around 4 pounds of pressure....

I think that Chevrolets of that vintage used zero pressure radiator caps.

laugh wink beer2


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The thermostat or the lack of one will not make it overheat. The most common cause of overheating is a radiator core plugged with rust. The rust comes from the engine because the water jackets in the block are filled with rust. First step is to get rid of the loose rust. Removing the freeze (welch) plugs on the left side of the block and using a wire going in and loosening the rust and flushing it out. Would suggest also removing the pet cpck (lowest point in the block and removing the thermostat and flushing from that directiom.
Next feel the front of the radiator with the engine hot and running. Sould be equally hot in all areas if it is clear...If not remove radiator and try flushiing in both directions with water pressure or take it to a radiator shop to be cleaned.
A 1940 did not come with a pressure cap. The 1948 was the first year to come with a pressure cap and its filler neck was designed for the use of a filler c
A 1940 is a rather hot running engine. Another thing that will help is installing a 1941 radiator. Fits right in and has greater cooling capacity.
Years ago it was common for the radiator/block to be full of rust after a few years due to leaving antifreeze in over a year, not flushing twice a year as recommended or using just clear water.
Modern antifreeze can be left in radiators for a few years with no problems. Best is a 50,50 mixture.
I run a 160 thermostat in my cars. Seems to be a happy medium for general summer use.

Last edited by Chev Nut; 06/17/14 09:41 PM.

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I just want to reinforce Gene's comments. The most important thing you can do is read and REREAD your manual's article on your car's cooling system, and follow the flushing directions. To do what Gene and I are going to recommend is like going into the hospital to get your appendix out! Nothing easy or fun about cleaning out an old cooling system with years of rust buildup. Having your radiator recored, because it is full of rust, is only a temporary solution, if the head and block have areas plugged with rust.

The pictures show two ways I have cleaned the rust out of my blocks and heads. I was too afraid to remove the freeze plugs. The first shows using an air compressor. This way would not work with an engine that has recently had fluid in its block. It did work on a recently hot tanked head and I highly recommend it. It only takes a minute to run compressed air through a hot tanked head or block, and you will know immediatley if there is any rust left inside.

Cleaning a head or block is like mining for gold. It takes a lot of patience You need to make up some probes out of coat hangers, a couple of lengths of thin shafted screwdrivers, or in the case with using compressed air, also bending some brake/gas lines to get as far into the block/head as possible (you attach the brake lines to the tip of the tool you use for spraying air with your compressor). That is why removing the freeze plugs works best.

To do either engine cleaning methods remove the engine block drain cock and the water pump. Do the work in an area where you don't mind making a big mess. Remove/cover any wiring, engine parts (generator for water?) that you don't want bathed in water or rusty dust. This is not a messless procedure. In fact I can not think of a bigger mess than this, and you can amplify it if you remove the freeze plugs. A nice windy day works best with air. I would start at cleaning around the inside of the rear water drain plug. Remove the entire drain cock and run a steady flow of water into the head. You could do this with the pump on or off if you remove the thermostat. The volume of water just needs to flow enough to keep the water flowing well out of the drain.

Using a coat hanger probe around the inside of the drain where the water is coming out. Try bending several different lengths of coat hanger wire to clean out the area. The longer the length of wire you can force in the better. You will find that the drain may plug up as you free up rust from probing around the drain or other areas. Just keep probing to reopen the water flow. When you have exhaused all your patience next remove the freeze plugs and start your probing all over around them. I don't see this as a 2 hour job.

By now you probably have a water mess over the entire engine compartment, and your wondering if you shouldn't have removed atleast the drivers side fender, and several engine parts, etc. Well you be the judge, because I would have.

I will post more info later, Good luck, Mike







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Last edited by Mike Buller; 10/09/19 08:22 AM.

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Excellent discussion and pictures on the cleaning of the rust inside the old 216. I spent years attempting to solve the problem with over-heating on my 1940. Once the block was totally cleaned like in the previous post, the only solution for me was to install a NOS 1941 Harrison radiator. Now the problem is resolved. Case closed for me.

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MY 39 WOULD OVERHEAT ALSO . NEW RADIATOR CORE ( $325 -/+ ) WITH A 180 DEGREE THERMOSTAT & SHE'S GOOD TO GO NOW. FRANK

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I had so much hope that this engine would be salvageable. It looked like an engine that was recently running. The head was full of oil, there were even fresh signs of anti-freeze near the drain. The dip stick even showed lots of good oil in the oil pan. Upon closer inspection I saw the tell tale 6 inch crack by the drain cock. The winter had been one of our coldest on record, and the garage it was stored in was not heated. I can only surmise that the crack in the block was fresh from this winter.

The problem with rust particles settling in a engine block is you don't know how many inches thick the accumulation is? Is it just an inch, or four? Are there passages at the top of the block, around the individual pistons, that are completely blocked? Are the particles of rust bonded together 1/8th of an inch in size or even a lot larger? Can anti-freeze even permeate 4 inches of accumulated rust? Only taking the head off can determine the condition of our old coolant systems that are overheating.

Looking at the following pictures tells you a lot about what can go wrong in your cooling system. The first picture shows the two freeze plugs on the engine. The second picture shows the drain minus the cock. This is our first sign of a block full of rust particles. The next picture shows the 5 inch crack in the block caused by the expansion of water/anti-freeze in rust particles. The crack was to the left of the drain. The next picture shows the front of the block where the water pump is installed. This is a good area to let your garden hose rest in while you probe with coat hangers and screw drivers the coolant system. You can clean out a lot of the rust this way but removing the freeze plugs will allow for a much better job.

The last picture is another heart breaker. It shows no build up of rust particles in the water inlets on top of the block. In some cases theses inlets will not even be openings anymore. They will be completely sealed off by corrosion. So I know, prior to the block freezing, water could have circulated well in this engine.

Please give me a call and leave a message if you have any question (989-832-7634). Good luck, Mike




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Last edited by Mike Buller; 10/09/19 08:15 AM.

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I decided to take out a freeze plug to see how much contamination was there. Unfortunately, It was obvious that a little fluid was still in the cooling system. Besides that there was about 1/2 inch of rust sludge. You can see some of it stuck to my magnet in the second picture. It was too bad that the previous owner had not flushed out the block and winterized it with some straight anti-freeze.

Hopefully, whoever reads this post will think about the implications of what can happen to a poorly winterized engine.
After I remove the rest of the engine parts the block will go to our local recycler. It is probably worth about $10.

I am planning to salvage the crank, head, oil line, oil pan, harmonic balancer, distributor, carburetor, generator, starter, clutch, pressure plate, flywheel, and a few other parts that can be reused.

Thanks, Mike

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Last edited by Mike Buller; 10/09/19 08:11 AM.

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As you pointed out, getting the block hot tanked is no guarantee that all of the junk is out. I assumed it would all be good after my engine rebuild and ended up with a radiator full of rusty mud. I had to pull the radiator to get it tanked (& fixed a couple of leaks) then flushed the cooling system using double the recommended amount of Prestone cooling system flush. The '38 no longer overheats and my radiator doesn't look like mud flats any longer.

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I just replaced the water pump with a rebuild and while off flushed the engine from the water pump holes in the block and the drain plug ....blowing air in both ends too . Did`nt pop the freeze plugs. Had the radiator boiled out and a couple soldiers done...put in 160 Thermostat...... all said, it made a big difference in the running temp . Stays at about 160 now and rarely gets near 180-190 on extra hot days. So, I think it`s all about how clogged your engine is and where you want to start. Mine may still have a lot of crap inside , but from a basic cleaning ,it`s made a big difference. Good luck!


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Hi Tiny,

Thanks for your picture and comments. I think we have now told a good story about why we need to do a good job maintaining our cooling systems.

I am very suspicious about engines that have been hot tanked as part of a rebuild. Hot tanking can loosen up a lot of crap in the cooling system. Taking one more step to blow out the block and head with 90 pounds or more of air pressure can tell you a lot. I spent over an hour blowing out a head that had been hot tanked. I think I got it all finally cleaned out!!! You know that it is clean when you can stick the wand on your hose attachment in any of the cooling system holes and nothing comes out of any other hole but the rush of clean air.

Thanks, Mike


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I purchased my 1939 in 1973 and it had 45,000 miles on it. Never had an overheating problem but in returning from a meet in 1981 I discovered a crack forming on the left side of the block. Found a new block and transfered everything over....then later took a big hammer and broke out the left side of the block. The water jacket had at least 3" of sold rust piled up. Could barely break it loose , was like old coffee groungs all stuck to gether. By luck it never plugged up the radiator.
even made it up Pikes Peak in 1976 without boiling over.

Last edited by Chev Nut; 06/18/14 06:18 PM.

Gene Schneider
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Today many shops don't hot tank anymore. They bake and shot peen cast iron.(EPA) Good to clean out most of the junk yourself first if taking to shop. When I worked in an automotive machine shop years ago many times I would take a badly crusted up, sludge filled blocks and heads out of the tank and wash them several times! Some of them were real bad and I used rods and wires to loosen the junk up. We didn't want any customer complaints or comebacks. Today's cooling systems seem alot better! On an engine rebuild with a real dirty system I would also recommend a new radiator core to keep possible problems to a minimum. Possibly use a coolant filter on initial test runs-might still get some loose stuff.

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Originally Posted by Master Six
Today many shops don't hot tank anymore. They bake and shot peen cast iron.(EPA) Good to clean out most of the junk yourself first if taking to shop.

I agree with Master Six whole heartedly. Why risk compromising a rebuild with a poorly cleaned coolant system? When I had my engine rebuilt I was assured that the cooling system was thoroughly flushed with the freeze plugs out of the block. I won't be driving my car for another year while I continue my body work. The engine has about 500 miles on it since my rebuild. The first thing I am going to do is flush the engine out before restarting it. Hopefully, I will not find any surprises?

Thanks, Mike


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Mike,

What's the brown car in the background?? Made me jump a bit as the outline of the rear fender and wheel opening looked like and earlier RR Silver Cloud?? Then it looks like a continental kit on the back??

Jim.

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Sorry Jim,

That's the front fender and cowl of my 41 Chevy. It has a set of 15" rims and some old Chevy hubcaps from I don't know what year.

Good night, Mike


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My 48 was running a bit hot when I first got it. Part of my problem was the vacuum shifter was leaking badly enough to make the engine run lean.


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I'm experiencing the exact heating issues like those listed above - runs hot and when shut off blows coolant. Since I had a 40 chevy 50+ years ago with similar problems I started with the obvious. I flushed block with a lot of water, removed radiator had it tanked and flow checked. Shop reported very little in radiator and thought it had been recored at some point. However don't know as the coupe has 33800 miles on odometer and had been in storage many years. Have got to dig deeper in the cooling system.
Will next check the H2O pump for damage, will replace it as a precaution and maybe save some future problem. If that does not solve the problem the head comes off next to check for a bad head gasket or potential crack. If all this fails will open up the block and start digging for rusty iron scale. Wish me good luck.

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If you do discover the head is cracked I have a new one.
Also have a new genuine Chevrolet water pump.

Last edited by Chev Nut; 06/21/14 07:54 PM.

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Mike,

Yes, quite often 41s have been mistaken for RRs. Unfortunately and sadly, none of the other years have enjoyed this phenomena of such internationally recognized style and quality. Especially, (not) 37s and 38s. Agrin

Why just the other day a group of local citizens ranging in age from eight to eighty looked at my 41 coupe in the parking lot at Walmart. Several asked me if it was a RR. Did too. They wouldn't believe me when I said it was a Chevrolet. They thought I was pulling their leg. Did too. It gets to be a nuesense. Does too. dance bike Agrin

Now on to the getting hot problem. The rust in a block will not, in itself, if not too severe, cause an old ,,, say 216, to overheat. Ones stopped up as the one Mike showed pictures of above will cause the engine to overheat. That is a severe case. As particles get to the radiator core they will tend to cause the top of the flues to stop up and that then will cause overheating.

A cracked block or head or a leaking head gasket will cause an engine to overhear.

A collapsing bottom hose will cause an engine to over heat.

A stuck or poor operating thermostat will cause an engine to overheat.

The WP will not cause an engine to overheat unless the impeller is rusted so severely that it will not circulate water anymore. That is really rare. If the shaft were to break well I suppose then the impeller will not turn and that will cause an engine to overheat. Usually bad water pumps are those that leak and cause the fluid to reach too low volume.

What to do. Take the block petcock out and flush the block with high air pressure and water going in the thermostat housing. Remove the thermostat for this.

Trip the fan belt and with the thermostat out fill it to the top of the housing and then crank it up and look for compression bubbles.

Fill it up and while hot and the thermostat open or out. Rev the engine. A stopped up radiator will cause the water to immediately rise in the top tank of the radiator. A loss of compression will do this also but with bubbles.

Merely boiling a radiator will not usually fix a radiator. They usually need rodding, as well.

Quick things to do are:

a. check are the bottom hose,

b. Flush out the block

c. Reverse flush the radiator with plenty of air and water. (Unfortunately, this will only result in enough flues being flushed to accommodate the pressure. Others will still be stopped up. This is why merely boiling a radiator will not fix severely stopped-up ones.

Look in the top opening of the top tank and look to the side at the top of the flues. You will be able to see a few. See if they look stopped up or have debris a-sticking out of the top of them. (Wow! That's a lot of tops right there.)

Timing and too lean gas mixture can contribute to overheating, especially if the engine is suffering from other water circulation problems.

Good luck and PM me if you have any questions. Remember if you top off an engine's radiator when cold then when the water gets hot it will overflow. Half tank or so when cold is fine. Gene has pointed this out many times.

Charlie computer

BTW: I apologize for this being so long. Do too.

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Removing the pet cock and flushing the block, even with good OLD FASHION radiator cleaner will not get the rust out of the block...believe me, been there and done that.


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Gene,

Didn't say it would but it may help. That is it may get out the loose stuff some and that is what will be clogging the radiator. I agree that the old fashioned tanking the engine is the best solution, by far. All I was saying is that simply because the bock has some rust forming at the internal surfaces may, in itself and without more, going to necessarily cause overheating.

That is what a reverse flush used to consist of. Merely, blowing air back through the block and the radiator. One at a time and separately. In some conditions, It was enough to allow the engine to run much cooler. For a time, anyway. Used a Kalamazoo air and water fitting for the radiator. Cost a buck fifty when I used to do it.

Boiling the radiator and flushing it after cost eight bucks and taking the top tank off, boiling and then rodding and reassemble and flushing the block was "bout fourteen bucks. Fixed any leaks after either boiling or rodding for that cost too.

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FUNNY THING , A RADITOR GUY CHECKED OUT MY ORIGINAL 39 RADIATOR . I SHOOK IT AND COULD HEAR CLUKS OF STUFF IN IT . I INSTALLED IT AND HAD OVERHEATING PROBLEMS . TOOK IT TO ANOTHER GUY AND HAD HIM RE CORE IT . NOW IT'S THE COOLEST RUNNING THING OUT THERE . EVEN HAD TO PUT A 180 THERMOSTAT IN IT TO GET IT RUNNING A LITTLE WARMER . I PREFER WARMER VS COOLER TO GET THE INTERNAL MOISTURE EVAPORATED OUT AND OFF THE OIL . FRANK

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THOSE CHUNKS ARE STILL IN THE ENGINE and unless removed will be plugging up your new core.

Last edited by Chev Nut; 06/25/14 08:40 PM.

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I didn't think the Thermostat made any difference in the Running Temp. of the Engine?


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