The Stovebolt Site Forums The Shop Area Engine Shop Constant Overheating Problem

I have spent the past 26 years restoring a 1941 Chevy 1 ton, have rebuilt the engine, transmission (4 speed w/ power take off) complete electrical, new fuel tank, and numerous items that would take too long to explain. Finally went down the road this past Wednesday. Used 4 gallons of water going 3 miles. Truck kept overheating.
I have flushed the radiator, block, heater core. Put 3 different thermostats and the truck still overheats. Disconnected the heater thinking that this was causing an air bubble, removed the stat in the head to bleed until antifreeze came out.
I am not filling the radiator past about 1 inch above the core.
Still when I go down the road fluid pushes out the overflow tube, then the temp gauge starts to get into the red I pull over and the radiator it boiling. After a few minutes I put in some more antifreeze and go down the road again.
(Really getting discouraged.)
The truck starts even when its hot. Then the temp gauge will go down to about 160, I am running a 160 thermostat.
Any assistance with this problem would be helpful.
The only thing that I haven't checked was the head gasket.
No water on the plugs, in the oil or coming out the exhaust.

Even with flushing the radiator may be stopped up to the point it can't cool. Could also be some blockage still in the block not letting it circulate fully.

One other thing to check is the distributor timing. if it is too slow or too fast it can create overheating problems.

It there a way to set the timing without a timing lite?
I have set the distributor with the timing ball on the flywheel, #1 TDC and the points gap at this time.

The way that I flushed the block was removed the the block drain, attached a fitting I hooked up to a garden hose, disconnected the hose at the water pump and turned on the hose. Got a lot of dirty water, then I put the hose into the opening where the thermostat would be, dirty water again came out the block drain. Did this until the water ran clear. Then I filled the block (putting a finger on the block plug) I drilled a hole in the bottom of a soda bottle. It fits into the thermostat opening great, then I proceeded to blow air into the bottle until it pushed my finger off the hole. This again pushed dirty water out... I continued this until I got clean water.
I did the same thing to the radiator, ran the water until it was clean again.
Hard to believe that there is still something plugging the water jackets.

Drill a hole in your thermostat to let the air out of the block. I also park on a very steep grade, nose up, to help burp the system,
Scott

If you open the petcock on the engine block, does it drain feely? If not, you have crud in your coolant passages in the block. Crud builds up easily and can cause your headache.

Well in the morning I will drain the radiator, block and check the block for more crud. Sooner or later I should be able to get everything out.
Any other ideas how to get the crud out?

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Do you have a vacuum gauge? If you do, connect the vacuum gauge to the intake manifold fitting for the tube to the wiper motor.

Set the timing at idle (500 rpm or less) to maximum vacuum. This is a little off the ideal timing but good enough to eliminate bad timing as your problem.

Great hint...will try that in the morning before I drain the system again.

Are you sure that your radiator cap is the correct pressure and good. You should be able to fill your radiator completely without it blowing over.

If Tim's trick does not help you, and you decide to drain the system, open the petcock on the block first. I put a funnel under the petcock to make things less messy. You should have a strong steady stream flowing out. If its not, you have crud in the passages. Using flushing agents, water pressure, and even coat hangers are ways to break the stuff free.

If after cleaning out the block you still have problems you may want to pull the radiator and have the local radiator shop do a Flow test. This way you will know if the radiator is truely cleaned out. One other thing I just thought of is this. Find someone with a laser pointer temp gauge and check the radiator in multiple spots and see if the temp is regulated.

When I was running the maintenance shop for a sand, gravel, and concrete company, we used the same muriatic acid that was used for cleaning masonry work for flushing cooling systems. It's available at any home improvement store or swimming pool supplier. Pour 4 to 6 ounces of acid into the radiator along with a fresh fill of clear water, and run the engine at a fast idle for 10 minutes or so. If it heats up, shut it off. Running water from a garden hose over the outside of the radiator will help keep it from boiling over while you're flushing. Drain the flushing solution, and run clear water through the radiator, then pour a couple of boxes of baking soda dissolved in water into the cooling system, top off with water, and run for 5 minutes. This neutralizes the acid left in the system. Drain and flush with clear water. The acid flush will clean up any rust deposits or lime scale. It might also expose some pinhole leaks in the radiator core that were being plugged by deposits. If so, take the radiator out and get it repaired or recored.

Now- - - -here's another possibility. You could be getting exhaust gas into the cooling system from a cracked cylinder head. Here's how to check for that possibility. Take the fan belt and the top thermostat housing off, and fill the engine with water until it's level with the thermostat hole in the head. Start the engine and goose the throttle a few times. Don't be timid about it- - -let it accelerate for at least a couple of seconds. If any bubbles show up in the water, you're getting compression into the coolant. Take the head off and get a machine shop to pressure test it.
Good luck!
Jerry

This morning I drove the truck to my brothers shop, on the way there, (about 8 miles away) the temp gauge went just into the red, I again checked the radiator, it was down about a half a gallon. After that I drove another 5 miles and the temp didn't go over 140. When I got to the shop I did remove the thermostat and upper radiator hose. Filled the housing and ran the engine. No bubbles were noted.
I left the truck there, Tuesday morning I will get some acid and baking soda and do a good flush.
I plan on checking the timing then also, found a way to use my 12 volt timing lite. Just need to get a battery to power the lite.
I want to thank you and everyone else who are attempting to help me get this situation fixed. I'm getting pressure from friends to get this fixed before the weekend, there is a Waterfront Car Show Saturday in Bangor, Maine they want me to attend.

Please don't be offended with this but...are you sure the thermostat is not in upside down? No one else mentioned it so I just had to ask.

When the engine was rebuilt, was the block cleaned? hot tanked, cooked, or washed? One could assume if it was cleaned at the shop it should be clean inside. Pulling a block drain plug will let you know pretty quick. If it is plugged, is there any way you can get a power washer wand to meet up with the drain and really blow through it?

It seems to me to be overheating really quickly, 4 to 5 miles? Mine isn't hardly warm by then. You sure the water pump impeller is good? Do you see water flowing in the radiator if you look down the filler hole? I would have to think even a poor radiator would make it 5 miles, the thermostat shouldn't hardly be open that quick. Something in the block is affecting water flow, maybe air pocket, wrong head gasket?

Joe

I had the same thing with a fairly new radiator that i had put antifreeze from old radiator. then it sat for 2 years while i finished it and the stop leak that was in the old radiator hardened. tried everything to get rid of it, finally bought a new aluminum and that did the trick. i also put in a high flow thermostat that i got at Auto Zone.

Do you dare try running it without the thermostat? If it's easy to do, it might tell you something.

When the engine was in the machine shop, I had it tanked and then pressure cleaned. If there is something going on in the block, it might be that I built the engine in 1993. It was then stored with the other parts. I spent the next 18 years in the military. Continued working on the truck but never got all the parts in one place until this spring. I have had problems with other parts that I reworked, the radiator was taken to a shop to be reworked, when I installed it, it leaked, I took it back to the shop some 10 years later and they fixed it at no charge. Then I installed the fuel tank that was repaired at the same shop, the fuel turned red from the slosh seal they put into the tank. Then like the like radiator it leaked also, again they repaired my spare tank at no charge.
You see I think problems find me.

I have tried replacing numerous thermostats. I was told not to run without the thermostat so I cut the spring and center section out of it. It didn't make any difference.
I have taken off the radiator cap to see if the water pump was working when the engine was at temperature, I can see fluid move through the radiator. The only thing that I haven't done was change the radiator cap. I am running a cap the doesn't have any indication of what the pressure is. I got it from Jim Carter as an original cap.

I got called one time on a 1940 Chevy sedan with the 216 and it would overheat almost before you could get out of the drive. It would start, but then sounded like it was laboring to run. Found out the owner had decided to reset the timing at the distributor and had it wayyyy slow. I turned the dizzy back to where it should be and no more heating issues.

Does it have plenty of power going down the road? Is it a little hard to start in the mornings? Does it "ping" when accelerating?

The truck starts great cold or very hot, runs down the road with all kinds of power. No pinging. Really has me baffled.
Going to work again on it Friday...the first thing that I'm going to check is the timing. Can't believe it's anything serious, I hope.

Well I finally got time again to work on my over heating problem, I found the timing out by 4 degrees, when I drove the truck home it again overheated. I don't know just where to go next, I'm thinking that it might be time to replace the radiator.
Does anyone have ideas of what I might check?

DR

I just had a similar issue with overheating due to bad timing. But after I got the timing squared away, it still kept overheating! It took me a day or two to realize that the bolt holding the distributor in the right place was backing off and allowing the distributor to slip back into a too advanced situation. Problem solved with a little Lock-tite.

Another thing to do is buy an infrared thermometer to assure your temperature gauge is accurate.

I had quite a situation today with my truck, I went to a car and truck show, on the way there it kept overheating to the point that is was boiling within the radiator. I filled the radiator to the top trying to keep and get all the air out of it. Seemed to work a little better. The last time I did it I drove about 5 miles with the temperature not going above 130 or so. On the way home (some 5 hours later) I went through the whole process again. I really believe now that it's air not getting all the way out of the system. In the morning I'm going to remove the temp stat from the head, then I'm going to plumb up a bleed valve where the stat originally was housed and put the stat in above the bleed, thinking that I will be able to get all the air out at the highest point.
If that fails I will attach a fitting so a water hose could be attached and back flush the system into the radiator.

Does anyone have any other ideas?

you could do what most everyone else does, drill a small hole in the flange of the Tstat just outside the opening flap, any air in the block finds it's way out that hole to the upper rad hose as the temp comes up, allowing the hot water in the block to contact the stat sensor so it will open .... but if the water in the rad is hot enough to "boil", the Tstat is opening and that's not your problem, especially if it went 5 miles at a fairly steady 130 - air trapped in the block prevents the stat from sensing the water temp and opening.... you also did nothing by filling the rad to the brim except give it more water to throw out as it heated and expanded

you may have a faulty stat, it should not allow the engine to run below it's rating [like that 130], if it's a 160 it won't open until 160 - you also likely don't really know what the temp is if that 130 is what the gauge said, use a laser digital thermoter to check around up front, the stat housing, top and bottom of the rad, front and back of block, and of course the water in the rad and find out what the actual temp is when it's warmed up, you could have a bad/weak water pump or a partially plugged rad, or as is very common with folks used to modern closed systems you are filling it too full, find out what the real temp is, do not depend on an antique gauge that simply shows "cold - hot"

Bill

Another trick is to place a few aspirins on the thermostat once you pry it open. They will melt away once the water gets to them. The drilled hole is about the best way since you have to remove it for either tip. Once its out, hang it in a pan of water on the stove and find out why is letting the engine run so cool, if it really is that cool.

Let it seek its own coolant level, once down a ways, it should quit spitting it out. mine used to like to be right at the top of the fins, any more and it push it out when hot.

Are you using a pressure cap on a open system? Try putting a overflow bottle on and catch what comes out so it can suck back in what it once after it cools off.
Joe

I started working on the overheating problem again. When I removed the temp sensor in the head, water began running out. I think this would tell me that there is no air at that point.
I have been reluctant to believe that I might have put the head gasket the wrong side down.
Going to try letting it run and begin checking the temperature at the places suggested.
I will then drill a hole in the thermostat and try that before I begin wrenching the head off.
I guess I will be busy the next few days in my spare time.
This is the best time of the year here in Maine to be riding around checking out the seasonal changes.
Must get this done early in the week.

Thanks for all the suggestions...

I went back and read some more, but don't see where you had your radiator professionally cleaned. I saw where you had run some water through it.

There could be enough passages open that water flows through, but not enough open to take the heat away as it should. Coolant moves through it much faster when going down the road than a water hose setup can duplicate.

Does this engine run hot when idling? Or only under a load running down the road?

On the 216 I don't think you can install the head gasket wrong. If it were bad and compression gasses were getting into the coolant system you would have bubbles show up while it was running when you had the thermostat out.

I think you need to go take a closer look at the radiator. Take it to a shop and have them open it up.

The radiator was professionally cleaned over 1 years ago, only installed it about a month ago.
It is very strange when it over heats, I can start the truck and let it idle and the temp will go up to the point that the water comes out the overflow tube, I shut it off and replace the water, start it again and the temp will go to normal. (Around 130) Usually when it is under a load it seems to act up more.
I have never run the engine without the thermostat, I was told that I need the back pressure which it provides.
Should I try it without a thermostat before I remove any other parts?

DR

Another thing that I did check today was, I went to remove the temp with stat in the head, when I did the water came out of the fitting under pressure, water was about 1 inch above the fitting. The engine was not running and was cold. The radiator was full to the top with the radiator cap on.
Just another clue in the mix.

DR

That would be about right. The temp sensor is slightly below the level of the top of the radiator level so some coolant would come out.

Try it without the thermostat. Usually the thermostat slows the water down as it enters the radiator so it has time to cool before going back into the engine. But it won't hurt to try it for a bit without it.

What brand t-stat are you running? It sounds like the t-stat is not opening properly as the engine heats. But you have replaced it once.

Could the water pump openings be partially blocked not allowing the water to flow properly? Could the impeller in the pump be bad?

Take the t-stat out. Fill the radiator to the top. Start the truck and watch for bubbles. Might have a few for a minute, but should stop. If you get bubbles while it's running and they don't stop, then you have compression leaking into the cooling system. May be the headgasket tore while installing the head, or the head may be cracked. They sell a dye you put in the water that tells if your have exhaust gasses entering the cooling system. Might see if your parts store can get you a small bottle.

"... I start the truck and let it idle and the temp will go up to the point that the water comes out the overflow tube, I shut it off and replace the water, start it again and the temp will go to normal"

repeat: if the water comes out the overflow as the engine warms, the rad is more likely overfilled, not over-heating - "replacing" to overfilled again with cold water results in temporarily lowering the system temp so it can re-heat and overflow again

another repeat: "normal" is NOT 130, it's whatever temp the stat is rated at, either the gauge is way off or the stat is sticky and sometimes not opening and sometimes not closing - start with finding out exactly what the temp actually is at various points on the system, and various times, when barely warm and after well warmed up, and when you think it's overheating .... and check your bottom rad hose, it may be collapsing when hot and restricting the amount the pump can suck, and that isn't obvious from the drivers seat - also make sure you're not using any thread sealant or teflon tape on the temp sensor

Bill

After all the assistance everyone has given me and checking everything suggested, the problem still exists. This morning I removed the water pump, it looked just fine.
Then I removed the head...the head gasket was installed properly and looked just fine, what I did find was an accumulation of rust in the water jackets. I pressure washed the head making sure that all the water journals were free of any thing that might be obstructing the water flow. After a few minutes all the holes were clean. I guess the lesson learned here was, don't start rebuilding a engine until you are ready to use it. This engine was rebuilt in 1992, wrapped in plastic and left in the garage. Here in Maine with the weather changing I figure that moisture must have accumulated making rust.
I am going to take a compressor and blow out the water jackets in the block prior to putting it back together.
The real downside is, cannot get a head gasket until the end of the week. Hope this time everything goes better.

Again, Thank-you all for the support and all the great ideas.

At least you found something, pulling it apart and see nothing would be really bad. Pull the block drains so the air and crap has a place to go.

Joe

I had that problem with an old engine once. It turned out to be improper valve adjustment. Once I got the valves properly adjusted the over heating stopped.

One of the earlier replies suggested you check for a cracked head. You mentioned that you had the engine work done years ago. If the head wasn't pressure tested AND magnaflux'd or if you have any doubts at all, then you need to. Everything about what you described is a cracked head. Was the head planed? It may be warped enough the head gasket is leaking.

Some other symptoms. What does the oil look like. Is it milky before or after running it or if after letting it sit when you check the oil plug, does any free water come out? At a minimum you have a head gasket leak, the worst a cracked head.

After letting it sit a couple of days, do one or more of the plugs look rusty or have rust on them?

The water is going somewhere, either in the oil, out the tailpipe, blowing out the overflow (compression gasses).

Some already mentioned by you and others, heating very quickly, heating with the thermostat removed, etc.

Just last week I saw all the symptoms on an old truck I'm helping my son with. I, like you didn't want to think that was it, hoping it wasn't, hoped it was somethng else, and tried to ignore the facts. When I pulled the head it didn't take the machine shop long to tell me what I didn't want to believe.

It might still be possible it is something else, but it sounds like you addressed all the easy ones. This isn't expert advise, but advise from experience (some very recent).

I read this whole thread, and saw numerous suggestions to drill a hole in the thermostat or to try running the engine without a thermostat, or to flip the thermostat over. I sure would have tried that before pulling the head.

Just sayin, and certainly no offence meant.

Good luck!

Kurt

you don't fill the radiator to the top or it will come out the overflow when it gets up to temperature, it is normally a couple of inches down. (in mine any way.) Another thing to check is if your gage is accurate.I.E. put one in (even just temporarily) that you know is correct, with actual degree increments that would tell you what your temp is. which is basically what people have been saying by using an infared gun. I'm still not convinced you actually have a problem