VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Overheating puzzle

Here is my peculiar predicament: Last October, after participating in a couple September shows with everything running perfectly, I stored my 1938 coupe pickup as always, in my shed, enclosed fully in a zip-up car cover bag. Last week (I know how late it is, but I live in MN!!), I took the coupe out of storage, dropped in the battery and it started right up, as usual (but I didn't have occasion to drive it). Today I took it for its first spin of the season, and within a mile or so my temp gauge was nearly pegged and antifreeze was on the windshield. After letting it cool down I nursed it home, figuring it was a faulty thermostat. I put in a new 160-degree thermostat (after checking it in hot water to make sure it worked), took it down the road, and again, in less than a mile, it was overheating.

Here are the other relevant facts: Entirely stock 216, which has run perfectly for the past several years; radiator serviced and cooked 3 years ago during restoration--has run perfectly until now, never even getting close to the red on the gauge. No apparent leaks anywhere. No water in oil. 2 heater hoses hot, top radiator hose hot, but bottom radiator hose not hot. After it cooled down after the second overheat, I started it again and watched for flow with the radiator cap off--didn't see any. Is this indicating a faulty water pump? The water doesn't seem to be circulating; belt tight and fan turning regularly. No apparent blockage in exhaust.

Can a water pump go bad/die simply sitting in cold storage over the winter (there is no leakage from the pump or anywhere else I can see)? If not, what else can it be--everything was running perfectly when it went into storage, then, coming right out of storage, in a mile or two to get over temperature in such a short time/distance? What other steps of diagnosis should I take?--take out the thermostat altogether and watch for flow?

It's a hassle to change the water pump in the 38, so I want to be pretty sure that's the culprit before I dig into it. I've never had a water pump fail on one of my old chevrolets, so I don't know if this is the likely culprit or not.

Any thoughts/suggestions will be greatly appreciated.

Thanks very much.

Jim

As long as the water pump is turning I think the water pump would be last on the list.
Did an animal build a nest in some place? A hose collaspe inside? Top and bottom hose get hot? Radiator core getting hot?

could your v belt be loose & slipping ?

The V-belt was a little loose, so I tightened it and it still overheated.

I thought of an animal with a nest somewhere, but it was totally enclosed in a car jacket over the winter; it's been uncovered for a week; checked the exhaust and it seems fine--where else could a critter interfere or position itself so as to cause this?

Top hose from radiator to thermostat housing is hot. Two heater hoses are hot. Bottom hose from radiator to pump is cold. I didn't see it collapsing--could this be happening without seeing it to the naked eye?

I haven't checked the temp of radiator with one of those heat-sensing guns yet.

Jim

one radiator shop said my 39 radiator was good to go > I still had overheat problems . took it to another shop for a new core . solved my problem .is this the original core ? or has it been re-cored ?

The inside lining of a radiator hose can delaminate. The resulting flap can impede water flow. Might squeeze the hose along its length to see of there is a spot that seems weaker. Or better yet just remove and look. While you are at it put a water hose in the top of the radiator and with moderate flow check how much comes out the bottom.

the39 said,
I ran into a similar situation in the past with a '59 panel truck. The radiator was clean (no restrictions and lots of flow), but did not transfer the heat well. In my case, the cooling fins were no longer making contact with the core tubes, so the heat was not being extracted from the coolant.

New core = problem solved.

Good luck, Dean

What ever happened here is something "uncommon". Note that it overheats in one mile, not the usual like at high speeds etc. That indicates that there is no water moving through the system.
I think the first thing I would do id remove the thermostat and the top and bottom hoses. The with water pressure see if water is passing through the engine (from the top hose down) and if it moves through the radiator core, while checking the "interior" of the hoses along the way.

Jim,

All the advice you have received so far is excellent.

While you have the bottom radiator hose off, I would back flush the radiator. Use an air compressor source an a rag or something so you can get squirts of pressure into the bottom hose. Fill the radiator first and shoot the air to it. It may clear some flues and enough for you tho note that it made a difference or not.

You said that the radiator had been boiled. It probably needed rodding. That is when it is boiled with the top tank off and then the flues cleared with a length of strapping material. You may have to visit a good radiator shop to have a proper radiator job done.

Some diagnostic things to do:

a. Fill the radiator to the top with the thermostat open or out. Then rev the engine and see if the coolant wants to overflow the top tank. If so, it indicates that the coolant isn't going throughout the radiator flues fast enough due to some being stopped up. (it could also indicate a combustion leakage but not without bubbles or a gush of internal air pressure.

b. While you have the bottom hose off. while holding your hand over the top tank outlet, fill the radiator and then release your hand and note the rise of the water coming out. You should get a good rush of coolant (water) about 5-6 inches high and no detectable sucking sound coming from inside the radiator.

As Gene, I do not think your problem is the water pump.

Over the winter rust and sludge may have coated the inside of the radiator flues. Some may have been already stopped up and the radiator at the threshold of being able to cool sufficiently for no previous problems. Now you may have more stopped up.

Good luck in finding the problem,
Charlie

Guys,

Thanks very much for the trouble-shooting ideas, etc. I really appreciate it. I get the thoughts on the core, but it seems that such a drastic change literally over the winter is peculiar. At any rate, I hope to be able to dig into it further this weekend. I will report back what I find.

Thanks again.

Jim

Just a word of caution. Do NOT subject the radiator in excess of 15 lbs of air. The radiator is not built to withstand a full shot of air. The remainder of Charlies hints are rather safe.

Jim,

If you're not opposed to the idea of using a fan shroud there are many postings about how to make one. I'm going to be doing that myself to duplicate an unavailable '34-'36 truck upper shroud 1/2. I have an original metal bottom 1/2. One thing I learned from those articles is to start with stretchy fabric like felt because it conforms really well to compound curves and apply resin to it. Then lay up the glass cloth on the felt.

The end results those guys produced are very impressive because fiberglass is so easy to shape and finish.

After reading those articles I'm ready to dive in even though my '36 PU has never overheated in the 50 years I've owned it. A fan shroud was an option for trucks and it will look "cool".

Ray W

Here's an update. I spent much of the day working on the problem. Water flows easily through the radiator and comes out clean. Checked both hoses and all was fine. I found some play in the water pump pulley, wiggling it back and forth--decided to pull the radiator, flush it out well, and change the water pump (I happened to have a NOS which I was saving for my 38 panel). Old pump didn't seem to want to turn very freely--I was hopeful. After all was back together, started it up and again the temp gauge rose into the red (though not as hot as last time). Needless to say, I was bummed. My neighbor has one of those heat guns that you can aim and shoot and the difference in heat on the radiator was quite dramatic--200 at top and top hoses; down at the bottom only 90-100. Obviously, the coolant is not circulating correctly.

Given all of this and everyone's several comments, it seems logical to conclude that something is amiss with the radiator--it is the original and while it was "cooked" and checked for leaks, it was not properly "rodded out", as Charlie has pointed out. Seems that it must have clogged up or rusted up on the bottom half enough over the winter to cause this irregularity. It's out of the car again (I'm getting quite adept at removing and installing it!) and I will take it to a radiator shop to have it fully serviced. Can't think of what else it could be. I'll be interested to see what they find.

Thanks again for all your help and suggestions. I appreciate it.

Jim

I am curious. Is the radiator a lot heavier on the bottom end?

If the core is plugging up that bad the block is the cause and full of rust. Could do the same thing again if not cleaned out.

It's hard to tell whether the radiator is actually heavier/how much heavier at the bottom.

Gene, I was wondering whether there might be gunk in the block as well. When I drained the antifreeze there was little if any residue--it was quite clean--though I didn't drain all from the block.

Is there any way to clean the block effectively while it is still in the car? Can I flush it from the water pump port, leaving the petcock open?

Jim

The best way is to remove the freeze plugs on the left side. You can remove the drain cock and poke around with a coat hanger wire in the opening for a test. Soetimes it is packed and dosen't flush out.

Harbor Freight, Home Depot, and a few other stores sell these, I paid $69 for mine in a sidewalk sale. Might help you with seeing what's inside your block. This thing has saved me a lot of hassle in many different situations.


p.s. No, Charlie, I haven't done that kind of inspection yet....

Hi Jim,

I would like to share a few previous posts on this topic. Unfortunately, until you remove your head or do some probing with a coat hanger in any access area of your cooling system you will not know the conditions that could be plugging up your block/head and causing your overheating problem.

The last few winters have been especially cold and in Michigan we have had below zero weather for extended amounts of time. If your car is stored in an unheated shed then it could be very prone to a cooling problem. Some of the corrosion throughout the system could have broken loose or shifted to cause a plug up somewhere in a passage in the head or block.

A lot of folks need to rethink how they are winterizing their vehicles. A cracked block is becoming more common where temperatures have been below zero for a long time, blocks are filled up with corrosion, antifreeze levels are not correct. I would be especially leery of buying a car from northern parts of our country.

Here is a link to the previous discussion. Overheating issue, I am

I do wish to commend you on providing good background info on what you have tried. Please keep us informed so we can all learn from your experience.

Best wishes, Mike

Problem Solved--but perhaps not the mystery.

Thanks to all for your advice and suggestions, whch were really helpful. Mike, you're right--keeping old cars up in a climate that witnesses several weeks on end well below zero termperatures is a challenge! Things go wrong just sitting in the frozen shed!

At any rate, here is an update: the coupe is now back running at normal temperature. Here is what transpired since my last post. I took the radiator to a radiator shop that's been around a long time, ready to ask for a full service or a core replacement. When the radiator man looked it over closely, put some water to it under air pressure, and checked its flow, it was his opinion that it wasn't plugged enough or had so restrictive a flow that the car should overheat, especially as quickly as it was doing. No rust or residue came out. He loaned me a tool that attaches to a garden hose and also to an air supply and suggested that I try to flush out the block--what a handy contraption. I went at it, inserting the tool in the water pump outlet as well as the thermostat housing (with the thermostat out). I would then drain all the water from the rear/lower petcock. At first I had some blockage--not too bad; I could insert a wire and start the flow, with some sandy gunk coming out. Then I would blow air from the petcock opening backwards and let the whole thing drain. I did this process more than a dozen times, until not one piece of sand, rust, or gunk came out, and all the water flowed out freely.

I put the whole thing back together this morning, put in water, and the temp gauge never got to the second mark on the gauge. I also tested the temperature of the radiator, hoses, block, etc., with the temperature gun and it showed close to equal temps all around, varying only by about 5 - 10 degrees. So, it appears that the problem is solved...

But not necessarily the mystery. In retrospect, it doesn't seem that the radiator was clogged at all, and while I did get some gunk and sandy residue and sediment out of the block, it wasn't overwhelming or anything like I've seen in some old tractor blocks or what was evident in Mike's pictures. If I had to wager a guess, I would say that something wasn't quite right in the way the water pump was functioning (as I reported, I was able to wiggle the pulley a bit sideways, and when I removed the pump and worked it back and forth, it became VERY stiff to turn). So, I replaced the pump with a NOS one that I had. I would also venture a guess that perhaps some scaly crud had formed somewhere inside the block over the winter and that it was preventing free flow. All of that backflushing with pressure probably dislodged the junk and now free flow has been reestablished.

I give kudos to my radiator man--I was ready to sink $300-400 into a new core, etc., and he was not convinced. Instead, he stopped his other work and checked things out with me there helping and came to the conclusion that the radiator had a good flow rate, etc., and that the problem lay somewhere else; then he volunteered to let me use his air/water pressure tool for the next several days. On top of all that, I also had taken in my radiator for my 38 panel truck that I'm restoring to have him check it over, etc. He called yesterday to check on things and when I asked what the charge would be for the truck radiator and his diagnosis on the coupe radiator (which took nearly an hour of his time), he asked, "How does $40 sound?" Not many oldtimers around like that, who REALLY are interested in solving problems and helping people.

Thanks again for all of the advice. I suppose that without a full service to the block while out of the car the same thing could happen again in the future--but things at this point seem to be working really well.

Jim

Rust on the bottom of the block will not cause an engine to overheat....until it breaks loose and plugs up the radiator core. Thats why if it were mine I would have checked for a large collection of rust in the bottom tank before taking it in for repair This could have been done by filling from the top and seeing what comes out of the bottom. Would have felt much better to see the actual problem.

Gene,

If you mean filling the radiator from the top and checking what came out of the bottom, I did that as soon as I removed it from the vehicle, and the radiator guy did that also. Nothing significant came out--just clear water. After checking that way, he ran water from the bottom up and again, nothing significant coming out.

I agree--would be better to have discovered exactly what the problem was; without knowing for certain, I fear it might happen again. Still something of a mystery.

OK, then we are thinking in the same direction.

While you had it out, I would have had the radiator properly serviced. That is I'd have had the shop remove the top tank and boil and then rod it. Any small pinpoint air bleeds that were too small to fix could have been taken care of by putting in a quarter to one-have a tube of Solder Seal.

Merely, just reverse flushing the radiator with air and water sometimes gives a false negative or negative (depending on the way you look at it). That's because if 50% of the flues are stopped up or partly stopped up, then the height and duration of the flow when a full radiator is released. Also, an experienced ear may hear the sucking sound of partially stopped flues.

Having said the above, I do hope you have fixed the problem and that everything stays normally expected from now on.

Charlie