The Stovebolt Site Forums The Shop Area Engine Shop 54 3100 Truck Overheating

Greetings,

I have a 54 Chevrolet 3100 Truck, 235 engine, I believe it is a second series. Looking for your guidance on recent overheating.

Recently I drove into town, truck drove fine, but then I had to wait in line (idling) and the gauge went to hot and it went to a rough idle. i shut the truck off and waited until it cooled off and then drove home (temp stayed normal).

I started by replacing the thermostat, started the truck, let it idle, it went to Hot again.

I removed the radiator. Looks to be ok, I ran water from a hose into the upper hose connector, the water drained out the bottom, water was clear.

Thinking it may be the water pump, I removed it. Looked to be ok. No play in the shaft, no leaks from the weeping hole. Took it to a local friend and he said it looked to be just fine (the cleanest 74-year-old pump he has ever seen). The fan belt was dry rotted a bit, so I replaced it. Put it all back together, let the truck idle and it overheated again. When I was letting it idle, I had the radiator cap off and after a while I observed water moving in the radiator, which led me to believe the thermostat and pump are working.

I put in new radiator fluid. The old was clean. I inspected the hoses, and they look to be ok. The connectors to the heater (which I don't have one) have a single hose that is kinked (has been forever).

In conclusion, the truck is getting hot when the gauge gets to H. It starts to run rough, so I shut it down. Any guidance is greatly appreciated.

Regards,
Victor

If it is a 1954 check the engine to see if it is a newer 235 with the waterpump higher than the origional the newer style engine as I have does the same ,there are kits that allow you to use a older waterpump that will put it in the proper position ,lower on the rad keeping the engine a little cooler.

If it's a '54, it's an Advance Design.

1955 is divided into first and second series. The 1955 second series is the new Task Force body style.

This is your first post in 7 years so can we assume that it's been running fine up to this point?

Have you checked the timing?

Thank you all for your replies. I appreciate it.

K - Just to confirm, you have truck with the newer pump, and it will overheat if idles for a while?
O - Thank you.
G - The truck has been running great for 7 years. My typical usage is to drive it to different locations. This was the first time, that I can recall, where I had to set idling for a while. I will check the timing

Is the heat riser stuck in the closed position on the exhaust manifold?

Rick

Do you mean stuck in the open position? While in the closed position, the heat is deflected away from the intake manifold.

Just make sure your heat riser valve moves freely in both directions and that the spring tension snaps it back when cold.

Hello Otto, I checked the riser and it seems to stay in the same position whether the enginer was hot or cold. I figured I should be able to put a screwdriver in the slot and move it, but it doesn't. I think it's stuck - is there a way to tell if open or closed? The slot is just about vertical.

Hi Pancho.

That could be the source of your overheating.

Spray the daylights out of that shaft with PB Blaster or a 50/50 mix of acetone and ATF. Try to loosen it up gradually. See if tapping it with a hammer frees it up. You can take the spring off to get it out of the way so it doesn't get damaged.

I'll have to go out and look at my truck to see which position is which.

For your viewing pleasure..........

Good luck!

My truck is a 54 gmc 9300 Canadian model that comes with a 235 .my 235 was changed when I got it and it has a newer 235 in it that has the waterpump in the lower position so when it is hot out and you are in standing traffic the temperature goes up . From this site I learned about the 54 engines having the waterpump in the same position as the older 216 engines .if your engine is newer like mine it will run hotter ,I am planning on getting a kit to relocate and use the older waterpump ,but in my area we don’t get the hot weather for long so it runs at the right temperature with the exception of the few times .

Thank you everyone for the help.
HandyAndy - Thanks for the pictures, I am a visual person, helped me understand how it functions.

Still struggling with getting the riser shaft loose, 4 hits with PB Blaster, struggling to remove the spring, I figured it simply would slip out...NOT

An interesting finding - when I was testing the riser spring, I was running the engine, to let it heat up. At first the radiator was cool, after about idling for about 10 mins, then the radiator became hot to the touch (which meant coolant was moving through the thermostat and the water pump is working). Engine was idling just fine. The temperature gauge got to the H, but the idle stayed smooth. It wasn't rough idling. I let it run another 5 minutes. I shut it off. My question now is whether the engine is truly overheating (need to find a way to measure the temp). The temperature gauge eventually returns to C. Will continue to focus on the heat riser issue, but am puzzled by what is happening.

If your radiator is full and you have the correct 4psi radiator cap on it and it isn't boiling over, it's probably not overheating.

You definitely need to fix that heat riser valve, though. New springs are available if yours isn't any good.

Even if the engine isn't overheating per se, the heat riser could be stuck in such a position as to direct too much heat to the base of the carburetor causing the fuel to be vaporized before it gets to the combustion chamber.

Tell us about your fan and shroud

Otto - I agree, that sounds more like what the source of the issue is. I am checking to see if I can find the spring locally, I know I can order it.

Panic - It has a 4 blade fan (pic enclosed) no shroud.

Otto - The radiator cap, while old, says it is 7 PSI - Do I need to change it to 4?

Yes. Install a 4 psi cap. Every additional pound of pressure raises the boiling point by 3 degrees.

It never came with a shroud and the fan is stock. I live in Atlanta and the stock fan with no shroud works just fine in 90+ degree heat.

Hello,

Started on working loose the heat riser rod, I went to work on the counterweight side and there is none!!! I am not sure if the previous owner (who loaned this truck to a high school class to rebuild) just cut the rod or what since the end of the rod and spring is still there. I put a screwdriver in the hole where the counterweight should be, and it goes all the way to the other wall. So, there is no valve in there. This must mean that exhaust heat is going both to the intake and exhaust manifolds.

I replaced the radiator cap (4 PSI) and ran it again at idle. I let it run for about 20 minutes. At about 10 minutes the temp needle was at H. At about 13 minutes radiator warmed up. I let it run another 5 minutes and it idled just fine. So, it does not appear to be overheating.

Given my current status, I think the next step is to test the sensor and gauge to see if they have any issues. Thoughts? Thanks again for all of your help.

Buy an infrared thermometer ($20 or so) and you can shoot temps all over the engine - upper and lower rad hose, T stat housing, head, carb base, intake manifold below carb, exhaust manifold, etc.

That will give you a good idea about how your engine is behaving

You are completely dead in the water without a heat control valve in the manifold. Some are comfortable with a stuck valve as long as it is stuck in the fully warmed up position. I am not comfortable with that scenario, but is better than nothing, which is what you have.
Chevrolet didn't include a cab heater from the assembly line for these trucks to keep the sale price down. Wouldn't one think that they could have saved money on the sale price by not spending money on a heat valve in the manifold? Must be it is there for a very important purpose, like preventing liquid gasoline from pouring down into the cylinder when the intake is cold, washing away the oil on the cylinders, creating premature engine wear.
In the case of the OP's scenario, heat is being applied to the intake manifold all of the time. That is not good either. It is likely the cause of the overheating issue.

52Carl - Thanks for your response, insight and guidance. I wish I knew the decision behind removing it. My curiosity is that it's been about 18 years since the engine/truck was rebuilt, so what failed/triggered this issue now.

Otto - Thank you. I have a friend who has the thermometer and I'll be meeting up with him later in the week and see what we find out.
As a side note, you had previously written your comments about the series. I re-confirmed that this truck is a 2nd series and when I read the reason for the conclusion (from a local antique car buff) is that is has an open rear-end on it.

Update on engine temperature readings.

Drove truck to a shop about 3 miles away. By the time I arrived, the temp gauge read H.

I had to wait about 30 mins to use the thermometer. We took initial readings - above the TS housing and below, radiator, upper/lower hose, front and back of engine. At that point the engine readings were 135 in the front and 140 in the back. Checked the temp gauge and it was at H. So, that tells me there is an issue with the sending unit or gauge.

Started the engine, revved it up to raise the temp. Focused on the TS housing and engine, we observed that at 181 degrees the TS opened and then the above and below temps on the housing read the same. The engine temp continued to increase, and the rear got up to 210 and stayed steady there. The front of the engine read 205. Had consistent temp readings on the hoses and radiator.

In summary, there is a 5 - 10-degree difference in temp between the front and rear of the engine. Interestingly, as I drove home the temp gauge started to move from H back to C but it only moved back a little and then went back to H.

So, I'll be doing some tests (or just replace) the sensor and gauge. I wanted to Thank everyone for your guidance and input, thank you Oz for staying on the thread. I am planning to rebuild or replace this engine in about a year or two. I will definitely make sure the heat riser valve is a part of that.

Make sure to clean out any sludge at the bottom of the water system on the engine accessed by block drain with a stiff piece of wire!

Ed

None of your temperatures sound like "overheating'. Keep monitoring them but if water isn't blowing out of your radiator cap, I think you're OK.

210 isn't even boiling, of course.

Of course the temp gauge will drop as you're driving. Fresh cool air flowing through the radiator as you drive will have that effect.

If you are using a infrared thermometer (pyrometer) be aware they often misread on shiny or semi shiny surfaces, a piece of black electrical tape on the shiny surface and the reading will be good, as mentioned before a cheap digital meat thermometer from the hardware or bbq store is great to put into the radiator, and also to confirm the infrared readings, btw infrareds do work well pointed at water, at least it does when it’s coming out of a faucet.

Not surprising it's hotter at the back. Water flows through the block then turns upwards into the head, across the head to the t-stat housing. Along the way through the block there are holes between the head and block which allows some water to rise and exit, the holes are sized so most of the water stays in the block, they progressively get bigger as you go back. Water exiting the thermostat is what you want to check, that will be actual temperature. Depending on the amount of crude build up, it could be hotter then normal due to no thermo transfer, and less coolant. If it stays around 200 you will be OK till you get time to clean it properly with a rebuild. Block temps vary a lot due to the thickness of the iron and how it was cast, core plugs are good place to check, they are thin and touch coolant.

I dont want to sound critical, but you are spitballing with the thermometer. Consider purchasing an under dash aftermarket temp guage. Electric or mechanicl, both styles are pretty accurate these days. Lets see what the water temp is by guage reading. Then you will know for certain whether you are having an issue or not. The factory temp guages are notorious for not being all that acurate.

Thank you all again for your insights and guidance.

Adding an aftermarket gauge would definitely helping in always knowing the temp. I would prefer to have it in a temporary capacity as I do want to keep the truck an all of its original parts as possible.