Major Overheating Problem!

[1964Stepside]

Hi all.

I just yesterday picked up a 1964 D100 Stepside here in the Bay Area and had to stop 6 or 7 times on the way home to fill the radiator again and again. All the water would boil off after only about 10 minutes of highway driving.

The original engine has been replaced with a 318 v8 from a 1969 Dart. I presume the radiator is stock, but am not certain.

Here's what I know about the non-cooling issue so far:

1. There is no overflow tank, and only an empty hole in the side of the radiator fill neck where one should go. There is no metal pipe where the rubber hose would connect, only a hole. Obviously, this pipe was broken off at some point.

2. The radiator cap has a vent lever and the gasket barely goes down far enough to cover the overflow tank hole. When the truck heats up, pressure from steam and hot water push the cap gasket up and start spewing violently from the hole, eventually draining the entire contents of the radiator.

3. I have confirmed that the radiator itself is not leaking and is not blocked. It has unimpeded flow from top to bottom.

4. I took out the thermostat during one of my refill stops hoping that maybe it was stuck and that was the problem. It wasn't and the overheating continued, even with the thermostat absent.

5. During another of my several stops, I filled the radiator and left the cap off while the truck idled for around 15-20 minutes. During this time it did not overheat and water never boiled out of the radiator. Very different behavior from driving it for even a few minutes. This can probably be accounted for due to the difference in heat generated when the vehicle is merely idling versus when it is running under load at highway speeds.

6. To test whether the water pump is working, I disconnected the top return hose from the radiator and started the truck expecting to get a steady flow of water as the pump circulated it through the engine. Instead, I got several "bursts" of water from the hose, but did not get a steady stream of water. Also, there would be several seconds in between bursts of water when there would be no flow whatsoever.

All this leads me to think that I probably have a bad water pump. Either this or I have a blockage in the actual engine block. Is that even possible? It's more likely a bad pump, right? I can only hope.

I'll be posting pics of my new project a little later, but I really need to get to the bottom of this overheating issue so I can drive it to pick up parts and such.

I appreciate any tips, suggestions or other trouble-shooting steps I can take to figure this out!

[truckluvr]

Your water pump test will not work like that because it will suck air which is causing your surges. Simplest way to check is with the engine at operating temperature and the radiator full, look in the filler cap. If the pump is working and the thermostat is open you should clearly see flow but water pumps will pump water until they explode. Don't ask me how I know... Sounds more like a blown head gasket or something because if your pressure cap is working properly the only way to exceed 15psi in the coolant system is by overheating or exhaust gasses. Do you have a temp gauge that is working? What is it showing while driving? If you suspect the radiator is inadequate just find a good 2 core radiator out of a 70's car or truck and install it. You may need to drill some new mounting holes in your core support but at least you'll know it'll cool better. As for your question about the block being plugged... It's possible but not likely. I've torn down 100's of motors and never found one plugged enough to block flow BUT I've seen them REALLY bad. Usually from people using plain water for many many years in the coolant system.

[1964Stepside]

The temp gauge doesn't actually have any numbers. There is an L, then a tick mark about 1/4 of the way across, one in the center, another at the 3/4 position, then an H. Once I start driving on the highway, the gauge steadily rises, until it hits High in about 8-9 minutes. By then steam and boiling water are spewing from the hole in the filler neck and other drivers are honking and eye-ing me warily...

If I only disconnect the return hose from the radiator to see if water flows, where would the water pump be getting air? From the disconnected return inlet? I've been told this was a reliable test for a failed water pump.

Your comment about the head gasket has me very concerned, because I know that is a major problem requiring an expensive rebuild, which I cannot afford right now. What else can I do to diagnose whether it is, in fact, a head gasket issue? Also, how would a blown head gasket cause these symptoms I am experiencing, especially the overheating? I'm not familiar with the problem.

Thanks for your reply!

[Oldguy]

A blown head gasket will allow combustion gases into the water jacket. This super heats the water and causes it to boil. A quick check is fill the radiator and fire the engine with the cap off. If you have a blown gasket you will see bubbles in the water. As stated earlier watch the water to see if it's flowing. I have seen water pumps that the impeller blades rusted off and wouldn't pump water any more. Good luck with the truck. Mike

[1965D100]

I'm thinking blown head gasket too...

Also check the oil, see if it has turned to sludge... If so, you got coolant leaking in...

[surfnuke9]

A blown head gasket would also have caused this behavior during his 15-20 minutes of idling that he mentioned.

New water pumps for a 318 are pretty cheap. I would try that first along with a good thermostat that you have tested to make sure it opens at the right temp. (I would use a 180F)

[1964Stepside]

Thanks for the tips guys.

I ran a few checks for a blown head gasket, but didn't really see any of the typical symptoms (no white steam in exhaust or coolant smell, no sludge or coolant in oil, etc.)

But, I have made some small amount of progress. A fellow on another Sweptline forum mentioned that maybe the lower radiator hose was weak and compressing under load. I found this to be true and replaced it with a hose that has the wire coil inside... no more collapsing hose.

I also JB Welded in a 1/8" brass fitting into the filler neck hole where the overflow tube had broken off. However, I don't yet have an overflow tank.. it's on order and the original is absent from the truck.

When I took it on a test drive, the temp gauge did not go all the way to High, only to about the 3/4 mark, so it seems within range. However, the radiator still boiled over and spewed steam and water violently from the newly installed overflow tube. After I parked, it continued to do so for about 3 full minutes until the radiator was bone dry. Once again, I added almost 2 full gallons of water to re-fill the radiator. I haven't added any coolant since this problem arose because it's silly to spend $12-15 a gallon just to have it boil off in 15 minutes.

I have yet to pull the water pump. I'm thinking I'll just buy a new one and pull it when I'm ready to install the new one instead of tearing it apart twice.

Any other ideas based on this new information?

Happy 4th!

[Dustbuster]

Swap the thermostat for a new 180 degree and get a new raeiator cap rated for the correct pressure. If that ALL doesn't work, pull the water pump and visually inspect the impeller and bearing. You should have seen major spew and nasty noises if it was the pump. Any idea how the engine swap was done and in what timeframe?

[elacruze]

What do you have on it for a fan?

I did this to myself once, had the exact same symptoms. Good at idle, overheat going down the road.
I bought a truck with a flex fan, didn't like it so stopped at a pick-n-pull for a clutch fan. Happy, no noise and should cool better.
But the fan was from a serpentine setup, and had the opposite rotation. It was blowing out the radiator, and when met with road air got no flow through because of the competing pressures. Bummer, Hal.

Don't overlook the obvious.

[1965D100]

Pull the pump as mentioned before. You might have some clogged engine inlet holes.

Clogged passage way:


Bad water pump:

[1964Stepside]

I have a new water pump coming in the mail... should be here in a few more days. I haven't pulled the trigger on a new radiator yet, want to get the old pump off, new pump on then see what I've got. New overflow tank is on the way too. I'll get a new cap from Kragen. What is the "correct" pressure? 14-15psi?

I've taken the thermostat out completely while I troubleshoot the overheating issue so that's not a consideration. Hopefully the new water pump, along with the new overflow tank and cap will solve the issue. Even if so, I'll eventually replace the radiator with one of those fancy aluminum 3-row jobs just so I know. Got plans for an engine oil cooler as well... Once I get it running cool, then I'll replace the thermostat and connect the heater hoses. While too much is never good, a little heat properly directed is always nice.

I don't know when the motor swap was completed. The guy I bought it from wasn't the one who did it and couldn't tell me anything about it.

Will update when I've made progress... waiting on UPS.

[1965D100]

Call your local radiator shop and see how much they charge to refurbish yours. Mine ended up on $75, good as new.

[BradyB]

Maybe my recent experience will help:

I have a 383 ‘70 swepty that hadn’t been driven regularly in over 10 years, I topped off the fluids and drove it home fine. I rebuilt everything I could get too, carb, belt/hoses, water pump, ignition, etc… The water pump looked good but it was leaking fluid and so I decided to just put on a new one while I had it apart, my truck had 54,000 miles at the time and there was very little corrosion around the pump and in the water channels.

With it getting hot lately I’ve had a few problems to work out. First off, running a hose out from the engine bay for the overflow, there never was an overflow tank, just a drain line. I flushed the fluid until it stayed clean which required me to run a water hose into the radiator and let it idle for a long time while disconnecting the lower house occasionally to drain the system. The system now stays nice and clean with out any rust in the fluid. I took out the “new” 195 degree thermostat that I don’t think was opening very well and purchased the extra expensive $9 180 degree thermostat. I installed a viscous silicone fan drive with a higher pitch 5-blade fan. It sucks more horsepower when it gets hot but at least it’s pulling more air through the radiator. I went to the junk yard and pulled a fan out of a 91 Dakota, I got a new fan drive for a 73 A/C big block D100.
The biggest difference I got was just replacing the radiator cap. The old cap had lost it’s ability to seal and that’s why I had been getting the fluid to boil over often.

I had an excellent test the other day, I was driving on the freeway with a good 35 MPH head wind, 95 degrees, and going 70 MPH with the engine over 3000 RPMS. The temp gauge was pegged at the far right but it did not go past the last tick mark all the way over to H. When I got where I was going I should have let it idle but I turned it off immediately and it boiled off its extra fluid in the parking lot. I haven’t put any additional fluid in it since then and it seems to be fine. Driving at 65 MPH makes it hot no matter what I do. It’s not over heating it just runs hot.

I stole my wife’s candy thermometer and stuck in the radiator. I let it idle and get nice and warm and then I put a towel on the front of the radiator to see what how hot I could get it. I was testing the thermostat mainly, I got the fluid up to 195-200 degrees and it was moving nicely through the radiator. The water movement changes with RPM remember, if you push the throttle and watch the fluid it will move a lot of volume through the radiator at about 2,000 RPMs. With the candy thermometer reading 200 degrees and the stupid dash temp gauge was past the middle mark. So I’m guessing that the middle of the gauge is about 190 degrees and the right H mark is about 220-230?

Driving home last night at 50 MPH the truck was happy with the temp gauge right in the middle. My trucks seems to be happiest at 45 MPH with plenty of air flow, the water pump moving a lot of fluid and the engine humming along at less then 2,000 rpm. I’m just planning on not pushing my truck when it gets really hot. If I want it at 200 degrees all the time then I’ll just have to get a larger radiator made.

As an FYI, my owners manual states, “Maintain coolant at a level 1 ¼ inches below the bottom of the filler neck.“ In regards to flushing the system the manual states, “On the 8 cylinder engine there are two plugs to remove (one on each side of the cylinder block).” I did not pull these plugs as I wasn’t sure where those plus are or how I remove them.

Good luck Buddy.

[BradyB]

And, don’t run your engine with out a thermostat, it will run cooler initially but the engine will begin to heat at different rates and cause a lot of thermo stress. The coolant moving fast through the radiator doesn’t even guarantee that it will run cooler. The water will run faster through the radiator and you might not get enough heat transfer. You’ll go from running cool to overheating very quickly- believe me, I know from experience.

[Hobcobble]

Assumptions:
a)Engine/heads/manifold coolant passages are devoid of blockage[s]
b)Radiator is of the proper size [H x W x Core Count] for your engine
c)Water pump is of the proper impeller configuration for HD cooling

Other things to consider:
1)7psi rad cap
2)Properly functioning thermostat
3)Small .125" hole drilled in thermostat flange
4)Stock 6-blade fan at the proper distance from the core
5)Fan installed correctly [not flipped over]
6)Fan shroud installed
7)Composite rubber "air dam" installed on the upper core
support that rests on the top rad tank. This piece keeps
your incoming air flowing through the core and not over
the top of the rad.
8)Proper ratio for your region for the water/coolant

John

[BradyB]

One more idea. Check the tranny fluid (with it in neutral and running). If your radiator includes a tranny cooler, some hot tranny fluid could increase the fluid temps. My truck was a quart low on tranny fluid and since I’ve filled it back up my coolant temps seems to be a bit cooler.

I know guys, I need to fix the tranny leak! My local dealer has the hard plastic reusable pan gasket for $16 (2464324ac).

[1964Stepside]

So, I've made some bit of progress... but I'm not sure if it works yet because other issues have manifested and I can't even start the damn thing now.

I'll be starting a new thread detailing my new issues, but as for the cooling problem, here's the latest:

I got a new water pump and 3 core aluminum radiator installed and my overflow tank is still in transit. The guy was on vacation for the 4th and shipped it late.

The old pump seemed to be fine, no rust whatsoever and it turned properly when the fan/pulley mount was turned. I replaced it anyway, just in case there was some "hidden" defect, although that's not likely.

Please see my new thread for the new problems/issues.

Thanks.

[dwightlightnin]

dont over look a air lock in the cooling system.Every time i put a new pump,radiator or hoses i pull the thermostat when i fill it back up with coolant because if youi dont and the thermostat isnt bathed in liquid it wont open and you will over heat fast.Ask me how i know.