The Stovebolt Site Forums The Shop Area Engine Shop Temperature spikes, water pump failure?

Hello all
After getting my 1950 truck running around town after it being down for about 26 yrs
Everything is pretty much new except the body
Noticed new problem with temperature spikes
Just a few days ago after driving for a week
Temperature gets above 200, 7lb radiator cap opens and discharges. Temperature drops down to 180
Drive a little, temp spikes back over 200, cap open and discharges, temp back to 180
So I thought it was a sticky thermostat. Replaced the 160 degree thermostat, and installed 10lb cap
Drove around tonight after new parts and same issue; I noticed the hoses are not too pressurized, top radiator hose and water pump outlet

Warmed up my 49' suburban to compare it; the hoses are a little stiffer when warm than the 50' truck

So I think the pump is going out? I meant to replace it but I could not find the correct one. It's a short type with the impeller sticking out and going into the block. I could only find flush type ones

Also, to add
Before this, after driving for a bit, I can hear the block and/or radiator gurgle
So maybe air pockets in the system?

Also, to add
Before this, after driving for a bit, I can hear the block and/or radiator gurgle
So maybe air pockets in the system?

Is it a stock 6 cyl or modified V8? If it is a 6 you are running way too much pressure in the radiator. Get a stock (4-6 lbs I think) cap.

Lou, you might have already done this if you are concerned about air, but if not, try removing the temperature sending unit when you are filling the system. That will allow all of the air trapped inside the engine to purge through the top of the head while you are filling it. Put the fitting back in when coolant starts to flow through the hole.

Be sure that your valve cover is attached with a good gasket when you do this. If not, when the coolant weeps from the sensor hole it will flow into the exposed head. Don't ask me how I know this!!

Some guys will drill a 1/8" hole through the thermostat flange to allow trapped air to escape. I prefer to use ones with a jiggle pin that allows air to escape but also acts as a check valve to not allow coolant to flow through the air hole. The last 180 and 160 thermostats that I bought at Autozone (their Duralast store brand) both had jiggle pins.

Matt

I use a Stant #10203 cap. It's 0# which I believe is correct for your engine. I'm under the impression that only the 5000 series trucks had a pressure cap.

If the pump impeller protrudes into the block, you have a newer engine than the truck. The only 235's with that type of pump are 1955-up, and the pump has to be modified by pushing the hub back on the shaft with a hydraulic press and cutting off the front of the shaft. Somebody at one of the resto-ripoff places sells an already-modified pump, but you won't find one locally.

This would be a good time to swap to the high-mounted 216-style pump by using the relocation plate Pre-68 Dave sells on Ebay, which will also position your fan in the proper relationship with the radiator.
Jerry

Thanks to all that responded
Figures why I could not find a new water pump because of the protruded water pump
I think I have a 59' 235 with 848 head

Get an original-style 1950 water pump and relocate it with this adapter. Make sure all pulley widths match.
Use a 0-4 psi radiator cap.

Ok, took out the temp sending unit, water gushed out, no air
So on to thinking again what's going on with the temp spikes

Ok
Another update
Drove around, temp rose to 200+ went back home turned the truck off temperature held, waited like 15 seconds, restarted truck and immediately down to 180 and a little vibrating needle during idle
Did this again and same result
This is the 3rd gauge from the filling station and tired of changing these

These engines generate lots of waste heat. The more work the engine does, the more waste heat is generated and it has to be eliminated. If your system is challenged because of some problems, it will overheat as more power is applied. By the way the waterpump moves the fluid around but it doesn't pressurize the system. What I am saying is the waterpump will not cause your hoses to expand or stiffen up.

Just horsen around I heard everyone was running a 7lb? It's a stock 6

In 1949 and in 1951, a 0 psi radiator cap was standard on all but 5000 series trucks (4 psi on them - low-speed, many stops, delivery van type bodies/trucks).

The 4 psi radiator cap became standard in 1954 trucks.

Would a 7 psi cap cause problems with the radiator and heater?

I have been told that the radiator core will not endure more than a 4lb cap....but I have no idea whether that is true... right now I am running a 4lb cap

Sorry to be so scattered with the cooling issues, if I recall, when I had the 180 deg thermo it would not open in time before spewing coolant out the discharge line; that's when I changed to a 160 deg and 7lb cap. From there, the system operated correctly, but I did not have a chance to drive but a few miles before having to rebuild the transmission. During that time, I had bad luck with the Filling Station mechanical temp gauges for getting stuck all the way cold and one stuck all the way hot; this is the third gauge.
I have had this truck for 15 yrs, but this is the first time driving it; I still have not really found the reason why the PO stopped driving it since 1992 (last registration).
It has a new Jim Carter radiator, hose, etc. the engine is a 59' 235 with a 848 head.


I want to confirm, I am starting to think it may be a temp gauge problem? I am having a hard time believing it will rise to 220, hold, but when I turn the truck off and re-start after a few seconds, it will immediately drop to 180. Is this an air pocket or bad gauge? This is the 3rd filling station gauge I have had to use
I will likely test it tonight by removing the sender and comparing in a jar of hot water with a secondary gauge

Any and all help is appreciated, we have some great minds on this site with many years of experience. I just gave this truck to my dad last Wednesday for his 69th birthday, but I want it right so it does not break down on him

Thaks again

I know that this thread is kind of old but my truck does the same thing.I think that it is just because of where the sending unit is at. Mine is between the radiator and the thermostat. When it opens, the hot water from the engine hits the sending unit and it spikes. Once the cool water from the radiator is circulated though the engine the water temperature at the sending unit will be cooler and the gauge goes back down. I think when the sending unit is in the other end of the engine the gauge won't show the spikes like that.

Gene
Are you saying the sending unit is in the upper radiator hose? Mine is in the factory location near the number six cylinder (head)