M109A3 (M35A2) Shop Van overheating .... my steps to cure

brit4x4

New member
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Jackson, CA
TL;DR;
Summary.
NOS Water Pumps will weep for 10 to 15 minutes after installation, mount the water pump with the weep hole up so that you can see when it stops weeping. If you are worried about debris falling in the hole coat it with some grease. If the seal starts to fail the water will push past the grease and with the hole at the top it is much easier to check.
Also, with the NOS Water Pump installed and before putting the radiator back in, run the fan mounting bolts in and out of the holes a few times. The NOS pumps have paint and possibly rust in the holes that will make attaching the fan super difficult if you don't do this.
Loosen the 4 bolts holding the radiator platform to the the front of the chassis, it makes removing and re-installing the lower hose much easier.
Fill with water only initially in case disassembly is required or leaks are found.
Temperature gauges may not tell the truth ... more to come on this.

The Story.
Last year, 2021, I moved the 120 miles from Santa Clara California to Jackson California. I have a 1975 M35A2 and a 1967 M109A3 Shop Van. My son drove the Deuce and I drove the 109. The first 20 miles were fine then the 109 started spraying rusty water from under the hood. Our 4 hour journey turned into closer to an 8 hour journey. Stopping every 10 miles or so to top off the water. The temp gauge was pegged at 240. We made it despite the outside temp being over 100 degrees as we drew near to Jackson.

Dismantling and flushing
I finally had the time back in March 2022 to start dismantling the cooling system. To help the radiator removal I loosened the 4 bolts holding the platform that the radiator sits on, this gave that extra bit of wiggle room that helped get the lower hose off. The radiator overflow tube was blocked. Flushing the radiator produced some nasty muck. I purchased one of those engine flushing tools that uses compressed air to force the water through the block. I removed the thermostat and the water pump including the housing. with those off I could flush via the top port (behind where the thermostat housing connects) and via the pipe that leads to the oil cooler. A lot of nasty stuff came out and I flushed back and forth until the water was clean and flowing more quickly.

Reassembly and some interesting lessons.
In the end because the bottom mounting on the radiator had rusted badly I opted for a new one from C and C Equipment. Nice black brand new radiator, the packaging wasn't great and I let them know, luckily there was no visible damage. However, the top hose connection is offset by about 3/4" from the thermostat housing port. I have managed to get them connected by using a longer piece of 2" ID hose, we will see how well that works. Again having the radiator platform loose made it easier to fit the bottom hose that is always a pain.

Water pump revelation :) the old water appeared to be ok, but I had a NOS one in the parts box, so I figured new radiator new pump. I bolted everything back together and filled the system with just water, I did not want to waste anti-freeze if it turned out that there were leaks or there was still a problem. I noticed that there was a leak, as I traced it I could see that it was the NOS Water Pump, and it looked like it was coming from the bearings. Radiator back out I took the water pump off and that is when I noticed the "Weep" hole. To verify that the water was coming from the weep hole I mounted the pump back into the housing with the weep hole at the top. I did not want to have to reinstall the radiator just to fill it with water to prove the weep hole was the source of the leak, so :) I purchased a shop vac step down hose adapter that fits perfectly into 2" ID pipe and then a rubber 2" rubber pipe cap. I cut off the unwanted part of adapter and inserted it into the bottom hose, with the rubber end cap. I removed the thermostat housing and filled the water pump. The weep hole, now facing up, was definitely the source of the leak. Well poop, I guess I need a new pump :-( but not wanting to give up I did some research, this is what I found :
"New water pumps need at least 10 minutes of idle time before the seals settle and the weeping stops", "yeah right" I am thinking. But I gave it a go, everything reassembled, filled the radiator, with water coming out of the weep hole but kept going until the water level was at the bottom of the filler neck. Then started the engine and stood there hose ready with water coming out of the weep hole and being flung everywhere by the fan. Slowly but surely the weeping stopped, I didn't time it but probably 10 to 15 minutes. Moral of the story don't give up on your NOS pump too quickly.

When the engine was overheating spraying water on the journey from Santa Clara, I had no idea where my laser thermometer was, so no way to verify the temps of cooling system components. The temperature gauge was pegged at 240. After reassembly, including a new temperature sensor I was hopeful that temp gauge would sit vertical at about 180. Nope, it climbed on up past that to about 220 and sat there. However, my laser thermometer was giving readings of 176 max and way less when pointed at other cooling system components. The thermostat is supposed to be fully open at 180, it was definitely open because the top hose was now hot and so was the top of the radiator. I now need to test the temperature gauge . It could also be corroded connectors and/or a wiring issue. I will post more as I find the causes and solutions.
 

williamh

Well-known member
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SanDiego Ca.
Gauges , sending units are not really as accurate as we would hope. More of a guide , loose wires , bad grounds etc. years of shaking around will cause things to go out of calibration. I have watched mine just start bouncing all over on a flat pice of ground. Put in a different gauge , sending unit and still. Gotta be a bad wire somewhere. Haven’t found it yet. Not too much in a rush. STILL HAVEN'T GOT MY SF97 🤬
 

ToddJK

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Steel Soldiers Supporter
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Sparta, MI
When my temp gauge went out, it was mostly the wires that was the problem. Very brittle and old. Had to re-wire the gauge to the sending unit. Even though I replaced the sending unit, gauge, and wires. Works now as it should and seems to be accurate thus far. I can tell when it runs hot, engine sounds and smells different. Even today as one of my brakes stuck, that engine was working hard and normal temp is around 165-170. It was getting up to 210 and it just sounded very different. Due to my flame heater line melting on the air intake and allowing air to get into the system and a loss of fuel pressure, it led to numerous issues, but if you know your truck, you will generally have a good idea when it's over heating.
 

brit4x4

New member
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Location
Jackson, CA
Update on the water pump - The vehicle has not been driven much since all the new cooling system parts have been installed.
Today I popped the hood and started her up. Always amazed at the instant start even after sitting for nearly a month.
The laser thermometer is showing temps below 170 everywhere but the gauge is way off.
Water droplets started hitting me, I looked down at the weep hole (I mounted it up, and plugged it with grease to stop dirt getting in) water was pushing passed the grease in a steady stream. I was only able to let her run for about 15 minutes, perhaps a longer run will again cause the seals to come to life.
If not does anyone have experience with getting a NOS Water Pump to seal ?
 

rustystud

Well-known member
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Location
Woodinville, Washington
Update on the water pump - The vehicle has not been driven much since all the new cooling system parts have been installed.
Today I popped the hood and started her up. Always amazed at the instant start even after sitting for nearly a month.
The laser thermometer is showing temps below 170 everywhere but the gauge is way off.
Water droplets started hitting me, I looked down at the weep hole (I mounted it up, and plugged it with grease to stop dirt getting in) water was pushing passed the grease in a steady stream. I was only able to let her run for about 15 minutes, perhaps a longer run will again cause the seals to come to life.
If not does anyone have experience with getting a NOS Water Pump to seal ?
Water pump seals do not "regenerate" with use. More than likely your seals are dried out and now that you used it, they are torn up. Also the weep hole is supposed to point down not up. That way you're not spraying coolant all over your engine when the seals go bad.
You can rebuild this pump really easily, and replace the seals with new modern "neoprene" or other materials that will last far longer than the old "rawhide" type seals found on "NOS" pumps.
 

cattlerepairman

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NORTH (Canada)
Further to @brit4x4 's water pump observations: I also ditched the 600 lbs cast iron rotating radiator destructor (the metal cooling fan; I might have exaggerated) and replaced with a cheap plastic one from Summit Racing. I used the largest diameter fan that fits into the shroud with trimming the fan blades (with a pair of scissors).
Why? The rotating mass of the metal fan is added wear and tear on the water pump. If the rad or fan ever move, the plastic fan is unlikely to tear the rad to shreds. The plastic fan moves A LOT of air. I was concerned about effectiveness, but the plastic fan is as good or likely better than the metal OEM fan. Oh, and when accessing nuts and bolts at the front of the engine I can simply push a fan blade with my hand and slide past without leaving a pound of flesh behind, as it happens with the metal fan!

Here is the post that made me think "nope, I do not need THAT": https://www.steelsoldiers.com/threads/some-days-are-good-some-not-so-good.61662/page-3

Look at post #46.

The stock Deuce fan is 20" diameter and the Summit flex fan 18" fits just fine: https://www.summitracing.com/parts/flx-104465
 
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rustystud

Well-known member
8,901
1,707
113
Location
Woodinville, Washington
Further to @brit4x4 's water pump observations: I also ditched the 600 lbs cast iron rotating radiator destructor (the metal cooling fan; I might have exaggerated) and replaced with a cheap plastic one from Summit Racing. I used the largest diameter fan that fits into the shroud with trimming the fan blades (with a pair of scissors).
Why? The rotating mass of the metal fan is added wear and tear on the water pump. If the rad or fan ever move, the plastic fan is unlikely to tear the rad to shreds. The plastic fan moves A LOT of air. I was concerned about effectiveness, but the plastic fan is as good or likely better than the metal OEM fan. Oh, and when accessing nuts and bolts at the front of the engine I can simply push a fan blade with my hand and slide past without leaving a pound of flesh behind, as it happens with the metal fan!

Here is the post that made me think "nope, I do not need THAT": https://www.steelsoldiers.com/threads/some-days-are-good-some-not-so-good.61662/page-3

Look at post #46.

The stock Deuce fan is 20" diameter and the Summit flex fan 18" fits just fine: https://www.summitracing.com/parts/flx-104465
The trucking and transportation industry went to plastic fans decades ago. There just far better than the metal "spinning blades of death" fans. Plus they save on fuel too. Less parasitic drag on the engine.
 

brit4x4

New member
6
7
3
Location
Jackson, CA
Water pump seals do not "regenerate" with use. More than likely your seals are dried out and now that you used it, they are torn up. Also the weep hole is supposed to point down not up. That way you're not spraying coolant all over your engine when the seals go bad.
You can rebuild this pump really easily, and replace the seals with new modern "neoprene" or other materials that will last far longer than the old "rawhide" type seals found on "NOS" pumps.
@rustystud Thank you for the advice - where do I find the neoprene seals ?
 
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