ENGINE TEMPERATURE AFTER SHUTDOWN

[joel gopan]

One of the idiosyncracies of the CCKW 270 is see the Temperature Gauge climb from its operating temperature to the neighborhood of +200F immediately after shutting off the engine. It will do so even as you exit your CCKW. That is normal. Mine runs at 175-180 Degrees F with the OEM Harrison thermostat, and also does what I just mentioned.
Joel

[Corne Lauwerijssen]

mine is doing the same, i have a 160 fahr thermostat

aLways let the engine cool down for about 5 minutes, this
to prevent cracking of the manifold.

Corné

[joel gopan]

Best way to prevent manifold from cracking in the usual place is to put the control lever in the Summer Position and leave it there year round.
Joel

[pfarber]

I thought it was just my engine that did that.

It also seems to spit out water (no overflow tank?) just after a topping off with antifreeze.

[dr deuce]

One day, I will make a special steam relief tube for one of my CCKW engines to try an experiment by installin a valve in it like the Chevys. All the WW2 mil Chevys, both US and Canadian have a valve on the steam relief tube with a tag that tells you to only open the valve when going up and down steep hills.

I have to wonder why the Chev shuts it off and the GMC leaves it wide open all the time.....

The steam reilef tube by the way is an odd diameter that is not readily available.

When you have a 160 thermostat and the temp outside is 90, you don't have much to play with for temperature differential!


Steve AKA Dr Deuce

[armydriver]

Again premier information from Joel and Doc. Thanks guys.

[joel gopan]

Early CCKWX,CCKW, and CCW used a Steam relief Tube, but it was discontinued at some point, and a bullitin was issued to install a kit that capped off the steam relief tube, layer in 1944 instructions were given to just crimp and solder the tube at the radiator, as the Cap GM 2175161 and Clamp GM 178302 are no longer available. Hey Doc, if GM said it was OK to do away with the system, it must be safe. They only had a half million plus CCKWs out there,and the GMC Technical Service Manager signed off on the change.

Joel

[dr deuce]

Not what I was talking about Joel:

As far as I know, they all had what was refered to as steam relief tube. It is just later ones did not go to the radiator. It went to the thermostat housing. The early ones went directly to the radiator.


Steve AKA Dr Deuce

[joel gopan]

Steve, I was talking Steam Relief Tube Part No 2141107 that goes to radiator. The other is called the Cylinder Head Water By-Pass Tube GM-2137477, that goes only from head to waterpump on later CCKWs. It also was called a steam relief tube in manuals prior to 43, but was later corrected to Cyl head Water By-Pass. The Original Steam Relief Tubes were ordered disconnected at some point in 42-43, and most likely not all got the change.

Steam Relief Tube was installed in all CCKWX, CCW, and CCKW up to Chassis 193573(1942) All others used the Cylinder Head Water By-Pass Tube.

Joel

[joel gopan]

Steam Relief Tube was 1/2" OD. As for kicking out coolant, the first few times the truck is driven after topping off radiator, the excess will be kisked out the overflow, as it seeks it's own level. When properly filled, you will just be able to see coolant below the Inlet tube located in the upper Tank. (Provided your CCKW has an OEM Radiator. It will stay at this level provided that your system has no leaks and the Cap is functioning so that it maintains pressure.
Joel

[dr deuce]

Chevys had the valve on both versions and CCKWs no valve. Why?

I had to replace the tube on one of mine. Maybe it was 1/2" but it is not a common size. I could not find anyplace that sold soft bendable tubing that size.


Steve AKA Dr Deuce

[joel gopan]

I just gotta believe that GMC knew what it was doing, after all there were 562.000 beautiful CCKWs produced, almost 370,000 without them, and then they had a kit to cap off those that had the Steam Relief tube, until GM just said to pinch off and solder the Tube. The Cylinder Head Water By-Pass Tube 2137477 that probably all of us have was what they ended up with. I have had no probs with mine after 22 years, it does not overheat, lose or leak coolant. I have found that those who do have cooling problems with present CCKWs usually have a defect in the sysyem, plugged radiator core, bad radiator cap/gasket, leaking or kinked hose, cracked cylinder head, etc. We have to realize that things are more probable after 60 years and PM has to be done to ensure they run properly. Why wait for trouble. I get a kick out of the Chief Warrent Officer from the Maryland National Guard who most likely pulled rank to returm the famous WWII MB Jeep (Vixen Tor) to Europe 50 years later and had all kinds of leaks, and a plugged Radiator as they just fired up the old beast after nearly 50 years and did not properly prepare its journey. I would have liked to have been able to take it myself, and would have gladly serviced that Jeep at my own expense to do all that was necessary to ensure it be operational.
Joel

[dr deuce]

The "I have to believe that GM knew what they were doing" has a great example:

The 'GMC clutch' is an example of them doing the wrong thing and causing great amounts of problems. Had they gone with the 10 and 3/4 Chevy clutch, there would be no label like that today. They did not need a non-standard 11.5 " clutch to hang onto 91.5 hp

Having worked in Engineering for years, I have seen the resistance to change something even when it is demonstrated that it is a defective/bad design or part. Hell I left one company because they had a product that needed just a little more time and money and the Pres stated that that was all he was going to spend, product and end-user be damned!

GM did lots of things in WW2 with these trucks. Mostly all of them were positive, but some were questionable to my Engineering mind.

The other example that comes to mind is the outer Banjo axle seal on the rears. There is NO comparison between that and the split seal. The Banjo seal was added as an afterthought and that is about how it works!


Steve AKA Dr Deuce

[joel gopan]

OK, but the Trucks function perfectly as designed, it is when we vary from the prescribed methods to maintain them, that we have problems. If repaired to spec. they give no problems. Don't cut the Engineers of the CCKW short, the CCKW did its job, and soldiered on for nearly 50 years with our allies,and some enemies. take a look at the trucks that the army has bought in recent years, and you will see Junk that does not perform due to poor design. Gamma Goat, Stewart and Stevenson 4X4 junk. I have a little engineering background and do not see the probs as flaws or afterthought. The CCKW was a "common sense" truck, simple and easy to maintain,and if driven and serviced as intended, it will make you smile. Remember, this truck was designed around 91.5 Horsepower @ 2750 RPM, try and stretch that HP and you upset the balance. The Army has punishment for acting stupid, civilian use of the CCKW does not. Too bad all CCKW owners are not Army trained on pre M-Series trucks.
Joel

[dr deuce]

Split axles were used on trucks with 320 cid 6 cylinder engines called US6 by some..... Ruskie's like em


Actually, the CCKW to me is about the best WW2 HMV you can own! It is years ahead of others in design. The OHV engine is easy to work on and with the exception of the clutch and a couple other minor items is very reliable!

I have put over 50,000 miles on my cargo CCKW since I bought it and other than a couple GMC clutches and the usual brake parts, seals etc have done nothing else. I went over 30,000 miles before I replace the engine that the manual says gets replaced at 10,000 miles


Steve AKA Dr Deuce

[joel gopan]

It may be 320CID, but the Brake horspower and Torque of the Hercules JXD and WWII GMC 270 are similar. If you look up the specs on the US-6 Studebaker, you will note that the peak HP (Brake HP) is actually less than the GMC.
Joel

[dr deuce]

I remember an article in MV or Army Motors, they had to run tests to see if the power train components could take the power of the JXD in the Stude


Steve AKA Dr Deuce

[joel gopan]

Check out TM9-2800, turn to Pages 274 & 275, there you can compare the Engine Specifications of the GMC 270 and the Hercules JXD side by side. Bigger is not always better. Note that the Brake Horsepower for the 270 is 91.5@ 2750RPM and the JXD is 87.0 @ 2400RPM.

As for Torque, The 270 Develops 216 Ft/lb@1400RPM
The JXD Develops 228ft/lb@1200RPM

Engines develop their Torque at a point much lower than the Max Governed RPM.

As for Brake Horsepower, that is defined as "Available HP", and that is developed a higher RPM than the torque, and drops off as RPM exceeds the speed at which the Brake HP is rated.

Draw your own conclusion, but the JXD is not a powerhouse when compared to the CCKW 270 engine. The Torque does come up a bit quicker on the JXD, but at Highway speed yhe CCKW is more powerful.

Draw your own conclusion.
Joel

[dr deuce]

Having owned a genset with a JXD(L) in it, I am glad I have the GM engines! They can say all they want about longevity, but as far as ease of repair, the GM engines have it over all the WW2 engines I have seen!

Why did they have to run tests to see if the JXD was too much for the splits?


Steve AKA Dr Deuce

[joel gopan]

That is what Proving Grounds are for. It is better to wring out the Army's equipment over here, than send them off to war to find out that they will not perform. I wish there was a way to see the results of the tortures they put new vehicles thru at Aberdeen, Detroit arsenal, Holabird etc., during WWII. A lot of the supercessions in the SNLs are a result of continued testing, and "in field" reports. There were kits available to update, for example Carburetors and Air Cleaners due to the laws of physics, there were changes to the bracing of Shop Vans to prevent cutting tires, Winch Gearbox Vents were modified,Trunion Bar seals were changed to neoprene,Fuel Pumps were improved, axle stops were developer to prevent axles from damaging Oil pans, tire treads were redesigned, Chassis were improved, Pitman Arm Diameter Increased, instruments were tpopicalized, Hot Climate Radiator, Radio Suppression was added, Rocker Arms were modified, Oil lines improved, Radiator overflow kits were introduced, Storage boxes were added to Open Cabs, Mudflap design was changed in 45, U-Joints were modified to allow better lubrication, steam relief tubes were eliminated, Exhaust manifold stud hole sizes were altered to allow expansion, rear wheel cylinders were zinc-dichromare coated on outside to prevent corrosion,front bearing retainers were redesigned on Banjo Transfers, to provide an oil dam, lube level plugs on Banjo steering knuckles were relocated. Lube oil fillers were raised on transmissions to increase capacity, pillow blocks were upgraded, PTOs were modified with improved shifter boots and guards, piston rings were changed around, valve clearances were changed, head Bolt Tightening sequence was changed, Pillow Block Lube went from oil to Chassis grease, Torque Rods went thru a change, SWB Tire brackets were modified, Voltage regulators were improved,Rokker Arm Covers were reinforced, Distributors were updated, Demountable brake drums wrere introduced, Hi Traction Differential gears were introduced, Radiator Core Support Mounting Bolts were upgraded, cranckcase ventilator air cleaners were modified,Crankcase Ventilator Valves were upgraded, Timing Specs were Changed, Generator Mounting Brackets were reinforced, then upgraded on production line to cast iron, oil pan gaskets were improved, Cast iron carburetors were introduced, Brake Hoses Rerouted, Fording kits were introduced, Heater kits were introduced, Hydrovacs were upgraded. Hydrovac Breathers were relocated, Light switches were modified, BO Drive Lights introduced, Fuel Tank Necks Changed,I could go on but this will give you a feel for the attention paid to the CCKW in order to make it more durable, or to improve performance.

I almost forgot, Governors were upgraded.
Joel