CJ2A Fuel pump and overheating

1945 - 196*, Willys CJ series, questions, discussions, regarding anything related to the post war jeep.®
ph@5200
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Re: CJ2A Fuel pump and overheating

Post by ph@5200 » Mon Jul 27, 2020 6:13 am

thanks everybody. Sunday I tried again and started the jeep without the thermostat in ( the thermostat looked clean and not rusted when I took it out). With the cap off the jeep started and I noticed what appeared to be large bubbles coming out of the radiator neck. At the same time a new problem started. The carberator began to leak gas which seem to be coming from the top of the fuel bowl. Not sure if this is related or the float stuck.


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Re: CJ2A Fuel pump and overheating

Post by Rus Curtis » Mon Jul 27, 2020 7:36 am

I can guess your carb float or valve is sticking, but I'll leave that troubleshooting to smarter people. Scoutpilot has already been on this thread and has way more depth than me.

Overheating.
Disclosure: On my project, I had a new thermostat installed. It stuck and shot water out of the radiator (it had nowhere else to go). I tested it in a pot of hot water (using a thermometer to measure) and at first it stuck and only opened when I neared boiling. After repeating the test multiple times, it was more consistent and reliable with opening. Nevertheless, I replaced it - 'cause I didn't want a repeat while driving. I suggest testing yours for your own satisfaction of whether it's sticking or not, but regardless I would also suggest consider replacing it - after you are comfortable that the coolant is circulating properly.

**A properly functioning system, e.g. after flushing and filling, will initially draw what coolant you have into the engine. Top-offs are normal for a radiator as you do this. But after observing the temp gauge to show a rise in temp., you will note the top hose is warm but not uncomfortable (no water is circulating). But as the temp gauge approaches the number (whether you have a 160 or 180 thermostat), there will be a noticeable increase in the top hose temperature, and you will see a "river flowing" inside the radiator - indicating the thermostat has opened and coolant is flowing. There may be a need for more coolant top-off in the radiator. This cycle will keep repeating as the thermostat opens/closes. Eventually, the coolant level will stabilize inside the radiator but show flow as the thermostat cycles.**

You've already driven your jeep without a thermostat (previous post) and observed an overheat. Since you're running at a higher rpm than idle while driving, I'd assume all bubbles would be pushed out of the engine. Assume.
I don't know how far you drove, how hard you drove or how hot it was during the drive but have a hard time visualizing that if your cooling system was full and unrestricted, you would still overheat. I would instead default to the engine running cooler than it should and not ever reaching operating temperature. I may be wrong. But this is why I keep asking about leaks. If you are leaking coolant out, you can wind up with an engine block that has an air pocket leading to an overheat. The weep hole on the pump can trickle almost unnoticed until you have lost most of your coolant. Sometimes it only "weeps" under pressure (driving) or may not show a leak until after parked forming a puddle underneath. Checking the radiator level often will help you keep tabs on it - especially if you don't see any droplets on the engine or garage floor.

While I'm at it, anything can leak; A radiator cap, a hose itself or a connection, a radiator, a pump, different engine gaskets. The one constant will be a lower coolant level in the radiator. Mostly, you see evidence of a leak somewhere. Spray, steam, drips, etc. With the cap off, there won't be any pressure increase. If no leaks are observed, seal the cap and let the pressure develop and continue looking for leaks. Sometimes, I've had to use paper towels to dab where I can't look (engine off and somewhat cool) before I can find a leak.

Any air pocket inside the engine can contribute to over heating. The sending unit for the gauge is located high on the engine and if not "under water" can measure higher steam temperatures. Many will drill a hole in the thermostat flange to assist with "burping" air after servicing the coolant system - I did this to my replacement thermostat. Since you saw bubbles come out (from your previous post), I would suspect air was inside your block. I could also "assume" your pump is functioning (but will hold off on that for now).

As the engine idles, the pump will push coolant into the engine block (drawing from the bottom hose). Idle may or may not be enough to drive the bubbles out. You can increase idle speed (1500-2000rpms) by ear, i.e. fast idle, to increase pumping. That should clear all bubbles. Then you should just see coolant moving across the top of the plates inside the radiator without any surges that could become gushers coming out of the neck. You've removed the only restrictive device (thermostat) so there shouldn't be any "backup" within the radiator.

If you do have backup, your radiator may have some blockage and may need help from your local radiator shop.
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Re: CJ2A Fuel pump and overheating

Post by Scoutpilot » Mon Jul 27, 2020 7:57 am

To your knowledge has the radiator ever been cleaned, rodded and cored? Is it new, old, showing signs of blue/green staining anywhere?

Before you began to work with the carburetor did you flush the fuel system of old gas and inspect the interior of the tank and the lines for corrosion? Leaking from the top could be a stuck float, but more likely it is trash in the needle and seat.
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Re: CJ2A Fuel pump and overheating

Post by ph@5200 » Wed Aug 05, 2020 9:18 am

Put a new water pump on and fixed the carb, I think it was the float. Running like it should. Thanks for the help.


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