Radiator

[Birddog7]

Folks, I am confused. I have been working on the 3A cleaning up the engine bay. Rerouting wires, new thermostat, battery holddown, etc. I had a hose running from the top of the� water pump to the top of the engine block. It went around the distrbuter, starter. Seeing how I do not have a heater I thought I could remove that hose and cap off the water pump and the top of the block. Since then the coolant has been flowing out the overflow tube right away when I start it. I thought I installed the thermostat wrong. I checked that and it was okay. I can run the engine for 45 sec and it starts pushing coolant out right away. You should be able to cap off like I did. What in the heck am I missing. Got super frustrated had to walk away (Have a electrical problem too, Battery not charging, ugh)

[1955CJ-5]

I think I read somewhere that if you do not have a bypass hose..that other little 4" hose that runs from the top of the water pump to the head, then you need to run a heater or at least a heater hose like you had before...I think the circulation is necessary for proper cooling........


But now the more I think about it, the heater was an option...so it should be fine without any of the plumbing....

Perhaps you have an air bubble somewhere?

[Carls_jeep]

The heater supply comes from the rear of the head and the return goes to the suction side of the water pump. You can't eliminate the bypass hose, at least it's not a good idea to do that.

[garage gnome]

My '49 didn't come with a heater and the port on the head was plugged and so was the one on the water pump. You can eliminate it.

[F Bill]

The heater supply comes from the rear of the head and the return goes to the suction side of the water pump. You can't eliminate the bypass hose, at least it's not a good idea to do that.

I am not aware of a bypass hose on the flathead or the F head 134 engines.
It sounds like someone just eliminated the heater with a loop of hose.

I do know that drilling a small hole in your thermostat to let air bleed thru when refilling the cooling system is a good idea, if it is not already there. Otherwise there is a chance you will have an air bubble in your system and it may overheat. Original stats had the hole, sometimes with a loose pin in the hole, but many aftermarket ones do not.

Also, do not fill your radiator to the top like you would on a modern car. There is no place for the extra to go as the coolant heats up and expands...so you need to leave some air space in the top tank. I usually keep my DJ about an inch below the top of the neck. It is hard to see with the baffle in my radiator but it naturally ends up there if you overfill. There is no overflow recovery system to save what is forced out but you could add one if you wanted.

[Carls_jeep]

Your right Bill, there isn't a bypass on the L134 so he won't be able to remove it.

[1955CJ-5]

The M-38 flat head had a bypass hose. And typically the military flat head did not even have the heater/water port at the back of the head drilled. I don't have a picture but i have this picture of my F-134 CJ-5 engine. It too has a bypass hose.

Just so we are on the same page, it's that little 90 degree hose that goes from the other threaded fitting in the water pump to the head..

[F Bill]

I went out to the shop and looked at the MC engine I have which does not have a bypass hose from the water pump, and at the F 134 drivetrain I have which I assume came from a 3B or CJ5, and neither has the bypass hose. I also had a MC engine in my old GPW, no bypass. I've got another in the barn and if memory is correct that one is the same as the one I have in the shop. I wonder if I have non M 38 heads?

However, as we have learned....never say NEVER with Willys. I haven't see that style of bypass before ....but it sure is a bypass on a F 134.

Anyone got a pic of an M 38 bypass hose to share?

[1955CJ-5]

Never say "never" with Willys and never say "always"...

I googled M-38 bypass hose or maybe engine and found a couple of pics....but i don't know how to copy them over here....

I found this..you can see that the port in the rear of the military heads are not drilled.....mostly...!

http://ww2jeeps.com/htm/heads.htm

Birddog,

Did you find you problem?? Maybe a bubble under the thermostat? I've read that guy's often drill a couple of small holes in the thermostat to help the bubbles escape before the thermostat opens...and before it overheats....

[Birddog7]

No, I still have a problem. Let me go over what I have done so far again. I removed the hose put a pipe plug in the water pump. I tried shuting the valve on the head it would not turn, then tried to remove the whole valve but it would not budge. So I took a small piece of hose pluged one end and clamped the other to the valve. So when I started it to check out my electrical problem. It started over flowing. I removed the thermostat checked it was okay and moved freely. Refilled with water,ran it, 165 deg. Happy Happy put cap back on. Next day started up again, same problem again in 30-45 sec, I since have put everything back the way it was. Today was interesting, started up, no overflow. But the bypass hose and bottom were really hot like normal. The top hose was COLD to the touch. the temp was on its way to 210 degrees. Shut down quickly. Then in about a minute. It sounded like Miss Sharon was coughing up a hair ball. Thats when I figured out the  thermostat was opening up. The top hose got hot quickly. I have new 160 deg thermostat installed. I had a 14 psi cap on but went to a 7 psi cap. I do not believe the rad caps or pluging the the heater outlets are  the issue. I believe it in the Thermostat. If my memory is correct there use to be a little 1/16 in hole in outer rim of the Thermostat to relieve the pressure of the water pump. Okay I am looking at two new 160 degree  Thermostats now they have a 1/8 inch hole next to the brass capillary with a little flapper in it. I will change out the Thermostat tomorrow again and see what happens. I probably got the only new Thermostat that did not have the hole in it.  The saga continues. 

[Carls_jeep]

Take the bypass hose off the engine. All your doing is running hot water out of the head and directly into the water pump and putting back in the engine. Put the plug back in the water pump and take a pipe wrench and remove the valve in the head and put a plug in it. Those two openings are only for the heater, not anything else.

The only way to test a thermostat is to hang the thermostat in a large metal coffee can with water covering it and an accurate thermometer and put the can on the stove and heat it up. When the water reaches the rated temp of the thermostat it should start opening up and you should read the thermometer when it starts to open. A 160 deg thermostat should start opening at 160 to 170 deg.

When the system is working right there should be coolant flowing into the top tank from the top radiator hose when the engine is at the temp of the thermostat.

Things that can cause over heating is a collapsing lower rad. hose or the liner can collapse without the outside collapsing. The radiator cores could be stopped up with calcium deposits. The impeller of the water pump could be spinning on the shaft. The block could be full of rust and calcium deposits. The thermostat may not be opening.    

[Birddog7]

Thanks everyone, I checked the two new thermostat's this morning they opened at about 165 degrees. I checked the impeller yesterday and it turns freely when I turn the fan blade. Carlsjeep never thought about the bottom hose collapsing or the liner. The hose felt like it was wire renforced. I was going to try a pipe wrench on the valve but did not want to break it off in the head. I soaked it with PB Blaster just being cautious. I am hoping to take the 3A to the Fall Reunion didnt want another issue with a busted fitting in the head. I have a electrical and oil filter issue too take care of before next Thursday.

[Birddog7]

Had little time to work on Miss Sharon today. To many Honey do projects. This is what I found, the new thermostat that I installed did not have a vent hole in it. I have to fix a hose to the oil canister before I run it again to make sure it is fixed. But I think that was my problem. Here is a picture of the Thermostat's with and with out the vent hole.

[Carls_jeep]

If the thermostat with the hole and rivet in it is good just tear the rivet out and use that thermostat. That's what I did with my thermostat like yours.

[Birddog7]

Carlsjeep, The thermostat on the left I reinstalled. That is not a rivet it is a little brass flapper that fits in the hole.