Tank heater leaking whoes!

I posted this over on M715ZONE to, but as I think its more of a mechanical issure versus type of vehicle issue hopefully you guys can help me get this figured out. My original radiator was shot, so I got the aluminum replacement off Ebay that everybody suggests. Works GREAT! (well the first one did until a week later and it started leaking, company was really cool about it all and I had a new radiator the next day and didnt have to pay for shipping, but thats another story). Well the old motor is down about halfway on compression on most cylinders lowest being 70 on the middle ones and highest being 105 and 100 on the front two. And its a little cold blooded in the morning. So I installed what I did on my CUCV M1008 a Katz brand tank heater that ties into the lower radiator hose and then runs into the inlet for the heater core. Its setup on a timer to start a couple hours before I get up for work. I hate overworking a starter and firing up a cold motor, the deisel especially but I figured what the heck cant hurt on the old worn out Kaiser? Well on really cold days I can go out there and there will be a 2 ft by 4ft wet spot, not a puddle but we spot under the truck. And its always from a hose connection. Its usually never the same hose but its always on the lower cooling, post thermostat side. Now if this had happened 2 or 3 times I wouldnt bother you guys with it, but its everytime it gets down into the single digits. The heater has a thermostat in it to shut off at a certain temp so even plugged in once it heats the water to a certain point it shuts itself off. It finds a new spot to start leaking. Now I'm gonna say what I think might be causing it and you guys can feel free to bash me with it if my thinking is off here. Its got a 13lb cap, the orginal was 15 for the stock radiator, to my understanding. Now this tank heater heats and circulates the water till it gets the lower end warm enough to open the thermostat which is a 180 degree, and then it releaves the pressure. But up until that point that tank heater is just heating water and building pressure on the lower side, maybe more so than the stock system was designed for. And it always leak on the low side, until the pressure gets past a hose clamp or is realeased by the thermostat. Thats what I've come up with, so go easy on me if I'm way off here. The next cap down is a 7lb which might run into a boiling issue. Maybe thats what I have to run in the winter and go to the 13lb in the summer months. Just throwing idea's out there. By the way, all new hoses, hose clamps and they arent over torqued or anything like that. And it likes to do it at that one larger hose on the passenger side block, the fun one to get to kinda behind the fuel pump. I thought about taking the radiator cap loose and running it cold and seeing if it still leaks, thought being it would releave the pressure through the cap, but then again if it really warms it up and it expands then its just gonna overflow outta the cap. Any help at all is appreciated and thanks for taking the time guys!
Cameron

You have a cold weather leak, are your hoses new,clamps new > and 7lb cap is fine for all weather unless your in a desert inviroment. Thats all i,ve run on everything i own for 40 yrs. Big equip is well known for cold leaks. Silicone hoses works the best for solveing this but on a 715 theres none

Thanks for taking the time to answer this post bcowanwheels! I installed the 7lb cap then I ran the heater, which got the truck up to 150 degrees then I unplugged the heater and fired up the truck. Its got a 180 thermostat in it and I shut it off right at about 170 degrees. My logic, correct me if I'm wrong is this is when the most pressure is on the cooling system, just before the thermostat opens up. I sat in the truck and watched the temp climb another 5 degrees after I shut it off to make sure the thermostat didnt open up. And let it sit overnight, the next morning there were no leaking hose connections and the upper hose you could squeeze. Didnt feel like it was going to explode. There was still some pressure in the system as I turned the cap the excess went into the overflow tank just like it was supposed to. Been driving it for a week and so far, so good. I'll keep using it as my daily driver through the weekend. If it makes it that far then I will tear into the M1008's leaky rear main. Have to be sure that the Kaiser is reliable before I open up another can of worms. When things heat up this summer I'll keep an eye on the coolant and make sure that the cap isnt lowering my boiling point too much. But with that new aluminum radiator it cools very well, even without a shroud.

Thanks again,'
Cameron

Most likely changeing the rear main seal wont cure your oil leak, most likely your engine is hi-milage and its getting blow by from rings and valves......

I think you got confused. No its the rear main. This is the CUCV we are talking about. I've replaced dozens of them and I know one when I see one. This motor has 32k on it and with the oil cap off no blow by and all the cylinders are within spec on a compression test. The Kaiser doesnt leak oil, it just burns it like mad, and thats the motor that isnt within spec on the compression.

I,am not confused, i meant the cucv oil seal. Those 6.2's are problem prone engines. I hope the best for you on that one.

I know that alot of people dont like the 6.2 but then again there are alot of people that do. I've put 10k daily driving on mine after it sat for who knows how long and all its needed is a rear main? I think that says something for the it. I was in the Army and cross trained to a 63 Whiskey (light wheel vehicle mechanic). There were always jobs on the print. Did we replace 6.2 motors, ya, it was rare but we did. Did they need it most of the time, no. Never replaced a 6.2 engine that didnt drive itself over to the motorpool. Do they have crank failures and weak bottom ends yes. For what it is in my truck it does just fine. If I wanted a Duramax I would have gone out and spent the money. With some mild upgrades they can be made into very reliable engines. With mine I'm installing the DSG stud girdle and Fluidampr. If I every get that in depth with it I might pull the heads install the better head gaskets and studs. Hopefully eliminating the weak links. I'm not going to hen peck and re hash a bunch of facts and opions and get into the 6.2 argurment, especally in the M715 section. Thanks for your advice on the coolant leak but I think I will put a $500's into the bottom end of a motor that while towing 8k lbs gets **** near 14 mpg and unloaded 17-18.

Well I'm going to post this, not as a "I was right you were wrong post", but more of a learning post which is what this site is all about. I am putting this in the M715 forum in this thread in case someone is planning on doing a 6.2 conversion and read the above comment and was turned off to the 6.2. I had made reference that I had a leaking rear main and I wanted to stop the leak in the M715 before I tore into it because Kansas weather is unpredictable at best and I dont want to be left without a four wheel drive. I was then told by another member, who was more than helpful with the Kaiser leaking issue, that my 6.2 was probably "high mileage" and worn out and that is what was causing my leak. Well 500 miles later I can assure you it was a rear main. Just like any other small block with a 2 piece main it went right in. So like I said I'm not stirring the pot, I just want people to know that removing the oil cap with the engine running and checking for blowby and a dry and wet compression test are gonna be the best indicator as to what condition your engine is in. Do these motors have some issues yes. My boss's knocked like you wouldnt believe when we bought it off GSA and he drove it for 2 years before it snapped the crank, heck I even have the piece for door stops to my garage. But while I was in there I installed the girdle kit and plan on a fluidamper to help out the bottom end. Both weak links. So I hope that the point of this got out there, not looking to pick a fight, but not all oil leaks mean a worn out engine, and 6.2's while not the most desirable can be made into reliable fuel effecient daily drivers.

Cameron

Thanks ducer, but so far the 7lb cap and not filling it clear to the top has stopped all leaking. I appreciate your input though and if it comes back again I will def try your remedy.