Dauntless 350 radiator issues

[sierrablue]

Hey, guys, I posted a thread a little while back asking about new radiator recommendations for the '71. I wound up going with one of the Summit clamp-in radiators for a SBC (note; if you get an LS radiator you can use a stock Skylark upper hose and run it to the passenger's side, which clears an HEI distributor much better) (rather than bolting it straight through to the support, which gives the potential of twisting the radiator). I was super happy with it; I can run my Taurus electric fan now, and it seemed to work really well.

After about a week, though, it started leaking where the tube goes into the tank. Not a huge deal, I bought some special JB Weld stuff and it was sealed up just fine. Now it's leaking again, worse this time, in the middle of the radiator somewhere.

Anybody have any ideas as to what caused this? I did an engine swap in November/December (B350 to B350), and at that point the cooling system appeared to be fine (only thing I'm unsure of is the heater core there). Then when I started driving it with this motor, the heater core was bad (didn't realize it at the time), and when that radiator that was in it went bad, I didn't get the foggy windows from the core anymore. I put in the new radiator, and the Jeep got completely filled with antifreeze smoke, so I replaced the core. Then it was fine for about a week and, well, I already explained that.

I checked for bubbles in the coolant when idling and warming up, and all that happened was the radiator overflowed (no bubbles; I added some coolant before startup), so I don't think it's a cracked head/block, or a bad head gasket. I replaced the cap with the radiator, a stock 16-lb cap. I'm not really sure what else to check; did I just get a bad cap? Did the cap work but not release enough pressure so the radiator blew? I don't want to spend hundreds of dollars every month on a radiator, but I also don't want to be leaving a trail of antifreeze everywhere. If it's anything too major I may wind up looking at a 4.0/AX15 build...put me up around 18 mpg with similar torque (and I don't need the horsepower). Should I get another radiator and run a 13-lb cap, since it doesn't really need much pressure around here anyway? Any insight/ideas would be greatly appreciated.

Update:
Today I went to leave, and within 2 miles it started blowing some steam into the cab; the new heater core has been blown out now, too. I got that exhaust fume tester thing, and there are no exhaust fumes getting into the cooling system. I did notice that when it's cold even, the coolant level in the rad goes up pretty fast, which doesn't seem right since the thermostat is completely closed and the bypass bypasses the radiator, not just the thermostat. It gets up to temp just fine, and pretty quickly, so the thermostat's not sticking...and even if it were I don't understand why there's so much pressure there at idle when it's cold. And since the heater core's out now too...it can't be radiator specific. The other engine never did this, but then I had a 160 thermostat in it and when I put the 195 in the timing cover gasket blew. So I have no idea...like I said above, if anyone has any ideas or suggestions, it would be greatly appreciated.

[sierrablue]

OK, I've come to some conclusions here, not sure how valid they are, but it's all that I can come up with at this point. If anyone sees any holes in my logic, please let me know.

Number one, I did an exhaust gas test, and it is negative. Which isn't all bad, because this engine is growing on me again...even though I'm well aware that I could get a $400 XJ that runs, swap all of the engine and transmission components over, and have similar power, fuel injection, and overdrive for less that $1000. Anyway back to the cooling system.

I noticed that the heater hoses have little pin holes in them--which could let air into the system as things cool and the system loses pressure...and it could do that without leaking any antifreeze, causing there to be more volume in the cooling system than there had been--and then when there is pressure, the holes get pinched shut and nothing comes out, so that adds strain on the system. Theoretically, the cap should bleed off that pressure, but with it being a 16-lb cap (which I read was really only necissary for hard core racing engines, and honestly right now it has close to 0 pressure and I'm having no overheating issues (not that I ought to at 30 degrees)) and all, it's possible that it either a) didn't get high enough to bleed off, or b) it topped out bleeding off but it wouldn't bleed off fast enough and something had to give.

The other thing I realized is that the overflow tank was sealed up pretty tight (and trying to keep things clean I put a plug there that I shouldn't have), so it couldn't release pressure like it should. I know this wasn't a problem for the first rad/heater core, because I didn't have the tank on immediately after the engine swap, when they started leaking. But it sure didn't help anything with these new ones.

Thankfully I can get a new radiator and heater core under warranty, so here's the plan at this point:

1: new radiator and heater core
2:while those are out, new heater hoses (others are fine and pretty much brand new)(silicon???)
3: I already got a 13-psi cap
4:teflon tape on temp sending unit insert

Basically I'm going to put everything back together as it is now, but I'm going to make sure everything has a perfect seal and lines up as it should. I may get a new hose for the overflow tank, too...we'll see. But I'd like to get my heat back (I've been running it turned all of the way down and "Off" so as to get as little leaking antifreeze past the heater door as possible...and the cap isn't tight and I shoved paper towels in the vents and it's STILL fogging up the windshield some), and more importantly at this point, defrost. Though I won't actually need the defrost when the heater core isn't making the windshield fog up...

[Heep-J4000]

I did read your thread but can't makes sense of some of what you wrote about what you are trying to archive.
It probably has also something to do with the language difference and I'm not reading it right!?

But for not having the windows fogging up in your Jeep
Disconnect the hoses that go to the heather core and loop them together with a piece of pipe and two hose clamps.

Get a new or one that is in good order (pressure tested) heater core and do the job once and for all the right way.

About a overflow tank , my Jeep never had one and it only once or twice after filling up the coolant it spewed a bit out the little hose at the radiator cap.
My Jeep was a daily driver for thirteen years!

[sierrablue]

I did read your thread but can't makes sense of some of what you wrote about what you are trying to archive.
It probably has also something to do with the language difference and I'm not reading it right!?

But for not having the windows fogging up in your Jeep
Disconnect the hoses that go to the heather core and loop them together with a piece of pipe and two hose clamps.

Get a new or one that is in good order (pressure tested) heater core and do the job once and for all the right way.

About a overflow tank , my Jeep never had one and it only once or twice after filling up the coolant it spewed a bit out the little hose at the radiator cap.
My Jeep was a daily driver for thirteen years!

So which parts are confusing you/the translator? I don't think trying to reexplain the entire thing would make things a whole lot clearer, so which parts do I need to elaborate on?

I know, and I would get the heater core bypassed completely in a heartbeat, but it's still snowing regularly and has been in the 30s all week (gotta love northern MN; on Monday it was in the 50s and the snow was disappearing), so I need SOME level of heat. With the radiator cap twisted so that it doesn't build any pressure, and all of the doors closed, it still provides a little bit of heat, without filling the cab with steam.

Yeah, I ran it that way for a while, but this way (assuming the cooling system holds together) it should keep it from leaking and it allows me to keep some extra antifreeze in the tank, should it burp itself and need some more. Not a critical component, I know.

[babywag]

sounds like typical poor quality aftermarket parts to me.
Wife's Charger is perfect example 4 radiators in couple years before I finally got one that didn't leak shortly after install.

best test for a cooling system is pressure test.

[Heep-J4000]

So which parts are confusing you/the translator? I don't think trying to reexplain the entire thing would make things a whole lot clearer, so which parts do I need to elaborate on?

I know, and I would get the heater core bypassed completely in a heartbeat, but it's still snowing regularly and has been in the 30s all week (gotta love northern MN; on Monday it was in the 50s and the snow was disappearing), so I need SOME level of heat. With the radiator cap twisted so that it doesn't build any pressure, and all of the doors closed, it still provides a little bit of heat, without filling the cab with steam.

Yeah, I ran it that way for a while, but this way (assuming the cooling system holds together) it should keep it from leaking and it allows me to keep some extra antifreeze in the tank, should it burp itself and need some more. Not a critical component, I know.

No need to clarify anything again.
I was reading but not getting into it enough.
Don't worry about me!

You need to get a new good quality or used but knowing it's in good order heather core and install it asap.
It's not really a good option to leave it like this leaking and fogging everything up.
It takes ages to vaporise for the coolant in the interior.

I used a heater core from a 80 jeep , it's a alloy one and does fit the early heater box.
Only you need to drill a couple extra small holes to secure it in place with the small screws.
The old brackets are not needed anymore with the later years heater core ,it has a bracket on the underside and top that clamps in between the two halves of the early years heater box

[sierrablue]

Thanks, guys. 4 radiators in a row does not sound like any fun...

I got a new radiator from Summit under warranty. Looking at the bracket I built, I have to watch that I don't overtighten one side; if I just keep cranking on it, it will potentially twist the radiator, which would obviously cause it to leak. I don't think I tightened the old one up too much, but it's just something I have to watch.

Got a new heater core, also under warranty. I got mine through radiator express; it's the only place I could find the stock '62-'77 heater core (just put in that yours is a '74 with the 401 and it'll come up). They offer it in aluminum or copper; the aluminum is cheaper so that's what we ordered (both times). The first time we got a copper one, but this time we actually got an aluminum core.

Anyway, it's all back together, so far so good. I put on a 13-lb cap just to be sure (really the only time you should need the 16 is maybe on a racecar). I also removed the plug I had on the overflow tank, so it can release pressure/air as needed. The level in that tank went down, so I think it burped itself and everything. And I got the interior all cleaned up, too, so it should be good.

Like I said, thanks again for all of the input. I'm back to Jeepin', and around town the bright blue catches everyone's eye. And most don't have their old rides out up here yet...heck, there's still snow on the ground up here (not on the roads or anything, but in everyone's yard).