MrSchaeferPants

87 Cherokee

It started with a leak, lower radiator hose leaking at the pump. It was the hose, no fluid above the hose (well like 1/2" above the end of the hose from it comming out) It only leaked, after driving, not immediately after it was parked and shut down, but I noticed the leak after we went inside for a while and came back later to go drive again.

We replaced the hose, clamps, did the thermostat and gasket for S&G since we don't know the last time it was done.

Didn't leak at all yesterday, (hose) with the exception of the surge tank as I was trying to bleed the air out, after a while I decided it was good for tonight, but wasn't happy with it. A few times the tank overpressureized, spewed steam and when I took the cap off antifreeze poured out, after I spent some time bleeding it, it seemed fine, after some start/stop warm up/cool down cycles, the fluid in the tank seemed to stay at the proper level. But I wasn't happy.

The upper hose got hot, but not hot enough like fluid was really passing through, and I squeezed and it didn't feel like fluid was ever really in there. The hose felt hot like, just because everything in the engine bay was hot from running. The two small hoses running from the pump get hot, hoses and "y" to the heater core is hot (heats good inside). The upper hose on the surge tank brings fluid back to the tank, should it be flowing into the resevior, and back down through the bottom hose, constantly cycling through that tank? And if so, the upper hose barely has flow.

Also, I'm still getting used to the closed system, I've read all the upgrades and fixes (and at a later time I might) but until then, I just want it working right.

I'ma take more time to bleed it today, I'lll try from the temp gauge sender on the back of the driver side head like I've read about, perhaps there's just not enough flow due to air, I dunno. But what confused me is the lower hose was leaking, in the same way again today. I tightened it, perhaps it wasn't tight enough, and needed re tightened as it was a brand new hose. I'll find out when my GF comes back from work (it's her jeep).

djb383

If the metal nipple the rubber hose slides over is pitted/corroded (not a smooth surface), no amount of clamp tightening will seal and stop a leak. Over tightening a rubber hose will probably cut/ruin it.

MrSchaeferPants

It wasn't pitted, or heavily corroded, bit of gunk and surface rust of course, but I took steel wool to it before the new hose went on. I didn't over tighten this morning, just tweaked the clamp a bit more to check, it's by no means cutting into the hose (I know what you mean).

I may get a new cap, because when it over pressurized, it was coming out of the threads, I don't know how that plastic cap is supposed to vent. Only vehicles I'm used to with a closed, reservoir system are military HMMWVs, but of course, the tank is heavy duty plastic, and has a normal radiator cap on it.

Normally I leave the cap off and run it (open system) and it's fine, but to fully cycle, the cap on the jeep would have to be on, so it can build up pressure and heat to open the thermostat right? I dunno, over thinking it. I guess I'll just wait till the cherokee's back and I'll try bleeding it some more through that gauge sending unit

As far as the hose, perhaps I missed something and it did have some damage, bent. Only two things could cause a leak right, like you said, damage so it doesn't seal or old worn out hose, and over pressure, but the lower hose should have no pressure, vacuum perhaps (collapsed hose) from the pump, but that's what the springs are for, or newer hoses don't need them.

djb383

The cap is what causes pressure to build. Raising the pressure in the cooling system raises the boiling point of the coolant. When coolant boils, it can no longer absorb heat. Pressure has nothing to do with the t-stat opening, the t-stat slowly opens/closes based on coolant temp only. Pressure (not heat) builds equally in the entire cooling system. The t-stat does not seal pressure, air or water tight......it reduces coolant flow when closed and allows more/variable coolant flow in the infinite number of open positions between closed and wide open. Once the t-stat is wide open (about 15 degrees above designed open temp), coolant flow is governed by water pump speed.