1991 Cooling Problems

Unfortunately, this is my 3rd post regarding this problem, just can't seem to get it fixed.

I have a 1991 Cherokee - I had put Bar's Leak in radiator to stop leaking (I know not to do that anymore) a few months back. About two months ago the temperature light starting coming on.

Since then, I have replaced the Temperature Sensor, Thermostat (twice), Radiator, Water pump, flushed an inspected all major hoses, flushed the entire cooling system multiple times. I have also tried "burping" the system as recommended at this sight (does this work for an "open" cooling system as well?).

I am now at a loss after spending over $200 with no fix. I am thinking the Bar's may have clogged the flow through the Engine. When the temperature light comes on, the upper hose from the thermostat housing to the radiator is not full with water. When you squeeze it, coolant is barely running through it (and I tried running it with no thermostat at all to see if that was the problem, but it did the same thing), also when the temp light comes on, the radiator cap is not even hot (the radiator itself is though). I have run both types of Prestone Radiator Flush and Cleaner through it with no results. Also, my (generic, not jeep) mechanic looked at it and said my head gasket, and everything else looked fine.

All in all, the best I can figure is that I have a major flow problem, and the only thing I can think of is that the Bar's clogged up the flow through the engine block. Anyone have any other thoughts on what it could be? OR how I could test or flush the Engine Block? Any help or suggestions would be appreciated. I have tried almost everything.

from what it sounds like to me is that your heater core is clogged. does your heat work well if not then there is your problem. to un-clog it you should take off both heater houses and then run some clr through it or vineger or somthing. leave it in there for a fewhours.

Unfortunately, I believe I have covered that route. I had bypassed the heater core altogether by running the hose from the thermostat housing to the water pump directly (and bypassed the Jeep's heater valve). So i think I covered that.
I bought a new radiator cap yesterday, I will see if that does anything. I doubt it will.

Thanks for the advice, if you can think of anything else I could check it would be appreciated.

DO NOT PUT CLR IN YOUR COOLING SYSTEM! it will eat aluminum parts (like your radiator, for example). :nono:

if you have hot air out of the heater, your heater core is fine. there is a valve that stops flow to the core when the heat isn't in use anyway so a plugged heater core shouldn't cause overheating issues, although in a bind you can bring the temp down a bit by turning the heater up to max-heat. It's misserable driving but I've limped home a couple times in the middle of summer with the heater on high.

if the coolent is flowing ok, then you may have just coated the inside with bars-leak residue and it may be interfeering with heat transfer from the engine to the coolant. you said you used both prestone flush's, did you leave the long-term one in for the full 3-5 hours at operating temp? there is also a product called 'water wetter' (there are other brands too) that improves heat transfer to and from the coolant making the system more efficient.

it looks from your post that you changed out most changable parts on the water side of the cooling system. how about the air side? is your fan shroud in good shape? clutch-fan working properly? is your A/C 'radiator' clean, with all the cooling fins straight, and allowing air to pass freely through it and on to your radiator?

Capt. thanks for the advice.

I have bypassed the heater core, so I know it is not that. I just tried replacing the radiator cap and I plan on making another go at trying to fix it tomorrow, so we'll see.

I don't think it is a heat transfer or cooling problem, but a FLOW problem. I don't seem to be getter proper flow in the Upper Radiator hose from the thermostat housing. And I have also run it without a thermostat to be sure it wasn't the thermostat. The coolant seems to 'trickle' through the upper hose going into the radiator when the thermostat opens. Also, after the temp light goes on and the radiator and hoses are all hot, the radiator cap is NOT hot, just warm, indicating it is not flowing through the radiator properly (and the radiator is new). The upper radiator hose does get hot, and when I squeeze it, I can feel coolant barely running through (after it gets hot)

Any other thought or suggestions would be appreciated still. I am at a loss. Thanks.

try this- with the thermostat out and water in the cooling system, unhook your upper radiator hose from the thermostat housing, then hold the end of the hose up and start filling it with a garden hose, the water should run freely out or the thermostat housing.

if it seems restricted- put the hose back on the housing and unhook it from the radiator, put your gardenhose in the hose (wrap it with a rag or something to try and get a good seal) and let the water pressure flow backwards through the system.

you could have loose debris in the system and sending the flow backwards may free it up.

i did this ever day for a couple weeks (and chemicly flushed it a couple time in the same period), along with using a small hose shoved into the radiator to syphon up any debris that was to heavy to float out of the radiator. over that 2 weeks I must;ve taken 1/4 cup of rusty debris out with the hose and I have no idea how much floated out with the regular water flow (but there was a lot more of that than the rust)

I don't know if this will help you but it doesn't cost anything and is worth a try.