Never ending Overheat

My jeep has had a temperature problem since I purchased it. I picked it up as a surplus vehicle from Colorado auto sales in Denver and one of their listed problems was overheating. Here is the life of the problem so far.

Purchased, drove to a car wash and pressure washed the radiator. Lots of Pea gravel came out. It still overheated while sitting in traffic but was ok while moving.

I got home and removed the radiator, it appeared as though there was a birds nest between the radiator and the condenser, and the black rubber had fallen down blocking the airflow. so I cleaned it out.

The jeep still overheated at idle and during low speeds, so I changed the fan clutch.

The jeep still overheated at idle and during low speeds so I flushed the radiator and replaced the thermostat with a 180* unit.

THe jeep still overheated at idle and during low speeds so I replaced the original electric fan

The jeep still overheated and I developed a heater core leak so I replaced it

The jeep still overheated at idle and during low speeds so I removed the mechanical fan, replaced the radiator with CSF 3 core, replaced the thermostat and radiator cap.

The jeep still overheated but only at slow speeds while running higher RPM's

The fan bracket broke and the e-fan rubbed a hole in the radiator.
I replaced the radiator with another 3 core CSF unit. and replaced the fan.

The jeep still overheated at idle and low speeds. So I moved the radiator forward, installed a Ford Taurus fan, and 10" e-fan. and replaced the thermostat.

The jeep still overheated at idle and low speeds, I discovered a drip from the water pump and when inspected saw that the flange face was pitted and would not seal, I installed a new water pump.

The jeep still overheated at idle and low speeds, and run cold in very cold weather. I removed the thermostat and the damn thing had a set of catches on it that never allowed it to close once it had fullly opened. I replaced the thermostat and re-filled the system


This is where I am today.
The jeep still overheats at idle and low speeds unless I use the High-speed of my Taurus fan, and my alternator can't keep up with the draw at idle. I have tried the super cool coolant, regular coolant, pure water.

It's not terrible, I can keep toggling the fan from high to low to keep it cool, but it's only 65* outside I shouldn't have to do this. There is no part of the cooling system except the overflow bottle that hasn't been replaced, and it's an open system. I hate to admit it, but I have no idea what is wrong. It isn't eating coolant, or putting oil/soot in the coolant, nor is it putting water into the exhaust. It isn't running poorly, it just keeps going over the 210* mark with 180* thermostats in it. The 180* thermostat is for the Jet Chip. Yes it still overheats without the chip.

My 92 Cherokke would overheat driving around town and run hotter than normal on the highway. I replaced the fan clutch, flushed the engine and radiator and pressure washed the radiator itself all to no avail. Turned out my catalytic converter was going bad and plugging up. My Jeep drove fine just ran hot because of the greater exhaust restriction. Later it plugged up completely on the trail and I had to be towed home. That is when I discovered it was the cat.

Have u replaced the sensors for the gauge. Thats the only thing I havent replaced and I over heat still as well.

Best and cheapest cooling band-aid: junkyard hood vents

Throwing out ideas, but are you getting the right f/a mixture at idle / lower speeds? Running the right plugs?

possibility of cooling passages in the engine being blocked??
Sounds like you've already replaced the entire system.

how hot does it get according to the instrument gauge? have you confirmed if the gauge is reading correct? the lower hose may be bad and collasping but usually only happens at high rpm. confirm the gauge is reading right.

Lemme start answering these.

Hood vents. I have had them for 2 years now, no change in overheating.

Catalytic converter. I have replaced it with a 3" high flow unit

Sensor. When I'm running down the highway it sits on 180, when I get into town it climbs, when it is cold outside with the open thermostat it would fall below 180 and when It gets over the line above the 210 line the system boils over. I'm fairly certain it's pretty darn accurate, and I have replaced it just in case. I did check it with an IR thermometer a while back and I can't remember any specifics so it couldn't have been off.

Fuel air mixture. I'll have to see what I can do, It was running lean at one point (blued the downtube)but I don't remember what I did to fix it. Spark plugs are stock Champions. I may need new injectors, I'm running the smaller 19# ford units, but changing those from stock never changed behaviour.

Hose collapsing, No. I always buy the spring reinforced hose, if the hose I buy doesn't come with a spring I re-use the one from before. I have also watched the hose as I rev the engine and no collapsing. This is usually an at-speed overheat culprit.

i had a new rad and rad cap but the cap for some reason did not have much resistance when trying to install it, meaning i did not have to push down too much to get it to latch. i did not think twice as it was a new part but it would cause it to boil over the same as you because it was never able to build or keep pressure. i would measure the depth of the neck and compare to the rad cap. i ended up replacing the rad cap with one that measured taller. Dam chain parts stores....

When you give up, can I have your 3 link?

Kthnxbye

Some kind of blockage inside a coolant passage in the block or head?

Yeah, but if I crank up the fan to high speed it cools off.

since you seem at wits end, im gonna throw a couple things out there, forgive me if theyve been done allready.
-double checks theres coolant in the head.... dry head is never good....

-heater valve? has it been replaced too? (no mention)
-is it noticeably weak, as if its running on 5 cylenders?
-you could allways try go-jeeps restricter... what else is there?.

good luck, i recently fixed my jeep after it was in the never ending overheat mode for probably a whole year... except mine was fine once it was moving at speed...holy crap did it feel good once it was fixed!

If it is warm enough where you are drain the system, remove the thermostat, and delete the heater control valve and refill the system with white vinegar. Drive for a day or two and drain it and do it again. Continue until it runs clean when you drain and then refill with 50/50.
Since everything has been replaced, you have a blockage somewhere.

Is it an auto? Maybe route the tranny fluid into an auxilary cooler only and not into the radiator or the auxilary first and then the radiator.

Are the fins of the AC condenser clean? Any blockages in front of the radiator?

Good Luck.

It ran with an open thermostat for the last 4 months or so. There may possibly be blockage in the block, but the fluid has been pristine with every drain/modify and refill and the interior of the head has almost zero corrosion in it, as if the head were replaced just before I purchased it.

It is an auto and has an external cooler, which I have moved from in front of the radiator to under the radiator to cover the overhanging portion of the taurus fan.

The jeep doesn't lack any power.

I have cleaned and straightened the AC condenser vanes and I have switched to a lower profile bumper so that nothing is blocking the radiator.

You know, now that you mention blocked flow, and I recount that the head seems new I suppose that it is possible that someone improperly installed the head gasket and blocked a coolant passage or two. If that is the case I guess I'm just going to have to live with it because I am NOT taking off the head on an engine that still runs.

By the way the heater control valve functions

yes the head gasket could be on backwards and the hole is restricted

I fought this monster myself, its a royal pain. All started when something inside the original radiator corroded and broke loose. The leaking radiator was obvious and didn't surprise me as it was 11 years old so I replaced it with a Modine 3-core. It started running hot and 2 weeks later the bearings on my water pump went out so I replace it, the upper and lower hoses, heater valve, T-stat, fan clutch, and temp sensor. Figured everything was due since they failed so close together and well I was already in there. Then the overheating began and much like you the only thing left was the block.

I ran a prestone flush through it and still overheated.
Drained the whole system and refilled with vinegar and ran it for a week.
Drained the vinegar and dissolved a box of baking soda in distilled water and ran it for a week.
Drained and refilled with 50-50 prestone antifreeze and replaced t-stat again. Still overheated.
I ran another round of vinegar for a week and baking soda for a week and this time when I drained the baking soda I pulled the t-stat housing, t-stat, and water pump and got in there with the hose for 15-20 minutes blasting away.
Sure enough I noticed some hunks of corroded crud in the bottom of the block after going at it with the hose. I'm guessing that they were pieces from the original radiator that broke loose and got lodged up in the water jackets. I reassembled everything filled with 50-50 antifreeze and I haven't had a problem since.

The other thing I'd check since it only happens at low speeds/idle is that you don't have an exhaust leak under the hood. Hot combustion gasses not being vented out from the engine compartment can cause an overheat all the same.

Good luck, I hate sorting out cooling issues!

so vinegar and baking soda? what mix and is this safe for everything?

He's saying to run the baking soda and water mix through after you flush the Vinegar to make sure you neutralize any acid left in the system.

oh ok so how long would I wanna run the white vinegar? Just full vinegar or watered down?