2001 Jeep Cherokee Head Possibly Cracked - JeepForum.com
 
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post #1 of 2 Old 07-14-2017, 02:51 PM Thread Starter
reundo
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1982 CJ8 
 
Join Date: Dec 2009
Location: East Tenn
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2001 Jeep Cherokee Head Possibly Cracked

Hey guys, so I have been reading through the forums and believe my cherokee probably has a cracked head.

Back story: I bought the 2001 cherokee sport 4.0 in the beginning of March and had to get the coolant system flushed as it was rust red and some of the hoses were clogged. I had it want to over heat a few times (running heat on high saved me) so I replaced the radiator with a spare I had from a cherokee many moons ago and it seemed to fix my over heating woes. I have also flushed the coolant several times myself since I bought it, trying to clear it up better. I have also been adding coolant more regularly than I should. I thought it was just air in the system at first

Now that it's been super hot out the jeep has gotten close to over heating and I could even hear the coolant boiling after I shut it off once today. It also had issues starting after a short stop at the store, acting as if it was miss firing and had low oil pressure time I was able to get it moving. I have not seen any trace of coolant or water in my oil. Looks like it normally does, but I also haven't drained any out to see if it separates.

So I am pretty sure the head and/or gasket is shot. I am going to run cylinder and coolant pressure tests Sunday. What should I be looking for during the tests? It looks like I should drain the oil too. Can I leave it empty while I do the work on the head?

Thank you!

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post #2 of 2 Old 07-14-2017, 03:34 PM
CJ7-Tim
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2000 XJ Cherokee 
 
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The almost overheating is probably from the poor cooling system maintenance, you will need to look at the rest of the cooling parts. See below.

Test for oil in coolant with a Blackstone Labs test kit, test for combustion byproducts in the coolant with a parts store test kit.

The mis-firing is probably just the common Heat Soak issue.

Overheating can be caused by anything that decreases the cooling system’s ability to absorb, transport, and dissipate heat, such as a low coolant level, loss of coolant (through internal or external leaks), poor heat conductivity inside the engine because of accumulated mineral deposits in the water jackets or radiator, a defective thermostat that doesn’t open, poor airflow through the radiator, a slipping mechanical fan clutch, an inoperative electric cooling fan, a collapsed lower radiator hose, an eroded or loose water pump impeller, leaky frost plugs, or even a defective radiator cap.

The cooling system is a group of related parts that depend on proper function from each of its component parts to keep the engine cool. Service the cooling system and replace any under-performing or suspected weak parts. Any component part of the cooling system that is not fully doing its job will stress the others, and your engine will overheat. Temperature creep on the 4x4 trails, at idle, or in stop-n-go traffic, points to a weak or failing mechanical fan clutch or worn out water pump fins.

The most important maintenance item is to flush and refill the coolant periodically. Coolant should be replaced every 36,000 miles, or every two to three years. Anti-freeze has a number of additives that are designed to prevent corrosion in the cooling system, but they have a limited life span. The corrosion causes scale that eventually builds up and begins to clog the thin flat tubes in the radiator and heater core, causing the engine to eventually overheat.

-Inspect/test or replace the mechanical fan clutch. A worn fan clutch will allow temperature creep at stoplights, in heavy traffic, and on the 4x4 trails. A fan clutch that “looks” OK is not the same as working OK.
-Inspect the electric cooling fan and the fan relay. Apply 12 volts and make sure the fan runs. Exchange the cooling fan relay with one of the others similar relays. Confirm that the e-fan starts when engine temps reach 215-218*. Repair or replace the fan or relay as needed.
-Inspect/test or replace the coolant temperature sensor that activates the e-fan.
-Replace the water pump. The pumping fins can deteriorate over time and the pump will not flow enough coolant to keep the temps under control.
-Inspect/replace the radiator hoses. Make sure the coiled wire is installed in the lower hose.
-Inspect all of the freeze plugs in the block and the ones on the backside of the head for rust holes and coolant leakage.
-Use a chemical flushing/cleaning solution to remove mineral buildup or rust, flush with clean water, and then drain and fill the radiator with a fresh 50/50 coolant and water mix. With neglected cooling system you may have to flush several times.
-Inspect the radiator for mud/bugs/grass clogging the outside and mineral deposits clogging the inside. Clean or replace as needed.
-Replace the thermostat with a genuine Jeep 195* thermostat. Cheap thermostats are cheap for a reason.
-Replace the radiator cap if your Jeep has one. An old worn out radiator cap will allow not hold system pressure which can cause boil overs and/or allow the coolant flash over into to steam. You will likely see the coolant temps suddenly jump from 210* to the Red Zone and back to 210* if your radiator cap is weak.


If you have covered all the points listed above and still have overheating issues, inspect and test the head for cracks and head gasket for leaks. Exhaust gasses entering the coolant can raise the temperature of the coolant or cause steam pockets in the coolant that will temporarily block the flow of coolant.


Read more about cooling systems here –
www.offroaders.com/tech/engine-overheating.htm
www.carparts.com/classroom/coolingsystem.htm



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