96jeeper

i know this is on the driver side under the manifold but it appears like there may be 2? Or is it a certain one? Just take it out and let it drain?

Jeep Driver

It's hot because it's lean.

96jeeper

I figured that. So my running rough probably spans from that too. runs like a sewing machine until 250 degrees lol

Jeep Driver

Check your temp sensors.........should be two of them.........one is IAT on the intake.

96jeeper

Temp sensors seem to work. Aux fan comes on. Plugs looked normal too me no indications of to lean or fouled

Anony

I'd do a cooling system pressure test. Possibly your cooling system is loosing pressure under different engine running conditions. The code indicates your engine is running lean and hotter than normal. Could be a combination of a lean running engine and not the correct pressure to maintain a cooler running engine.

XJ's cross-flow cooling system is more susceptible to not working correctly when there isn't enough pressure, (heavily relies on being pressurized). The pressure prevents the coolant from boiling and cools the engine under stress and higher temperatures. Even a very small amount of pressure loss will effect the cooling system efficiency.

I'd double check the hoses and radiator cap. Brand new radiator caps have been know to leak when pressure rises to under their rating.

Some water pumps are marked (usually on the impeller) to indicate the type of water pump and rotation.

I'd also perform leak-down and compression tests, will at least provide some more engine condition information. Since it has no history, possibly the previous owner was having similar problems.

97grand4.0

Agree. New cap, radiator pressure test, (there are tests also for coolant to detect hydrocarbons to diagnose a head gasket) compression test to rule out head gasket.

Now,.. the lean running is a concern!, that would have me looking at fuel pressure tests very quickly..does it ping at all or knock? Lean is a very bad thing, and can burn holes in your pistons if bad enough. A weak pump or plugged regulator filter the usual culprit.

The swelling hoses are also a clue. Could be engine compression bleeding into the cooling system? Have seen cooling systems belching coolant with a bad head gasket. Compression test. Radiator pressure test (most part stores rent these for free if you return them). Your clutch fan and the electric fan both need to be working, the clutch fan should show resistance and shut off with the engine, not continue to spin after shut off.
I would start with a new Stant cap and then pressure test and compression tests

96jeeper

Old cap and new cap both acted the same. Ive replaced everything but the head gasket with no signs of improvement. Dont think i have a pressure problem seeing as it will swell hoses on shutdown and hold pressure tight unless i remove the cap. Im starting to think its exhaust/compression gasses in the coolant even though im loosing no coolant. It will idle for a hour before it overheats but driving it heats it up in 10 mins. Fuel pressure is strong ive checked it at the rail. Its not actually running lean when then engine hits 250 then it runs lean.

97grand4.0

OK now we may be getting somewhere.

Fuel pressure needs to be checked running and bleed down test also, if the regulator screen is blocked it could be going lean on you.

Driving it overheats in 10 mins could possibly be head gasket, but, you need to verify that before undertaking it. A very reliable way is to have a sample of the coolant checked at a radiator shop for the presence of hydrocarbons. Another test to do is compression. Third would be leave the pressure tester hooked up when it overheats and see what is happening to the pressure. Is there any coolant in the oil? you need to check this stuff out imho.
As mentioned by another poster above, 'it's hot BECAUSE it's lean' not lean because it's hot. This is also very possible, somethings leaning it out too much and the cooling system is fine. Hope this helps.

96jeeper

I have had no running issue other than heat which came out of nowhere no signs leading to this. The fuel pressure is good the compression is good ive double checked that. Only thing i dont have access to is a coolant tester for exhaust gas. NO coolant in oil anywhere. It is not running lean i haven't even had that code come back since the first time. Im thinking bad head gasket or clogged passages in block not allowing pressure or water to move properly since i had sludge/stop leak in the overflow and radiator. This cooling system was obviously not maintained in the last 5 or so years and then i put about 300 miles on it in a week so i it may have clogged the passages.

97grand4.0

Borrow a radiator pressure tester from autozone or advanced. Radiator cold, put it on, pump it up to 15 or so, and see if it holds pressure. If it does, it's not your head gasket. This is just basic fact.

Also you could see how that swollen hose reacts under pressure, which, should be replaced anyhow. Maybe that's leaking now or somewhere else.

Again, does your clutch fan shut off when you turn the engine off? Or does it spin a few times. You need a helper for this one.

You said you replaced the thermostat, any chance the stat is bad, or in backwards?

BlueRidgeMark

There's one other thing that can make an engine overheat. Retarded timing.

Check your distributor for a bad rotor.

Yes, it's a long shot. It's also free to check, easy to check, and cheap to fix.

96jeeper

Fan clutch works fine its only a week old. Thermostat is new and has been tested and not backwards, even ran it without the stat and no change. Well against judgment i replaced the head gasket and another new water pump. Problem hasn't gotten any better. Haven't had anymore codes and it idles and drives like new with plenty of power but its still running hot. 235-245 and wont cool down unless aux fan is on and vehicle is moving. I should have had the head checked while it was off but nothing seemed out of place. I can check the cap and rotor but would assume the timing is fine since it cranks right up and runs and drives like normal aside from wanting to overheat. I never ran it hot or had it boil over or leak. Nothing in oil. Just stays in 230-250 temp range i shut it down before the red.

97grand4.0

Well, you're narrowing it down. How did the pressure test go?

BlueRidgeMark

You can assume, or you can check. Both are free. Your choice.