incontrol7

I am aware of the cracking head issues on the 4.0L.. but heres my dilemma.

Noticed coolant coming from the lower radiator hose last summer. I figured it just wasnt sealed good so i just kept topping off the coolant and readjusted the clamp. I did this for a few days until one day as I was driving to work on the highway it just overheated out of no where, by the time I pulled over to the side of the road the engine just died.

Steam was pouring out from under the valve cover area. I assumed it was a head gasket. Being so frustrated I havent touched it until this weekend. What I found odd was when i removed the thermostat and housing it was bone dry inside even though there was plenty of coolant in the reservoir. Wtf? I pulled the spark plugs and they dont seem like they are in bad shape.

I drained the oil and there appears to be no coolant at all in the oil. Never did a compression test or coolant pressure test.

Thoughts?

djb383

Since u didn't post what year XJ, I'll presume it's a '91 up "open" cooling system. Never, ever trust that the cooling system is full based upon coolant level in the bottle alone. U must (when the motor is cold) remove the rad cap to check coolant level. It should be full to the top of the neck. A properly functioning radiator cap on a cooling system that has zero, zip, nada leaks is absolutely necessary. Fix any/all leaks as soon as they r noticed......don't put off repairing any coolant leak. Small leaks just get bigger....they never fix them selves.

Firestorm500

Head gasket possibly blown into the coolant side.

Either that or you ran it out of coolant, then it overheated and blew the head gasket.

Assuming it is going to stay above freezing in your locale, put oil back in it. Fill cooling system with plain water and run it for a while at idle, then on the road and see if it overheats again.

Have a buddy follow you and don't get far away from home.

incontrol7

Its a 99 XJ. When i was cruising at highway speeds the coolant temp needle was slightly past the middle hash mark... i did notice it. Then it suddenly shot up and as I was pulling over to the side it just died. The reason I assumed it was head gasket is because of the coolant days before spewing from the lower radiator hose. As i figured the high cylinder pressures were causing the coolant to come from the weakest point to leak...

I popped the valve cover and everything looks pretty damn clean in there... but i was puzzled to find pretty clean spark plugs and a bone dry cylinder head. But i wasnt sure if the coolant maybe just leaked back into the radiator ect from it sitting since about last september.

With that being said think its worth to continue removing the head?

Does the coolant flow "out" of the head when the thermostat opens like most engines? or does the supply go "In" the head through the thermostat housing?

djb383

Start with a cooling system overhaul and go from there. The XJ cooling system is not an area to be neglected.

Like most motors, coolant flows thru the block (front to back), up to the head (back to front). When the stat is closed, coolant flows (exits the head) thru the bypass loop. As the stat opens, coolant flows (exits the head) thru both the radiator loop and the bypass loop.

tlang

Im not sure why some one would completely overhaul a cooling system on a vehicle that might have a blown head gasket to determine if it had a bad head gasket. If the shop did that when one of our family members brought their car in there would be posts about how horrible of a shop they were.

I would start with buying a block tester (see link below.) This a far cheaper option than over hauling the cooling system. A block tester uses a liquid chemical to determine if there are any hydrocarbons (from the exhaust) present in the cooling system. A five gas analyzer is a much more precise way of measuring HC's. I understand not everyone has access as even ours at the shop doesnt work currently. If its a bad leak the block tester will for sure pick it up.

**PLEASE NOTE** this does not mean that any other faults in the cooling system should be over looked, if you have a radiator cap with no rubber left, start there. The obvious parts should be addressed first. (sounds like the op has a decent idea of what to look for) Does is look like there is a trail coming from the recover bottle area like the bottle was over filling?

Whats the coolant look like?
Any other leaks?
radiator cold in the center but warm on the edges?

Try looking at all of it as it can be easy to find evidence for a predetermined failure.

incontrol7

The coolant doesnt look dirty at all in the overflow bottle but i was adding water to it as it leaked through the lower hose to top it off. It never had a problem until a few days before and like i said it was leaking coolant from the lower radiator hose on the driver side... i thought it was just a leak so i readjusted it. maybe a day or two later it over heated and steam was POURING out from under the hood. when i popped the hood it was pouring out from what looked like under the valve cover but maybe it was from the bottom of the head, i couldnt tell or look that hard. I did try to crank it over again 10 minutes or so after i pulled over and it just cranked but didnt even start. Im going to guess its a head gasket that was over pressurizing the coolant system which caused the hose leak in the first place. BUT like you said id like to be a little more certain before ripping the head off. doesnt seem like the overflow bottle was over filled and is actually still within range on the bottle since everything. the radiator cap looks to be completely fine.

Firestorm500

Why haven't you done what I suggested in post #3? Cheap and easy.

Speculation is useless at this point without starting diagnostics.

incontrol7

Touche...

I will this weekend. I will keep you guys posted.

incontrol7

I guess i didnt see the point of just filling it back up and running it because of seeing the coolant steam just pouring out... obviously thats not a coolant level problem unless the head just got that hot and was evaporating the coolant?

Kingfisher

If you put water back in it maybe you can see exactly where it's coming from.

djb383

Read between the lines of the OP. I just thought it was odd the first guess regarding a overheat was regarding a cracked head/bad head gasket It was plainly stated in the OP that it was obvious that a hose was leaking last summer and the fix at the time was to keep topping off the cooling system. Sounds like maybe a little neglect/complacency has occurred over time regarding cooling system maintenance. Leaks that are not addressed pronto just get bigger, never fix themselves and most likely cause major problems when not repaired promptly. The only cooling system i can think of that would be cheaper/easier to overhaul, than the XJ, is maybe a 4 hp Briggs & Stratton engine on a lawn mower ....I am being facetious.

Is it possible the head and/or it's gasket caused the overheat....maybe. Is it possible the overheat caused damage to the head and/or gasket....maybe. Testing for a cracked head/blown head gasket, as stated by Firestorm500 in post #3, is a good idea. Be sure to tell all your family members to check for a cracked head or blown head gasket the moment they see a coolant leak instead of asking themselves "how long has it been since cooling system maintenance was done".