So last night when I was leaving work at around 10 pm I turned on my jeep and it was making a weird noise, that at first I thought sounded like it was a clunking sound so I turned off my jeep right away to see if I could hear it again after I rolled down the windows and it seemed to get quieter, third time I turned it on (still haven't moved it) I didn't hear the noise at all.

This morning, when I turned on my jeep it was making this sound, but a lot louder. Turned the jeep back off same thing over and over, I tried about 4 times. I go and check the coolant level because about two weeks ago or less it was completely empty. Once again the coolant was completely dry when I had it checked out, especially since the check engine light came on and the code read as Cylinder 6 Misfire (P0306). My buddy showed me a thread about the head gasket crack and I recognized some of the symptoms from that thread, i.e. misfires and I've also had problems with the oil pressure gauge but I'm not sure if that's also a part of the same issue or if its separate, the gauge will go up but then drop back down and the 'check gauges' light will turn on. What my mechanic told me is something about one of the piston rod springs possibly being broken keeping one of the valves not closing properly, which would cause the backfire in the engine. He said he won't know anything until the valve cover is off and taking off the oil pan for the oil pressure issue. Has anybody experienced this problem before?? From the sound of it, this would be my best case scenario since I could just replace that, and he said that it looks like the thermostat housing gasket was taken out and only replaced with silicon by the previous owner. ( I've had this jeep for a month and 4 days)

Also a side note, when my buddy was following me to take it to the shop, he noticed some type of smoke come out of the exhaust but couldn't tell whether it was from the cold weather or not. It was cold today and the jeep had been parked all day so it was cold too) but after 1-2 minutes it went away.




....and I was going to go hang out with some girl today

 

Pull your dipstick out and check to see if the oil has antifreeze in it, if it does you either have a blown head gasket or the head is cracked. These engines are known to crack the heads if you overheat the engine. If there is antifreeze in the oil that will effect the oil pressure. My buddy thought his gasket was bad and I told him if he has the head off to replace the gasket to have his head checked and of course he didn't and it ended up being his head was cracked. He ended up going to advance auto and bought a remanufactured head and we put it on and his oil pressure stays around 50 psi on the freeway and 25 psi at idle, hope this helps.

 

x2 to everything. Whenever you experience unexplained coolant loss, a cracked head is a very likely candidate unfortunately. 2000-01 XJs have the 0331 head which is very prone to cracking.

 

Yeah, well both times i filled it with water since it already had coolant so just to top it off, but that's one of the things I checked, my buddy checked too and he said my oil looks fine. He would actually be able to tell.

yeah that's what i was reading in the other thread unfortunately. although I haven't overheated my jeep to where it turned off. The first time My coolant disappeared the temp gauge only went to the red line and made that noise but everything was fine. Who knows about the previous owners

 

im his so called "buddy" but i also checked the dipstick and i took off the oil cap cover off the valve cover and everything seemed very clean....his thermostat housing is leaking which we assume where all the coolant is leaking from and it seems like a small leak where it would take a week or two to drain..my dad is the one who is the true mechanic who we took it to but it was a little late and he wasnt able to take a good look at it but he seems to think it is the rod spring, believes the valve isnt closing properly and making a misfire in the engine. think that is possible?

 

Yeah, what he said! ^

 

Subscribing because I want to see this jeep on 35's and off road with us.

 

When the jeep is hot still remove oil cap look in rockercover between cly.# 3&4 for any sign of a crack should show up as a green crack color of coolant.Rough idle could be carbon holding a valve open very possible (run some seafoam thru it ) rough idle at hot restart would be the heat soak issue, possible fixes are to get the heat sheild for cly.# 3 from dealer and to wrap injectors with heat sheilding used on spark plug boots,also I did the swap to the four hole ford injectors,and you could also wire elec. fan to run on a temp switch or just a toggle switch so it would run after engine is shut off to aid in cooling. The 2000-01 motors hate the heat from when you shut off the engine.I would look into an aftermarket head to solve any issue that might arise,any 0331 aftermarket head addresses the weak area on the factory head,or any head from 2002 on will work.Also fix your t-stat housing lol good luck,keep us posted.When you do and oil change I use a 12qt bucket that way you can tell right off if you have alot more than the 6 qts minus the little for filter you know you have coolant in your oil.This was how I caught my 2000's cracked head,(oil didn't have any milky apperence to it at all), but yet our 2001 has had no issue's at all so they don't always go bad.

 

that seems fair but it seems like too much work if this jeep is eventually going to run on 35's which i am sure it is and we need it to be reliable off roading in the middle of now where....my only concerns were if we change the engine to the 95-99 if we need to change the wiring harness and or the ECU also?

 

Yes you do it is a differant set up for 2000-up harness may work but if you swap it all it will simplify everything.

 

if it ends up being the head gasket issue what do you suggest, we just change the block to the 97-99 block or to swap out everything?

 

Update 3-7-12:

So I take off the cover and I'm inspecting everything and low and behold I discovered my jeep's rod is Houdini. The picture speaks for itself.





In picture at the top: Screw driver
Not picture: rod.

 

Dang, that sucks. Did you take the valve cover off yourself? If so, you could proabably un-bolt the manifolds, remove the coil-on-plug rail, etc and pull the head off. CamShaft might be toast, if that pushrod fell through, heck, Alot of things might be toast from that pushrod. Bearings might be toast from coolant loss, coolant accumulating in the oil. I would look for a 2002 thru 2004 Grand Cherokee 4.0 or 2002-2006 TJ 4.0 for a replacement.

 

Tomorrow we are going to try and get some time to take off the oil pan and see what's the situation from the oil pump because the loss of oil pressure might of been the issue for the push rod to be damaged like that, if we end up taking the head off we will replace it with a 97-99 4.0 head

 

There is a hydraulic lifter directly below the push rod bore making it impossible for the tube to "disappear" into the engine, unless ofcourse the lifter "disappeared" as well.