ive been wondering this for a long time.

 

Yeah, when i put it in reverse and give it a lil gas, the RPMs drop down pretty low between 300-250. It doesnt die just runs rough until i put it in Drive or Park then idle jumps back up to normal.

On the highway and even driving around town it runs fine. When i first take off i sense a little bit of hesitation but once i get going it runs fine, no running rough.

Thats what im afraid of. Did every 00-01 have the 0331 head? Where is the casting # located? Id like to check to be sure it is indeed the 0331.

So all my posts yesterday were while i was at work. After my last post, i drove the 25 miles home from work and it ran fine. I had it filled to the brim with water/antifreeze and it stayed right at 210* and even a little below at times on the highway. On the highway a couple times i did notice a bit of hesitation in acceleration.

Anyways i have today off so should i go ahead and do the thermostat and radiator cap as a first step or no?

 

Head # is on driver side, may need a mirror or if you have time remove the intake/exhaust manifolds

 

Just want to back up a bit. Are you sure that you are over heating? Did you blow any water from the radiator when it got hot? First thing you want to do is verify that it is getting that hot with a inferred heat gun. Test it by pointing it at the t-stat housing. If your heater is blowing cool air usually mean there is no fluid in the heater core. Even though you said that you burped the cooling system you may still have air in it. Change out your t-stat with a 195deg and burp the system again. Hopefully it didn't crack the head.
Post the out come one you find something out.
Good Luck!

 

While i didnt use an infared heat gun to verify overheating, im fairly certain it was. The amount of water it took to fill the system back up made me believe, for some reason, the cooling system was quite low. Low enough to cause such high temps. I will try to find an infared gun to test for sure. But for now it seems to be running at proper temps now that i added fluid to the system. I am planning on still changing out the t-stat. Ive read a couple places that drilling a hole in it helps for added coolant to flow through. Is that a good idea?

 

If you are going to be running her as is. Keep a real close eye on you fluids. You should also change out you radiator cap while you're at it. I have also read about drilling the small hole in the t-stat. But I have never done it myself. I also know that you can buy one with the hole already in it. Unfortunately I don't remember what brand it is. You can probably borrow a temp gun at the auto parts store.

 

Yeah ill be doing the cap as well. What brand t state should i go with? I was going to get an OEM from the dealer but they're closed today for the 4th. Ive heard about the hole drilling but not sure to do it. I guess its done in the mounting flange on the top. Not sure if i should do that or not.

 

Just bc u can't see any water/coolant in the oil doesn't mean u dont have a blown head gasket or cracked head.. but it sounds to me like alot of these guys are just jumping to conclusions. First step get. A thermostat (185) if it still gives u problems and there isnt any coolant on the ground, ur systems burped, get a pressure tester. If it doesnt lose any pressure .. get a new radiator

 

If you can wait until tomorrow you should get both the t-stat and rad cap from the dealer. As for the drilling I really don't know and I don't want to guess at it ether and give you the wrong info.

 

I cant wait til tomorrow unfortunately. I work Thurs and Friday and todays basically my only day where i have time to work on it.

Im hoping a $4 Murray (from Oreillys) works fine? Seems too cheap to me.

 

The recommended temp for the t-stat in Jeep with 4.0 is A 195deg. Not 185.

 

Well considering they average about $10 at a parts store for a brand name... $4 may not be bad, but does seem to be on the low side. You'll want a 195* as well.

If you said you did your water pump, could be it's not seated or sealed correctly. Check all your hoses for weeping. A little drip here and a little drip there, you can run cool for a month. Then suddenly boom, no coolant, overheat.

I suggest checking your hoses for drips, or chalky white dried up residue. As well as whatever's been mentioned.

 

Thermostat or cap? You can dunk the thermostat in a pan of water on the stove and measure the temperature it opens. If you don't have a thermometer that can read up to 180-190, it should open shortly before the water boils. I don't know of any way to pre-test the cap.
If you have a Napa store around, I've had no problem with their t'stats or caps.

 

Yeah... so i wonder.. why in the world would they make t-stats that open sooner....hmm
I know what the factory service manual says... but why would you not want it to run as cool as possible? Especially when he's having overheating issues.. a cooler running engine is more efficient. Its not gonna make much of a difference but personally id rather run a little cooler.. thats like saying you should never mod your jeep in anyway bc it would change factory specifications.

 

that statement is incorrect engines are designed to run at a designed temperature with youre logic why bother putting in a thermostat at all, i mean its summer who needs heat