Help with 2000 Wrangler 4.0 coolant issue
- Thread starter ObedaTJ
- Start date
SBarber1
TJ Enthusiast
I had the exact same issue that lasted about a year and I replaced all the same things, I even tried pressure testing and could find nothing. Never could see any coolant leaking. Mine ended up being a very small leek next to one of the hoses that was small enough that it was just vaporizing out under pressure and heat and was not visible. I finally refilled it and added an bottle if uv coolant dye. Next time it started overheating in a couple weeks I inspected it at night with a uv light and found the leak and fixed it. No issues sense.
SBarber1
TJ Enthusiast
Mine would not start to overheat tell it was very low. Here is my thread with links to dye. Only a couple bucks.
https://wranglertjforum.com/threads/wrangler-tj-overheating-help.6078/page-3#post-182671
https://wranglertjforum.com/threads/wrangler-tj-overheating-help.6078/page-3#post-182671
Okay so that was quick, the coolant level in the reservoir has gone down significantly, only this time faster than the last. The mechanic ruled out a blown head gasket because there are no symptoms even close to a blown head gasket. We have not ruled out a cracked head though just yet, and I honestly hope it isn’t a cracked head but how else could I tell? He told me it would misfire but it does not, no codes nothing. This is driving me nuts
SBarber1
TJ Enthusiast
Try the dye and flashlight. Quick easy and at worst your out $30 bucks for both. It will eliminate the possibility of a leak. I wish I would have done it sooner. Took me a year to find a problem that took less than 5 minutes to fix.
I was just looking at your old reply, thank you! I got the dye but I can’t find a flash light, do they all work?
SBarber1
TJ Enthusiast
SBarber1
TJ Enthusiast
ErikOffroad
TJ Enthusiast
Either the dye and flashlight trick or u can probably rent a coolant pressure tester from a auto part store and see if it holds pressure
SBarber1
TJ Enthusiast
Yep I went the pressure tester route first, none of the adapters fit properly for me.
After the engine has cooled, like overnight, take the oil cap off and look down in there and see if you see the color of your coolant in there seeping up. If so, it’s cracked. There used to be picture on the net of this crack because it’s so common but I can’t find it.
There are several relatively cheap and easy ways to tell if your head is cracked without tearing the engine apart.
1. Try the UV dye in the coolant.
2. Buy the kit to detect combustion gasses in your coolant.
3. Send an engine oil sample out to a lab to get analyzed.
4. Perform a cylinder leak down test (unfortunately I don't think a regular coolant pressure test has high enough pressure to detect a hairline crack, but a cylinder leak down test is over 100 psi so that should work).
Try these things before you take the Jeep apart. Best of luck to you.
1. Try the UV dye in the coolant.
2. Buy the kit to detect combustion gasses in your coolant.
3. Send an engine oil sample out to a lab to get analyzed.
4. Perform a cylinder leak down test (unfortunately I don't think a regular coolant pressure test has high enough pressure to detect a hairline crack, but a cylinder leak down test is over 100 psi so that should work).
Try these things before you take the Jeep apart. Best of luck to you.
So say my head is cracked and I needed to replace it, is it that hard? Because my mechanic is asking 900$ just for labor. My dad thinks he can do it but he said if it’s too hard he doesn’t want to ruin anything for me, I trust he can do it though because he has past mechanic skills and works on cars from time to time. I would take it to a shop but I really need the money for my books for college.
Also which one do I buy, it’s a Wrangler 4.0 2000 sport, I don’t even know if it’s the 0331 head but I’m assuming it is
Also which one do I buy, it’s a Wrangler 4.0 2000 sport, I don’t even know if it’s the 0331 head but I’m assuming it is
I paid 1600 for mine to be replaced with new oil, gasket, filter, lifters, pistons, rings, bearings, and such. I had it planned out because I know these 0331 heads suck. make sure to check the cam, pistons, and timing chain. Sometimes a piston skirt will crack. We found a good head from junkyard to save a little. I think it was 150.
2000-2002 had the 0331 head that tended to crack but the later TUPY update that fixed the cracking tendency still used a 0331 head. You can use a flashlight to look down through the oil cap opening between the #3 & 4 cylinders to see if it has the TUPY on the casting indicating it's the newer stronger design.
Last edited:
I chose a new head from "Clearwater Cylinder Heads". It cost me $450 shipped to my door. I have about 12,000 miles on it now and it still runs and performs flawlessly. It's not too difficult to change if you know what you're doing. It's more like a tractor than a Ferrari. But don't jump the gun. I would do some more tests.
You're checking your oil level? Has it gone up at all? Your Jeep is chugging coolant, so if it's a cracked head, some of that in theory should be in the oil. The fact that your oil analysis came up clean still suggests this might not be a cracked head, even though all the other symptoms point in that direction.
I’m checking it, not gone up at all. The oil really doesn’t look like it is mixing at all. And there is really only one symptom here, and that is the coolant disappearing.