Strange coolant loss
 

So learned a hard lesson about tap water and cooling systems last year. Even though I read and had been told how it's bad about a year and a half ago or so I replaced some cooling system parts and filled mostly with tap in a pinch. Well one thing led to another and I didnt get around to a proper drain and fill. That winter it froze otw to work but luckily I didnt pop anything and had a shop flush and fill. Months later the radiator failed then the water pump and heater core. So I replaced everything end of summer last year and all has been great. Until today. Now it has been at least a few months since I checked levels but today otw home from work the gauge creeped above 210 a hair and I thought that wasn't right. Its in the 20s. Then I had cycling heat and knew I was low on coolant. Stopped at the parts store for some 50/50. It took a whole gallon and seems pretty full now. No visible leaks and it made it home with no issues.

Where did it go?! Nothing in the oil and no drips. Can that much evaporate? Could I have just not had it completely full and lost less than Im thinking? Strange

It's an 18 year old used car........read my Man Law sig.:thumbsup:

You are either leaking it or you are burning it. Your job is to determine which.

Job #1 is to get the vehicle up on a hoist and perform a comprehensive search for a leak, (with a warm engine/fully pressurized cooling system) paying special attention to the radiator seams, water pump weep hole and all hoses. Performing a "cooling system pressure test" is an excellent test to run as it helps isolate any leaks in the system.

If you cannot find any leaks and the pressure test passes, then I'd suggest you perform a compression test on all cylinders. The spec. for the 4.0 is 120-150 psi, with no more than a 30 psi variation between cylinders.

Good luck and keep us updated!

Thanks for the quick replies. I understand completely and why it seemed so strange.

I will look closer during daylight tomorrow. I expected coolant to be running out after filling it back up but nothing in the parking lot. Nothing in the driveway with a flash light. No milkshake oil etc etc.

Im due for a replace/rebuild on the engine so this may be the nail to make it happen. Over 300k and have had a tap/knock under light load and 1700 rpm and up for about 10k or so. I just havent found the right motor yet. There is a 2001 wrecked 2wd with 160k around me for 500$ but then I would need to address the head issue likely so Im still looking. I cant bring myself to drop the coin on a reman yet though I would like to.

Thanks again. Ill update tomorrow.

Just saw a 98 (I think) in the NoVa Craig's list for $750. That's engine and trans, already pulled.


Re-think a re-man. Quality control is a crapshoot. You'll likely wind up with mismatched cylinders & journals.

Buy used and do it your self for the same money or much less. Then you'll know it was done right.

I also have an issue with dissapearing coolant on my 89 4.0
Every three days I have to refill the reservoir, and sometimes even a bit more than that. No drips, no milky oil (actually my oil looks great as I use LPG as fuel and the oil remains clear).
So I have two choices in my mind for my issue:
1. the coolant plug at the rear of the engine could be leaking while pressurized, and the small drips get evaporated due to the heat in the area.
2. a head gasket failure, communicating a water passage to the combustion chamber, resulting in coolant going straigh to the cylinder and then to the muffler as steam. (that has happened to me on other vehicles)

those are the only choices that came to my mind, maybe one of them is attacking your jeep as well

Option #2 is the most probable by far.

A short update. No visible leaks this morning in the driveway, coolant still full. 45 mile drive to work and still the same.

Will hopefully be putting my JKS crossover shock mount on over the weekend and have time for a thorough inspection.

Thanks for the craigslist info. I really havent looked a ton and mostly DC/SoMD even though I work in Alexandria duh lol. Im going to shop for a suitable replacement and have it rebuilt and then swap. I have too much blood, sweat, curses, $ and tears in this XJ not to make it right.

Thanks for the help and insight.