Big_Taxi

Hi, everyone. This is probably super common but I’m not the most car savvy, so this is mostly to clarify what I’ve learned by lurking.

Ive been losing coolant pretty slowly lately, maybe 2 cups every two weeks or so. Engine is running well, no overheating or white smoke (I do have a howling issue, there’s another thread for that), but I decide to try to dig deeper on the possibility of a cracked head. My dipstick looks totally fine, and my oil cap looks like pic attached.

What do you think?
Can I look into the oil cap while the engine is running?
Can I take the radiator cap off to check for bubbles while the engine is running?
What else should I do or not do t check this?

Thanks, I know this is a common thing but I’m an idiot with things like this.

tjwalker

Here are a few things to get you started.....as I mention in step #4, research this in-depth for more information on this issue.

1. Perform a complete inspection of all cooling system components for LEAKS. You're either leaking coolant or burning it. You'd much rather be leaking it! Pay special attention to the side seams on the radiator. They seem to be a weak link for small leaks that are hard to track down. You can rent a cooling system pressure test kit from many parts stores to help you identify if you have a leak.

2. You can't look into the valve cover with the engine running but you sure can with the engine off. Get the best light you can find. Sometimes (certainly not all), folks can actually see the head crack between cylinders 3 and 4 this way.

3. There is a test kit you can get from Napa and other places called a "BLOCK TEST". It sniffs your coolant for the presence of hydrocarbons. Hydrocarbons are the byproduct of the combustion process and your coolant shouldn't have them but they will if the cylinder head is cracked. About $30 and simple to perform.

4. Search this forum and others for "CRACKED 0331 CYLINDER HEAD + JEEP CHEROKEE" and you'll find hours of light reading. Knowledge is power with this issue if you are experiencing it.

5. How is your oil pressure? If you do have a cracked head, the coolant will eventually wipe the bearings inside the engine which will result in low engine oil pressure. If you do have a cracked head, the key is getting to it quickly before the engine is toasted, otherwise you have bigger fish to fry like finding a salvage engine along with a Clearwater or later model 0331 TUPY cylinder head which doesn't have the known defect. FYI, the oil pressure spec for the 4.0 engine is as follows:

*Not less than 13 psi at HOT idle
*Between 37-75 psi over 1600 rpms

6. Don't buy anything on the shelves in a bottle that says it will cure a blown headgasket. Most of those won't even do that and if you have a cracked head, it won't work and can clog your cooling system.

Good luck and keep us updated!

Spencer_P

DO NOT open your radiator cap unless you can hold the coolant hose for an extended amount of time without burning your hand.
Looking at your oil cap, it looks milky...

Morat

Try taking the belt off and see if your water pump has any play/rough bearings. They can leak when they're shot - and make a racket too.

00cherok

Agree. That cap looks milky, which "can" be a telltale for a cracked head which '00 and '01 are notorious for...

Morat

It does look milky, but not excessive. OP - do you do lots of short trips? If so, try a decent run (30 miles or more) to make sure that isn't just condensation. You may have a bad head, or headgasket - or just a slow leak that is hard to spot because coolant is hot and evaporates.

Ralph77

Also agree with it looks milky.
But thinking not condensation.
My '00 XJ, my DD, is pretty much just used for short trips.
Mine never looks like that and I check every Monday.
I live 1/2 mile from work and go out of my way going to and coming home from work
I have these routes that when I pull into the parking lot at work, or home, she is just reaching operating temperature and I can see it dropping as the thermostat opens.
I do take her for a good run once in awhile cause I know driving her as little as I do is not the best thing.
When you own an '00 with the 0331 head you have a tendency to keep an eye on things.

dave1123

When you own an '00 with the 0331 head you have a tendency to keep an eye on things.

You said it, brother! The amazing thing is this is the first jeep that I've owned that hasn't used a drop of coolant in 6 months! BUT I'm watching it like a hawk!

Big_Taxi

Great responses, thank you everyone. I drove probably 2.5 miles before looking at the cap, it is my DD. It looks milky, obviously, but the dipstick looks fine, so maybe it's just a slow leak into the engine?

I'm going to dig for a coolant system schematic so I can take a look at that, as well as follow up on other pieces of advice. Another thing I found while digging is that apparently you don't smell coolant with a cracked head, because it burns off, and I would say that I think I smell coolant while the car is still getting up to operating temp. A leak or evaporation?

I think oil pressure is fine, but I'm going to get an oil change before a 150 mile trip to Buffalo next week. I have the Blackstone test kit ready to go, so I'll just ask my maintenance team to take a sample for me.

Thanks for your help!

BlueRidgeMark

Do a test for exhaust gasses in the coolant. Checking the oil via dipstick is NOT an adequate test. Water in the oil doesn't always happen with a blown head gasket or cracked head, and even if it;s there, it might not show up on the dipstick.

Big_Taxi

Thanks, I think that might be my next step. The $50 kit needs to be attached to a vacuum line while the engine is running. Is this something that's reasonably easy to do? I've seen a few how-to vids but just dont want to **** anything up.

dave1123

SAE says the engine must run fully warm for over 30 minutes or 15 miles at highway speeds to completely evaporate any condensation from the crankcase. Try that BEFORE you do your oil change to see if the sludge disappears. If it does, you don't have a head gasket leak.

Big_Taxi

So I ran for 30 minutes around 205 degrees, pretty normal. Stopped for breakfast and checked the cap, and it was the exact same pattern of snot, absolutely no change. So I figure that's bad news, but just to be sure I wiped it off. After the drive back, 205 degrees for 30 minutes, I check again and the cap was completely snot free, nothing at all. I'm still going in for an oil change and to get my Blackstone sample taken, but any thoughts about that?

Jeepwalker

Yes, double-check for leaks. As suggested before, look under the water pump (weep hole) for a minor leak ..and also the hoses and heater core. Use your nose to sniff in the radiator while it's running. Your nose is pretty sensitive to combustion gases.

The fact is, vehicles can go years in a slow coolant loss situation, even if it is the head gasket. My wife's WJ Jeep has been using coolant and a milky oil cap for about 8 years. It's up to about 220k right now. Heck, maybe the gasket will never 'blow' before the motor (or trans) goes. I just keep my eye on things and add a little coolant once every couple weeks. I've had other cars in the past that went years till the head gasket went out.

Keep your eyes on things. I personally wouldn't freak out about it.

dave1123

Here's one other item for your edification. The older water pumps used to have a "weep" hole on the bottom of the fan shaft bearing. Later this was changed to a "weep chamber" which holds about a teaspoon of coolant that's allowed to evaporate without any visible signs of leakage. After the leakage overcomes the chamber's capacity, it will leak into the back of the fan pulley and get thrown off on initial startup. I discovered this when we did the brakes on my 2000 WJ. After installing the calipers and rotors, we started it up on the lift to bleed the brakes. Coolant began pouring down the front of the engine, then stopped! Okay...water pump! Looking in an AC Delco catalog for the right part number, this chamber was explained. The reason for it was stated as all shaft bearings weep a little even when they are new and this chamber eliminates premature replacement. At least that's the corporate rational. This engine was using about a pint a month for a long time. Sometimes you could smell coolant when it sat and idled, but could not find any leakage.