99 XJ, 4.0, AW4, app. 200,000 miles, build date 5/99
Never overheated. outside temps range from single digits to the mid 20's
No codes, idles smoothly

I've been losing coolant with no noticeable external leak. The coolant loss rate is app. 1 quart per 1500 miles. Over the weekend I removed the oil cap and discovered a small amount of "milkshake" on the bottom of it. Upon inspection it seems only isolated to cap bottom and some threads. The valve train looks normal as far as I can see. The dipstick shows no sign of this which might not be clear in the attached pic. The pic of the cap bottom had about a teaspoon of "milkshake".

Blown head gasket or cracked head? What would be the best course of action?

What is the app. shop time to swap a head? Labor rate here is $65 per hour.

Any and all advice will be appreciated and helpful...

 

with your very good explanation, sounds like a cracked head instead of blown gasket. Not a pretty sight either way. I know the thermostat housing will corrode and can leak there under pressure. Swapping heads is not that difficult. Even working slowly, can still be done in a weekend no sweat. I believe the only way to know for sure is to remove and have your head magnafluxed.

 

Where on the head are the casting numbers to verify what head I have?

 

Left side of the head..check out the pic.

 

Thanks!!

 

Took a quick look but couldn't locate the numbers despite knowing its location. In my defense, it was in the single digits outside with wind chills below zero. I'll look again today. From my searching and reading, 99 Cherokees have the 0630 head. 99 Grand Cherokees had the 0331 head.

 

Those 0331 numbers are not what you want to see on a head.

 

Going to order a Clearwater head. Spoke to them briefly and their new head can be used by all 3 head casting numbers......