Like all things, the internet is providing me with too many variable answers...

My 99 has a bit too much goopy goop under the oil fill cap. The oil dipstick appears to be decent but I am concerned with the head. Its a 99 4.0 I6. Trucks runs amazing. Coolant is brown right after a flush but we think someone put stop stick in the radiator. Before I replace the radiator, I would like to know how I can rule out a cracked head....

Any info on the 99 year model or ways to determine (I have ordered a oil test kit), is appreciated.

 

Is your head stamped 0331?

 

going to check tonight. It's on the drivers side right below valve cover?

Also, truck only has 106k on the clock.

 

Yes. See the bottom left of the picture below. You could also use a coolant test kit for combustion gasses if there is concern.

 

so not visible without disassembling

 

No, the head casting number IS visible without disassembling. But you likely will have to do a bit of cleaning on the lip of the head. But definitely can see it without removing a thing, but use a good light.

That being said, if you have a 99 and it has a distributor and spark plug wires, not a coil rail....you almost assuredly have the 0630 head, unless the head was changed somewhere along the way. The 0331 head was standard in all 00-01 XJs.

 

Look on the driver's side next to the #4 cylinder. You should be able to see the number peeking out from under the valve cover without having to remove it. If you have a '99, yours came from the factory with a 0630, which has the casting mark in the exact same place.



Even though it's extremely unlikely you have a 0331, you could still have a blown head gasket, which can manifest with the same symptoms. And 0630 heads and 4.0L blocks can also crack in certain conditions. They just don't do it nearly as often as 0331 heads.

The oil analysis will tell you if you definitively whether you have coolant in your oil. If you do, plan to change the head gasket and inspect thoroughly for other damage when you have the head off.

 

Well how does a 99 with 104k on it have milky oil cap? We have established stop stick in radiator and I plan to replace and flush the motor good, but my friend/mechanic has a good feeling I have a bad head. The oil pressure stays well above 40 under load and between 30-40 at idle.

 

Blown head gasket, most likely. Or it could just be condensation not being handled by the detergent in your oil if you're using really cheap oil. The oil analysis will tell you for certain.

 

IF I do not have the 0331 head, I am going to chalk it up to a possible blown head gasket, however, I do not use cheap oil, not my style.

I replaced the valve cover a few weeks ago and even the top (inside) of it had milky residue.....its very odd.

 

Probably condensation on the cap. Short trips will do that. You need to really drive on the interstate for a while to get the water to boil out of the oil and system.

 

oil analysis - https://www.blackstone-labs.com/

 

It's a pretty common thing for older cars in the winter to do this. A couple things can cause this.

1. A bad thermostat, not allowing the engine to warm up enough, such as stuck open or opening too early. Or too low of a temperature of a thermostat (should be 195 degree)

2. You're short tripping it and not letting it get up to temp, such as a not getting on the highway much.

3. Bad head gasket.

 

0331 head won't fit on a 99 as far as intake and exhaust ports.....

 

1. New T-Stat & 195
2. New Water Pump
3. Radiator leaking since flush and heater core flush (was stop stick plugging things up)
4. We know I need a radiator.....

BUT, why is the valve train so damn milky? Head gasket is all I can think of.