rangermonroe

91 4.0 with 225 on the clock. I has been burning a little oil and getting progressively worse.

No oil that I can see in the coolant. New cap, recently flushed.

Two questions:

Before I yank the head, is there something else that I should rule out first?

Is replacing the head bolts necessary (torque to yeild)?

belvedere

I would do a compression test and pressure-test the cooling system.

Are you in a cold climate? Have you been driving a lot of short trips lately (oil never gets fully warmed up)?

rangermonroe

Coastal Georgia. No odd trips.

Firestorm500

Coolant in the oil creates milkshake on the dipstick.

Short analysis says pull the entire engine and do a complete rebuild, or sell it now.

JackJare9455

hes basically asking you if you ever get the engine oil hot enough to dissipate any water vapor that can accumulate in the crankcase.... but we are talking about vapor here.. a slight sludginess that builds up in the oil fill cap area...

you sir.. have a blown head-gasket..

you can attempt to pull the head and slap on a new gasket.... but you better hope the head re-mates to the block.. i would have it checked at a machine shop to make sure...

like firestorm said... rebuild... or donor engine

scottmphoto

You "can" reuse the head bolts but I have always been told that you should use new ones. That is what I have always done.
If you pull the head, check it real good for cracks. Take a good straight edge and lay it on its side on the mating surface. use it to check to see if the head is warped. if it is, you may be able to find another at the JY or have it machined at a shop.

ej's xj

Head bolts can be reused until they are stretched too far... theres actually a spec for how much stretch they can have...but for $25 a new set is worth it

Firestorm500

Elaborating on my earlier post...

If the oil looks like chocolate milk, the bearings have not been lubricated properly. Therefore, entire teardown and rebuild.

salad

Yup.

Practically, though, it depends on how long it's been like this, what your oil pressure is, and how long you intend to keep the Jeep for. If you want to see more life outta the engine do a rebuild. If this only appeared within the last 20 miles and you still have good oil pressure you can probably get away with running it for a while.

rangermonroe

My oil pressure is still running above 40psig.

As I never have had any major trouble out of these engines, I just wanted to confirm my diagnosis that the HG was shot, and not something like a timing chain cover on the 22R.

Hoosier8

Hah, I used to have a 46 Jeep that was so loose that water would drip through the seam in the hood and gather in the flathead spark plug depressions and leak into the engine and turn the oil into a milkshake (I like that description). If I didn't catch it, the engine would eventually freeze but it was so loose that it would start again and I would be on my way.

belvedere

I'm sure in TX that's true (and we now know the OP lives in a warm climate, too), but here in SD, I've seen vehicles with oil so "milky" that you'd swear it was a head gasket. When you can go weeks in the winter with temps around 0F, and people making very short trips day after day (maybe never even getting coolant to temp, let alone oil), far more than a vapor or slight sludge builds up in the engine. I just wanted to make sure that wasn't the case here.

BlueRidgeMark

Yep.

bigbadon

If one breaks while your torquing them down you'll wish you had replaced them!!

rangermonroe

Just to be clear... while I don't live in "Igloo, North Dakota", it has been cold and rainy here. Much colder than normal, with alternating mild rainy days. It has frozen several days already this year and didn't get over freezing for a whole day last week. Then it rained for two.

Yeah, yeah... I know... poor little frozen me!

Running the heater keeps the engine bouncing at operating temp on the ride home today. I will keep monitoring this, and am going to do a compression test this afternoon.