Baystate Jeepers

4.0L, 20yrs old, 126k, all original and is slowly consuming oil and antifreeze. Several fluid top-offs are needed in between oil changes. The valve seals must be shot, but now starting to think the head gasket is going. Runs fine otherwise.

Anything I should check before diving into a head gasket project?

Are you able to pressure test the system?

Don’t have the right tools or a garage. Is it worth having a shop do that?

Check waterpump and radiator for leaks first.

MDSRACING398 wrote:Check waterpump and radiator for leaks first.

I've looked and heat cycled it and can't find any leaks.

If coolant is getting by the head gasket and into the crank case , the oil will look milky on the dip stick. Dose your windshield fog up using the defroster ? Is the pass side floor wet ? If you run the Jeep till its normal temp with the cap open (Off) it would send bubbles if the head gasket is leaking into the cooling system. The true way is to pressure check the cooling system , its going some where. If its leaking into the crank it would show overfill or your wearing out the bearings and rings. You could do a compression test on each cylinder . Not looking for max compression , it has 120k on it. Looking for more than 10% difference between the high and low. Im one of the Ct. dudes . If your close I can test both systems for you. FjR68

Thanks Frank! Oil has looked fine but haven't checked in a while. Heater core is fine. Haven't tried the cap off test. I could have a small coolant leak but I sure can't find it... I scheduled a pressure test at Lou's next week so I'll see what they say. I'm consuming a quart of oil every 2 -3k miles and losing the equivalent of the coolant overflow tank every month or two.

My lights just flickered a couple of times!

I have seen a HG go on rare occasion and only leak into the exhaust, thou this usually gives off either a nice blue and or white smoke, if its small enough you might have trouble seeing it.

You can have the oil tested for coolant by Blackstone Labs. Look them up. They will send you the sample kits to send back to them for testing.

Motor oil appearance usually doesn't mean squat. It needs to be tested.

That said, there aren't many engine head gasket jobs that are easier than a Jeep 2.5/4.0/258.

I second that statement. I would include the 4.0 V-6 from Ford. FjR68

A simple compression test will tell you whats going on . A quart in 2/3k tells me the valve guides and or the rings are worn . A 4.0 is stought engine and depends on oil changes to live. We had a member that wheeled hard for years and in a drive way , it would slowly start moving down the driveway in gear due to lack of compression whether its valves or rings . It also ran good for him so he wasnt aware . A compression test will tell you a lot. A pressure test on the cooling system will find any external leak. Hope all goes well. FjR68

I agree with the others, a compression test is the most definitive way to see what is going on. I have had oil get into my coolant overflow tank and could smell the oil in the coolant, and I have had the white smoke out the exhaust that smells like a sweet burning smell almost like maple sap that has boiled too long. Good luck man let us know what the results are.

I agree, do a compression test but also a leak down test. Leak down is a better diagnostic of from where things may be leaking.

Welllllllll ? What you find out ???????? Im hanging here ? FjR68