Hey all, I am in need of some dire help!

Went out today live in Durham, NC, was about 25 degrees, turned on my 90 XJ 4.0 AT to go the store (hadn't driven the jeep for like 1.5 weeks, been driving the wifes car since shes on vacation), when I started it, had a loud tickingish noise, figured just cold needs to warm up. Drove about 1 mile, and ticking wouldn't go away, and then all of a sudden Jeep started going to ****, dying on me, rough idling, ticking got super loud, it stalled twice but got it started back up, was barely able to get it back home. Got it home, and popped hood, noticed smoke coming from exhaust, could also smell some (Coolant? Maybe)... took a video anyone have any freaking ideas wtf happened? It had oil in it, I just checked it last time I drove it, and added a little oil and when I say little I mean like 1/8 of a quart.

Youll notice in the video rough idle, ticking, and it'll dying there at the end of the video on its own.

1990 jeep xj renix 250k miles, automatic transmission.

Please any help is appreciated it.

here’s a better longer video




https://youtu.be/kNUuEw0NQbw

 

I'd say pull the valve cover off and see if anything looks amiss. That noise doesn't sound good.

 

prior to pulling the valve cover, I would perform a compression test, as its easier to do with valve cover on, and also a manifold vacuum test with the engine running, as it is one of the simplest ways to diagnose an engine fault.

These two tests should reveal for certain whether you have an issue with piston or valve train, then start taking things apart

 

Was your coolant antifreeze or mostly yellow water

 

Merry Christmas All!

Spent my Christmas morning trying to figure out what went wrong. The first thing I immediately noticed was coolant reservoir was completely empty, and then I drained my oil, which was obviously mixed with coolant. I am guessing the previous owner didn't do a good job combining coolant/anti-freeze and water, and the water froze since we had below-freezing temperatures the last few days. Water froze and I am assuming bursted and destroyed my head gasket?? That is as good of a guess as I got. I drained a significant amount of fluid from the oil pan. I do not remember my coolant being low, as I checked 2 weeks ago or so when I checked my oil as I always do. Any ideas about what to do next, what to look at, or what anyone recommends next? It is cold out so, so far only drained the oil and got to looking at that. I need to clean up the garage and make some space to get the Jeep inside.

Unsure if I should go ahead and move forward, replace the head gasket, and hopefully didn't damage the motor significantly. Or if I should prepare for a full head/valvetrain rebuild. Or should I just get a used 4.0 from a junkyard, rebuild it, and dropped that ***** inside. The problem is my Jeep is my daily, luckily I skate by for the next month using my wife's car since she isn't working until the beginning of February.

I am mechanically inclined and watched a few videos on head replacement and feel pretty confident I can do it. Not sure what else I should look at in terms of that could have been damaged because of this or what else to do.

Not sure how I should proceed... any ideas on what you all would do would be appreciated.

 

oil and coolant mix. Do not run motor anymore. Coolant in oil can wipe out bearings, and cam and such quickly.

If you must run motor for diagnositic, do an oil change first, refill with coolant and only run for short time. if any bad noises stop!

a leak down or compression test can be run. Ideally these tests are done with a fully warm engine. but in the engines current state Id not attempt to fully warm it up. Instead do tests cold, best if done in heated garage with time to warm up in that heat (i.e. over night)

close examination of drained oil for metal bits is good to do.


When coolant freezes in motor many things can go bad, cracks internally or internally in block or head is a common bad symptom. Head gasket only bad is possible but perhaps unlikely if froozen coolant.

to confirm freezing take a sample of the coolant and see if it freezes or not. or if you have a hydrometer for coolant testing, use that. that will tell you if coolant was freeze proofed or not


Yes you may need a new motor, then again maybe it is simply a head gasket fail and has nothing to do with freezing coolant. If it frooze it maybe is worse than if it didnt.

how many miles on the motor?

Are you sure the coolant froze?

 

So I got to thinking and really got to thinking, my coolant reservoir about 2 weeks ago, was not empty but was not at the full mark, and I do remember like 6 weeks ago, I added some coolant because I noticed it below the full mark, not by a lot but a noticeable amount. So I might have been losing coolant, and maybe my headgasket was already going bad and this was the tip of the iceberg...? But is it a coincidence that it was cold outside and it happened like this during freezing cold temperatures?

I am not sure if the coolant froze or not, I am just assuming since it was below freezing yesterday and the past few days. Motor has 251k miles on it. I am unsure if this it is just a coincidence that it was cold out and this happened, or if head gasket just failed and was already failing. Like I just mentioned, now that I really think about it I have lost some coolant in the last few weeks, nothing significant like but a noticeable amount. It could be head gasket was leaking slowly and it being cold really just finished it off.

The coolant I removed is mixed with oil, I can stop by auto parts store and pickup a hydrometer and see, if the water ratio was higher, only problem is the coolant is mixed with the oil. Until I can get the jeep into garage and drain whatever coolant is left it'll be difficult. I will also be making room in the garage today, and push it in. As of right now, it won't be turned on.

 

Problem is frozen coolant could have ruptured through anywhere....head/ block/ only gasket if lucky but doubtful. Sadly most of your motor is now suspected bad.. you can completely rebuild a stock motor for a grand or so. You probably didnt eat your pistons, and you can get your crank checked at a machine shop. New rings and bearings 👍 Same for the head. You might only need a new donor block. For better or worse, I've built enough 4.0's that i can have it completely stripped down to parts in 2 to 3 hours You might have cracked your radiator, run out of coolant, boiled whats in block. Many possibilities...sadly most bad. Might as well start pulling stuff off now to save time while you figure out what to do. If you have to send to a shop for the rebuild....not worth it. You will have to do all work except machine shop checking. The heads heavy. 2 people lift

 

​​​JUst to add to your Christmas joy you might want to check the trans dip stick to see what the atf looks like....if the radiator suffered some sort of internal disaster could be coolant in the trans via the oil cooler.

 

You got an engine hoist? Pull off hood instead of working around it. Take off radiator to get tested..makes more room . mark hood on hinge mounts for easier alignment when done. Not sure of interchangeable or compatibility with the earlier motors. There is a good sticky on that in the preambles links

 

I do, I’ve never done a swap on a jeep, but have on BMW. Hopefully isn’t so difficult. I guess I’ll do a junkyard rebuild. Any recommendations or videos or stickies you can throw my way? Never done an engine rebuild but guess there is a first for everything. Guess it’s time to invest in a new daily.

I figure it’s best to just do a 4.0 rebuild or if I can find a running one, then to do gasket to just find out block is cracked or something. all considering who knows how the damage is. Guess my wife is getting what she ultimately wanted lol… for me
to get a new car and stop relying on the XJ. I guess it’s best I find a new daily anyway. Just was enjoying no car payments.

 

No wife ever liked their husbands...JEEP Its a great engine to learn how to rebuild. Since yours is scrap anyway, pull head, look inside. If its in your budget, find a engine hoist from harbor freight or pep boys. With a coupon i got mine for 125...but that was a while back. If you junk your jeep...pull all useful parts, you will be thankful later

 

I have a hoist got mine from HF, when they use to give you those 20% coupons every week and now they don’t. I’m going to do a rebuild… will end up doing a junkyard swap first found a motor near me that they have video of it running 3 weeks ago. Will swap that into mine, and rebuild my 4.0 over time. Who knows maybe I’ll do a 4.6 stroker 😉 I’ve swapped engines into several BMWs no way Jeeps can be harder than that.

 

What year is the new(old) motor from the junkyard? Do you plan to swap the renix components over to the junkyard motor?
Should be a good winter project.
74Plb

 

JY motor is same year, 1990 renix motor. I plan on removing my motor Wednesday or Thursday this week and will inspect what is able to be swapped, and buy new whatever isn't salvageable.