A little story & then the ones in the "know" please weigh in.
I purchased a 89 cherokee base 4.0 last summer & have been fixing up things.
I did the brakes & new tires on all 4 corners. Put a new rotor, dist. cap, plugs, wires, fuel regulator, cleaned throttle body, cleaned the air sensor, fuel filter, replaced all 6 injectors with rebuilt Bosch. Replaced the ground wires to the firewall & so forth. And of course the oil & filter as well as air.
After all of this she was running really good. Smooth.
Every now & then I would have to add a few ounces of fluid to my overflow bottle but very little. According to my instrument it never ran hot or really even close to it.
Last Sunday I had to make a trip that was close to 100 miles. Upon arrival I stopped for gas & when I cranked up it was like firing on 3 cylinders. Shaking bad. I pulled out & after bout a half mile everything smoothed out. Then at the next light she quit. Just shut off. Cranked right back up & drove fine for about 20 more miles. I had 1 more stop so I left in running for maybe 3 minutes & came out & she had died again.
Took me an 30 minutes to get her cranked. I couldn't tell if she was flooded or starving for fuel.
Drove fine until I would have to stop at a light. Wanted to die then.
Took it to a recommended today shop & the guy calls me an hour later & says "somebody has been driving this thing hot & you have a cracked head & it will be $1500."
I'm like WTH.......??? I never drove it hot. It has been running fine since June.
Is it likely this has happened ALL OF THE SUDDEN?
Sorry to be long winded.......

 

You will likely need a 2nd opinion here. Whenever somebody tells you of a diagnosis, specifically ask them how they came to that diagnosis.

A proper diagnosis always requires specific testing. You certainly would be entitled to that information before getting out your checkbook.

One of the first tests that I would run with a suspected head or head gasket problem would be a simple compression test. The compression test for the 4.0 is 120-150 psi, with no more than a 30 psi variation between cylinders. That would seem a logical place to start. Cylinder leakdown test would be even more informational if compression test doesn't yield clues.

Is it possible that the problem is with the head or gasket? Sure. But a blown head gasket is going to be a whole lot cheaper than a cracked head.
You deserve to know for sure before the tools come out.

 

Well I go by the shop after I get this call & he says "you have a bad radiator & that's why you have been adding fluid." Then he shows me with a light the bottom of the radiator & it looked rotten & it was wet & green from where it had been leaking steadily on the frame.
I asked him if that alone could be my problem & he says no....your fluid hasn't been circulating properly & that's why it's running like this now especially when the engine warms up.
So I say well maybe it's just the radiator & the head gasket?
He says "I won't know until I tear it down & have the head tested"

what would you do?

 

That is very good news. You want a coolant leak to be external, not internal! So a new radiator, not that big of a deal.

But I'm lost as to why he would not want to run a compression test NOW, rather than try to diagnose it later when the head is off.

A compression test takes about 20 minutes. I'd ask him to run one and if he doesn't want to, ask him why he doesn't want to. A compression test is awfully good at pointing to a bad head gasket.

 

Thanks for your response. I'm gonna stop him AM before he gets started "tearing down" & ask him about a compression test & also the leakdown test.
If the compression checks ok(whoever does it)...... would that not steer away from a blown gasket or cracked head?
This jeep has not been driven hot. Needle barely to the middle even in the hot summer stalled in traffic.
I realize I have a bad radiator but that still doesn't explain why it stalls & quits after the engine warms up or has been sitting at a red light for 3 or 4 minutes???

 

Not to disagree with Tom or anyone else but I might take three minutes to do the AC voltage from the CPS test described in the link, (in the link) in my signature. Random dieing, then cranking up again, and all sorts of other mischief are it's Hall-marks. (ha ha, "hall effect" transducer!)

You just unplug it, hook a dvm on it's two wires crank it and look for .35 or better AC volts. I won't say mine "missed" as it was going all the way out, but was surely much smother all around after I changed it.

Here it is: Renix CPS Testing and Adjusting
　
　
Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark.
Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.
The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.
Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.
You should get a reading of .5 AC volts.
If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.
Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.
A little trick for increasing the output of your CPS is to drill out the upper mounting hole, or slot it so the CPS bracket rests on the bell housing when pushed down. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.

 

I'd find another shop, or at least ask why he wants to proceed as he stated. Diagnosing a head or gasket leak does not require a teardown. You can certainly do it that way, but a leakdown test, compression check, combustion gas test of the coolant, cooling system pressure test would all be far less intrusive and costly.

I'd start with something very simple. Pull the plugs. If you have enough coolant leaking into a cylinder to kill the cylinder, you'll find the plug for that cylinder either clogged with deposits....or steam-cleaned lily white.
You'll also smell coolant at the tailpipe...that's where it ends up after the cylinder clears it out. White smoke? Any?

From your symptoms, aside from a radiator leak it is just as likely you have a bad injector, bad plug, bad cap or wire or several other relatively inexpensive problems as a cracked head or blown gasket.
Of course you really might have a gasket leak or head problem, but I'd sure do what I could to diagnose that before spending the money to pull it.

 

update : I interrupted his "teardown" & got her back home. Cranks & runs fine for about 5 minutes. I'm gonna have leakdown & pressure test done right after Christmas.
What I have noticed with her just sitting in the driveway there's a puddle of watery kinda yellowish fluid coming from the rear of the engine. I put a pan under it overnight & it's not green. It's kinda yellow & watery. Didn't appear to have oil in it.
If I crank it....... starts right up with no skip or anything for about 3 to 4 minutes.But after about 90 seconds it starts spraying a clear fluid out of the tailpipe. More than your normal condensation spray. I don't let it run.....somethings up.
The dipstick is got perfect clean & clear oil. From what I can see through the oil intake hole it's clean & clear with no water or coolant visible......
thoughts?

 

take it to a shop and have them do the comp check , and cyl leak down. I am thinking that you just have a blown head gasket. Doing the tests though will check to see if it's something else like the head itself is suspect.

 

Is it a manual? Could that be brake fluid from your hydraulic clutch? The slave cyl. might drip from the bell housing.

For my 4,000'th Post here on Christmas Eve I want to say thank -you to my friends here on Cherrokee forum who have brought me up out of the stone age, (the 80's).


AND, if you have an 87-90 with absolutely anything wrong, check your CPS! Only takes a minute, and that thing can do anything.

Merry Christmas!

 

another update : compression test was 105 down the line. Is that ok & within specs for an 89 4.0 with 200k?

The dude that did the test said I didn't have a blown gasket or cracked head. Pressure test on cooling system says I need a radiator which I already knew. That's being done.

My question to him now is where & what is the fluid coming from at the rear of the engine? Sometimes it shows up & sometimes it doesn't. It's coming from "rearward" & runs down the exhaust/tailpipe where it comes down & bends to go to the rear of the jeep.
Sometimes after it runs for 3 or 4 minutes it will just be dripping & puddle on the ground..sometimes it's as dry as a bone. The fluid is watery & has a yellow tint to it. Doesn't taste sweet & doesn't appear to have oil in it. Has no odor that I can detect.
Could this have something to do with the heater system? I don't get water inside on the floor board but here lately when I turn the heater on I hear a little squeal coming from behind the dash.
thanks.......

 

Another update.......got the radiator in & no leaks......... cooling system fine. No cracked head or head gasket.
Now the last problem is still one of the ones that started this saga.
When she warms up to normal operating temp.......she starts spitting & stalling. Sometimes even quits period. Won't re-start until she cools down.

any ideas?

 

The #1 cause of "thermal" (heat related) stalling is the crankshaft position sensor.

The #2 cause is the ignition coil

Both can be tested but testing of the crank sensor can sometimes be inconclusive.

 

thanks......I did a google for "hot stall" & seems like everybody that's had this problem it has usually boiled down to the CPS......after throwing parts & $$$ at everything else....

 

I've got one set of leads for a $5 Harbor Freight DVM with baby alligator clips that lets me clip into that un-plugged socket and see over .35 ACV, in seconds. Without those clips it might take minutes....Catching it when it's gfinking up might make sense.