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Unknowingly overheated..now ripping into the motor

5K views 63 replies 14 participants last post by  cbenez1 
#1 ·
Hey everyone..

I was driving my 1998 Jeep Cherokee 4.0L down the highway today around 65-70 miles per hour on my way to Boston, MA when I began to hear some faint ticking. The ticking began getting worse and before I know it I was losing power in the engine. I decided to pull off the next exit and the moment I did I lost the engine completely. When I came to a stop I realized then the engine overheated and was smoking pretty bad.

Keep in mind, MY GUAGES DO NOT WORK. Therefor I had no idea it was heating up. Regardless I had it towed and began checking the engine over

I found that the cooling fan does not work, I jumped it straight from the battery and no movement whatsoever. Also, checking the coolant it was completely empty except for the reservoir which was now a dark mud color instead of lime green. I pulled the spark plugs and all were good except for Cylinder #1, which was no longer gapped and it was soaked in gas whereas the others were dry and proper.

I proceeded to a compression test and my results are as follows,
#1: 0
#2: 60
#3: 90
#4: 120
#5: 120
#6: 120

My guess is a blown head gasket? The oil seems undisturbed, no antifreeze in it whatsoever.

Any ideas? I won't be able to break into the engine until tomorrow.

Also, besides the gauges not working she ran like a top before this incident.

:cheers2:
 
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#2 ·
you have no compression in #1 cylinder? I am thinking a good educated guess, would be to call a priest and put that powerplant to rest. The ticking could have been a myriad of things that caused the overheat. Sounds like a stuck valve, which would explain the ticking. If I've seen one, I've seen a hundred where No. 1 cylinder is dead. That's because it's always the one starved for oil. The way the block sits in the engine bay is tilted backwards, therefore No.1 always gets jipped of oil. Thats why its important to keep it full and changed regularly. Let us know what you find.
 
#3 ·
Mywrangler94 said:
you have no compression in #1 cylinder? I am thinking a good educated guess, would be to call a priest and put that powerplant to rest. The ticking could have been a myriad of things that caused the overheat. Sounds like a stuck valve, which would explain the ticking. If I've seen one, I've seen a hundred where No. 1 cylinder is dead. That's because it's always the one starved for oil. The way the block sits in the engine bay is tilted backwards, therefore No.1 always gets jipped of oil. Thats why its important to keep it full and changed regularly. Let us know what you find.
How would the #1 cylinder get starved of oil? Unless the oil level was so low that the pickup tube wasn't sucking up any oil, it should get the same amount of oil as the other cylinders being a pressure lubed system.
 
#4 ·
well, if you take a look at your engine in your engine bay, notice the engine tilts backwards. Does water roll uphill? Physics don't change in a Jeep. Its the highest point of the head. Hence, the oil tends to run down quicker, its not a flaw, just how it is. Which is why I say, to change your oil when your supposed to and to use what your supposed to. And, if you didn't know, No.6, every now and then, tends to blow the skirt off the piston. Which has happened to me once and to 2 of my customers. In any event, thats from my friends at Chrysler, I didn't make it up. Did that answer your question?
 
#6 ·
I'm pretty sure the tilting of the engine isn't starving Piston 1 of oil or else it would have been designed differently.

This engine was upkept and ran like a champ before overheating caused this problem. Regular oil changes has nothing to do with it. I'm sure if I was able to watch my temp gauge I would have caught it on time and I wouldn't be tearing into the motor. I think a combination of low antifreeze, a nonworking cooling fan, no fan shroud, an aging cooling system and the fact that the heat index was over 100 degrees is the cause

I'll be ripping apart the motor today and keep you guys updated.
What a way to spend my birthday weekend :thumbdown:
 
#9 ·
Yes. Severe overheating can lead to detonation. Detonation can literally knock chunks out of the edge of the piston. I had this happen to me on a Ford 2.3L four cylinder.

If you lower the piston, you will probably see where the combustion gases may even be flame cutting the side wall of the cylinder.
 
#11 ·
The head looks OK but I was considering taking it to a machine shop just to make sure it is good. How much would refinishing a head run me roughly?

The dealer wants $194.00 for a single cylinder.. and doesn't include the ring. Autozone has a set of 6 with rings for $122.00. Does anyone know if it will be an exact fit?
 
#12 ·
Always get the head machined after its pulled off,the head can have the slightest warp in it and can cause head gasket failure very quick,plus it will give you an idea if there are any cracks.I would try rockauto.com for parts way better than AutoZone plus much cheaper.
 
#21 ·
Head.

Decent machine shop should deck the head and do valve job. Around $250. will need the valve seals to give to shop. usally cheaper to order full gasket set, make sure valve seals are in it. Need to check the bore and make sure no scratch/gouge. would assume bore is scratched.......Ticking is usally the overheated oil, viscosity way to thin and everything was ticking/slamming.... Need to deck/surface head after major overheat, hope u can check the block deck too....Don't wanna do the work then blow headgasket...
 
#25 ·
BassMasterCHS said:
Coming off of a rebuild due to a similar failure to my engine, I'd be looking at a complete rebuild.. Or swapping in a used engine.
Well I'm going to try and fix this one. If not I'm not even going to bother with this jeep and sell. I have enough problems with my YJ that I can't keep up with both.

I got that cylinder polished , rechecking my measurements ten times I'm getting 3.875 or roughly that on all. Am I safe buying the standard size piston from autozone?

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This piston really wore. The rings are seized and almost none existant
 
#26 ·
Well I'm going to try and fix this one. If not I'm not even going to bother with this jeep and sell. I have enough problems with my YJ that I can't keep up with both.

I got that cylinder polished , rechecking my measurements ten times I'm getting 3.875 or roughly that on all. Am I safe buying the standard size piston from autozone?

View attachment 656366
Ummmm..........I don't even know where to begin here, but allow me to ask some questions:

1. HOW did you measure the cylinder bore? You need to measure both top and bottom and you need measurements in both the axis of the crankshaft and the width of the block. This measures the bore for taper AND roundness.

Here are the factory specs. for a 4.0:
Diameter -- 3.8759 to 3.8775 inches.
Taper--max of 0.001
Out of round--max of 0.001

If your bore does not meet the above specifications after "polishing", then it needs to be bored oversized and an oversized piston fitted.

2. HOW did you polish the bore? Did you use a hone? I suspect not, since I see no cross hatching marks. If you did not hone the bore, you can forget getting the rings to seat to the walls and you will have the same damage to the rings as before in very short order.
 
#27 ·
AZ Jeff said:
Ummmm..........I don't even know where to begin here, but allow me to ask some questions:

1. HOW did you measure the cylinder bore? You need to measure both top and bottom and you need measurements in both the axis of the crankshaft and the width of the block. This measures the bore for taper AND roundness.

Here are the factory specs. for a 4.0:
Diameter -- 3.8759 to 3.8775 inches.
Taper--max of 0.001
Out of round--max of 0.001

If your bore does not meet the above specifications after "polishing", then it needs to be bored oversized and an oversized piston fitted.

2. HOW did you polish the bore? Did you use a hone? I suspect not, since I see no cross hatching marks. If you did not hone the bore, you can forget getting the rings to seat to the walls and you will have the same damage to the rings as before in very short order.
It was honed with a specific honing tool I bought from Harbor Freight, a 2-4" one. It's 3 pronged with a spring with stones at each prong..rotated by drill. Is it supposed to leave cross marks?

I did not measure it personally, my father did with a measuring tool also from Harbor Freight..he measured inside and got 3.875. I can remeasure or have him remeasure. How do you figure taper and out of round?
 
#29 ·
Exactly what tool did you use to measure bore diameter? The most common tool is a set of telescoping guages and a micrometer of the appropriate size. Is that what you used? A dial caliper is not good enough.....
 
#30 ·
I will add one other comment--damage like I saw in your photos generally needs an oversized bore with a matching piston to properly correct the damage....
 
#31 ·
AZ Jeff said:
I will add one other comment--damage like I saw in your photos generally needs an oversized bore with a matching piston to properly correct the damage....
My question is.. Will one oversized piston and 5 standard pistons run smooth?
 
#41 ·
I know you are replacing the engine, which is an easy way to solve your VERY big problem, but I must answer your question here, because someone else answered wrong.

Using one oversized piston with all others of "normal" size is not a problem. In fact, the factory used to do that quite often in the old days before the machining equipment could make very consistent bore diameters and piston sizes.

It was NOT uncommon at all to find engines straight from the factory with oversized bores on one or two cylinders. They would mark it with special punch marks on a certain spot on the block (described in the FSM) that would clue the technician working on the vehicle to the other-than-standard bore diameters. This was also done for main and rod bearing sizes as well.

It's rare for this to happen nowadays, since the machining equipment at the factories generates MUCH more consistent dimensional parts.
 
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