4.0 Weirdness

a_kelley

a_kelley

mechanical fixer
Joined
Jan 26, 2010
Location
Rutherfordton
I got a few puzzling issues with my 4.0.. stumped a few people I know that dabble in motor internals.

#1. The dipstick is rusting up at the top 4-6" of the stick.

There is no water in the oil. (verified with oil change) I'm thinking that its rusting from heating/cooling/condensing cycles?

My coolant level in the reservoir is staying where it is, and the upper rad hose is always full.

#2. The motor runs right about 210 unless its sitting idling, in which case it rises to 230 but the electric fan never kicks on. Burped coolant system pretty well and it has good hot heat.

#3. I do have black/brown particles in the coolant, is that combustion gas residues (crack in head or poor sealing head gasket/around the head bolt that hits the water jacket by the water pump)?

#4. Oil smells like gas.

Bad sealing ring?

The lowest compression is 135 (center two cylinders), highest is 150 (cant remember which ones, but two are at 150, and two are at 145).

#4. When I shut off the motor, I can hear a tick tick tick tick for a short while.

When I had the motor out, it would do the tick tick tick when you stopped turning it over (a revolution or so -- by hand). Is that a lifter bleeding down or a crack in the head?

Motor has 226k miles. One rod bearing is slapping around on no load/deceleration at/from high revs.

These have been bugging me awhile as to what they were caused by.. any illumination would be appreciated.
 
Probably just condensation, but could also be from a blown head gasket. Compression pressures indicate that it probably isn't, though. However, since your oil smells like gas, it could use some new rings. I'm assuming you do regular oil changes.
 
Ray VanBuren said:
Probably just condensation, but could also be from a blown head gasket. Compression pressures indicate that it probably isn't, though. However, since your oil smells like gas, it could use some new rings. I'm assuming you do regular oil changes.
Click to expand...

I need to flush the dipstick tube to be see how long it takes to rust up.

Regular for me is every 5k - 8k miles. Which I don't suppose is too bad, because The '88 Manual only calls to change it every 7500mi. (my '03 toyota camry called for every 5k!)

I was thinking the rings were leaking and that was the gas but the compression test confused me.

The rod bearings rattling on the cylinder would make it egg shape the cylinder, so wouldn't putting rings in be pointless? (without bore and crank grind, in which case I should just look for another motor to build, or save this one to build and get a JY motor)

Looked up new compression on a 4.0 -- 150psi. Under 10% so its not too bad I suppose. I'll either run it til it quits and stick a JY motor or build a 4.Stroker + replace it before it fails..
 
a_kelley said:
I need to flush the dipstick tube to be see how long it takes to rust up.
Regular for me is every 5k - 8k miles. Which I don't suppose is too bad, because The '88 Manual only calls to change it every 7500mi. (my '03 toyota camry called for every 5k!)
I was thinking the rings were leaking and that was the gas but the compression test confused me.
The rod bearings rattling on the cylinder would make it egg shape the cylinder, so wouldn't putting rings in be pointless? (without bore and crank grind, in which case I should just look for another motor to build, or save this one to build and get a JY motor)
Looked up new compression on a 4.0 -- 150psi. Under 10% so its not too bad I suppose. I'll either run it til it quits and stick a JY motor or build a 4.Stroker + replace it before it fails..
Click to expand...
Yeah, it would be pointless to re-ring. Just run it til you find a replacement. BTW, what year is th 4.0?
 
the only oddity about the compression is that it is side by side...which screams head gasket head issue...
 
i would just check and make sure the fan motor hasnt gone bad. if it spins over when you bypass the fan relay then you probably just need a new fan relay. with a motor with that kind of mileage of course you will have some blow-bye via the rings. the ticking you hear when you shut it off is normal. if you dont see water in the oil or vis versa i wouldnt worry. the particles could just be the water pump starting to break down (ive gone through 3 duralasts). shes a 4.0. it wont give up. my 4.0 has 204000+ miles and i know it has blow bye. i just use a good oil filter, whatever full synthetic is on sale and every other time use Lucas or Slick 50. both work great. i would mainly work on the fan though... the dipstick could have come from another vehicle.. or been sat outside somewhere...clean the rust off and let er go:bounce2:
 
'93 4.0L

Dipstick was on this motor only. And only recently began this rust thing.

Fan motor is good. Relay works. Wire to computer is good. Computer is good. I think it may have a combustion gas-> water jacket leak at the back end of the motor, causing rear head temp to be higher than computer temp sensor sees (or the gauge is wrong). But the particles in the antifreeze could just be crap in it. But weird thing was was that the compression in the rear was higher than the front. I put a head gasket, water pump, thermostat on it like 8k mi ago. Doesn't mean that the head wasn't warped. Anyone know who sells the dye to put in coolant for combustion gas presence?

The ticking is normal? but what is it exactly? lifters bleeding down?

I'm not worried about any of this, just wanting to know whats doing it, or why. All the spark plug insulators are orange, and Chiltons guide says its high speed glazing.. Plugs are Champ RC12YC, which is stock plugs if I remember correctly.
 
as the motor gets older the oil pump likes to lose some life. with the configuration and the angle of the motor the front will recieve less lubrication than the back.if you just changed your head gasket then it may just be some excess water that fell into the oil pan. as far as the ticking goes i just figured it was the oil bleeding back down the block and the block itself cooling down. as far as the fan goes does it work when the a.c is turned on?
 
gt500swim said:
as the motor gets older the oil pump likes to lose some life. with the configuration and the angle of the motor the front will recieve less lubrication than the back.if you just changed your head gasket then it may just be some excess water that fell into the oil pan. as far as the ticking goes i just figured it was the oil bleeding back down the block and the block itself cooling down. as far as the fan goes does it work when the a.c is turned on?
Click to expand...

that makes sense. main bearing wear will factor into lubrication as well. fan does come on with the MAX A/C setting
 
ok as long as it works independantly. the only thing that im pondering about is if the fan in your jeep works the same way as my 98 xj. because whenever i got the xj over 210 degrees my electric fan would automatically turn on and not turn off until it reached a lower temp. that and it always works intermittently if my ac or defroster is on.
 
This is a very common problem with the seal or o-ring (depending on year) on the end of the dipstick leaking and allowing moister to build at the top of the tube and rust the dipstick. No kidding, I found this out about 15 yrs ago and would have never believed it until I tried it, the way I looked at it was its a lot cheaper if it actually fixes it than replacing a head gasket that may not be the problem. Good luck.
 
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