Need Advice!

[gtmud]

Here is my delema, I have an 88XJ (205K), Laredo 4x4, 4.0, auto. Body is in desent shape, minus sun damage, interior is abit tore up. The engine however is the issue, it has and overheating problem which I beleive is due to a weak w/p. I replaced the oil pressure s/u. Found that after it warms up that its about 20-25 psi(vehicle guage) and I can hear the bottom-end making noise. I am considering just doing a rod/ main bearing and oil pump change out, versus spending $1200+ on a reman. engine from Advance auto. I got this for free, so far just bought about $120 worth of parts to find this out. Any suggestions, I have done the whole bearing change out before and got plenty more life out of an engine, but with the overheating I am afraid that this engine has already been stressed to its max, and I should get the reman. engine. What do you all think.

[gtmud]

No inputs? Oh I also have changed the oil with SAE 30. New oil filter. No change in pressure, unless I get it to about 2K then the guage will register just shy of 40 psi.

[JDPascal]

Originally Posted by gtmud

Here is my delema, I have an 88XJ (205K), Laredo 4x4, 4.0, auto. Body is in desent shape, minus sun damage, interior is abit tore up. The engine however is the issue, it has and overheating problem which I beleive is due to a weak w/p. I replaced the oil pressure s/u. Found that after it warms up that its about 20-25 psi(vehicle guage) and I can hear the bottom-end making noise. I am considering just doing a rod/ main bearing and oil pump change out, versus spending $1200+ on a reman. engine from Advance auto. I got this for free, so far just bought about $120 worth of parts to find this out. Any suggestions, I have done the whole bearing change out before and got plenty more life out of an engine, but with the overheating I am afraid that this engine has already been stressed to its max, and I should get the reman. engine. What do you all think.

Hi gtmud.......

From your description of the oil pressure, your engine is above the minimum spec given by chrysler so your main issue that I see is the noise from the bottom end.

Oil pressure is also affected by the camshaft bearings and other clearances in the valve train.

For the price I think that a pan removal and a bearing and oil pump inspection would be the way to go. With a good reference, you can take the oil pump apart and check clearances and for scoring before you consider replacement. Also, plastigage several or maybe all of the main and rod bearings before you go wholesale replacement. With the inspection like this, you know what changes you can expect and just because you have it apart doesn't mean that you have to change parts.

High engine temperature can definitely affect lubrication by thinning the oil but usually is more detrimental to the cylinders, rings and valves.

What do you think???

JD

[gtmud]

Thanks JD,
The only time I hear and noise is when I rev up the engine, once it reaches a constant RPM noise goes away, almost like " piston slap". About the plasticgage. How is this done, normally I have just gone through and did the bearings and oil pump. Also I will hear a tapping coming from the distributor, affected by RPMS.
I have already removed the MECH. Fan and installed and electric (14") in its place due to the mech. missing its shroud. The temp seemed to come done to a more managable level, maybe after the w/p change all will be right, as far as the over heating goes. Still concerned about the oil pressure though.

[JDPascal]

your "piston slap" fits with serious overheating or excessive engine wear.

The 4.0 oil pressure spec calls for a minimum of 13 psi at idle and 37-75 psi above 1600 rpm so you are within spec but on the low side of it at higher rpm.

The Haynes or chilton manuals should have a section on plastigaging in the engine overhaul section. If you need more info, I can send you some on it.

The tapping in the distributer could be worn shaft bushings.

JD

[gtmud]

Time to hook up and actual guage, so i can see exactly what the pressure is. Then I figure I'll go on from there.

[Saudade]

Basically, you put a small piece of plastigage on the journal and then torque down the cap. Once you remove the cap you can see how much the gage squashed. By measuring it's width (using the wrapper it comes in), you can determine the bearing clearance. Getting the clearance right is essential.

Does it make the noise in neutral or only under load?

I have a '88 as well and have wrestled with overheating too. After changing the radiator, thermo, fan switch and expansion bottle and cap (all at different times for different reasons), mine runs no higher that 210 (or so) as indicated on the dash gauge.

[fergmonster]

actually piston slap is very common, and can go on for 250k + miles!! mines been doing it forever and has 265k on it........

[Arctic4lo]

If you do, in the end, decide to go with a reman. for the 1200 chunk that your local distributor charges, I would suggest looking into a full on stroker. You'll have the rebuilt engine youre after, plus about 75 horse and 100 ft/lbs extra, for appx. 200 to 400 dollars more.

[badron]

With that many miles on her. Your oil pump is tired and the bearing and pistons are sloppy. Cheapest fix for extending engine life is.
Plan A: Do an eyeball check of main bearing? First pull the spark plugs to relieve compression making it much easier to spin motor. Pull main caps DON'T mix cap everything must go back on the same place they came off. Check the bearing it self. Tornup bad? consiter the crank bad. Then check for scaring of mains. run your finger nail (if you got any) across the cranks bearing surface. If you can feel a scar with the nail that main would most likely eat up a new bearing quickly. If you have two or more bad main(s) you need to think about a used crank or motor. Now check rod bearing same way. Don't mix rod caps or turn them around. mark them somehow. If the crank passes. Install new bearing on mains and rods, new oil pump. Tork everything down to spec. Just let the pistons slap. Bad crank? If your very lucky you will find a good used crank. Don't put a turned crank in a motor with that many mile on it. Waste of time and money.
Plan B: A good used motor. With a lot fewer miles on it. Don't spend oney on an engine not much better off then the one you just pulled.
Plan C: Biggest bucks a full rebuild. including Valve job.
luck

[tblack]

After 205k miles the old 4.0 deserves some TLC, but not complete retiremant unless it has a history of abuse such as long intervals between oil changes. The logic is that if it has never been rebuilt and you got the thing for free, just invest in a new short block or rebuild the existing one. The noise, if it is indeed "piston slap", is normal especially for an older high-mileage engine. My 2000 Cherokee developed piston slap at 15k miles and I change the oil and filter every 2000 miles. My '94 with 120k miles really had clacking noises. As far as overheating, does it steam? How hot is it getting? Mine has been running between 210 and 220 degrees since I bought it new. It's a big engine in a small compartment, but it needs to run 210-220 after warm up to keep all the sensors and stuff happy. If it runs over 220 degrees then I'd start to think about correcting that. And if the noise is a dry knock instead of a chorus of clacking, just rebuild or replace it and you'll be over it. Bottom line is the Cherokee is not a Lexus. It's noisy, rough, thirsty and lets you know it's a Jeep from the time it rolled off the assembly line. And at 205K it has almost traveled the distance to the moon.
tb

[badron]

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but it needs to run 210-220 after warm up to keep all the sensors and stuff happy.
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The best I can tell !!!!!!!!! The highest temp needed for sensors is 190/192 (PLEASE jump in if you know better). The 210 F is needed to improve intake fuel vaporation. (<---wish I would had study my spelling more). To help ex gases temp stay high for cats and O2s. This high coolant temp is really important in the winter but may not be need at all in the summer. Come this summer I'm dropping in a lower temp thermostat before my trip. I got a felling my loaded-to-the-max Cherokee will generate all the heat the O2s well ever need.
Once again please forgive my spelling. My spellchecker/ball and chain worked 12 hours and is in bed.