90_cherokee

So im doing a cylinder head swap on my 90 XJ 4.0.Got the cylinder head off and now im doing some clean up,prep and inspection as I wait for the Reman'd head to arrive from the big brown truck(UPS).

Everything looks really good. The combustion chambers are nice and dry,the spark plugs are all a uniform brownish white color and totally dry.The Tops of the pistons have little if any carbon bulidup on them. This engine looks VERY healthy. It does have a ridge at the top of the cylinders,and I dont see any crosshatching.****EDIT**** Upon closer inspection There is indication of Crosshatching in the cylinder walls.

Looking at the tops of the pistons I see an arrow,the word FRONT and the number 50.

On some engines I have seen in the past,the number on the piston indicates an oversize/overbore of the cylinder. Is this the case in this matter? Has my engine been bored out .050 some time in the past? Or is this just a Jeep part number thing?

Oh and before I forget. Everytime I have ever done a head gasket or removed the head from a vehicles engine,regadless of how well I drain the coolant,I always get just a little coolant and oil mix from the little residual coolant in the system. Not a great amount,but i do take note of it. So would it be safe to say an total cooling system flush and an oil change is in order once I get this put back together?

CoffeeCommando

I'm not sure what the stock pistons look like. I had Titan do my engine initially, unfortunately. I do know that my current onts have an arrow that point to the front of the engine, and on the side they say something about "60" because that's how far they're bored.

mentalbreakdown00

pics would help, but it does sound like it has been bored .050 over....

90_cherokee

Heres a pic of #2 piston.

CoffeeCommando

I would be very curious as to why it's bored .050 over AND you're swapping the head. This sounds like it might be related..

Anything you're not telling us?

90_cherokee

The reason for the head swap is due to an issue I have read about MANY times. The bottom T-stat Bolt got the head sheared off when I tried removing it. I tried to drill it out and install a bolt extractor,it broke off inside the bolt. I tried drilling in a different spot on the bolt and ended up breaking off a piece of the casting from the head. Tried JB weld,and then running a Tap into it,but the JB Weld wouldnt hold and the bolt kept pulling the threads out. Im sure there was another way of fixing it,but I just gave up,bit the bullet and bought a Reman'd Head from J&C Enterprises in W.Virginia. $289 Shipped with a 1 year warranty.

I just didnt want to fuss with it anymore,not knowing if my repair would have been good enough or not. At least with this new head,Ill have piece of mind. Knowing what I know now,Anti seize will be my friend when putting some of this stuff back together.

mentalbreakdown00

That def looks like .050 over, if you have a bore gauge is gonna be the only way to know for certain.

CoffeeCommando

It's probabl .050 over. Those walls should look like a mirror. I had mine rebuilt with less than 5 thousand miles and the crosshatches were gone.

It has the crosshatching still and you didn't know it was rebuilt recently?

90_cherokee

The whole .050 thing really doesnt concern me too much,just thaought it was an indicator and wanted confirmation.Ill see if I can get a Bore Gauge to confirm.

90_cherokee

The guy I got the truck from didnt indicate anything about a rebuilt engine,when I asked about the Trucks history.He owned it since 2008,and it had 125k on the Odometer when he got it,according to the title. I got it 2 weeks ago and it had 140k on the odometer when I got it.

CoffeeCommando

It's an indicator it was rebuilt, and not long ago. The question is... why and by who?

It obviously doesn't have a rebuild title otherwise you would have known about it and have the title in hand. Now the question is who built it and did they do it right. You're swapping the head on it and that's not a good sign. The fact that you had to do anything with it, especially the thermostat, is not a good sign.

Engine overheating means engine rebuilding. Thermostats relay engine heat. Now you're ordering a new head because the thermostat housing is unserviceable.

The more you tell us the more we can help. I expect to see more posts from you in the future about engine maintenance/rebuilds until then.

CoffeeCommando

Everything about a new vehicle should concern you. Things like that didn't concern me either. I'm now 3 engine rebuilds smarter and I'll never let something small escape me.

You also might let a small tick not concern you... but damn are they expensive. One wiped out cam, a set of lifters and 3 thousand dollars later I learned my lesson. Twice.

Johnny9Inches

While you have the head off, check around the cylinders, where the coolant flows for any build up too. I was recommended to change out my freeze plugs when I did my head swap (0331) to (0630). I checked all around the jackets and everything seemed to be clear, flushed it and left it alone.
But when I removed the heads on my 88 Camaro, there was so much build up from the previous owner dumping in that stop leak crap. I hosed and dug for two days before it ran clear. Just saying since you have the chance to clean and check it might as well.

Johnny9Inches

Also drain you oil, if you got water in there it could damage the bearings on either the CAM or the Crank, which means yet another rebuild. Not worth the money when all you need to do is spend $20-$30 and do it right.

90_cherokee

The back story goes like this:

I bought the Jeep and in the coolant reservoir,it looked like it had DEX COOL(Reddish color)

So I have the Jeep a few days and start going through it,and notice the coolant is actually more of a muddy/rust color/ Upon draining it was reddish ,pink like Dex Cool,which I dont care for I like the normal green stuff... I found a Tstat in the Glove Box,so I thought the vehicle may not actually have one installed.Thats where the teardown of the T-stat started. Turns out it did have a T-stat installed,but it was goobered all over with RTV(Not pretty) The vehicle wasnt overheating,I just wanted to do my own Preventative maintenance for my own piece of mind. I dont know when the coolant system was ever last serviced by the Previous owner.