another blown motor thread!

[Pragression]

New XJ (new to me) overheated. Just picked it up a couple days ago been going through it performing maintenence, like i should.. except, last night on a taco bell run. She died! Overheated, even though the gauge never showed until it shut off. Pushed her home.

So this morning I start looking further into how bad the damage is and see if she will start up. Nope, cranks but wont start. Fresh battery, good fuel, fresh fluid in the radiator just in case it did start up.

So moving further, I pulled the plugs, noticed some condensation on plugs 3 and 4 but thought it could just be condensation from being cold. Cleaned and re-installed.

Tried to start again. Nope. Checked plugs. Once again, condensation on 3 and 4.

So, Im thinking its a head gasket. Hopefully the heads not cracked.

Mix all this with a rear main that leaks like a kitchen sink ( I knew about this just hadn't got around to fixing it yet.


-- so heres my main question -- if I get into the head and it is cracked, does anyone know where I can get a good motor? Haven't been to a pick-n-pull out here yet but Im worried they are all picked and pulled already. I need this up and running ASAP. I live up near Placerville but commute to the Bay weekly and was trying to make sure she was reliable, then this happened.

Any help is greatly appreciated.

 

[Pragression]

Figured I should mention.. its a 1998 sport, 4 door, with 4.0 I6 and 4x4.

 

[sneakyjap96]

I would start by pulling the head can be done fairly fast. Inspect from there If just a head gasket replace and go from there

 

[Pragression]

That's the current plan.

Assuming the head isn't cracked. How prone are they to warping? Regarding valve seals, how necessary / difficult are they to replace?

I don't much experience with valve trains. Most of my wrenching experience has been on Rotary engines.

 

[GordoSmasho]

Just an fyi. Reman heads are very resonably priced. 3-400$ depending on where you get it. Thats about the price of a used engine. A ton easier than a motor swap. Ive done bothe multiple times.

Headsonly.com

 

[fewloosebolts]

I did a head swap the last time I did a gasket job. Picked up the earlier 7120 casting head on ebay, very reasonably priced.

 

[Pragression]

Going to open it up tonight.

Gordo, thanks for the heads up (no pun intended) about headsonly.com. Very reasonable pricing.

Fewloosebolts, do you know what years the 7120 castings come in and will they bolt up to my 98?


When I get the head off. If it's still flat can I just install a new head gasket and not worry about valve seals?

 

[fewloosebolts]

7120 is 91-95 and generally considered the best 4.0 head. It'll work on any 4.0 block, mine for instance is a 97 and has a 99+ intake manifold. If there's no cracks and if you're sure there's no warping, then you can just do a head gasket job. 4.0's are known to blow head gaskets so that could very well be the only issue. Only reason I swapped my head was I replaced my head gasket and it blew again a couple months later. Since swapping the head, I've had no issues, at least not with the head or head gasket

 

[Pragression]

Head is off, and cracked. Looking for replacements tonight. Headsonly.com seems like a pretty good option.Double what I was quoted at a jeep salvage yard in Antelope but they're rebuilt with warranty.

Worried I have bigger problems though. How likely is it I cooked the rings too.



Fewloosebolts- I looked into the 7120 head, was told it required using the 99+ intake manifold. Which I didn't have a problem until he told me I wouldn't pass smog anymore. Was he correct? "He" being the guy on the phone at salvage yard.

 

[fewloosebolts]

Any intake will work, the 99+ is just a superior design. What year is your rig? Technically it shouldn't pass smog due to the visual, however it is an oem part, doesn't affect emissions, and to the average (read non-jeep enthusiast) mechanic, it'll look stock. It's never been an issue for me, but I do have a 97 which is very similar to the 99+. If you have a 96 or earlier, it might raise a red flag, but as aforementioned, any 4.0 intake will work.

 

[Pragression]

The head.

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[Pragression]

This is what Im worried about..

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[Pragression]

It's a 98 so definitely something to consider.

Apologies for pic size.

 

[smokinu]

i was lucky and found a junk yard that had a 95 head 7120 casting for my 91. they guaranteed for no cracks or money back. took it to an engine shop and had them check and surface it. as well as new seals and stuff. cost me 80 bucks at the JY and 120 in machine services. i would go that route as a last resort.

since you have it apart. go ahead and replace the head bolts with arp studs.. the stock ones are torque to yeild and should not be re used more then once. and judging by you just picking the truck up, you dont know how many times its been apart.

 

[fewloosebolts]

ARP studs are the one thing I didn't do that I wish I did.

 

[Pragression]

The ARP's are reusable?

 

[GordoSmasho]

After having done a few head swaps i would think studs would make the removal of the head much more difficult. Already have to leave the back bolt in but loose just to get it off and clear the firewall. Wouldnt studs make it that much more difficult. Arp sells bolt kits.

 

[fewloosebolts]

That's a good point, it is tight back there. I think with some finesse they can work though. The biggest advantage is that studs give the clamping force without the downside of being twisted at the same time so they have a more evenly distributed torque and don't stretch as much making head gasket failures less frequent. I'm not sure if they're reusable though

 

[smokinu]

After having done a few head swaps i would think studs would make the removal of the head much more difficult. Already have to leave the back bolt in but loose just to get it off and clear the firewall. Wouldnt studs make it that much more difficult. Arp sells bolt kits.

in my 91 it was tight but i was able to get the bolt out and removed the head no issue. it went back on with no issue with the arp studs.

 

[GordoSmasho]

in my 91 it was tight but i was able to get the bolt out and removed the head no issue. it went back on with no issue with the arp studs.

Good to know. I suppose not all xjs are the same. Motor and trans mount condition could effect the position of the engine as well. There is no way even after clearencing the firewall a bit that i could get the back bolt out on mine. On mine it had the threads above the 12point. Not sure if all are like this but thats how all three of the 97s ive had were.