Replace a 4.0 cracked head after driving 800+ miles with coolant in oil?

[JohnEP]

To those people who have actually replaced a 2000-2001 cracked 4.0 head after running it 800+ miles or more with coolant in the oil:

I have a 2000 Grand Cherokee 4.0 with 140k miles. I have been feeding it coolant over the past 6 months, and I have only driven it about 800 miles over that time (this is not my daily driver, but I like it when I need it). I have put in about 4 gallons of 50/50 coolant total over that 6 months. Then, oil dipstick showed 2 quarts over-full, chocolate milk-shake. Oil cap had green foam on underside...

With a fresh oil change this week, my oil pressure settles at 19psi after: 15 min warm-up idle, driving it 6 miles, then letting it idle for 10 minutes. Engine sounds great at idle, at 4000 rpm, and even under load of acceleration. No knocking, no anything.

Rather than swap the engine, I am planning on a rebuilt TUPY head replacement. So, I am asking: has anyone had their bearings fail AFTER replacing the head, in an engine that held 19psi oil pressure at warm idle before the head-swap? If so, how long did the bearings last AFTER the head swap?

Thanks,
JohnEP

 

[sidriptide]

when bearings go bad because of contamination, they go quickly.
what is your PSI under load?
odds are you will be fine, as long as you are positive the head will fix the problem.

 

[JohnEP]

when bearings go bad because of contamination, they go quickly.
what is your PSI under load?
odds are you will be fine, as long as you are positive the head will fix the problem.

Above 1600 RPM, oil pressure is 40 or over.
But this is the question: after replacing my head, should I expect my bearings to slowly disintegrate? Easy to say, "yes, they will probably wear faster," but does anyone have actual experience replacing the head, and seeing oil pressure loss over the next 5k miles?
JohnEP

 

[Talyn]

If your oil pressure is good I would run it with a TUPY head. Do multiple oil changes to get rid of the coolant.

Oh.. and stop driving it like that.

 

[JohnEP]

Should I replace the lifters while I'm in there? Any easy way to check them? Engine sounds good as it is....

 

[Talyn]

Faulty lifters will make a clacking noise. If it sounds good don't change them. You will have to go through the cam break in and use break in oil.

 

[kastein]

I would flush it with crummy oil (the cheapest you can get) a couple times as soon as you put it all back together.

I doubt you are going to wreck the new head if the motor goes south again, so I would probably put a good TUPY head or new casting from ACH/Odessa (et al) on it and see how it goes. Being in the rust belt you can probably pick up a 91-99 era 4.0 in good shape for fairly cheap. If your bottom end ends up blowing anyways, as long as you don't beat it up trying to get it home you can always swap your almost-new head onto the cheap 91-99 motor, drop it in, and keep on going.

 

[JohnEP]

If your oil pressure is good I would run it with a TUPY head. Do multiple oil changes to get rid of the coolant.

Oh.. and stop driving it like that.

OK. I will hold you accountable for this advice (heh heh)...
So hear we go... I've got the old 0331 head off now. Got some great pics of the strap/pole system I used to lift it off the block, and a great close-up pic of the crack in the head. Posting rules say I MAY NOT post attachments. I am quite proud of these pics. Wanna see them? Tell me how to post them!

JohnEP.

 

[kastein]

I'd upload them to a photo host - say, imgur.com. Probably one of my favorites. Once uploaded just copy the string titled "BBCode (message boards & forums)" and paste it into a post here and it should show up.

 

[JohnEP]

 

[JohnEP]

 

[kastein]

Only works if you're logged into CherokeeForum I think.

 

[JohnEP]

 

[JohnEP]

Only works if you're logged into CherokeeForum I think.

Crud. I tried. But really, why cant I simply attach something here directly???

JohnEP

 

[kastein]

It uses a bunch of bandwidth is the reason I think... I generally don't because attaching things and reuploading them on every site I use them on annoys me. I'd rather upload in one place (imgur, tinypic, etc) and then just copy the embed code anywhere I need it.

 

[JohnEP]

To save bandwidth, space, and time, I'll just leave the pics on cherokeeforum.com for now.

But HERE is the kicker: the gasket I am scraping off the block is printed "Victor Reinz"! No way this is the OEM gasket, right?

That means this is now the 3rd head being installed on this engine! Well, this time, it's a TUPY... 3rd time's the charm... I noted the the head bolts were NOT painted; certainly time to replace them anyways. All rockers were solid when I took the valve cover off. Therefore, I plan to leave the original lifters in place. Engine has about 140K on it.

Wish me luck and goodwill,
JohnEP

 

[JohnEP]

Gasket now cleaned off the block. Next step: rinsing off the lifters inside the engine??

Careful as I was cleaning off the gasket, I can see a small chunk of gasket sitting on top of the lifter hole (where the oil pumps into the lifter rod). I blew it off with some compressed air, but I can see other pieces of gasket down in there. Should I rinse this out with... keronsene? carb cleaner? will it just drain down into the pan? Or, disconnect the fuel pump relay, and turn the engine over a few times (with the head off). Will this flush that junk down?

Also, what about the debris that made it down to the piston rings? I plan on carb cleaner and shop vac, but your advice appreciated.

BTW, I got the thread chaser kit from Autozone for the head bolt holes and ran it up and down with the air wrench. Not sure it really did anything.

Thanks,
JohnEP

 

[Talyn]

I wouldn't pour anything in there hoping it to flush out. There are a few cavities int here that the flush could get stuck in. Vacuum it out if possible.

 

[JohnEP]

I wouldn't pour anything in there hoping it to flush out. There are a few cavities int here that the flush could get stuck in. Vacuum it out if possible.

I took the narrow crack/crevice attachment off my house vac; it was narrow enough to fit down into the slots of the engine block to suck the oil/debris off the lifter tops really well. I used my nitrile-gloved-hand as a 90 degree joint to "connect it" to the end of the shop vac hose. Worked great. Thanks.

To "clean" the gasket debris off rings, I spayed carb cleaner on the front side of the piston gap (onto the upper piston ring), while I sucked it off with the shop vac from the rear side of the piston. I left the shop-vac motor/lid "unclipped" from the base, just in case the electric motor might spark the carb cleaner... I figured: better to blow the top off the vac, than have a sealed bomb. Nothing ignited...

Dropped the new TUPY head onto the block, right onto the guide posts first try, no sliding around. Used a short rope tied to 2 bolts protuding from each side of the head. Two friends lifted the head with a pole slid through the rope loop, while I guided it into place as they lowered it onto the block.

Forgot to squirt a bit of motor oil on the rings before I put the new head on. I planned on putting a bit of 15W-40 Rotella T on them (anti-wear zinc phos). Oh well... Maybe I'll squirt some through the spark plug holes.

Got some Permatex High Temp Thread Sealant for the head bolt that goes through the coolant passage near the thermostat.

This play-by-play is for your interest, and maybe valuable to those who come after. I would never have dared attempt this project on my own, if it were not for the documentation provided on the internet by others who have done this themselves, and active support from Talyn and others like him. I'll keep you posted.

Thanks again guys; your comments/advice appreciated,

JohnEP

 

[5-90]

To those people who have actually replaced a 2000-2001 cracked 4.0 head after running it 800+ miles or more with coolant in the oil:

I have a 2000 Grand Cherokee 4.0 with 140k miles. I have been feeding it coolant over the past 6 months, and I have only driven it about 800 miles over that time (this is not my daily driver, but I like it when I need it). I have put in about 4 gallons of 50/50 coolant total over that 6 months. Then, oil dipstick showed 2 quarts over-full, chocolate milk-shake. Oil cap had green foam on underside...

With a fresh oil change this week, my oil pressure settles at 19psi after: 15 min warm-up idle, driving it 6 miles, then letting it idle for 10 minutes. Engine sounds great at idle, at 4000 rpm, and even under load of acceleration. No knocking, no anything.

Rather than swap the engine, I am planning on a rebuilt TUPY head replacement. So, I am asking: has anyone had their bearings fail AFTER replacing the head, in an engine that held 19psi oil pressure at warm idle before the head-swap? If so, how long did the bearings last AFTER the head swap?

Thanks,
JohnEP

Me being me, I'd pull a couple of rods & a couple of mains for visual check - bearings that are wiped out due to contamination are usually obvious.

If they're wiped out, recommend replacing all of them (including the camshaft bearings. I know, I know...)

However, it's possible that you haven't wiped out your bearings. But, the first commandment is, "Thous Shalt NEVER Assume, for to do so makes an ASS of U."