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Indy 06-21-2010 02:05 PM

Blown head gasket or cracked head
Ok .. so I am pretty sure that my head gasket is blown or the head is cracked. Symptoms are:

  • Loosing coolant slowly (no visible leaks)
  • White smoke out of exhaust (sweet smelling)
  • Misfire in Cylinder #1
  • Low compression in Cylinder #1
So, here are my questions:

  1. While I am going to open the engine up, is there anything else that I should/can do (other than machining/magnaflux the head, cleaning cylinders/pistons and replacing the head gasket)?
  2. Should I buy the head gasket set or just the head gasket itself?
  3. Is it ok to drive about 15 miles/day for about 2 weeks?

Thanks guys!!!

flatline 06-21-2010 02:29 PM

If you have over 100,000 on the motor I would consider rings and bearings while you got it apart. Always seems that when you do the head and not the lower end, the extra compression blows out the rings. but not always. could also change water pump, cam, lifters push rods. I would avoid driving it, and do a comlete rebuild.

rrich 06-21-2010 03:18 PM

Just replacing the head gasket won't affect compression except in that one cylinder, bringing it back up to where it should be. No need to worry about the bottom end - unless you've been getting lots of coolant in the oil.

And that could happen if you continue to drive it. Or that cylinder could fill with water while it's parked, then when you go to start it BAM - hydraulic ed - bent connecting rod, scored crank etc.
Play it safe - drive something else.

100,000 miles on a 4.0 it's just getting broken in.

The headset isn't much more expensive than the gasket alone - and you'll need some of the other gaskets too - valve cover, thermostat etc.
-- But -- Buy the gaskets AFTER you have it apart - there are several different head gaskets for the 4.0 - Murphy's Law says you'll buy the wrong one if you guess.

Indy 06-21-2010 05:08 PM

flatline - I have already replaced the water pump and don't have enough bank right now for the complete rebuild of the motor.

Good advice rrich (like always).

I have almost 170k on the motor and seems like it will last me another 100k if I keep up with the maintenance. If needed, I won't mind opening it up again.

So for now, I will just replace the gaskets, machine/magnaflux the head, clean whatever I can. Keeping my fingers crossed and hope it is not a cracked head.

Indy 06-23-2010 01:51 AM

Picture time ...
3 Attachment(s)
Alright guys/gals .... I took the head out today and sent to the machine shop for magnaflux, cleaning, resurfacing, valve job (if needed).

How to get in the jeep ....
Attachment 20855

while cleaning the carbon deposits on the cylinders ....
Attachment 20856

Cylinder cleaning done ... still need to clean the gasket area .. will do that tomorrow
Attachment 20857

rrich 06-23-2010 06:17 AM

If the head is cracked, in my experience welding it seldom lasts long.

There's a place in Texas that sells new heads cheap, complete, valves and everything - they advertise in some of the magazines. Supposedly they sell them for about the same price as a good valve job on yours. I haven't used one from them, but I've heard nothing but good things about them.

Maybe others on here know their name and have comments?

Indy 06-23-2010 12:46 PM

Ok ... just talked to the machine guy and he said he saw a crack in the head (between the valves) even without cleaning it and stuff. He will call me later on today after the full inspection.

So ... as rrich mentioned (thanks), I would rather have a new head than welding it up. Can you please recommend me one or if you happen to know the one rrich mentioned?

I have almost 170K on the motor ... do you think it is worth it to just completely rebuild it?

Noobie ? (first time working on the motor) ... What should I replace if I decide to rebuild it?

Also, what would be the cost difference if I rebuild it vs stroke it?:punk:

doclouie 06-23-2010 02:18 PM

X2 what rrich said. Do not bother welding it up as it will not last. I am not familiar with the company he is talking about, but I would start calling around salvage yards locally.

rrich 06-23-2010 02:43 PM

They advertise in off road magazines with a small ad. Texas head rebuilders or something like that.
I don't have a magazine here to look at.

I'm sure someone knows.
If nobody pipes up with the place, I'll make a phone call to a shop that's installed several - and loves them.

Junkyard head - junk!

With that many miles a new head may blow out the rings due to better compression - it's chancy - a quickie rebuild may be in order - and you already have the head off. Re ring it (be sure to break the glaze) and put new bearings in - can be done with the block still in the vehicle. Shouldn't be too hard.

If you take the chance and not re-ring it and it gets too much blowby, you'll have to take the head off again!

Indy 06-23-2010 02:46 PM

Thanks doclouie and rrich...

Any recommendations from where to get the rings and bearings? Should I worry about the crank and cam shafts, pistons, push rods etc?

adkjoe 10-16-2010 08:57 AM

From the back of 4 wheeler magazine

Hinsley Head Rebuilders.... lubbock,TX

Indy 10-16-2010 11:40 AM

Thanks for the replies guys! It's been 4 months now and I am very close to finish my motor. Except the block, rods, oil pan and valve cover, everything else is brand new. I have over bored the block and using a stroker crank from SCAT. Its going to be a 4.7L engine with about 275HP and 340TQ!

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