Blown head gasket?.....or cracked head?....Is there a way to diagnose?

[Runnin'OnEmpty]

Hi guys, this problem is on another 2000 Sport I recently
acquired (God help me). It's showroom new with about 60K miles, but it has the famous cold start-up miss,
along with a very small loss of coolant. It's the 4.0
OHV engine.

I've changed the upper plenum gaskets, and
noticed it already had a new lower gasket (Fel-Pro),
and the uppers were recently changed also. It's already
got new plugs and wires, so the previous owner has
tried to chase the problem down without success.

When you open the radiator overflow tank, there's a
strong fuel odor, and after shutting the (warm) engine
off, there are small bubbles that percolate up from
the radiator into the tank.

What are your guesses...bad head gasket or cracked
head?

Thanks for any comments,
ROE

 

[coco944x4s]

Really it could be either. You can get a test kit that has something you either add to the radiator or remove some coolant and add in the container to test from presence of combustion gases. ALL this will do is serve as a double check to tell you yes you have a blown gasket or cracked head. Really the only way to tell is to remove the head. Is it setting a code to tell you which cylinder is misfiring? I helped a friend of mine once that was working at the dealership with me on a 2000 4 door with the OHV in it. It would set a cylinder misfire code (PO30X, X being the cylinder number). We tried changing plugs, wires, coil, and finally after all the standard tune up work was done, it was finally decided to check for a cracked head. He got it pulled apart and on the cylinder with the miss, the head was cracked between the valves. Seems to be a not uncommon failure with the 4.0 ohv to crack that way.

Anywho, best thing to do is check for any codes to see if it has a specific cylinder missing so you know which side to take apart, or figure on pulling both heads off and sending them to the machine shop to have both checked. Sorry i couldnt be of more help, COCO.

 

[Runnin'OnEmpty]

Thanks for the reply Coco. There's no misfire codes
present so far, and the rough running after start-up
only lasts for a few seconds. After it clears, the
truck runs great. I was sure it was the plenum
gaskets leaking, but that was not the case.

I pulled the plugs this afternoon, to have a look.
They're new, and all looked the same except for
number 1, which had a light tan colored ceramic.
The other 5 were white. This makes me suspect
cylinder number 1...???

I wonder if these heads are more prone to crack
at a certain cylinder?

 

[colintrax]

Sounds like a blown head gasket. But the spark plugs are supposed to be a little tan, google images of what spark plugs should look like. Also hayne's manuals have imagines in the back.
My leaky cylinder put a green hue on the spark plug. VERY small leak though, $10 stop leak fixed it.

 

[Runnin'OnEmpty]

I would be a happy puppy if it was only a leaking
headgasket. Guess there's no way to tell for sure
without pulling the head; however, I've read that
the later model OHV's weren't as prone to cracking
as were the eariler models. Something about beefier
castings.

These plugs are apparently very new, and that must
be why they're white. The number 1 actually had an
orange tinted tan color to it. Very odd looking, so
that must be where the fault is.

Since they'll be needed anyway, I'll go ahead and buy
a set of headgaskets and see how close the coolant
holes run to the number 1 cylinder. I dread pulling
this thing apart again, but gasket replacements
sound a lot better than heads....

Thanks for the replies.

 

[colintrax]

Try head gasket stop leak. Worked for me, and its alot cheaper and easier than pulling the heads. Good idea to do a coolant flush with it

 

[Runnin'OnEmpty]

Try head gasket stop leak. Worked for me, and its alot cheaper and easier than pulling the heads. Good idea to do a coolant flush with it

I've been looking at the different kinds of stop leak.
Might consider it as a temporary measure. The key to
using this stuff seems to be to totally flush the system
after using it. That keeps the radiator and heater core
from clogging up, I guess...?