Head gasket?

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pigpen4x4

pigpen4x4

10 Year 15 Year
Joined
May 15, 2007
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46
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287
Location
Aberdeen, NC
Well, I did a wet and a dry compression test and here are the results starting with #1 cylinder.

dry was 120, 28, 29, 120, 115, 120
wet was 120, 30, 29, 120, 115, 120

My thoughts are a blown head gasket. What say those of you with more experience?

Also, can the rear main seal ('77 2F) be replaced with the engine in the FJ40? Thanks for the help!
 
pigpen4x4 said:
Well, I did a wet and a dry compression test and here are the results starting with #1 cylinder.

dry was 120, 28, 29, 120, 115, 120
wet was 120, 30, 29, 120, 115, 120

My thoughts are a blown head gasket. What say those of you with more experience?

Also, can the rear main seal ('77 2F) be replaced with the engine in the FJ40? Thanks for the help!
Click to expand...

I've heard that if the wet test doesn't improve things you should be looking at your valves. Head gasket could explain it too, but there are often other symptoms; do you have oil in water or visa versa?
 
pigpen4x4 said:
Well, I did a wet and a dry compression test and here are the results starting with #1 cylinder.

dry was 120, 28, 29, 120, 115, 120
wet was 120, 30, 29, 120, 115, 120

My thoughts are a blown head gasket. What say those of you with more experience?

Also, can the rear main seal ('77 2F) be replaced with the engine in the FJ40? Thanks for the help!
Click to expand...

Valves as a possibility the other been rings, though you usually see a slight rise in the wet test with rings. As for head gasket, you have water in your oil or visa versa?

Pull the head and check the Valves put a new head gasket on then if you don't have to tear the motor down.

EDIT: Scary amaurer we post and think alike at the same time
 
The low numbers next to eatchother could mean the head gasket... but, chances are you'd see oil in the water and water in the oil. Going to have to pull off the head no matter what to fix it right? Gaskets would seem to be the least $$ tho.
 
I haven't drained the oil to check for water yet. Guess I need to do that, as well as the radiator. I pulled the valve cover and didn't notice any glaring problems...more investigation needed I guess.

GreenBomber said:
The low numbers next to eatchother could mean the head gasket... but, chances are you'd see oil in the water and water in the oil. Going to have to pull off the head no matter what to fix it right? Gaskets would seem to be the least $$ tho.
Click to expand...
 
you should know right away if the head gasket is gone when you pull your valve cover....when i did mine it all i had to do was check the fill plug and just look in at my rocker arms ect and you could tell right away...i did quite a number on my head though so that could have been a extreme case...
 
You can certainly have a loss of compression W/O any coolant in the oil or vice versa if the headgasket is breeched between cylinders. But, like Greenbaum sez, you'll know soon enough.

Ed:beer:
 
I agree with the last post. I had bad# on a motor and it was getween cyl. I would still have head checked and maybe surfaced. It could also be a bad cam but not likely.
 
pull the rad. cap and top it off. Start up the FJ and if you have a breach across at the water jacket, it'll blow bubbles out the rad. on every compression stroke
 
Good info, thanks. I will try that. I was thinking more likely just a breach in the gasket between cylinders as others have mentioned, but your suggestion is definately a quick and easy check.

ruger280 said:
pull the rad. cap and top it off. Start up the FJ and if you have a breach across at the water jacket, it'll blow bubbles out the rad. on every compression stroke
Click to expand...
 
Hi All:

Can't help you with the compression numbers, but yes, one can replace the rear main seal with the engine in the truck. Buuuut, it requires removing the transmission and all the clutch components! :D

Also, I've been told having the engine oil pan removed makes the installation of a new rear main seal much easier.

Good luck!

Alan

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pigpen4x4 said:
Also, can the rear main seal ('77 2F) be replaced with the engine in the FJ40? Thanks for the help!
Click to expand...
 
Absolutely the gasket between cylinders....I just did mine having had the same issue. Blows all the compression into the nextdoor neighbor. I'll see if I can find a pic....
 
Its a head gasket issue. the fire ring separating the two low cylinders burnt out, possibly from warping, bad torquing or pre-ignition or overheating. since the bores are close together there is no any coolant passage in the headgasket between the cylinders, so its unlikely to show coolant in the oil, or vice versa.

If t was leaking coolant into the cylinder, you can tell by rolling the motor over to get the pistons in the suspect cylinder to the top of their respective strokes, and shining a flash light down the spark plug hole. If the pistons look more clean than the others(generally they will be clean aluminum color versus the carboned black color...) it normally means that the headgasket or a cracked head is leaking coolant into the cylinder)
 
First off, thanks to everyone for their help. I pulled the head and my problem most definately was a blown head gasket. I took the head over to a friends house and after some cleaning and testing we found that I will probably need a new head job. The valves weren't seating completely and it looked like the head needs to be machined. I have some pics, but I'll have to post them later since I'm at work right now.

SHHHHH!!! Dont tell my boss! You know you all do the same thing! :beer:
 
Cool.. Go ahead and shave the head a bit to bump up compression....gave me a nice little bump in power when I had mine off for a blown head gasket.
 
I just did my head last month. It sure runs a TON better. For reference, it cost me about $200 for a full blown valve job and reground head. I had a bent valve, and some bent valve seats.
 
I had these symptoms.. Initial thoughts were head gasket.. Compression figures in two adjacent cyliders were down by the same amount, and wet test figures didnt change.. No contamination in the water and oil.. Pulled the head, new gasket, valves set and same problem.. So what I did was make an adaptor to inject compressed air in the cylinder.. Hand rotated the crank till both valves were shut.. Listened in the exahust, intake and checked for bubbles in the radiator.. Nothing. Pulled the oil filler plug, and I had air coming out of there.. Checked the other cylinder, same deal.. Moral of the story - never be too quick to assume head gasket without properly diagnosing!
 
Here are a few pics. I dropped the head off today for a complete head job. Should be around $110 given there are no unforseen issues. :hillbilly: Here are the cylinders in order, bottom to top, from #1-6

pigpen4x4 said:
First off, thanks to everyone for their help. I pulled the head and my problem most definately was a blown head gasket. I took the head over to a friends house and after some cleaning and testing we found that I will probably need a new head job. The valves weren't seating completely and it looked like the head needs to be machined. I have some pics, but I'll have to post them later since I'm at work right now.

SHHHHH!!! Dont tell my boss! You know you all do the same thing! :beer:
Click to expand...
DSC07540sm.webp
DSC07541sm.webp
DSC07542sm.webp
 
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