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Blown head gasket diagnosis question

46K views 88 replies 15 participants last post by  Clint 
#1 ·
Symptoms:

coolant loss
no heat
coolant smell
power loss
Small amount of white smoke when cold.

No signs of coolant in oil.
No signs oil in coolant.

Did a block test, checking for combustion gases- test came up green x2 (maybe engine was not warmed enough)
tested on known good running car and it came back blue

compression test resulted #3 has only 100 psi, remaining cylinders were all about 200 psi

added oil to # 3 and got up to 125 psi

Added air to #3 and can hear it coming out of intake.

Could this be an intake valve problem?

I thought I would hear air through radiator based on coolant loss.

Gonna do a leak down test today to get more data.

Since I hear and feel pressure loss at intake I'm concerned.
I want to be absolutely sure its head gasket.

Thanks
 
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#2 · (Edited)
What kind of truck?
Looking at your past posts, you have a '06 SE 6 speed that you owned for two months. It has 144,000 miles and you just replaced the cats.
FWIW, white exhaust vapor when cold is normal.
I'd say you have a dead cylinder that probably contaminated the cats.
Overheating and or cracked head due to lack of coolant or antifreeze.
Do you hear a huffing sound in the exhaust?
You need to pull the head to find out whats wrong.
What does the previous owner say?
 
#3 ·
If your block test fluid is changing colors you have exhaust gasses in your cooling system. That with the missing coolant would be enough for me. I'm assuming of course that you're not getting coolant on the pass floor due to leaking heater core and there are no external coolant leaks. Where are you smelling coolant? If the exhaust smells sweet like coolant that is another indicator. In any case you're going to have to pull the heads like upflying said to find out what's going on if you have a down cylinder, even if it was caused by something other than a blown head gasket.
 
#6 ·
2006 4.0L 6 speed

I'm taking the head off to have a look.

No signs of dripping coolant
Coolant smell is at engine and hard to be specific on which bank
No smell of antifreeze at exhaust

I thought that if their was a blown gasket at a middle cylinder it would affect adjacent cylinder. Both 1 and 5 cylinder tested good.
 
#9 ·
theres a few routes you can go here.
if you want you can spend thousands of dollars and have a brand new top end.
if you are only removing one head? i wouldnt do anything to one head you arent doing to the other.
gaskets, timing guides.
ive yet to see a water or oil pump fail on these motors. not to say its not possible but they just dont go out.
but you could do oil and water pump while you are there.

other than that i wouldnt touch much. you are going to be surprised how many bolts you need to remove to get the head off.
its kinda a nightmare.
 
#10 ·
Yes I'm seeing that :surprise:
And thanks

I'm giving me a week to get it done so i'm not rushing and can research. But its about 24 deg in garage...

I'm thinking i'll just do the timing chain with gasket (hoping that's all it is) but if they are designed to last to xxx.... is it just overly precautions.
 
#13 ·
I would get the gaskets you know you will need. Valve cover, head, timing covers. Upper intake should be fine but I would replace the lower intake gasket. A kit would be fine but any kit you buy will have enough for two heads.

And if you have unlimited down time order it as you need it
 
#17 ·
The fact that your #3 pressure came up when you put oil into the cylinder tells me the rings are bad on that one. If you were hearing the air hissing at the TB (and not 'thinking' its there but actually at the valve cover) then the intake valve is bad, probably burnt.
 
#23 ·
true, but with #3 lower than the rest by 100psi & coming up by 25psi is what would make me think a ring issue. It usually held true for me on my old GMs when I was a teen...
 
#19 ·
Thanks
Truck is burning no oil. Don't think problem with rings.

when i put air into the cylinder (#3) and I could hear air at intake, I don't think i was at TDC.
I have a Harbor Freight leak down tester and i'm pretty sure i was doing the test wrong.

Anybody know a good way to get the crank pulley off?
I have an impact with 700 lb of torque that don't get it off. Disappointed with this tool now as it was labeled to work :)
 
#24 ·
I can say getting the crank pulley bolt off was intense.
Bump start motor- no
700lb torque impact- no
tying a ratchet strap around pulley with 6' of breaker bar- yes

Timing cover is also a PIA to remove. All bolts out but still can't pop it off. Feels like you have to push pretty far.
 
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