Clacking/tapping noise due to blown head gasket

[CJD]

Pride, you're right...that's why I'm stumped. I follow the backfiring theory, but I wouldn't describe that sound as a "clacking tapping" sound. But it could just be semantics on what it sounds like.

Even with a blown gasket, I would think the compression check would show at least some reading. That is what has me thinking that the valves may not be closing all the way. The clacking would be when the cam lobe takes up the slack and the lifter smacks the pushrod. I don't have a theory as to why it wouldn't make the same noise in gear, though.

But, the main thing is, with 0 compression in 2 holes, the head will have to come off to fix any of the possible causes.

[roosm]

Pride, you're right...that's why I'm stumped. I follow the backfiring theory, but I wouldn't describe that sound as a "clacking tapping" sound. But it could just be semantics on what it sounds like.

Even with a blown gasket, I would think the compression check would show at least some reading. That is what has me thinking that the valves may not be closing all the way. The clacking would be when the cam lobe takes up the slack and the lifter smacks the pushrod. I don't have a theory as to why it wouldn't make the same noise in gear, though.

But, the main thing is, with 0 compression in 2 holes, the head will have to come off to fix any of the possible causes.

Well, I havent really listened alot to the sound, the sound of my engine possibly tearing to pieces aren't really my soundtrack. It is quite a bit of other noises going on at the same time.
On an other note, english is my second language and this is the first time I even use the word Clacking... =)
I guess someone else described an issue which I might have prediagnosed as my own problem as having a clacking sound when in gear and so I did too.

Just to try and go with the theory of backfiring being the noise (which was actually what my mother who was in the boat and who has actually heard backfiring before described it as).
Why wouldn't it be heard when out of gear?


I don't really understand how the whole valve-thing works and what would cause it not to clack. Especially only when in gear.
It is strange is what it is...

Couldn't the 0 compression be caused by the leak in the head gasket between the cylinders and the spark-plug being removed from that cylinder. I guess if I put a spark plug in that cylinder and try again I could get a different reading?

Mike

[CJD]

Sorry to say, I'm pretty familiar with the sounds of my engines self destructing!?!

You can re-do the compression check, but the bottom line is the head has to come off, whether it's a head gasket, valve, or anything else that would cause a loss of compression.

[2500HD]

Agree that the head has to come off, One possibility for the backfiring sound is the compression and firing could cause a backfire through the intake of the other cylinder. Why it would be under load only is beyond me. Send it off and they can tell you if the head is good or not. I would suggest doing your injectors while your there. When i did my head this spring i took a peek at my injectors and i couldn't believe it ran at all. I looked up the vortec specs and it turns out i could use the same one's out of a 95 camaro an reman's where only 29 bucks each. The other thing to do while your there is new rockers and rods, and don't reuse your head bolts buy new ones.

[CJD]

2500 just reminded me...with a stuck valve you will frequently NOT getting intake popping at idle. But, under load the mixture goes richer, and there's more volume of mixture in the cylinders, so that can trigger the intake front firing. That could explain what's going on. I guess a bad gasket could cause the same...but that would still be extremely rare compared to stuck...or burned...valves.