Airlock????

[Gray]

[/FONT]
1995 GMC Suburban 6.5 TD- When I first purchased the vehicle I was told it needed a new water pump and a head gasket. I replaced the water pump and recharged the batteries and then rotated the motor. The motor would rotate one full cycle then suddenly stop with a boom. (A sound like someone shoved a metal bar in there and physically stopped it) After this I was advised to remove the heads. I am in the process of removing the heads. But after researching online, I was wondering if it wasn't an airlock problem in the first place. What do you think? Any help would be appreciated.
-Graytopia:confused:

[KallyI]

Hi, I'm not sure what you mean by "airlock"? Based on what you describe, it sounds like an hydraulically caused stoppage, in other words, antifreeze, or water has gotten into at least one of the cylinders. Liquid can't compress, so it has no where to go, and could cause the engine to lock up. "Air", being a gas, can compress, so it shouldn't cause the situation you describe. Did you ask the seller how they determined that a head gasket needed replacement? If the head gasket does in fact need replacement, it could have leaked antifreeze into one or more cylinders.

[Gray]

Here is the section I found on this forum. http://www.thedieselpage.com/members/airlock.htm
Thanx you are starting to make me feel better. I am in process of removing exhaust manifold to check for water/antifreeze.

[TurboDiverArt]

[/FONT]
1995 GMC Suburban 6.5 TD- When I first purchased the vehicle I was told it needed a new water pump and a head gasket. I replaced the water pump and recharged the batteries and then rotated the motor. The motor would rotate one full cycle then suddenly stop with a boom. (A sound like someone shoved a metal bar in there and physically stopped it) After this I was advised to remove the heads. I am in the process of removing the heads. But after researching online, I was wondering if it wasn't an airlock problem in the first place. What do you think? Any help would be appreciated.
-Graytopia:confused:

I think you mean "hydro-locked" meaning as other have posted caused by anti-freeze/water in the cylinder.

My suggestion before you start pulling tons of stuff off the engine, pull the glow plugs. Very easy on the drivers side, more difficult on the passenger side. Pull as many as you can and try to spin the engine. Even if you only get 5-6 of them out easily it's possible you might get lucky and pull the correct one. If you get the right one you will be able to spin the engine as the water will be expelled out the glow plug hole. If it spins then look for the glow plug hole being wet, it should shoot out! If it still doesn't spin with the "easy" glows out then I would pull the rest and try again.

I would not spin the engine with the starter. Starter is expensive and you can crack the starter head off. We broke two of them on one of our racecars when it hydro-locked from a cracked head and our turbo engine is only 10:1 compression. We thought it was a head gasket the first time, replaced head gasket and cracked another one when it filled up again. Also, we lost a tooth on the flywheel and had to replace it.

If you lose a flywheel tooth you'll have to pull the transmission to replace. Just pull out all the glows and spin the motor and see if water comes out. If not and it's still locked up with the glows out then you don't have a hydro-lock situation but you have a mechanical lockup. Maybe a dropped valve, maybe a broken crank/rod.

The second thing I would try after the glows is to pull the valve covers and pull the rockers and try to spin. Leave the glows out as it'll spin easier. If all the valves are in the closed (up) position and it still doesn't spin then it's not a dropped valve.

If that still doesn't work then you will have to pull the heads and see if the pistons are moving.

Art.

[Robyn]

Generally a hydro lock will leak past the rings if the engine sits for a while.
The "Sounds like a metal" leads me to believe you have something broken in the bottom end such as a rod,crank ect.
I have seen a few of these.
I would not even mess with it in the rig. Yank it out of the truck so you can get a good look at it.
Get it on a stand and drain everything and then yank the pan and have a look see.

If its got that big of an issue, most likely its not going to be resolved in the chasis.

Good luck and let us know

Robyn

[rameye]

Question is did you have the timing gears exposed at all???

If so you may have very easily dropped something onto the chain...there is no room...something dropped wont just slip by.

Turn it over with a bar...if it keeps getting stuck in the same location, I betch you got something on the chain and its binding on the gear.

Dont ask me how I know this...