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GMC V6 and V12 Engines Engine repair and rebuilding

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  #1  
Old April 6th, 2013, 11:30 PM
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GVDobler GVDobler is offline
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Default Water leak and it looks bad.

Trying to bring my 305V6 back to life. I had to put a new radiator in. Went to fill it and out of the passengerside comes a small stream/flow of water.

The engine is in the Suburban and I can't see where the leak is. It appears to be too high for a freeze plug. It is lower than the exhaust manifold. It could be about where the head and block connect.

Question: Is it possible that the head gasket is leaking or is that just wishful thinking? Or is it possible to have a cracked head, then what? If it has a cracked block then that's the end and I will replace it with an inline 6. It would be easier for me to pull the head in place, than to remove the engine from the Burb.

I have never had it running, although it turns over. Fuel line and wiring has kept me from starting until now.

Any suggestions would be welcomed.
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Last edited by GVDobler; April 6th, 2013 at 11:40 PM.
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Old April 7th, 2013, 02:33 PM
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Default Re: Water leak and it looks bad.

Sound like a broken block, your going to have to remove parts so you can see it is you can't see it any other way.
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Old April 7th, 2013, 07:02 PM
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Default Re: Water leak and it looks bad.

First, try crawling under the engine to see if you can locate the source of the leak. If you can't see the leak that way, remove the exhaust manifold. That should give you an unobstructed view of the head and block.

Ray
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Old April 7th, 2013, 10:18 PM
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Default Re: Water leak and it looks bad.

Here are the questions I have:
(I'm not a mechanic.)

1. Is it possible to have it leak from a head gasket? It appears to leak about in the middle, close to the dipstck.

2. If it is a cracked cylinder head, what should I pay for a replacement? And are they available? Are the left and right different?

3. If is a cracked block, then is it a just a boat anchor?

4. Does the tranny come out with the engine? It is a granny-lo floor shifter. There are column shift stubs on the steering column, so I'm sure the tranny is not original.

5. Will an inline-six bolt to the existing perches? Transmission? This might be an option if the V6 is not rebuildable.

Thanks for any answers.
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Old April 8th, 2013, 05:04 AM
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Default Re: Water leak and it looks bad.

1. A head gasket can leak water, but normally not badly enough that you can see a stream coming out.

2. Used heads are available, usually removed from failed engines. Left and right are the same. I can't offer any firm price info, but I would definitely expect under $100. If the head needs additional work (valves ground, etc) that would cost extra. I would strongly recommend that you have any used head magnafluxed before installing it or having any work done on it.

3. There is a widely accepted procedure for repairing cracked castings. It consists of installing a series of overlapping threaded plugs. If your engine is otherwise good, this would be preferable to starting over with another block.

4. You can pull the engine with the transmission attached. However, I have found that it generally goes easier if you take the transmission off the engine first. The 4 speed transmission weighs almost 150 pounds, so you don't want to try this without a jack or a strong helper.

5. An inline six will install fairly easily if you use a Chevy truck bellhousing. Your rear mounts will be the same as they are now, but you will need to install Chevy perches for the front mounts. You can keep your present transmission.

Ray

Last edited by raycow; April 8th, 2013 at 05:17 AM.
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Old April 9th, 2013, 05:18 AM
George Bongert George Bongert is offline
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Default Re: Water leak and it looks bad.

I might be putting my neck on the chopping block here, but I personally doubt that you have a cracked block due to freezing, although it is possible for it to happen. From overheating? Possible, but not very likely. From extreme overheating? More likely, but in order for that to happen, the engine would have to be run without any coolant at all. Warped head or cracked head(s)? Again possible, and again from extreme overheating. Bad head gasket? Possible, and at that it would have to be extremely bad, and the only way to determine that is to remove the head from the engine. I have worked on many engines, and have seen some very strange occurrences, such as a head gasket bad enough to leak water into the combustion chamber of an engine. The head of said engine was checked for cracks and warpage, and found to be OK, and the block also was checked and found to be OK. Replacing the head gasket in this particular situation cured the problem. As others here have suggested, remove the exhaust manifold so you can get a better view of what is going on with your engine, and that would be where I would start, and with a mechanics inspection mirror, you can then inspect the freeze plugs for any unusual appearance, such as rusting, or obvious rust pitting or pin holes. A bad freeze plug (with a small hole rusted in it) will produce the stream you describe. I would be extremely surprised if your leak has anything to do with either cylinder head or block. From what I know of the big block V-6's, and the experience I've had with them, block and head cracking would be very rare, unless it would have come from freezing, or very extreme overheating. And in the event of freezing, your block would be leaking from more than just one side or area of the block, and the same would hold true in the case of extreme overheating, warping, or cracking the heads, and in the latter case, overheated heads more often than not crack internally, usually in the combustion chambers. Best of luck to you on this one, Jon. I'd be interested in knowing what you find out about your engine.
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