Block coolant leak

[Jason]

I have a small coolant leak in my engine block.

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The leak was caused by corrosion inside the block. I had the engine apart 9 months ago for a rebuild and I know from looking inside that the damage is limited to that area. Yes, it seems obvious that I should have done something about it when I had the engine apart, but at the time it didn't look like the damage was anywhere close to all the way through, and I didn't give it much thought because it wasn't leaking before the engine was disassembled.

I've talked to a local machine shop and they say they can weld it, but the block has to be completely clean inside and out and the cylinder liner removed.

Does anyone have any suggestions on how to fix it without removing and disassembling the engine, or am I doomed? It would be nice if I could make it a few years before having to pull the engine again.

I've tried sealing it with Belzona 1111 (an industrial epoxy). It lasts about 2000 miles and then coolant starts seeping through the epoxy.

Other ideas I've had..
Drill out the area, tap the hole, and screw in plug.
Make an aluminum plate/block that can be "bolted" up against the hole using the nearby oil and coolant drain plugs. I have a small CNC mill, so cutting aluminum blocks into arbitrary shapes is easy.

[DMCMW Dave]

Drill out the area, tap the hole, and screw in plug.
Make an aluminum plate/block that can be "bolted" up against the hole using the nearby oil and coolant drain plugs. I have a small CNC mill, so cutting aluminum blocks into arbitrary shapes is easy.

You are correct, the proper repair is to weld it up.

BUT I've heard of the drill and tap thing working, for many years at this point. Not something I've done, but I know a guy. . . . . The plug has to be large enough to get to solid metal but not too deep so as to not hit cylinders. Keep in mind that it is holding back boiling water at 16PSI so be sure it is sealed accordingly.

[Bitsyncmaster]

What I would do it drill and tap for a machine screw. Then use a thick locktite when you install the bolt.

Looks like you may have a few more spots there but I would just try fixing the leaking one.

[NightFlyer]

What I would do it drill and tap for a machine screw. Then use a thick locktite when you install the bolt.

Looks like you may have a few more spots there but I would just try fixing the leaking one.

I once did that to a Buick 3.8L that had a small block leak due to corrosion. Worked like a charm and lasted me 4 years until I sold the car on :thumbup2:

[Bitsyncmaster]

You would also need to drain the coolant if you use a Locktite type of sealant on a bolt (screw). Probably best to drain even with other sealers.

[David T]

You would also need to drain the coolant if you use a Locktite type of sealant on a bolt (screw). Probably best to drain even with other sealers.

There are sealers used for sandholes and other porosities in castings but I never had much success with them. If you do use the drill, tap and screw method you should try to use similar materials, ie, an aluminum screw into an aluminum block. Otherwise eventually corrosion because of dissimilar materials will make it leak. There is also a "stitch" method for cracks where you put a screw in and when you drill the one next to it you drill into the first one a little to lock them all together. I have seen and done that successfully on blocks, cylinder heads, and other areas. I never did one in aluminum though, only cast iron. For them I used S/S screws. Welding is very much up to the individual person's skill and how well you can get the block clean. Not always successful because of the expansion and contraction due to the heat of the welding procedure and the operating temperatures of the block. Over time many welded repairs of blocks crack again. Pre-warming before the welding is very important and slow cooldown to relieve the stresses. The biggest drawback is all of the disassembly and reassembly. You don't want to go through all of that only to have it leak soon after! If you do try the drill, tap, and plug method you can still, later if necessary, try the welding repair.
David Teitelbaum

[Bitsyncmaster]

I would not use an aluminum screw into aluminum block. Without lubrication the two would bind up and you may not get the screw in far enough. I once made some aluminum hydraulic cylinders with machined end caps in aluminum and learned the hard way not to thread aluminum into aluminum.

[NightFlyer]

I would not use an aluminum screw into aluminum block. Without lubrication the two would bind up and you may not get the screw in far enough. I once made some aluminum hydraulic cylinders with machined end caps in aluminum and learned the hard way not to thread aluminum into aluminum.

I'll second this - I learned this lesson the hard way as well :tongue2:

[Ron]

I'm going to be the oddball here...
IFF you are against a wall- I would flush the system with a good agent, drop some BlueDevil block sealer in it, following the directions to a tee, put a new thermostat in it and start saving and praying. I hate 99.9% of the miracles in a can. I used to laugh at people using block sealers for decades...didn't even want to hear it when it came to head gaskets, but I have seen others use this stuff successfully more than once lately, long term. It will not hurt a rebuild in the future like some, so there is nothing to loose... It looks like a perfect candidate if there ever was one.

[Jason]

I would not use an aluminum screw into aluminum block. Without lubrication the two would bind up and you may not get the screw in far enough. I once made some aluminum hydraulic cylinders with machined end caps in aluminum and learned the hard way not to thread aluminum into aluminum.

So what would be the best material? Stainless steel?

[David T]

I'm going to be the oddball here...
IFF you are against a wall- I would flush the system with a good agent, drop some BlueDevil block sealer in it, following the directions to a tee, put a new thermostat in it and start saving and praying. I hate 99.9% of the miracles in a can. I used to laugh at people using block sealers for decades...didn't even want to hear it when it came to head gaskets, but I have seen others use this stuff successfully more than once lately, long term. It will not hurt a rebuild in the future like some, so there is nothing to loose... It looks like a perfect candidate if there ever was one.

Another "Miracle in a Can" is Bar's Stop Leak. It does work, at least for a while. I would not consider it a permanent repair though. I agree an aluminum screw into an aluminum block may not be the best choice but ordinary mild steel is no good. Maybe S/S? I do not have any experience repairing an aluminum block. If you are considering welding and completely dismantling the motor, if you can find another motor cheap with a good block (even if it is not running) it may be cheaper than trying to weld up your old block.
David Teitelbaum

[NightFlyer]

OK, I'll share the best kept secret to repairing aluminum:


http://www.youtube.com/watch?v=TZ5sD9hQTyw

[Jason]

OK, I'll share the best kept secret to repairing aluminum:

I have some of that stuff lying around, but I'm afraid to try it.

I think with the engine assembled it would be hard to get that spot on the block hot enough.
If I did get it hot enough it might damage the paper cylinder liner seal, or cause some warping and mess something else up.
I believe that once you use it on something it makes it extremely difficult to properly weld the part later.

[David T]

I have some of that stuff lying around, but I'm afraid to try it.

I think with the engine assembled it would be hard to get that spot on the block hot enough.
If I did get it hot enough it might damage the paper cylinder liner seal, or cause some warping and mess something else up.
I believe that once you use it on something it makes it extremely difficult to properly weld the part later.

There are all kinds of alloys of aluminum. There are thin parts and thick castings. That rod is more like a solder and it doesn't always stick but it is great at repairing soda cans! One of the problems, especially with that rod, is getting the metal properly prepared and that means cleaning, preheating and slow cool-down.
David Teitelbaum

[Jason]

I would not use an aluminum screw into aluminum block. Without lubrication the two would bind up and you may not get the screw in far enough. I once made some aluminum hydraulic cylinders with machined end caps in aluminum and learned the hard way not to thread aluminum into aluminum.

As an experiment, I drilled and tapped a hole for a 1/2-13 bolt in an aluminum plate and threaded in an aluminum bolt. It went in ok. Had a kind of funky rough feel, but I was able to thread it all the way in and back out again with my fingers.

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What drove me to do this is that the more I read about galvanic corrosion the more it looks like aluminum is the only safe material to use. Also it looks like that in order to cover all the damaged area I'm going to have to drill two holes that might end up overlapping slightly. So I may have to put in one plug, and then drill and tap the second hole cutting into the first plug a bit. If I use a plug material that's harder than the block I'm likely to screw up the second hole.

[Bitsyncmaster]

As an experiment, I drilled and tapped a hole for a 1/2-13 bolt in an aluminum plate and threaded in an aluminum bolt. It went in ok. Had a kind of funky rough feel, but I was able to thread it all the way in and back out again with my fingers.

21748

What drove me to do this is that the more I read about galvanic corrosion the more it looks like aluminum is the only safe material to use. Also it looks like that in order to cover all the damaged area I'm going to have to drill two holes that might end up overlapping slightly. So I may have to put in one plug, and then drill and tap the second hole cutting into the first plug a bit. If I use a plug material that's harder than the block I'm likely to screw up the second hole.

Love it when people experiment:hihi:

As long as your threads are not too tight and you're not going to deep you can probably do it. But try it with the sealer you plan to use just to make sure. When I had problems the threads were machined to tightly (also large 1.00 inch dia). You could do it no problem with an oil on the threads but when I put the locktite on I could not get it seated before it jammed.

[NightFlyer]

I have some of that stuff lying around, but I'm afraid to try it.

I think with the engine assembled it would be hard to get that spot on the block hot enough.
If I did get it hot enough it might damage the paper cylinder liner seal, or cause some warping and mess something else up.
I believe that once you use it on something it makes it extremely difficult to properly weld the part later.

Personally, I've never used the stuff, however, I do have some family members that have and swear it's the best thing since sliced bread. If it was me, I'd be willing to give it a shot before the drill and cap method - after all, the worst thing I see happening is the leak reappears. I honestly don't think it requires the kind of heat that would cause any kind of warpage or damage the paper liner sealer. But that's just my own opinion.

[Jason]

Well, here is what I ended up with.
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Two aluminum plugs threaded into the block and sealed with Permatex Cold Weld. Ugly, but holding so far.

I really wanted to use screws with copper washers to make the seal, but because of how close together the damaged spots were and the shape of the block surface that wasn't possible.

[Jason]

I've driven the car 500 miles, and so far no leaks.

[Josh]

I've driven the car 500 miles, and so far no leaks.
Good to hear!!