Heat Exchanger able to be repaired?

[Jimmy Buoy]

My one main heat exchanger had been leaking coolant into the seawater side of things since buying the boat last year. Upon inspection it was found that a few tubes were causing the problem (probably from insuffcient winterizing prior to owning) so the outfit I bought it from offered to have it repaired at a rad shop near their shop.

This was done during the winter. The first repair didn't completely seal it (I tested it after pick-up) so I let them know and they seemed embarassed and asked me to bring it back. I did, and I tested it again (briefly at home) and no apparent leaks.:smt038

Well, I've since reinstalled the exchanger/new coolant & splashed the boat but found the antifreeze level to again be dropping. It seemed most noticable after the engine cooled off and the level would be down about 1.5 quarts from where it started. Also, there was some brownish looking scum in the coolant. It doesn't look like oil and it's not slippery. Smells and feels like rust to me. I didn't consider the exchanger since it was fixed and started thinking head gasket or intake gasket leak, but the engine is not overheating (155), runs strong, and starts without hesitation or stumble. No coolant visible in the oil, and the oil level has not increased after my 1.5hr run at 3500 RPM. I even took all the plugs out and checked the cylinders with a long pipe cleaner for evidence of fluid while applying 20lbs of air pressure to the closed cooling system - no fluid in the cylinders. (the plugs looked normal too). :huh:

So I started taking a better look at the heat exchanger. It definately is leaking at one end in the area of the repair ( 3-4 tubes plugged with solder from previous repar). Not holding, but it's not a stream of fluid - just seeping. I'm assuming that under the heat of running under load, the leak becomes worse.:smt089

Question... (finally)... Is there any use in having another rad shop that is recommended for repairing exchangers having a go? Or will I just be wasting some money that could go towards a new Exchanger (approx $750).:wow:

I'm getting tired of knowing the engine room better than the rest of the boat.:smt013:smt013:smt013

My apologies for the long post.

 

[Asureyez]

These solder joins are subject to failure over time. If yoru bonding system is not 100%, you could be loosing the solder to electrolysis as well. No repair cans tand up to that.

Check the bonding system before reinstalling anything.

I personally would repair the HE, but take it to a shop that knows what they are doing. The unit should be ultra sound cleaned, thenevery tube resoldered by hand. (The remove old solder by heat and run new solder into every tube end, not just the suspect ones. Soldering over failing porus solder is not a repair, its rip off. Then reassembled and the whole rig pressure tested. Such a repair would cost about 200-250 bucks all painted and ready to install.

 

[Jimmy Buoy]

Chad, thanks for the reply. From the repair you described, am I to assume that resoldering the ends of the tubes would still leave each and every tube open for cooling water to pass through? That would be great, but what if the leaks are from cracked tubes...

In my case, it is likely that two or three tubes at the bottom of the exchanger have failed within the tubes themselves and not where the ends are soldered to the plate. A couple of these tubes are at the outside of the circle (against the outer HE wall) and would not be easily removed/replaced without chopping off the ends of the HE casing since the ends are tapered inward to help seal the end cap. This may be why the ends of these tubes were filled with solder by the last shop, but they obviously aren't holding.

Have you ever heard of shops replacing individual failed tubes when fixing these units?

I assume that being in Florida means you would have more experience in exchanger problems - my boat was previously in Florida salt water.

Thanks,

 

[doozie]

I had the same leak, if you plug both ends is doesn't matter if the tube is split in the middle. I had a good friend who knows his way around this tye of stuff fix it, the tubes i don't think can be replaced. When we did it we made a plug to go in both ends and then silver soldered it in. Working great so far. Bob

 

[Jimmy Buoy]

I had the same leak, if you plug both ends is doesn't matter if the tube is split in the middle. I had a good friend who knows his way around this tye of stuff fix it, the tubes i don't think can be replaced. When we did it we made a plug to go in both ends and then silver soldered it in. Working great so far. Bob

I'm a bit confused. Does it or doesn't it matter if a split tube is pluged at both ends to seal the leak?:huh: How many tubes needed to be plugged in yours?

After talking to an experienced rad shop here, I am considering biting the bullet and getting a new one at this point. According to them, there is a concern that solder was poured into the affected tubes which could cause some small pieces of solder to break off and enter the engine's coolant possibly killing the water pump and maybe even the engine shortly afterwards. :smt009:smt009:smt009

Is this even remotely possible or is he just a bit off?:smt101

Also, with 5 tubes sealed is there enough water capacity flowing through the system at higher speeds to cool the exhaust manifolds?:wow:

 

[Asureyez]

If the tubes can be reached from the outside of the core, the defective tubes can be cut out and stubs squeezed closed and silver soldered. The trouble is getting the tubes clean enough for new solder. Plugging from the ends gets to the same place as long as they prepare the surface properly. A pressure test by the shop is important, usually a 24 hr or 48 hour pressure hold.

Also if boost pressure is max at 25PSI the shop shouldn't test at 150 lbs either and blow the tubes out.


The issue is this is tedious work. If the tubes are good, what a technician does is actually re-solder each tube back to the end plate on both ends. If you loose one or two tubes, probably not a major issue, but loose 10% or more it would be reasonable to expect reduced cooling, and lower boost pressure ie lower power and less efficent fuel burn.

 

[rondds]

I could be wrong but I thought tubes are replaceable. I took one of my HE to a radiator shop that does a lot of marine work. I had no leaks but the engine ran hot and I was at my wit's end. They boiled it out, found one bad tube, replaced it (that's what he said), pressure tested it, re-sprayed it Mercruiser black. $130 later that engine runs 20 degrees cooler (now the same temp as the other engine).