Rebuilding my engine cooling system

[GILow]

Hi Cruisers,

I have the engine out while I attend to some nastiness in the keel tanks. Since the engine is out, I figure I might as well rebuild the cooling system, which is ok, but old, the engine was installed in 1986.

The engine is cooled with freshwater circuit and a heat exchanger. The heat exchanger is in good condition, I had already pulled it out and rejuvinated it a year ago. The raw water hoses are all new, I replaced them when I did the skin fittings a year ago. But the cooling water">engine cooling water hoses are all pretty ordinary. The engine is a converted light truck engine, and quite frankly, some of the hose runs fitted for the marine conversion are wierd. Maybe they were designed to minimise the footprint of the engine, or maybe the designer was on their first day on the job, but I think I can do better, certainly I can make it simpler.

My question is, what materials to use? Basically I have a fresh water circuit with a conventional anti-corrosion/anti boil additive. The current setup uses copper elbows for the bends, and an odd collection of rubber hoses between them. The copper appears to have held up ok, and if there is no reason to do otherwise I would buy new copper elbows and make up the system in the same way, with new rubber hoses for the straight runs. In other words I would make up the system in the same way it was originally made, though I would vastly simplify the layout of the hoses and reduce the number of bends in the system by about 50% or more.

But, I do wonder if there are any problems with using copper, or would stainless be better? (just to be clear, this is a fresh water circuit, not sea water.). Copper is easier for me to handle as I can braise the joins very easily using a MAF gun and solder, stainless would be harder as I am not yet very proficient at stainless welding, and I do not have the dedicated gas for my MIG welder. Also, I suspect MIG welding stainless pipes would be a bit beyond my skill level. My recent stainless welding attempts have been structurally ok, but not as neat as I would like.

Also, I have never seen stainless in an engine cooling system before, so I wonder if there are problems with it being combined with an iron engine block.

Can anyone point me in the best direction?

Matt

[RaymondR]

I installed a self marinized Kubuto diesel about four years ago which is raw water cooled; no heat exchanger and sea water circulating through the engine block. To keep it neat I used all copper pipe in 3/4" size. I silver soldered all the joints to provide mechanical strength as diesels tend to vibrate a fair bit. To date I have not had any problems. Since I am circulating sea water and the potential for corrosion is fairly high I fitted anodes by substituting T's for bends and the anode plugs screw into one leg of the T.

You should not have any corrosion problems and the copper pipe and fittings allow a very neat installation without all the hoses and clips.

[Cheechako]

Can you just eliminate the elbows and bend the hose? The less clamps the better! Maybe consider type L copper elbows if you replace.... I think those are thicker...?
Copper better than stainless.

[a64pilot]

I think you find aluminum is usually used due to a rather large cost difference in the metals

[GILow]

Some interesting thoughts here.. thank you.

In no particular order, tried to figure out a way of doing the whole thing in rubber hose, and it is tricky, not least because I can't go to the auto parts store and ask for a 1995 Toyota Camry top radiator hose or the like. You can imagine the response if I went down and asked for a heat exchange hose for a Nissan ED33 marinised by Diecon in 1986.

I did go down to the local super-cheap auto, who have a MASSIVE bin of assorted hoses, to see if I could combine a few to make what I needed. I sat on the floor at the back of the store for over an hour trying to cobble something together but most automotive hoses seem to be very specialised shapes. Fair enough, too, there's not much room under a car bonnet.

Straight rubber hose at least was easy to obtain, hence my thought about using copper elbows with a couple of straight runs of rubber.

But RaymondR, you have me thinking maybe all copper with just rubber connectors to the water pump inlet and heat exchanger.... sounds neat. The heat exchanger is directly connected to the exhaust manifold by a 3 inch length of hose, so that part is easy, it's just the return from the heat exchanger to the water pump that was a bit odd.

As A64Pilot suggests, a bit pricey, particularly since my cooling pipes are all 40 mm (1.5 inch), but very neat. I could also make up a mid engine bracket to support the pipe in a way that minimises vibration and flexing.

So provided nobody knows of corrosion problems with copper used in this way it sounds simple.

Matt

[JPA Cate]

Matt,

You write as if you think you'd be able to leave the whole deal alone after you made it up. But if it is all complicated, and joined, what do you do if you get one pinhole? If it's all one complicated piece, then you'd have to saw and solder and replace, if possible. I think you might benefit from using as many straight runs of hose as you can, at least the hose will damp some of the vibration.

A.

[GILow]

Fair point, a trade off between the advantages of one simple assembly lacking joins now vs what it is like to maintain...

Bugger, not so simple...

Matt

[philocat]

I'm currently marinizing a kubota and like you have also sat down at the hose shelf in supercheap. FWIW I selected a CH1516 hose for holden which fits 1'1/2 and has a useful 3x90 bends.

All copper sounds expensive and the low strength joints will be vibration stressed in any long pipe run. I'd also be hesitant using copper against steel and relying on anodes as RayR has done even more so with raw as opposed to corrosion inhibited fresh water. At the very least I'd have a rubber hose connection to engine and then anything metal in between is not that critical so long as electrically isolated. My previous engine had ss tube and rubber circuit and lasted 25yrs and I suspect even galv pipe fittings should be adequate given the engine itself is also steel.

The weak link as I see is the integrated heat exchanger common to many commercial marine engines, so I'm glad you have refurbished yours. It was this aspect which swayed me to marinise myself rather than buy a Beta/Nanni to aviod raw (or fresh) water adjacent to ehaust ports where leakage would be disastrous. Im using separate water heat exchanger plus lag and surround the exhaust manifold with several raw water 15mm copper pipes. I'm also using those same pipes to jacket the dry exhaust till it gets above the waterline thereby eliminating the water lock, anti siphon etc.

So I have chosen cheap rubber hose with ss tube joiners with the trade off of more hose clips. Any leaks should be noticeable and importantly easily fixed at sea. Have u looked at corrugated hose which may bend enough for you?

[GILow]

Ah, I didn't explain that too well. The heat exchanger is a separate item, not integrated, thankfully, I've read some horror stories. Just the layout is such that it runs transverse across the block immediately behind the head, and so the distance from it to the exchaust manifold is less than half an inch.

Good point about the all copper problems. Thanks also for the heads up on the holden part, there'd be enough in that to do the whole job. I need 3 x 90 + 1 x 45 elbow in 1.5 inch to do all the bends I need. Then I could reverse my logic and use a single long copper pipe for the one straight run from the front of the block to the back. But then there'd be 10 hose clamps... not ideal.

The idea of using copper was that I could braise at leat two of the joins and thus eliminate 4 hose clamps.

I guess I could easily make up the two composite bends (both would be effectively S bends, one using two 90's and one a 90 and a 45) in copper, and make a spare for each, then carry those spares on board just in case. The straight length could be rubber, in deference to the points made so far, again with a spare carried.

Yes, currently there is a steel spiral reinforced corregated pipe to make the initial bend from the water pump inlet to get the hose around to the side of the engine and on its way to the back. I don't know how old it is, but it has started to collapse slightly. Orginally I was hoping to find another like it in the common hose types, then I could carry a simple spare but I had no luck with this. But then I got to thinking about how complicated the current setup was and started to rethink the whole thing.

Matt

[GILow]

Originally Posted by Ann T. Cate

Matt,

You write as if you think you'd be able to leave the whole deal alone after you made it up. But if it is all complicated, and joined, what do you do if you get one pinhole? If it's all one complicated piece, then you'd have to saw and solder and replace, if possible. I think you might benefit from using as many straight runs of hose as you can, at least the hose will damp some of the vibration.

A.

Just thinking about this some more... it occurs to me that repairs might be pretty simple if I kept the whole run in the same size pipe. Any leak could be managed by cutting the system in half at that point and sleaving it with some spare rubber hose.

A length of straight rubber hose carried on board could be sliced up to meet all of the likely needs. For instance the joins between the copper assembly and the water pump inlet and heat exchanger outlet would be made from the same hose (also providing the wisely suggested electrical isolation).

Carrying a fully assembled spare would not be so practical though... a bit big.

Just leaves the question of vibration management...

Matt

[transmitterdan]

Vibration is a concern with diesels. Some times the rubber hoses act as vibration eliminators. If you redesign it into all one piece of soldered copper pipe it could crack apart in a very short time. Never assume the designer was an idiot unless you are in possession of incontrovertible proof.

[GILow]

Originally Posted by transmitterdan

Vibration is a concern with diesels. Some times the rubber hoses act as vibration eliminators. If you redesign it into all one piece of soldered copper pipe it could crack apart in a very short time. Never assume the designer was an idiot unless you are in possession of incontrovertible proof.

Yep, fair point, I think the problem with the current setup is that it is overly complicated for my particular needs, turning up behind the injector timing chain housing and going behind the injectors before turning up again around the oil breather with an extra S bend to the heat exchange.

I suspect this was all in aid of minimising the footprint of the engine.

But any leaks will spill all over the injector pump, not ideal.

I don't think the designer was an idiot, but perhaps overly optimistic about the reliability of the many, many connections. And interestingly, the first section of pipework consists of no less than 7 braised bits of copper pipe. Now Diecon had a pretty good reputation for marinising engines, and they were happy to put that much braised copper into the equation. But I take the point about vibration, particularly as I am dealing with a 3.5 litre 4 pot. And they sure do shake.

At least I have the luxury of knowing how much space I have to play with and so can avoid the whole mess around the injector pump and come straight down the side of the engine at about mid block height. Something Diecon could not assume.

I figured I could support a long copper run with good brackets, but as I ponder all this today, I am starting think along the lines of braising the two S bends at each end, and connecting these "S"s to a long straight section of well supported copper pipe beside the engine. This makes the system effectively 3 separate copper components, connected by rubber hoses, meaning a total of 6 hose clamps, which is ok by me. I suppose I like the straight run of copper pipe as it would be easier to support and would even radiate a small amount of heat, it all counts.

Matt

Matt

[JPA Cate]

Matt,

Relative to your engine shaking, have you replaced the motor mounts? If not, now's the time, while it's out, to get 'em ready to go. Yes, diesels vibrate, but new motor mounts can make a huge difference. Thirty years is a long time for rubber.

Ann

[GILow]

Ha ha. I WISH I had rubber engine mounts! Nope, our dear old beastie is hard mounted straight to the stringers. No doubts in your mind about whether the engine is running or not. 3.5 litres of rock'n roll'n vibration let you know. Depending on tHe engine revs either the whole galley rattles, or the deckhouse, or, mostly the fillings in your teeth. Hardly needs a tacho.
Matt


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[Neptune's Gear]

imo you should be more worried about that. solid mounts are not a great idea, and the lack of give will eventually cause problems. any room to change the solid mounts to flexi ones without stuffing the shaft alignment??
Cooling. Copper is fine - used as cooling connectors on my VP2003, been working 25 years!