I was under the impression that hard lines are more reliable than hoses. Hoses being more popular due to production costs and likely resistance to vibration. Anyways I started in on replacing my coolant lines to the turbo with hardlines. I'll admit im a bit concered about the hoses and just being on the hot side of the engine. Previously the were a 6AN braided line, rubber /stainless reinforced with a nylon "skin". I made my first replacement line, which i put two loops in to make a coil to compensate for vibration and expansion.

Up to this point it has seemed like a good idea, until I had a retired ASE Master Technician inform me that errors have been made in going hardline. Right now I'm only doing coolant. That is of course if the knowledgeable folks here guide me to another path and keep the hoses, or at least hybrid them.

 

I'm doing something like this, hardline with a section of flexible line. Here you can see the oil and coolant lines and also the heater hose hardline.

 

Im doing stainless hardlines with double ferrule swagelok fittings for oil and water on my turbo set-up as well.

Hardlines can be more reliable than flexible lines or if poorly implemented less reliable.

1) no Aluminum. Aluminum has no lower limit of hardening with movement. Every heat cycle the insides of bends will get more brittle from movement till they crack.

2) even with stainless/ steel hard lines you need to design in stress relief bends so it can expand and contract with heat cycles without putting stress on fittings or only flexing too short a section of hardline

3) fittings. common single ferrule automotive hardline fittings are terrible. You want stainless Swagelok front/back ferrule fittings.

4) conversion fittings can introduce additional points of failure. Example, if you have aluminum 2 bolt to NPT adapter for turbo oil feed line you noe have 2 bolt gasket and NPT threads that could leak. I tried to pare down to only 1 fitting per end of the hardline instead of adapters. Sometimes that gets expensive as a certain fitting configuration can be a specialty fitting.

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The idea of hardlines near the turbo to flex lines over the engine is a good one. The flex lines will keep stress out of the hardlines and fittings with heat cycles without having to carefully configure hardline bends/routing.

The only downside is more fittings/potential leaks.

 

I'm using Copper-Nickel hard lines, much easier to work with than stainless and strong enough and approved to be used on high pressure brake lines.
I'm using JIC / AN 37 degree flaring tool and respective stainless ferrule/nuts and AN fittings.
I'm using an4 on turbo feed, an6 for coolant and also an6 from the oil pedestal to the front feed for extra front bearing oil.
I -may- use an4 hard lines on the x2 wastegates for coolant and air ports but it may end up being a spaghetti of lines idk

 

Thanks for sharing. Would PTFE work for the flex line?

 

I bought PTFE -an hose and associated -an fittings once for a turbo oil feed line over the engine to a stainless hard line over the turbo.

Didnt end up using the PTFE stuff.
Ptfe hose is scary fragile. Its just a regular unreinforced teflon hose inside an unbonded stainless braided sheath. It kinks, tears and melts very easily.

 

I've used this one, it's a little stiff and prefers mild radiuses

 

mock up using aluminum tubing . The idea is to have a hardline come off the rear plate, anchor point on center plate from available bolt hole, second tube coming from water pump housing. Two lines brazed or welded and go to hoses, connecting to the hard lines off the turbo. I may just put a flare on the end and use a rubber hose and secure it with a fuel line clamp.

 

Aluminium fittings seems like paying a premium for failure to me. Having worked both in mining and pressure calibration space either proper threaded steel fitting swaged and pressure tested using quality hose material or swagelok fittings is the way to go if you want to spend money. Those swagelok fittings will work from fractions of a Pascal absolute pressure to megapascals, even in an oven bake out enclosure.

 

@Slides what's your take on AN fittings

 

As in steel but to that form? Most of the threaded stuff with face seal in mining, at least here is JIC but they aren't extraordinarily different. I just don't like aluminium for anything I need to tighten, and there is the fatigue life thing too. I know plenty use it but if I'm paying the same for swagelok or 350bar rated JIC fitting hose I know what I'd rather use.

 

Well this is disappointing. I just ordered tube nuts/sleeves and stainless seamless line today to make coolant lines and to finish the oil line haha.

AN -6 (6AN) Banjo Adapter To M14x1.5 Stainless Steel Banjo Bolt Assembly BLACK | eBay

Would fittings like this help with expansion and contraction of the line? It seems like they would a bit, since they can swivel, but I know I'd lose the snap ring EVERY time.

 

Stainless seamless tube will work well if you plan your tube routing/shape to account for expansion/contraction.

Dont go straight from one component to another, make the line a giant "Z". A bend right off one component and then opposite bend right at the other component.

Those swivel banjo bolts would add points of failure

For example I found regular name brand (Russel or Aeroquip) AN swivel fitting O-rings last a couple years on rotary oil system before they start weeping).

 

Oh, I thought I'd have to add loops or similar, I'm not trying to add all that haha. My lines would have multiple bends in them anyway, although I'll have to see if I can add some Zs.

Ok I'll stick with more standard banjo fittings.

Thanks!