How crush prone are coolant lines?

[Andy Somogyi]

How often are oil cooler lines crushed? How much of a concern should protecting the sections that goes under the jacking point be? On my last car (not a 911), at autocross days, I'd routinely clip cones right at the rear rocker panel point and drag them under the car. This wouldn't be good with easily crushed oil lines.

I'm fabricating coolant lines for my 76 project, and I'm keeping the rocker covers. I've calculated all of the flow and heat dissipation numbers for the commonly available tube and pipe materials, and I've determined that I can make either steel or aluminum lines work.

My choices for materials are either 0.065" wall steel or 0.065" wall 6061T6 aluminum tube.

The steel tube is obviously much much more crush resistant than the aluminum tube.

However the steel tube is heavier, and poses some challenges from a corrosion perspective, even if I have them zinc-cad plated. Here, if water or dirt collects above them, they might rust.

The advantages of using an aluminum tube is approximately double the heat dissipation capacity, but this is still small compared the heat dissipation capacity of the cooler. There are no corrosion worries about the aluminum tube in so far as rust is concerned, and I'll of course make certain to electrically isolate it from the chassis.

BTW, I'm making lines because my car didn't come with them, and I'm fabricating them myself for a variety of other reasons.

[chrisbruck]

Most of the "crushed" lines I've seen have always resulted from someone not paying attention while jacking it up. Don't ever trust a tire shop or non-Porsche shop to lift it up.

I've done a few track days and never worried about the cones and oil lines. My bigger concern was the front spoiler and fog lights getting whacked.

[Andy Somogyi]

Originally Posted by chrisbruck

Most of the "crushed" lines I've seen have always resulted from someone not paying attention while jacking it up. Don't ever trust a tire shop or non-Porsche shop to lift it up.

I've done a few track days and never worried about the cones and oil lines. My bigger concern was the front spoiler and fog lights getting whacked.

Good to know. My car's staying stock Euro height, but I'm fitting an IROC front bumper. However, I'm fabricating a aluminum bumper bar to go behind it (very much like the 964 bumper bar), and I'm also bending a aluminum lip to go around the bottom of the bumper.

[steely]

+1 to what Chris said, most damage done to lines is when the car is lifted incorrectly.
Might have the same affect on steel or aluminum lines. (btw?)
The stock are brass I believe, heat xfer coeff is somewhere between steel and aluminum, plus the brass is more ductile/plastic - won't fracture as fast. (brinell hardness?)
BTW some folks even use braided steel for their lines, if this is an option for you.

[911pcars]

Originally Posted by steely

+1 to what Chris said, most damage done to lines is when the car is lifted incorrectly.
Might have the same affect on steel or aluminum lines. (btw?)
The stock are brass I believe, heat xfer coeff is somewhere between steel and aluminum, plus the brass is more ductile/plastic - won't fracture as fast. (brinell hardness?)
BTW some folks even use braided steel for their lines, if this is an option for you.

Yes. While aluminum has superior heat transfer characteristics and is lighter than steel or brass, it can work harden and crack from vibration if there's insufficient support. Observe how modern aluminum refrigerant lines are supported in the engine compartment. To reduce that possibility over a long run, I'd use short lengths of soft (flex) lines at each end, maybe even mid-route to be safe. They're still very susceptible to crushing from external sources (rocks, curbs, lifting devices, etc.).

Sherwood

[GH85Carrera]

If you do most of the jacking of the car yourself, or a shop that knows 911s, you will never have a problem. After 22 years of ownership, I have never been close to crushing lines. If I am jacking I use the jack pad on the side of the car.

If you take it to a typical tire shop, you are likely to have an issue.

[chrismorse]

You seem quite capable, but if you just want some lines, try calling Chuck at Elephant. They sell the finned lines and chuck had some take offs, (old lines) that I bought quite reasonable from him.
chris