yes, it’s the bane of life, dealing with untrustworthy parts. Especially galling when the conventional wisdom of this forum is that the oil cooler hoses need replacement when they are over 10 years old. I was feeling pretty good about replacing mine. Up to the day one of them blew at the 3 year mark.

Z

 

Wow. Keep the thoughts coming. I'm enjoying the fodder for thought. On the subject of weakening the tubes, I do have my doubts about that. I wonder if the possible variability in the quality of the original crimping is a contributing factor to the mistrust in the integrity of the used tube. Meaning: I expect Jack is right about the low bidder mentality at the factory and I wonder if some sweatshop worker shoving the things in an increasingly worn machine in a hurried fashion doesn't create a wide range of results in terms of strength and OE condition. Were the burrs all removed prior to assembly? Were the tubes dropped or stepped on before assembly? Did they pay attention to the "glazing" of the surface and it's contributory role in allowing the rubber to separate from the tube? The questions abound.

When I started this repair process I examined the tubes in detail including using a borescope to see if there were any cracks or distortions visible to the eye. I was satisfied that none existed. In fact, I was a bit concerned because I had used an old AC hose as a test of the crimper and ferrule and it did distort visibly. I was appalled until I realized that the tube was literally half the wall thickness of my cooler tube and when I tested using the actual tube I saw nothing to be concerned about except the slick surface of the tube which was remedied by the "twist sanding" mentioned in the thread. XALTY's comment about using purple High Tack was not lost on me either. I had considered a bonding agent at one point but reserved that for a future experiment. I do think it has merit.

My opinion is that, pending close scrutiny of the tubes, I see no evidence that the integrity of the tubes is compromised as a normal, predictable result of a prior crimp. The crimping process would not thin the walls. If anything, it would compress the tube creating more density and/or distorting the tube. That distortion was not present in my tubes. A point of clarity here that may help: my hose did not "blow out" as is apparently common. Mine started leaking profusely at the ferrule as a result of the rubber separating from the tube wall. That led me to believe that either the crimp was weakened or the rubber thinned out or both. Once I cut the ferrule off, the hose showed no signs of splits or cracking. It had simply weakened and separated from the tube enough to allow pressure to push oil past it. Kinda makes Jacks clamp suggestion more interesting especially if one were to use the "constant torque" style clamps such as the Breeze units. One bit of logic I used was that if I used the aluminum ferrules, the expansion/contraction rates would be as similar as possible compared to a steel one and that seemed relevant.

Another note from me: I understand that a hydraulic specialist would be skeptical of re-using the tube because anyone who has seen the sides of steel tubing blown out on bulldozers and such has a respect for the strength of hydraulic systems. But we're talking about certainly less than 100 psi of pressure here. It's a different situation.

So at this point I am still confident in my approach though a few adjustments would surely be incorporated in the next repair but nothing I believe to be critical to the integrity of the finished product. I simply replicated the original engineer's design profile but with much closer attention to detail than the average low bid factory worker. You guys make my brain hurt. I love it. Thanks!

 

tedgasthm, from what little I've have gleaned from reading here on this forum and experienced working on cars in general, air conditioning hoses are made way better that these oil lines. AC hoses have (or at least some) have a steel sleeve inside the aluminum tube under the crimp to keep them from collapsing or deforming, plus a mild or shallow barb like surface on the OD. How thick were your aluminum tubes. AC tubes are about 1/16" through there length except at the ends where they are swaged down a little in thickness.
Jack

 

with all due respect for you, and especially some high degree of well deserved admiration for the effort you are making with the oil cooler hose conundrum, I believe you
are not thinking through completely the statement: “….compress the tube creating more density ….”

The way metal is made more dense, as in the forging process, is to have it supported on all sides whilst pressure is brought to bear on the only remaining open side.

But when you are crimping the tube metal that has already been crimped once you have no way to enclose or support the underside / inside of the tube while the crimping process is pressing from the outside. That’s the only way to make the metal “more dense”. A crimping tool, or any kind of clamp is never by itself going to make the surrounded metal more dense. It just squeezes it.

And if the squeeze is tight enough to do any good, the metal will thin at
the point where it is stretched and collapses inward. That’s just basic physics.

Engineers know this well, and a well designed part will be thick enough to have a margin of safety built in so some minor thinning will be inconsequential.

But who is to say that a re-crimp will still allow for a safety margin ? With these hose assemblies being a trouble spot for our cars, a degree of over engineering is certainly called for.

It’s bad enough that the original crimp has thinned out the metal tube. Re-crimping it just adds to the weakening at that point.

Which is what my hydraulic tech pointed out to me in language more precise than what I am using.

Welding on a new end that has never been clamped or crimped is the sure fire way to bypass all of these possible pitfalls and concerns. At the same time, a welder can add a slight bead around the end of the tube which will
serve to be insurance that the hose cannot slip off of the tube.

Getting a competent welder involved
in your project will be a win-win for all concerned.



if you read my post closely I mentioned that the aforementioned hydraulic technician did indeed know of the application of our hoses and made his determination based on the pressure and operating environment of our cars, not that of the bulldozer’s environment and pressure. Therefore, he was not making an apples to oranges comparison.

looking forward to observing the evolution of your project.

Z

 

JACKP, you had asked the question about the thickness of the AC tubing I used in experimenting with the crimper. That piece of tubing was in my scrap pile and I thought it was from an AC hose but damned if I remember. I did get the impression that the grade of aluminum might be an issue too as it seemed soft. I do know that it was very thin walled and had no steel liner in it. I put a caliper on it tonight and it read 1.4 mm and I do remember comparing it to the cooler tube. As I recall the cooler tube was right at twice the thickness of the other (AC?) tube and I took heed of that when I tried my first crimp with the new hose. I also felt that the quality of the aluminum in the cooler tube was better in terms of density. Because the thinner tube had distorted, I looked closely at the cooler tube to see if there was any sign of the same issue and saw none. At this point, I am curious to hear from anyone who has ever had the aluminum portion of these tubes blow out or break. There was another thread started by one of the contributors herein that may be a good place to inquire. Think I will.