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Oil Cooler Fittings - Steel or Aluminum?

flickroll

flickroll

Well Known Member
What's the conventional wisdom for the material for hose fittings that screw into the oil cooler? I try to uses steel fittings FWF whenever I can, but wondered which is best for this application. Thanks
 
The problem with using aluminum on the cooler is more about the threads galding and you never being able to get them out if you need to.

Those are some beefy fittings and I doubt anyone has ever seen one break in that application under normal use.
 
Brantel said:
The problem with using aluminum on the cooler is more about the threads galding and you never being able to get them out if you need to.

Those are some beefy fittings and I doubt anyone has ever seen one break in that application under normal use.
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Thanks for the response. I did read somewhere that once the fittings have been in for a while you shouldn't try to remove them. If they're in good you run the risk of damaging the cooler trying to get them off.
 
I rarely see anything BUT aluminum used in the oil cooler or engine case. I also can't recall ever running across galled threads if teflon paste or another anti-seize is used. Finally, I have never seen one break.

I'm sure all these conditions have occurred somewhere to someone, but I would say they are generally rare.
 
Stay safe! Forward of the firewall.

Depending on vibration, length, rigidity of hoses

I would play it safe. If the fittings are less than -8 on the cone end and/or less than 3/8 npt. on the other end, I would use Cad Plated Steel. The cad plated fittings have a color that is Black or yellowish gold. Along with being more durable they will also withstand a higher temperature in case of fire.

I would apply this practice to Fuel and Oil Systems.

It's your thing, do what you want to do.:rolleyes:
 
It is quite common...

Toobuilder said:
I rarely see anything BUT aluminum used in the oil cooler or engine case. I also can't recall ever running across galled threads if teflon paste or another anti-seize is used. Finally, I have never seen one break.

I'm sure all these conditions have occurred somewhere to someone, but I would say they are generally rare.
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...and I remember it happened to Dan C. on his RV-7 when his web site was up...

He had Pacific Oil Coolers fix it, and their comments on aluminum fittings are here -

http://www.oilcoolers.com/article_oil_cooler_woes.asp

I wouldn't worry too much about the thicker large size fittings melting - heck your case would melt first - but galling is likely....:(
 
az_gila said:
...and I remember it happened to Dan C. on his RV-7 when his web site was up...
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I'll give you that NPT fittings aren't exactly "maintenance friendly", but they rarely need to be removed, so in that respect, galling is not an "issue".

az_gila said:
...I wouldn't worry too much about the thicker large size fittings melting - heck your case would melt first - but galling is likely....:(
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Its funny that people worry so much about aluminum fittings and lines FWF in case of fire, but completely overlook the paper thin aluminum oil cooler in their risk assessment. I wonder how long the cooler would last with the 1600 degree blowtorch test... 10 -15 seconds?
 
Firewall forward on lines that vibrate, I prefer steel due to the potential for breakage. This is particularly true for big -6 and -8 lines for fuel and oil. Lots of aluminum fittings in use as well, just a preference.
 
Advice from Pacific Oil Cooler Service Website

see http://www.oilcoolers.com/article_oil_cooler_woes.asp

_________________________________________

DAMAGED THREAD ISSUES

.......................
VERY IMPORTANT:

......... In fact, throw all aluminum fittings as far away as you can from the work you are doing - and use steel fittings instead. Steel fittings, when installed with some type of lubricant on the threads, will almost never gall, bind up, or damage the threads of an aluminum oil cooler. In addition, steel fittings will un-screw cleanly from the cooler - even many decades later. None of these things can be truthfully said about aluminum fittings.


Steel is the fitting material of choice if you want to avoid damaging the threads of an aluminum oil cooler. Additionally, steel fittings will un-screw from the oil cooler cleanly and with no thread damage, even many years later. No matter what they?re made of, never ever screw fittings into an aluminum oil cooler without first applying some form of thread lubrication - and use aluminum fittings only as a last-ditch resort.

If you must use aluminum fittings for some reason, make sure that the threads are clean and defect-free, use Teflon tape or an anti-seize lubricant made for use on threads, and work slowly and carefully as you begin screwing the fitting into the oil cooler (and cross your fingers, also).

When pipe-threads are involved, be sure that the fitting is going to snug down and achieve a seal before the shoulders above the threaded portion of the fitting come in contact with the top of the boss on the cooler. When the shoulders on the fitting touch - or come anywhere close to - the top of the oil cooler?s boss before a seal is made, it means that the threads in the cooler have lost their taper and the cooler must be replaced.
________________________________

Bill Brooks
Ottawa, Canada
RV-6A finishing kit
 
Relentless at Reno

Got some photos today in an email that showed the root cause of Relentless losing its prop was due to oil starvation from a broken aluminum AN fitting for one of the oil cooler lines on the accessory case. Loss of oil pressure caused the prop to run away.
 
rocketbob said:
Got some photos today in an email that showed the root cause of Relentless losing its prop ... Loss of oil pressure caused the prop to run away.
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Now that's what I call a runaway prop! :)

Are those photos you can share? I'd be interested...
 
Steel. You can get them at a hydraulic supply dealer.... Many of them in the bins say "china". I pass on those however.
 
Toobuilder said:
I rarely see anything BUT aluminum used in the oil cooler or engine case.
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Well that's true of most RVs, but that's simply because that's what Vans supplies with their FWF kits. As always Vans components are purely price driven. In the end it's cheaper (and easier) for builders to use what they have been given rather than discard their fittings and source the much more expensive AN steel fittings (virtually twice the price).

Personally I opted for steel. And thanks to RocketBob for the heads up.
 
Thanks everyone for your replies. Based on everyone's input I decided to go with steel oil cooler fittings. The failure on Relentless sealed the deal. Thanks again.
 
Has anyone experienced corrosion when using steel fittings in an aluminum hole? I'm considering using steel fittings to terminate my hard aluminum lines at the firewall pass-thru. But I am a bit concerned about corrosion forming in the fuel line and going undetected for long enough for it to cause some serious problems.

Thanks,
Phil
 
General Consesus FWF

I'm getting ready to hang my engine and was reviewing this thread. Is the general consensus to use steel fittings in all the required places in the Accy case? If so, can one find the special fittings for the OP and FP lines in steel, or do you have to make them? I have them for the oil cooler, but just thought about the rest of them.

Thanks
 
Not From a Broken Fitting!

rocketbob said:
Got some photos today in an email that showed the root cause of Relentless losing its prop was due to oil starvation from a broken aluminum AN fitting for one of the oil cooler lines on the accessory case. Loss of oil pressure caused the prop to run away.
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I should have rebutted the above statement sooner. I spoke to the crew chief for Relentless a couple of days after their spectacular engine failure. They DO NOT believe that the broken oil fitting in the back of the accessory case caused the failure. They have pretty strong evidence that the first failure was actually the oil filter mount casting (stock lycoming). They think that the filter mount failed from fatigue from the "G" loads and it and the filter fell onto the fitting/oil hose below it. The filter and the broken part of the aluminum casting were found somewhere out on one of the runways near the location where the oil loss was experienced. There was a witness mark on the filter where it was believed to have hit the oil fitting. Also note that they were using one of the "long" filters in this plane which would certainly increase the cantilevered loads on the filter mount.

Skylor
 
DanH said:
The crew chief is probably confused about the order of events. Failure of an oil filter casting due to flight G loads is unlikely. Failure due to the very high accelerations of a severe vibratory inbalance is quite possible:

http://www.relentlessairracing.com/...r.com/prog/images/lavori/55.jpg&w=1905&h=1057
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Are you sure about that? The filter mount casting was pretty thin in one of the mounting bolt locations, and the broken casting showed some discoloration in that particular location as if there may have been a crack propagating for some time prior to the failure. Since the filter itself is cantilevered off of the mount and they were using the long filter, the mount would certainly see significant loads during in flight "G" loads.
 
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