P

Pilottonny

Well Known Member
I finished the oil cooler attach plate on the baffles yesterday and made an attempt to install the fittings and oil lines on the cooler. Although I was not to happy about the fact that the fittings would only go in approx. 2-3 threads deep, I tried to see if I could get the fittings facing the right direction. Tighthened the fittings slightly, without over duing it and figuered out I would propably be able to tighthen them a bit more with the lubrication of the Loctite thread locker on the thread. So I undid them and.......... found that the threads were already binding. I now have one of the inside threads of the oil cooler that is stripped (about 1,5 - 2 threads deep only).

I plan on finding a tapered 1/2" tap and run the tap in there, holding the oil cooler upside down, so nothing can get inside. I may have to cut the end of the tap, to avoid it damaging the coolers internals. Did anybody have to do this? Any advise how best to go about it?

As every downside has an upside, I will end up with the fittings engaging on a few more threads and the possibility to position the fittings properly, without having to overtighthen.

Any advise welcome.

Regards, Tonny.
 
Last edited by a moderator:
Tonny,

You should be using STEEL fittings on the oil cooler. Guys that
have been using Aluminum fittings are stripping out the threads.

Hope this helps.
Boomer
 
I used aluminum fittings with no problems.

On the other hand, notice that the threads in the OIL COOLER were what stripped...not the threads on the fittings. Using steel fittings would not have helped in this situation. I used Fuel Lube on all of my pipe thread fittings.
 
The reason you should not use Aluminum fittings in an aluminum orifice is that the aluminum galls when assembled with itself. This may strip the fitting or the cooler when you go to disassemble. But, given that a $300 part will always fail to protect a $5.00 part (the irrevocable murphy's law) it is often the internal threads of the oil cooler which fail.

I had the same thing happen to me. In the end, I used it as an excuse to buy a SW cooler.

But, always steel fitings in aluminum. You can use tite seal or any other oil soluble sealer...but tite seal is what I used. Never ever use plumbers tape, or sillicon because they can cause an internal oil blockage.
 
Jamie said:
I used aluminum fittings with no problems.

On the other hand, notice that the threads in the OIL COOLER were what stripped...not the threads on the fittings. Using steel fittings would not have helped in this situation. I used Fuel Lube on all of my pipe thread fittings.
Click to expand...

Jaime, It's when you try and take them apart when they will gall. It will ruin both the fitting and the cooler. Don
 
Grease The Tap

If you go the route of running a tap in to clean up the threads, holding the cooler so the tap is upside down is ok.

I find dipping the tap in heavy grease before threading it in will keep the chips in the grease on the tap.

Ted
 
Aluminium fittings come with Vans FWF-kit !

Greasing the tap is a good tip, Ted.

With regards to steel fittings: the aluminum fittings come with the Vans FWF-kit! and are also on the drawings.

I have used aluminium fittings in other cases (oil line fittings into the engine, MAP-line into the engine) but never had a problem with the threads galling.

Will it be easy to run the tap into the alumnium ? I guess the alumnium is quite soft. Anything I need to know, before a I ruin the oil cooler completely?

Regards, Tonny.
 
Tonny, I'm afraid the best solution is to buy a new cooler. Since material has been removed from the cooler (threads damaged), you can't just "tap" them back into existence. You would need to go significantly deeper on the threads to fully repair them, and then your fittings may go too deep into the internals of the cooler.

If you think there is adequate depth, go for it, but you don't want something nagging you forever. The pain of buying a new one will pass soon...

You are in good company by the way...many a cooler has met an identical end during a "test" assembly.
 
I've used thousands of aluminum fitting in aluminum parts (my buisness builds performance boats and engines, We have $100k worth of Goodridge fitting on the shelf,) and you should be using something like Loctite PST 567. Its a thread sealant and lubricant. You can install and remove aluminum fittings and remove them dozen of times without hurting any threads. I can't tell you what the proper fitting for your application is, but to try and fix your coolers threads you need a "short projection" tap, try MSC direct, they are designed to cut the NPT thread form with out much of the tap protruding inwards. If its just a thread or so a bad thread, and your new fitting has 1-2 good threads above and below it, it will seal up fine.
 
Ted RV8 said:
If you go the route of running a tap in to clean up the threads, holding the cooler so the tap is upside down is ok.

I find dipping the tap in heavy grease before threading it in will keep the chips in the grease on the tap.

Ted
Click to expand...

Ted's idea of holding the oil cooler so that the tapped ports are at the bottom during tapping, is an excellent idea. Any metal chips will fall out, not into the oil cooler. For added protection, have an assistant put an air pressure blow gun (at about 30 psi) to the port not being tapped. The air rushing out of the port being tapped will ensure that nothing ends up in the cooler.
If you only got two turns of the fitting into the cooler, it sounds like the port was not tapped deep enough. I doubt that you will "over tap" the hole, as was previously suggested. That said, go slow, as you can always tap more, but you can not "un-tap" the port.
I like steel fittings on an oil cooler for a different reason. I've seen aluminum fittings that failed due to metal fatigue. The fatigue life of steel in this application is almost infinite. I would rather take the 1 ounce weight penalty, than risk ruining an expen$ive engine due to loss of oil pressure. :eek:
No matter what material you use for the fittings, apply some sort of thread sealant to them. That's just my opinion and worth what you paid for it.
Charlie Kuss
 
G-force said:
snipped I can't tell you what the proper fitting for your application is, but to try and fix your coolers threads you need a "short projection" tap, try MSC direct, they are designed to cut the NPT thread form with out much of the tap protruding inwards. If its just a thread or so a bad thread, and your new fitting has 1-2 good threads above and below it, it will seal up fine.
Click to expand...

Mike gives excellent advice above. You can also modify a conventional taper tap by cutting off some of the end of the tap. I use a die grinder with a cut off wheel to do this. Apply some sort of tap lubricant to the tap, prior to cutting it. Apply more lubricant as needed to keep from overheating the tap during cutting. Overheating the steel will dull and soften the tap. Using the correct tap is easier, but may not be convenient, depending on your access to machinist supplies.
Charlie Kuss
 
Last edited:
Purely personally

But I would be very concerned that the slightest chip should fall in the oil cooler during the tapping operation..I believe the oil cooler rebuilders flush them thoroughly.

So as an idea, could one not stuff some kind of rag down inside the whole (just big enough to completely fill the hole) and covered in grease.

after the tapping vacuum out as many chips as poss then extract the greasy rag with a pair of nose pliers?

Just an idea.

Frank
 
Buy a new one, or send it out to a professional shop like pacific oil cooler. A new SW is a little over $400. The repair and flush is about $100 plus shipping.

In a brand new engine, what could a razor sharp chip do?

How much is the engine worth?

How much is the airplane worth if you can't dead stick it, or something goes wrong?

A chip can score a bearing, spin a bearing, and throw a rod. Can you dead stick a brand new airplane with an oil soaked windscreen?

This is just one of the lessons that you only learn after you needed to, but don't take risks with the oil system on a brand new aircraft engine. Even if you use a special tap and grease it and vacum the port and have an assistant blow air through it, how will you know? Heck, I wouldn't have taken that chance on a $5,000 racing engine, and I could always pull over if it blew.
 
Another method

frankh said:
snipped
So as an idea, could one not stuff some kind of rag down inside the whole (just big enough to completely fill the hole) and covered in grease.

after the tapping vacuum out as many chips as poss then extract the greasy rag with a pair of nose pliers?

Just an idea.

Frank
Click to expand...

Another way to prevent getting metal chips into an area, is to fill said area with shaving cream. The shaving cream will hold the chips. The chips and shaving cream can be removed using a shop vacuum. I've used this technique many times when I had to drill, tap and HeliCoil a hole (spark plug hole or valve cover bolt hole, etc). Any residual shaving cream will not hurt anything, as it is only soap. Just another idea, like Frank's.

Charlie Kuss
 
1/2" NPT ?

Hello everybody,

Thanks a lot for all the replies! There is certainly some very good tips there, but one thing I must say to those that tell me to just go and order a new oil cooler, is this: I can always do that after I have tried to fix it and the fix did not work! A true "experimentalist" is obligated to, at least try to, solve the problem by himselve before just starting to throw money at this particular problem!

I do not see such a huge problem with the contamination of the oil cooler, I can use grease, keep the cooler up-side down, can even put shaving foam in, vacum, blow out with pressure and finally rince. If any particle is left after all that, I gues that is what the oil filter and screens are for?

So I had a tap ordered at work. After some experimenting and bribing the right people, that turned out to be the cheapest way for getting tools that can be purchased in Europe. I just return them to the shop after I have used them (or sometimes "forget" to return them, if I find the tools could be very usefull in the future also). But............yep, wrong tap! So back to the store keeper tomorrow and try to convince him that our company definataly needs to stock a 1/2" NPT-tap.

1/2" NPT, that is the thread that is in there, right?

Again, thanks a lot for all the input.

Tonny.
 
Pilottonny said:
Hello everybody,

Thanks a lot for all the replies! There is certainly some very good tips there, but one thing I must say to those that tell me to just go and order a new oil cooler, is this: I can always do that after I have tried to fix it and the fix did not work! A true "experimentalist" is obligated to, at least try to, solve the problem by himselve before just starting to throw money at this particular problem!

So you buy the new oil cooler after the fitting breaks out in flight spewing oil over the hot exhaust stacks and maybe you survive the whole thing? At the very least send the cooler to someone like Pacific or do yourself a better favor and get a Stewart Warner cooler that you will probably need anyway. And use steel fittings! Don
Click to expand...
 
Do as you please.

But as I understand it the oil goes from the cooler to the oil gallies, it goes through the filter before and not after the cooler.

This is not an experiment, it is simply attempting a repair without the proper tools to perform it and double check the work...at least a cooler service could test and flush the one you have after a repair.

When it happened to mine, I destroyed the cooler so that it would not accidentally get installed on another aircraft...just can't see taking the risk.
 
You must log in or register to reply here.