Oil Cooler Lines Constantly Seeping.
 

Title is the crux of the issue, I will outline what I have done so far and why I am so confused as to where to go from here.

Few months ago I decided I was going to make my own harrop oil cooler at 1/2 the price. Fabricating the brackets and scoop turned out to be the easy part.

So far I have installed 3 sets of lines, first set leaked at all 4 fittings (cheap fittings). Second set was Frangola fittings that I assembled, just one was seeping. This set was a set of Frangola crimp fittings I had 2 lines made with and the same fitting from round 2 was still seeping.

Graciously Mishimoto warrantied the core that had the leaky fitting.

Here we are at round 4, still using the third set of lines. I pressure tested the lines on the cooler core at 200psi with zero pressure loss over 30 mins. After installing it on the car I am somehow seeping at one fitting on the cooler and one fitting on the adapter plate.

I am at a loss, is this just the nature of the beast? The fittings don't seem to be leaking enough to pool oil, just until they're wet, even after a 60 mile drive.

Sorry this was long winded, I'm just a little frustrated with all this. Hope this is the correct forum for this, and hopefully someone can point me in the right direction. Thanks.

These gaskets are a godsend. I keep extras on hand.




https://www.pegasusautoracing.com/images/M/3202X4.JPG

I didn't realize these were a thing.

I know AN fittings seeping is a fairly common problem. Even with top brands.

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how did you pressure test the lines? air? water? oil, cold/hot?

where are the lines leaking? you mention crimping, is it leaking at the hose but before the connection, or at the threaded connection point?

what sealing methods have you attempted so far?

i've always used this:
https://www.homedepot.com/p/Oatey-Fa...6212/203529858

or this:
https://www.homedepot.com/p/Hercules...8062/100153125

depending on my mood.

both i've had great success with perfectly sealing anything.

Neither of those is supposed to be used on AN flares. Is that what you used them for?

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no. but as long as you don't tell the flare, it doesn't know!

AN flares aren't all that different from gas pipe fittings, and few plumbers would ever install a gas pipe fitting without using some sort of pipe dope...

Yup. I went all Aeroquip but even they were a crap shoot. I've also had good results lapping but those gaskets are amazing.

AN/SAE fittings can be finicky at times.

If they are aluminum, make sure to torque them properly. It's surprising how much torque they can take, but certainly don't overtorque them. Also, try align them and ensure they stay aligned without too much stress/effort (don't rely on the tightening of the nut to bring them into alignment). Maintain the alignment as best you can while you tighten them to get the best chance of an even seal on the face.
The operational recommendation is to use the FFWR method (Flats from Wrench Resistance), rather than a torque value for consistency:

• http://blog.parker.com/turn-vs-torqu...ions-leak-free

In practice on my own oil cooler's AN-10 fittings (5/8" ID), it starts to get quite tight near ~1 flat. That's a bit off from the 1/-1/2 flat recommendation, but you can try getting them as snug as you can (taking note of how many flats/rotations you tightened to) run the car a while, and come back to check for leaks again. If it still leaks, add a little more torque. Just don't exceed the # of flats tightness.

The second consideration while you repair is loose/residual oil in the threads from assembly/re-assembly. After an adjustment/tightening of the fitting, run the car a few times and keep cleaning the fitting and observe if the amount of oil is consistent or reducing.

If all else fails, use Seco7 seals.

AN fitting technically shouldn't need any sort of thread sealant but it’s easy cheap reassurance you won’t have any issues as getting an AN fitting exactly torqued to spec not over or under and the chances of having a cheaper fitting being “faulty”. I see no down side in using it.

Permatex 59214 High Temperature Thread Sealant
Don’t use tape, use this. 400F and oil compatible.

The question is: if you use too much and it squeezes out into the oil line, it could come loose and block an oil passage. Is it still a good idea?

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+1 Main reason it should not be used with AN fittings. ...in this application, at least.

Whenever I've used AN fitting, I don't tighten them much. If you're putting any force into tightening it, it is more prone to leaking in my experience.

Do not use PTFE tape

Just make them a little snug and allow the system to put pressure to them. After a few warm/cool cycles, make them a little more snug. I've even gotten Mishimoto AN fittings to hold this way

Don’t apply too much?

Just a little bit on the rear half of the male threads will do the trick and not squeeze into the oil line.