I have a 85 GSL-SE. New oil cooler lines, connectors and new crush washers. Like new oil cooler but from a an outfit I dealt with for many, many years with no problems and frankly it looks aftermarket and built like a tank compared to the stock oil cooler.

There is no leak at the engine block with either oil line. At every connector with the crush washer I tightened to the prescribed torque. Where the hoses connect to the connector I tightened snug but not too tight. Definitely no leak where the lines connect to each connector (brass fitting).

But at the cooler it's leaking like a drop every five seconds. Mostly from the top bung but I think the bottom bung, too, though less.

I have removed the cooler and examined it carefully. I have not been able to find any evidence of a crack or even hairline crack. I even used compressed air and a soapy water mixture to try and find a leak. I carefully cleaned the very end of the bung so it had a nice connection with the crush washer. Still, it leaks.

Any ideas?

 

this might be a silly question but are the thread pitches the same for the bung and hose fitting?

 

Do these connectors happen to be -10AN or -12AN?

 

I just went through this over the weekend. For starters, do you have the stock black cloth covered oil lines or AN braided lines?

I've come to the conclusion that buying the right tools for the job is smarter and faster than guessing and being discouraged.

If you have the popular -10AN braided lines, then get the pressure test kit and go to town.
http://www.pegasusautoracing.com/pro...p?Product=3272

Test each line by filling them up with 140psi of air and holding them in a bucket under water. Look for bubbles.

Then, replace the copper crush washers with Dowty seals size 3/8 BSP. They seal much better. Torque the adapters to 30psi dry no silicone or teflon tape.
http://www.pegasusautoracing.com/pro...p?Product=3240

Install both oil lines to the cooler, but don't hook them up to the engine. Put the pressure test plug kit in the other ends of the lines and pressure test your oil cooler. Fill a spray bottle full of water and laundry detergent. Fill up to 140psi, Spray continuously and look for bubbles while listening for the hiss.

I have a nice battery powered air compressor made by goodyear that goes up to 140psi, with a gauge on the top. If it holds pressure for an hour, you're good. For kicks I kept it pressurized over night just to be sure.

Threebond 1194 works great on the male threads of oil lines. http://mazdatrix.com/q-supply.htm

 

treebond is good stuff. or http://www.permatex.com/products/Aut...ad_Sealant.htm

 

As for the questions asked...

It is the braided -10 lines (not stock black cloth) from Mazdatrix. I got the complete "set" connectors and crush washers. The pitch of the connectors appears to match the bung exactly.

There is no evidence of the lines leaking but agree to be thorough they should be tested.

Thanks for the suggestions.

 

Another test you can do is the swap the line arround. What I did was mark one end on each line. Then I swappped them around. This told me if it was the connector leaking or the welded bung on the oil cooler. Sometimes it hard to tell where the leak is. In my case I had made up my own lines and one was leaking. Put a new AN fitting on and worked great.

 

I'm pretty sure that the fitting that the line threads onto also threads into the oil cooler (if that makes sense). It is a threaded double ended fitting. One end threads into the oil cooler line and one threads into the cooler itself. Try taking this fitting out of the oil cooler, wrapping it with thread tape and then reinstalling it and reinstalling the line back on to it. It may be leaking through the threads into the oil cooler.

 

The thread is cracked - common issue on the oil coolers. I had one driving me nuts, so I kept tigntening - then saw where the crack was... there isn't any sealer that will work on that fitting for long.
Pull the cooler out, clean off the bungs, and have them rewelded by a TIG welder. Then re-tap the threads and you'll be good to go..... kinda - the issue with the oil line setup is that as the engine twists it puts torque on the cooler lines. The stock lines are fairly soft, but an aftermarket line can be stiff enough to transfer torque and loosten one end of the line. Specifically the line leading from the front of the engine to the cooler.

One solution - since you probably need it welded anyway, is to convert to a banjo bolt like they did on the 2nd gen oil coolers. Finding fittings and all that will fit in the needed space isn't easy though.

Good luck.

 

Yeah I took a good look at mine while running, it's cracked at the lower bung. rotary-works replacement oil cooler to the rescue! It has AN fittings welded into the oil cooler already so no need for adapters and no more thread cracking. No more crush washers.

http://www.rotary-works.com/mm5/merc...gory_Code=RDOC

 

Well, in the end it was indeed a hair line crack in the upper bung. Took a magnifying glass to confirm but that was it. It was a used cooler I ordered from a reputable source so I opted to return it rather than try to fix it.

My wallet is a bit lighter .

But, with the new cooler everything is working great and no leaks .

 

awesome info...and glad it all worked out..I am following the advise on my leaky oil cooler now....cjf