How-to: Rear Oil Line Replacement (lots of photos)

[ljibis]

Thanks to information found in numerous posts on this forum, I successfully replaced both oil lines connecting to the rear fender thermostat last week. Since this seems like a pretty common issue, and there is a lot of documentation here about ways to attack it, I thought I'd post my experience. Hopefully it will benefit someone in the future.

The car is a '77 911S with the trombone front cooler. I believe the oil lines were original to the car. I'm not an expert on this at all, so take this for what it is. It was just my experience, your mileage may vary. Also, no comments on the general filthiness of my car...I'm working on it!

Here are the lines and thermostat before I started. These had been soaking in PB Blaster for several days but they absolutely would not move. I wasn't going to try a torch in my solvent-soaked work space.



I decided to use the cutoff wheel method noted in several posts here. I started by cutting the lines off really close to the nuts to buy some room to work. I used an air-powered cutoff wheel. Expect a bit of a mess...





I then used the wheel to cut slots in the back and side of the nut. This was pretty nerve-wracking, but taking a few quick measurements on the new lines gave me an idea of how much metal I had to work with. In the end, I was able to cut all the way through down to the threads.

Once cut, I used a prybar to open up the slots a bit. A combination of the prybar, the oil line wrench, and a hammer were enough to start the nut turning off the threads. Even when spread open by several millimeters it took a lot of coaxing.



The nut eventually turned off of the thermostat. As you can see here the threads are clean. This felt good...these sorts of projects usually don't work out for me.



Victory. You can see how chopped up the nut got from all the cutting and beating...



After what I learned with the first nut, the second was a bit easier. I won't post any photos of that to save space. Same deal, different line!

Here is a photo with the new lines installed, which were purchased from our host and fit very nicely. My buddy has had trouble with leaks after replacing the lines, so I spread a bit of anaerobic gasket maker on the threads right before installation.



The welded-on bolt holding the oil line bracket snapped right off on me, so I secured the oil lines with a couple rubberized brackets usually used for electrical work and a Nylock nut.



The engine has been reinstalled, and I've been driving it for about a week. So far there are no leaks, so I guess it worked out.

Overall, this was not a fun project. That said, using the cutoff wheel provided a pretty reliable outcome and I'm not sure I'd ever try anything else. Thanks to those who suggested this method, and to everyone that's contributed to discussions on this subject. Your advice saved me from buying a new thermostat!

[JFairman]

The rubber hose part was slowly leaking and I didn't want to buy a new line so using a cut off wheel on a die grinder I carefully cut a slice in the crimped ends without hitting the barbs underneath, spread the slice with a large screwdriver, removed the old rubber hose, and sanded and painted the steel line black.

Then google searched for small T-bolt clamps that I could not find locally, and bought the stainless #16 braided line that is 22mm ID and carefully installed it so the ends wouldn't get frayed, shread my fingers, and look like crap.

Works and fit perfectly, only cost about $25 in parts, looks nice, clears the 315x30 rear tire with room to spare, and doesn't leak at all.

It's been on there almost a year now.

[Tom '74 911]

ljibis -
I did the exact same thing when I replaced the hardlines going to my front fender cooler. I soaked the nuts and thermostat w/PB blaster many times over the course of a few months - and ended up cutting them off. At least they yielded in the end!

Originally Posted by JFairman

Then google searched for small T-bolt clamps that I could not find locally, and bought the stainless #16 braided line that is 22mm ID and carefully installed it so the ends wouldn't get frayed, shread my fingers, and look like crap.

Works and fit perfectly, only cost about $25 in parts, looks nice, clears the 315x30 rear tire with room to spare, and doesn't leak at all.

Do you remember where you sourced those wide clamps?

Thanks,
Tom

[Gogar]

Is that a little bit of blood in pic #7?

Thats how you KNOW it was a good repair.

[JFairman]

Do you remember where you sourced those wide clamps?

Thanks,
Tom[/QUOTE]

I got them from MSC Indutrial Supply Co. $4.36 each
Ordered them online.
http://www1.mscdirect.com/CGI/GSDRVSM?PACACHE=000000050430435

[Tom '74 911]

Originally Posted by JFairman

Do you remember where you sourced those wide clamps?

Thanks,
Tom

I got them from MSC Indutrial Supply Co. $4.36 each
Ordered them online.
http://www1.mscdirect.com/CGI/GSDRVSM?PACACHE=000000050430435[/QUOTE]

Thanks!
Tom

[ossiblue]

ljibis,

Nice work and great patience. One word of caution--you mentioned putting some thread sealer on the stat to prevent leaks. The seal is actually made by the convex/concave male and female fitting on the line and thermostat, not the threads. If there is a leak, either the nut is not tight enough or the line is misaligned in the seat of the thermostat. If anything, you should put anti-seize compound on the threads. If what you applied hardens, you may face the same headache you just went through when things need to come apart.

[jonbot]

JFairman, awesome tip about those hose clamps. I doubled up with the typical "worm gear" type, but your solution is much better. I'm going to order some of those, thanks again for the tip.

[rsiegel]

Once the pipe is cut off flush with the nut, has anyone tried putting an impact wrench on the nut?

That braided line idea is sweet. I'm terrified of a "cascade failure," where, in trying to get the line off, you ruin the thermostat, then in replacing that, ruin the lines running to the nose, then in replacing those, ruin the front oil cooler...

[euro911sc]

I'm pretty sure you would toast the t-stat if you put an impact on there. Though, I have never been there, that is my impression from reading a few of these... Simply, the AL threads will stick to the steel line nut and come off with the nut.

Best regards,

Michael

[rsiegel]

To do the braided line trick and have it mate up to the hard oil line that wraps around the back of the engine, does anyone know the metric thread size of the 36mm nut and its flanged fitting, and/or a source for this crimp-on part? Finding the braided hose is the easy part.