Best way to flush the oil lines

[Sunroof]

My large Heart looking thermostat that is mounted in the rear right wheel well of my 1973.5T has not functioned in over 20 years! Luckily I have never ran with a hot engine, BUT its time to replace it. I do have a front mounted oil cooler (none fan type) and I am sure I have gummed up oil in both lines leading back to the thermostat. Big question is what is the best way to clean it out? Compressed air? solvent (which)? I plan on leaving the lines and cooler intact so I have a good three-four foot line run that could be gummed up.

Thanks
Bob
1973.5T

[BK911]

Curious what the experts say, but I have used mineral spirits.
Dump in a can, swish around a bit, then let sit in various positions for an hour or so at a time.
Put outside in direct sun if possible.
If concerned with sludge, maybe add a handful of nuts.

Edit:
The mineral spirits will usually leave a residue behind.
Flush well with water.

[Dpmulvan]

I wouldn't try to flush oil lines on the car, I would remove and run something like sea foam through them. You should concentrate on your first battle which is removing the thermostat.

[tdw28210]

FYI, I got my oil lines apart using 2 BF pipe wrenches from that Chinese hardware store. It took some work and I eventually need some heat, but I got it done.

[Sunroof]

I do not intend on removing the oil lines, just the thermostat (whole thing). I will not touch the lines going to the rear oil cooler since those are fine, but the long run to the front mounted oil cooler and return, which will be open when the thermostat is removed. The car will be jacked up but I can make sure that the rear is lower to allow for gravity flow to the back of the car with whatever solvent of cleaner I find will do the job.

So, I will need to push whatever solvent is best to the front oil cooler with sufficient pressure to clean out the lines and remove all sludge. Any and all suggestions on method and solvent is what I am seeking.

[BK911]

Pull the lines.
Your engine is much too valuable to take a chance of damaging it.

[shoooo32]

My SC's thermostat was stuck when I bought it. I just removed the Tstat, cleaned up the bore with scotchbrite and re-installed it with the rebuild kit sold by our host. Then topped up the oil and ran the car to normal operating temp and performed an oil change. Car runs fine and the oil temps are in line with other SCs running a trombone cooler.

Now I don't know how long mine was stuck for but pulling the lines didn't even cross my mind. The lines running to the trombone showed no signs of "sludge" and the oil that came out was very much a liquid.

To the OP, I would investigate and make a decision once you're in there.

[T77911S]

i would remove the front oil cooler to do the lines.,

that's going to be messy.
I would go get some soft rubber hose that will fit over the end of the oil lines then feed it to a large bottle like an old 1 gal oil jug to catch the crap coming out.

[Flojo]

I did not have the issue of a stuck thermostat, but I did clean the inner of my oil lines back then (as I had to change the 3 rear lines anyway, system was open).
I pulled the lines, removed the oil cooler, swapped the 2 front flex lines.
to flusch the lines with lots of brake cleaer (closed the ends of the lines with a cap and gaffa tape and let it sit, then move it around then let it sit again. repeated 3 times.
last flush was with some scotsh brite pad attached to a string to give them lines a pull-trough-scrub.

a lot cam out during that cure.

rinsed the cooler as well!