XK 140 Oil Filter Housing Leak

TUP · February 3, 2019, 8:19pm

I have a 1955 XK140 which I have restored. I currently have approximately 2,500 miles on the clock and most of the post restoration wrinkles are worked out except a continuing problem I am having with oil filter canister leaks. Oil pressure is 55 psi at driving speeds and 42-45 psi at idle when warm. The problem I am having is with leaks occurring at the canister “O-ring.” I do not have any leaks at the top of the canister head where the 9/16” AF bolt which pulls the canister up into the O-ring, my problem only occurs at the interface between the canister, O-ring, and groove. Specifically, the problem is that after driving the car 100 miles or so, the long bolt loosens ¼ turn requiring me to pull over and tighten it. If I don’t, a leak will occur and the O-ring will be damaged, requiring it to be replaced. Here is a photo of my oil filter assembly and a close-up of the groove where the O-ring fits. The groove is deep, smooth, and clean.

Right now, I have no confidence I can drive the car on a tour without pulling off the road every 100 miles, getting out a ratchet with a 9/16” socket and a long extension, popping the hood retightening the bolt, and pressing on, hoping a leak won’t develop. It is quite frustrating and has shaken my confidence in the engine.
Over the 2,500 miles I have driven the car, I have changed this O-ring perhaps 4 or 5 times, replaced the canister with a spin on adapter, and now removed the spin on oil filter and gone back to the original set up. The best results I’ve had are with an O-ring recommended by Rob Reilly of this forum that has an “X” shaped cross section. It has lasted the longest, but the long bolt still loosens ¼ turn every 100 miles. Most recently, I started the car up after an overnight run and watched the oil start to seep out of the canister at the O-ring. Fortunately, I was able to shut it down, tighten the bolt, sealing the leak, and make it home without being towed.
The top section of the bolt is sealed with a 7/8” OD, thick rubber washer. I have sandwiched an aluminum, Stat-O-Seal washer on top of the rubber and below the flange on the bolt. I’ve never had a leak at this interface.
I’ve done at least 50 or more oil changes on my classic cars with spin on and canister oil filters and never had a leak. I’m baffled. I’m afraid if I tighten the bolt too much I’ll strip the threads in the canister or tear the O-ring. Does anyone have any possible solutions to this dilemma?

Rob_Reilly · February 3, 2019, 10:45pm

Oh, geeze, did I really recommend the X-section o-ring for XK140? I don’t remember it. I remember discussing its use in 120.
The 140 canister has a straight cut edge, not a curled lip as the 120 has.
A square cross section o-ring would be best to seal against the straight cut edge.
I don’t think a round cross section o-ring would seal very well against that edge. It would have to be perfectly concentric, and these canisters aren’t that good.
I measure the groove in a 140 filter head as 3.943" x 4.175" so I think the right size would be #241, McMaster-Carr part number 1170N114 in Viton or 4061T263 in Buna-N. It may be a tight squeeze to get it pushed into the groove.
I use a square cross section o-ring in my 120, no leaks.

TUP · February 3, 2019, 11:01pm

My apologies Rob, you remembered correctly, I did not. I went back and read the threads and you mentioned ordering McMaster-Carr “O-rings” in a square cross section. I ordered several different types, and found the easiest to install and most trouble free sealing rings were the ones with the x-cross section. I had much difficulty with the square, and I agree the round probably wouldn’t seal properly as the 140 lip is thin and flat. Again, my apologies.

However, the main problem I’m having, at least now, is the long bolt which pulls the canister up to seal the “O-ring.” Why does it continue to loosen? I’m having difficulty believing it’s not tight enough, but perhaps I’m simply not putting enough torque on the wrench.

John_Walker · February 3, 2019, 11:07pm

Note to self: Check the tightness of that bolt after putting a few miles on a fresh oil change.

TUP · February 3, 2019, 11:21pm

I just thought of something: Maybe the seal that I’ve been using, the one with an “X” cross section, is causing the problem. I’ll try using a seal with a square cross section and see if that makes a difference. It does have a fit ever-so-slightly tighter than the x section seal.
I’ll give you an update once I’ve made the change and had a chance to put miles on the car to prove or disprove the theory.

Robin_O_Connor · February 4, 2019, 12:42am

Are you certain that the bolt is loosening? Have you placed a witness mark on the head?
How about drilling the head and lock wiring it in place, once you are happy it is oil tight.

davidxk · February 4, 2019, 2:40am

Robin read my mind! First need to confirm the bolt is actually loosening with a dab of paint. Actually may be worth 2 dabs - one across the bolt head and canister, and a second across the canister and the housing in case that is moving. If it really is loosening (as witnessed by a discontinuity in the paint dabs), then drill the bolt for safety wire and find a convenient place to tie it off. I also wonder if the statoseal washer you’ve used on the bolt is making it more likely to loosen. Did you find it to be necessary?

TUP · February 4, 2019, 5:07pm

Thanks to all of you for your comments. Based on your comments, I think I’ll try going back to basics. That is, installing the original type rectangular cross section seal and removing the Stat-O-Seal washer. In addition, as suggested, I’ll set the long bolt up for safety wire and paint witness marks on the bolt and canister. Sometimes the simplest solution is the best.