Healey 100 oil leak

[Healey 100]

Healey friends:

I am sure none of you are shocked to hear that Healey's leak from the rear main. My 100 has leaked for 35 years, I have grown accustomed to it, though I hate the mess it leaves when I park it.

What's new is that I have just rebuilt the engine with new bearings, pistons, rings, etc. She runs great, but her rear main oil leak seems even worse now. If I drive her hard for a while, the oil seems to collect somewhere in the bell housing, and when I slow down or stop, a ton of oil comes out quickly, making a thick slippery spot about a foot in diameter!

I know the 100 has no seal per se, but it does have a drain to catch overflow and direct it back into the oil pan -- through a little tube attached to the bearing housing. I was wondering if this tube was necessary. Won't oil flow out the drain much faster without the tube? The tube is about 7/16 OD, 3/8 ID by 6 inches long. I would think gravity flow through a short 7/16 hole would be a lot greater than through this tube. But I am sure it was put there for a reason.

It would be relatively easy to remove this tube. Does anyone have any other suggestions? I need to fix it quick or bring lots of oil and the hazmat team with me to San Diego....

Bill S
Albuquerque, NM

 

[Dave Russell]

There are several places for a "rear main" leak.
The tubular cork or felt plugs on the sides of the rear cap are hard to seal. Many folks replace these seals by filling the holes with a two part quick set compound such as one of the compounds used for plastic bumper repair. A single part compound such as the various silicones will never set in these deep holes.

The bottom of the main cap "must" sit flush with the adjacent block surfaces. If the cap is lower, extra gasket material must be inserted over the cap to take up the gap. Some gasket kits include a tiny cork strip to be used to fill this area. I personally cut a section from another gasket to use as filler since the provided tiny strip would not reliably cover the cap area.

Sealer should also be applied to the main cap to block parting lines.

The rear main crank journal scroll must fit the crank case & bearing cap with no more than 0.002" clearance & be centered. If everything is perfect, there will be very little leakage.

After market seals can be installed but on the Four, require milling the rear main cap & some very precise fitting. Also machining the rear main crank journal.

The drain tube appears to exit at a lower pressure area in the crankcase than the rear main cap does. I think removing the tube would not help.
D

 

[Healey 100]

Dave:

These are good suggestions and include stuff that I did not do when I assembled the engine.

But the leak is on the bell housing side of the assembly, there is no apparent leak on the engine side of the rear plate. Wouldn't most of the leaks you mention appear on the engine side of the rear plate?

I speak a little bit from experience, I resealed that bearing cap and dowel seals several times in the years I have had my Healey -- yet it never really affected that leak. My rear cap is an extremely tight fit into the crankcase -- it is very difficult to R and R this cap, it is hard to believe the quantity of oil I see is getting through those parting lines.

I never thought about that drain tube before, but slow drainage out of the trough in the cap could overwhelm the slinger. This car does not leak much until I drive it non-stop for while, like 20 or 30 miles at highway speed. I note that Norman Nock recommends putting a PCV valve on the 6's to lower crankcase pressure to improve drainage from the rear bearing.

Just a few thoughts, I will improve the sealants around the cap if I drop the pan (again -- aaggghh!!), but I am not confident that will do the job.

Bill S

 

[glemon]

Bill, don't know if this will make you feal any better, but when I first rebuilt my Healey 100 motor I got the same thing, and I had installed the Dennis Welch seal kit. Funny thing is it only happened the first couple hundred miles of break in then went away--my theory is blow by from the pistons couasing crankcase pressure until the rings seated properly--but really have no idea, but it did go away--not completely, but to a point where it was much better than before the rebuild, after a couple hundred miles or maybe a little more.

Greg

 

[Dave Russell]

The back of the block is sealed to the front of the plate with a gasket, I hope. This gasket should also seal the rear of the cam bearing. There is no place for leakage to go anywhere except behind the plate.

There is an extra tapped hole in the bottom of the rear main cap. With a piece of bar stock sized & drilled to line up with this tapped hole & to bridge the cap studs, a "puller" screw can be inserted into this tapped hole. Since this hole is not very deep You usually have to pull the cap a bit, back out the screw, add shims to relocate the bar & pull some more.

Believe me, the side of the cap may be press fit & the cap securely tightened to the block & things will still leak without good sealer. I recently went through this on a "ground up" engine rebuild.

If it is a late BN1 or a BN2, you can't get the darned cap off without pulling the transmission to gain access to the two plate to bearing cap screws.

The PCV might help. On the Four there is no place to access a vacuum connection. Best would be to remove the balance tube between carbs & add a connection to it.

Don't discount the need to add extra oil sump gasket thickness at the main cap location if there is any doubt. The top half of the slinger housing to block joint on the top half has a gasket which must not leak. Similar problems can happen with the front main cap but it doesn't seem to be as much of a problem.

One last thought - You might be able to remove the pan, thoroughly wash the affected areas with brake cleaner, probably several times, & apply Glyptal sealer to the INSIDE of the cap vertical AND horizontal parting lines. Make sure it flows into the cap parting joints. Very awkward with the engine in the car but it can be done. The last time around, this plus the extra sump gasket thickness worked for me.

While the engine was apart I did the needed machining & installed a DWR external seal. I had a fit when the rear leaked & thought it was the new seal. In desperation I tried the above sealing methods first. It worked & there was no problem with the DWR seal.
D

 

[Healey 100]

Healey Friends:

Thanks for all the suggestions. I think I am going to drive it a few more miles (there are 200 miles on the engine now, and it is still leaking) and hope it heals itself as per glemon's car.

If not, I will remove the rear cap (mine is an early BN1, there are no screws holding the cap to the rear plate) and reseal it vertically and horizontally. I think I will use an anaerobic sealant, according to the specs I have read this is an ideal sealant between cast machined parts like these bearing caps.

The plugs Moss is selling for those holes along side the caps are loose-fitting felt, not the stiff cork I am used to. Should I stick with the Moss plugs? I am going to be working upside down, filling those holes with epoxy or sealer isn't going to be easy.

I think I am going to remove that drain tube, it's probably a placebo, but I think the bearing trough will drain faster without it.

Thanks again, I will keep you posted on how it turns out. If you have any other suggestions, please keep them coming...

Bill.

 

[Dave Russell]

Healey Friends:
If not, I will remove the rear cap (mine is an early BN1, there are no screws holding the cap to the rear plate) and reseal it vertically and horizontally. I think I will use an anaerobic sealant, according to the specs I have read this is an ideal sealant between cast machined parts like these bearing caps.

The plugs Moss is selling for those holes along side the caps are loose-fitting felt, not the stiff cork I am used to. Should I stick with the Moss plugs? I am going to be working upside down, filling those holes with epoxy or sealer isn't going to be easy.

I think I am going to remove that drain tube, it's probably a placebo, but I think the bearing trough will drain faster without it.
Bill.

Omit the plugs. You can remove the original plugs & sealer with a hand turned drill bit. The correct sealer is fairly quick setting. With a flexible tube in the end of the injector the holes can be filled from upside down fairly easily. Maybe a piece of tape over the end of the hole to hold the sealer while it sets.

As I said before, the drain tube exits in a lower pressure location than at the bearing cap. I would keep it, but your choice.
D

 

[BUNDYRUM]

Hello Healey 100.

I would most definately leave the drain tube in the rear main cap for this reason. The end of the tube usually sits close to or at least below the level of oil in the sump. If you remove the tube there is a chance that crankcase pressure will blow back up the drain hole and you will have even more of an oil leak (and you thought this wasn't possible).

What a lot of people don't quite understand is the purpose of the left hand thread machined into the crankshaft. It's to carry air from the area behind the flywheel so there is a positive pressure to force the oil from the rear main bearing back into the trough around the inside of the main bearing cap and thus back into the sump. If the left hand thread doesn't protrude past the rear main cap (due to manufacturing tolerances and such) then it cannot work.

This can be a difficult area to seal up but it can be done.

If you find that this is so the easiest solution is to machine (a file works well as that's what I used) a 45 Deg (or thereabouts) bevel/chamfer on the rear corner of the 2 parts of the rear main cap where the thread sticks out. This allows air to be "picked up" by the thread.

The next step I did at the time of the rebuild was to make a fixture for the 2 parts of rear main cap and mount it in the lathe. I then machined out the material to make the trough the same width and then filled it in with an epoxy. when it had set I then machined a groove in the epoxy to take a Jaguar rear main seal.

There are so many solutions out there and it seems that there are some very good ones that have been put together with a lot of serious thought.

If I were to do it again I would machine off the back of the rear main cap and machine a 2 piece housing to bolt onto the back of the block and fitj a Chevy big block seal.

I did this on my BN7 and am happy with the results.

Regards

bundyrum.

 

[zblu]

sounds like what I had done to my early 100 bundyrum, its a chev 350 part from memory, not sure of the part number though

 

[pan]

I am not a fan of lip seal additions to these old engines and do not think they are any better than a properly assembled rear main. But I had an unfortunate experience with the rear main bearing after my last engine rebuild.
The leaks from the bell housing were disastrous, and several attempts to correct it were unsuccessful. The reconditioner suggested that crank-case pressure was the cause and that running in would see it reduce, etc.
Anyway, to cut a long saga short, what had happened was that the rear main cap had been machined until there was 0.008" clearance between the "slinger" and the cap!
Another engine repairer was able to close the gap back to spec. The leak is much reduced but tolerable.
Threats of legal action to the first repairer got a satisfactory financial settlement.

 

[Healey 100]

Healey Friends:

Epilog RE my rear main oil leak:

I removed and refitted the rear main bearing cap. Although I thought I removed this cap 30 years ago without removing the tranny, my memory was faulty: the transmission and rear plate must come off to remove the cap.

It was not obvious where the leak was coming from, I noticed that the back of the flywheel was dry, but the inside of the bell housing had lots of casual oil around. I found a small leak on the transmission front plate which I fixed with a new gasket and sealant.

I found some damage to the rear of the bearing cap from folks removing the cap by pounding on the extension of the cap that encloses the slinger. I always use a puller to remove this bearing cap. I fixed this damage with JB weld so the cap would fit snug against the upper collector that bolts to the back of the block.

The flimsy Moss felt plugs that seal the vertical joints between block and cap were soaked in oil. On reassembly, I cleaned these holes thoroughly and injected Permatex "Right Stuff" elastomeric sealant into the holes. I drove the sealant home using a 5/16 bolt as a piston. When I did this, excess sealant appeared outside the block through the horizontal parting line, convincing me that the sealant was filling this hole completely. I also made a new gasket for the rear plate and carefully sealed the vertical and horizontal bearing cap joints between the block and the rear plate.

I wanted to remove that little oil drain tube, but I decided leave it in based on Bundyrum's comments on this thread.

This whole process took a couple of weeks and lots of time on my back under the car. I finally got it all reassembled and off I was on my first test drive.

Result: Leaks about the same as it did before -- perhaps a little less, but just like it has leaked for the 34 years I have owned this car. Oil collects continuously in the bell housing, and gushes out when you slow down, especially after a drive at freeway speeds.

I don't know if this problem is correctable -- but I think it has little to do with how the rear bearing cap, rear plate, or transmission cover is installed. As I said in an earlier post, I went through this process years ago with the same result, but I wanted to try it again just to be sure.

Meanwhile, I will be going to San Diego driving this car all the way. Don't worry, I'll bring lots of oil...

Thanks to all for your suggestions and keep them coming -- there is probably one more thing I am forgetting that would cure this problem....

Bill S
Albuquerque

 

[judow]

..."I'll bring lots of oil..." AND so will we

 

[Healey 100]

Healey friends: Is this a breakthrough??

I went and returned from San Diego, about 2000 miles total. Healey BN1 ran fine and even handled the extreme heat around El Centro and Phoenix reasonably well.

She still leaked oil like crazy, I estimate 300 to 400 miles per quart. Not good numbers for a freshly rebuilt engine. She always left a real mess at gas stations and hotels, along with an ugly dotted line from the road to the parking space.

Leaking occured mostly after sustained high speed running at freeway speeds. Short trips under 5 miles or so left acceptably small spots. I decided the leakage was caused by the drain from the rear main being overwhelmed when the engine runs fast and produces more overflow from the bearing.

When I got home, I decided to remove the pan and take off that drain tube, something I have always wanted to try, see earlier posts. I figured I was out of options anyway, I had already done all the stuff suggested to seal the back of the engine and she still leaked a lot.

Well guess what, 50 miles of high speed driving, and no leak at all! Could it be the flow resistance from that little tube mattered? I think so, but time will tell. I made no other changes except to remove that tube.

Bill S
Albuquerque

 

[Dave Russell]

Healey friends: Is this a breakthrough??
Well guess what, 50 miles of high speed driving, and no leak at all! Could it be the flow resistance from that little tube mattered? I think so, but time will tell. I made no other changes except to remove that tube.
Bill S
Albuquerque

It is entirely possible. The instructions that came with the DWR rear seal said to even drill an extra drain hole in the rear main bearing cap.
D