MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Stopping an OD oil leak?

I have a late model side-fill OD trans in the '71 MGB. OD works fine and even had new synchos put in last time.

The one issue I can't seem to resolve is the OD leaks. It appears to be coming through the bolts holding the main plate on. I bought a new screen/gasket and carefully cleaned and replaced but that didn't resolve it. Replaced the solenoid gasket while I was there.

I've given up however, with the wealth of knowledge here I wondered if someone has heard of this and a possible cure?
Max71

Apply a little bit of Permatex #2 around the bolt holes, then insert the bolts.
Steven Rechter

I believe I tried something like that before on advice from a MG mechanic. Needless to say it didn't work. I looked and do have Permatex #2 which I would only have bought for that purpose.

From different videos I conservative on putting compounds on there only because J Twist and others mention it could gum up the OD.

I see your point, though.
Max71

Others have also tried using metal sealing washers that have a neoprene/rubber inner ring where it meets the bolt with some success.

I agree that it is not good to aggressively apply any type of sealer to the edges of the o/d filer.
Steven Rechter

I've just changed the solenoid gasket, and used just a smear of sealant on both faces and the bolt threads, but it still seeps a bit.

I cleaned the whole of the bottom face including solenoid cover, sump and relief valve plug as best I could, then put a sheet of blue paper (hand wipe) over a sheet of polystyrene, with a board underneath, and jacked up the 'sandwich' under the OD, just enough to start lifting the gearbox on it rear mounts.

Left overnight the paper moulded itself to the OD, clearly showing all the screw heads, solenoid cover, sump and the plug. There was a very slight oil stain at a couple of the screws, possibly because they hadn't been completely clean, but the biggest stain radiated out from where the wire goes 'under' the solenoid cover.

I avoided going any deeper when changing the gasket, but I think the next step is to get the kit with the three O-rings and another gasket, and maybe see about increasing the packing round the wire.
paulh4

Steven, Those washers with the sealing ring are called "DOWTY Washers" in case you need to google them.
Allan Reeling

Very interesting Paul! I have a tiny weep around the solenoid cover, but nothing very bothersome at all. Isn't the packing around the solenoid wire rubber (from memory could be wrong).

I considered a couple things:

1. If the cover ( in this case with magnets isn't at all not completely true. Especially the bolt holes.

2. As you stated the o-rings. But if the OD is working fine and it will under normal operation have oil that needs to be held back by that filer screen/gasket I imagine its not the culprit however most likely best to change anyway.

I seem to recall I tried small washers with a smear of the Permatex on the face towards the cover. No success.

Just for visual reference here's a moss exploded diagram of the OD


Max71

"Others have also tried using metal sealing washers that have a neoprene/rubber inner ring where it meets the bolt with some success."

I missed that part. Its interesting. I wonder how rebuilders lick this problem?
Max71

I reckon a smear of ThreeBond 1215 on both sides of gasket and cable entry, and Loctite 561 on the threads will stop it. I'm pretty sure screws are BA threads make sure housing threads and screws are correct thread.
Mike
Mike Ellsmore

When rebuilding or servicing an OD I just use plain gaskets with a smear of grease - no sealant.

The only sealant is Loctite 270 used round the brake ring to seal it to the front and back housings.

Do not overtighten the small bolts securing the filter & solenoid covers - this WILL lead to leaks.

Make sure the cover surfaces are flat - both can be distorted from overtightening.

The solenoid will only leak oil if the O rings are not sealing - the plunger chamber should be dry.
Chris at Octarine Services

"Isn't the packing around the solenoid wire rubber "

I think it is.

There has been discussion of the O-rings elsewhere. There are three in the kit (as at the left of the attached composite image), but the drawings that show all three aren't clear enough to see where they go, and photos I have seen only show two of them.

There is a large one that seems to go against the face of the wider part of the solenoid body, a medium round a narrower part above that (as in the middle image from Rimmers), and a small one that seems from drawings to sit between the plunger and the ball.

But Leacy (right image) seems to show both on the plunger, which moves up and down of course, so I can't see anything sealing the solenoid body to the casing, nor the plunger to the internal part of the solenoid to prevent oil appearing below the solenoid.

I'd like to know exactly what I'm going to be dealing with, before I commence surgery.

paulh4

The large and medium size ones fit as per the picture and seal the solenoid cap to the casing - the very small one is fitted to a groove in the plunger itself and seals the plunger to the inside bore of the cap.
Chris at Octarine Services

See attached image

53 and 55 are the two seals that fit on the outside of the cap and 60 fits on the plunger.

Chris at Octarine Services

Is this a correct concept?

For the larger cap with the magnets, over tightening ie causing the cap being out of true is the main result of weeping? As per discussion?

Paul, now you have me wondering if I should renew the o-rings. OD works great other than weeping. Kind of want to leave well enough alone. :-)

Discussion gives a clear idea on those o-rings.
Max71

What holds the solenoid in place?
Steven Rechter

"What holds the solenoid in place?"

The square plate with 4 screws clamps the solenoid outer casing into the recess and pushes the casing upwards to make the largest O ring seal against the top of the recess.

Chris at Octarine Services

Thanks Chris. After puzzling over more pictures of solenoid coil and casings I had come to the conclusion that the plunger, small O-ring and ball were under/inside the cap that carries the large and medium O-rings, so I can now see how a combination of all three should prevent oil getting to the bottom of the solenoid, any single O-ring NOT sealing will allow oil to get past.

"Kind of want to leave well enough alone. :-)"

Er, yes! Following my attempts at finding the source of the leak above the OD is now playing up. The last two times I have taken it out it works fine when cold, but after a few miles it will rapidly drop out, cut back in then drop out again, and after that it won't work at all. I suspect electrics, current is a little on the low side at 0.7A engine stopped and 0.8A running, both hot, and a resistance of 17.8 ohms hot and what I think (needs to be rechecked) 15 ohms cold, which what I noted many years ago when checking both my cars. Whether that is enough to cause this problem I don't yet know. Resistance measurements are through the wiring and gearbox switch, so needs to be checked at the solenoid wire when I can next get underneath, also measuring current when driving from cold and comparing working with not working.
paulh4

Sounds to me more like a oil pressure problem - either in the pressure relief valve or in the seating of the pump one way valve.

Both are accessible from under the car though the pump valve sits under the filter cover and needs a suitable two pin tool to unscrew. Undo it gently and if you are lucky only the ball & spring will come out - if you are unlucky the whole pump assy will drop and then it is quite tricky to get it all back in without the plunger falling into the od case and out of reach!

The spring in the pump valve often gets compressed over time and stretching it gently so the ball stands well clear of the plug when sat on the spring will solve the problem.

Dirt in the pressure valve assy will also reduce oil pressure.
Chris at Octarine Services

More tests today show the current ceasing when the OD drops out, so electrical.

I've now connected another wire where the solenoid wire joins the harness wire, brought that into the cabin to a low-wattage bulb, as well as having the ammeter in series at the manual switch.

Even though static tests showed 0.9A on the ammeter and the bulb glowing, as soon as I got on the road and into 3rd there was a brief flick of the ammeter up to about 0.9A, with the bulb glowing, then it dropped down to about 0.1A which is just the bulb current. Annoying I didn't get a period of OD engagement to give a clearer result, but it does look like an open-circuit solenoid coil. I'll have to try it again when fully cold.

Incidentally, further thought makes me think that the medium O-ring is there to isolate the input side of the solenoid valve from the output. If that O-ring fails it would prevent the input side reaching full pressure, which could easily prevent the OD engaging. It's the other two O-rings that keep oil away from the cover plate.
paulh4

VERY unusual for the solenoid to go open circuit.

I thought the solenoid drew around 3 amps but might be wrong - long time since I tested one but I do remember that my little battery charg3er was not up to the job and needed the starter charger to activate the solenoid.

If there was a leak on the middle o ring then maybe - but we are talking pressures of around 400 psi so it would need to be a bad leak!
Chris at Octarine Services

The LH solenoid draws .8 AMPS. I encountered a similar problems a couple of years ago. After checking the electrical system three times, I found that the solenoid had, indeed, gone open circuit. It would work OK then not work at all. This is on a rebuilt, in England, 4 synchro/OD Black Label transmission. Also, the solenoid actuator rod looked like a piece of rebar! I cleaned it up with a flat file and installed a new solenoid. The OD has never worked so well. Instantaneous engagement and disengagement. RAY
small

As I said - it is almost unknown for the solenoid winding to fail - yours must be the exception that proves the rule.

However the solenoid does earth through the copper spring plate fitted to its base and I suppose it is possible for that connection to go bad - especially if someone has used other than the correct gasket on the bottom plate.
Chris at Octarine Services

Just under an amp with the LH OD, and 15 ohms, but the D-type takes 17 amps to pull-in and 2 amps to hold as it has a two-stage winding. No current flowing in mine at all now, even stone-cold, I suspect pulling the wire about to connect my additional test wire has seen it off altogether.

The solenoid casing is in contact with the sides of the aperture in the main case it sits in as well as the bottom plate, so as long as the copper spring mentioned is making good contact to the end-plate, and the end-plate to the remainder of the solenoid body, I would have thought that would give plenty of opportunity to get to earth. However once oil starts seeping down the sides of the solenoid body, perhaps not. As the O-rings are obviously leaking as well I've opted to replace the whole thing and be done with it.

Incidentally, given the spring on top of the coil, I'd have expected that to push the solenoid body out of the OD casing a little, by pushing it away from the end cap, but it didn't.
paulh4

It was the coil, but not the winding itself. The copper spring on the upper end, which is a copper disc that should have the opposite sides turned up, was completely flat (left image), whereas they should be bent away from the coil (right image). Replacing the gasket and putting a smear of sealant on both side had moved the cover plate down a fraction, which reduced the remaining spring tension even even more.

The old one made no attempt to push itself out of the casing with the cover removed, but was easy to remove by wiggling the wire. By contrast the new one was poking out by 2-3mm when fitted, would push fully in but pushed itself back out again. So fitting the cover put the spring under tension, to make a good connection to the solenoid body.

The original objective was to cure an oil leak, which was down to the O-rings. So rather than fiddle about changing O-rings and coil, I replaced the whole thing. And by tweaking the spring on the original, and replacing the O-rings, I will have a spare ... which I doubt I'll ever need.

paulh4

Brilliant Paul! This should be a paper on OD solenoids.

You didn't mention it - this did solve the oil leak, right?
Max71

As yesterday was the first time I had driven it since the change it was too early to say. But being outside on the drive for a couple of hours while I put the interior back yesterday afternoon, and overnight, no drips :o)

It also shows that the sump and relief valve plug seem to be OK - or at least they weren't the main cause - time will tell. Being so close to the solenoid cover any oil escaping from that gets onto those other parts. But having cleaned those before fitting the new one, they showed no signs the next day, so again I'm hopeful.

That leaves a very occasional drip from the main gearbox drain plug, and another from the back of the engine. The former is from the threads, as I cleaned it and the area around it with carb cleaner, and yesterday there was the faintest sign of glistening on the threads but nothing on the casing round it. Being a tapered thread it may respond to a little extra tightening, otherwise it will have to wait until the next gearbox drain and refill and Teflon tape - which won't be any time soon.

paulh4

Paul, yes the threads are tapered and as they are steel tightening into the alloy case, I find that undoing a couple of turns and retightening usually stops that annoying dribble. Never had to use teflon tape yet...
Chris at Octarine Services

Just a followup: See if you notice any smoother operation.

Mine works fine (aside from leak) however that box has several hundred thousand miles on it and I'm wondering with all this talk of O-rings if its a good idea in the near future.

On the solenoid. Engagement is fine. Disengagement can be rough. Kind of slams into non-od. I know this could be a difference in RPMs.

Since I don't have any experience with anyone else's MGB OD I'm wondering what is normal and what isn't.
Max71

It definitely should not slam out of OD - the high pressure oil is made to join the low pressure flow via the relief valve - thus damping the movement of the clutch cone so that take up is smooth.

Either your valve is faulty or the OD needs a service with a good clean out and new O rings.
Chris at Octarine Services

Maybe very slightly smoother on engagement. You can get a jolt disengaging on the overrun with the LH-type, which is why people talk about feathering the throttle or using the clutch, which the factory specifically said you should not do. It can be a problem forgetting to turn the manual switch off when changing down from third to 2nd, as when changing back up again it will automatically re-engage, which is probably inappropriate, and it jolts when you turn it off. I got fed-up with that so built a circuit that locks it out when changing down, until I put the manual switch off and back on again - bliss.

The D-type had a relay and vacuum switch arrangement that meant it didn't disengage after manually turning it off if you were on the overrun, only when accelerating, or if you should take it out of an OD gear.
paulh4

Very helpful. I notice its gotten worse. Its an LH black label side fill style ( all I could get at the time w/OD).

Looks like a project coming up. From what I've seen clean everything with carb cleaner once the parts are out, yes?

Be interesting to see if that screeen is collapsed as in the Twist video. Shame I didn't think of attending to this when I had new synchros put in....

Thanks Chris and Paul.
Max71

You can try some in situ cleaning by replacing the gearbox oil with Dexron auto trans fluid.

Once you get it out then use clean kerosine / paraffin and a soft paintbrush to clean everything.

I use a wash pot on a high pressure air line to blast out all the dirt from the oil galleries and wash out the bearings / valves etc.
Chris at Octarine Services

If the transmission/OD is a side fill, you have a Blue Label OD. RAY
small

Originally the side fill would indeed have had a blue label OD on 4-cylinder cars, unless it is a V8 which always had the black-label. But bear in mind a black-label OD could have been retro-fitted to a later gearbox, and may have been deliberate if it was installed to a chrome bumper car.

The speedo gearing is very different - 1280tpm on the black label, 1000 tpm on the blue label, leading to gross under-reading if a blue-label is fitted to a chrome bumper car (over-reading if a black-label is fitted to a rubber bumper) unless the speedo is dealt with as well.

Out of interest I've seen a green label on an MGB, with the correct model designation as for a black label, and heard tell of red labels.
paulh4

If I remember correctly the red label is the V8 version and the green label is the MGC one - the main difference is the strength of the sliding member springs.
Chris at Octarine Services

Makes sense, although my V8 is black like the 4-cylinder. Will check the reference number tomorrow. ORS did say that if they ran out of a particular colour they used whatever they had to hand, saying it is what is stamped into it that is important. In fact re-reading my note the green label was on a factory V8, with the V8 reference number.
paulh4

Lol - nowadays you can't rely on what the label says or what gearbox it is attached to - unless you owned the car from new!
Chris at Octarine Services

It does keep things interesting. RAY
small

Hmmm. I best look at the label again! :-)

Question to you all, especially Paul. I have all the 0-rings on a wishlist at Moss. I'm wondering for the solenoid if I should just order a new one complete like Paul did?

The car has over 500K on it and this transmission has around 300K of those miles. The OD works fine, except for slamming out of OD. Which hopefully rebuilding the valve will help (as suggested here).

Chris - sounds good. I'm just a little nervous about screwing up a working transmission. Under your experienced hand its no problem I'm sure. The tranny just makes me nervous especially how difficult it is to get out.
Max71

I've got the O-ring kit now, so will replace them on my old one, as well as tweaking up the sides of the copper spring on the end of the coil to give a better earth connection than before. The small O-ring is very small so will be a bit of a fiddle. Other than that as long as you don't lose the ball or damage it or the seat I'd have said new O-rings is all that is required to cure a leak.

The maybe slightly softer engagement with the new solenoid - and it is only fractional if at all - is probably due to the good O-ring being a tighter fit and damping the movement of the plunger slightly. As told to me by a pal that worked for Laycocks for many years, the usual way of softening/sharpening OD engagement is to vary the number of shims between the valve plunger and the spring - increasing the thickness sharpens, decreasing softens and slows it down. Note the contents do vary, my V8 and roadster have differences, and a picture sent to me by someone else shows a different variation.

paulh4

Is that picture from the person you mentioned? It looks different than the Twist layout or the Moss schematic.

Wish I knew the magic shim thickness to slow it a bit. Will do my best.

Thanks!
Max71

That's my roadster, the V8 was similar but without the coarse screen, possibly stuck up inside. Attached is the other one I mentioned, with a tube with a cut-out instead of a screen. I noted at the time that Twist showed this the other way round i.e. the cut-out facing the hex plug.

Changed the O-rings on my spare in about five minutes. Just needs a very small screwdriver or thin probe for the small one, the medium one is easier, the large one just drops into the groove. The kit included the ball and cover gasket.

None of the usual suspects seem to show the relief valve shims, just a complete valve assembly. The Laycock manual has them as 'selective washers', perhaps only available from Overdrive Repair Services in Sheffield.

paulh4

Twist has it wrong - the manual clearly says the cutouts fit in first and line up with the oil drilling.

Apart from the outer container all the rest of the parts are the same.

The shims set the high pressure which should be 400-420 psi.

It was never intended as a serviceable unit - replacement as a whole only. But yes, ORS might be persuaded to sell the shims or I may have a few if any one is desperate but check the oil pressure first - needs a suitable adapter to fit in place of the plug and a suitable oil pressure guage.
Chris at Octarine Services

Great info! Is this the correct sequence - as a reference?

(don't have a guage to measure pressure so what's there will have to suffice)

Max71

Yes, correct sequence, the shims go on the right hand side of the spring as in the picture.
Chris at Octarine Services

ORS do have a gauge http://www.overdrive-repairs.co.uk/buy-spares.php?cat=LH%20Type%20Spare%20Parts%20List

I assume it is capable of showing the high as well as the low pressure, but looks like it still needs the adapter 18G251E. This http://www.healey6.com/Technical/OD%20Gauge.pdf how to make an adapter.
paulh4

Thanks Paul!

Here's the corrected image for future reference.

Max71

Finally had some time to get into it and I'm a little stumped on some bits. Let's start with the above first:

Mine is a Blue Label and has a coarse screen instead of the tube shown above. I'm including a pic. My concern is the diagram shows some more bits for this low pressure valve. Like a ball and spring and spring cover. None of that came out of the hole. Is that missing? Is that inside the case and no worries?

In this post is the assembly. The next is a shot inside the hole.


Max71

Inside hole:


Max71

Here's the diagram showing more bits:



Max71

Next is the sump cover. This has been leaking for years. I believe in frustration I took advice putting gasket sealer on it and carefully tightening down the bolts.

However, it's seen better days. Any suggestions on the heavy grinding of the washer and getting a good seal? Naturally, I have a new gasket.

Max71

Here's the inside. I learned to get a true sealing surface by sanding using glass as a surface so it's flat. Should I go all out until there are no lines?

BTW, the magnets were full and had to really be cleaned off. Hope that's not something to be nervous about. The OD functions ok.



Max71

Finally, the same issue on the label cover. Is there a method to fix this deep divot from over tightening?

I generally do not use gasket seal on gaskets except for some water etc. Do you guys recommend any sealer on either of these gaskets?

Max71

If anyone knows the thread pitch and head size of these I would appreciate it. Some seem a little stripped and I somehow lost one I was going to take to see if I can a match....
Max71

To clarify - I mean the head of the bolts are a little messed up. Plus lost one for the sump. No idea how....
Max71

Not missing - the spring & ball are inside the little bullet shaped unit that fits on top of the spring. Just check that the little ball is not stuck inside and moves down against the spring.

The perforated cage is more common than the tube type and makes no difference.

I would use a thin flat washer under the bolt heads on the covers. Gaskets should go on dry and seal fine if the surfaces are flat. The sump gasket contains the filter screen and should have a slightly tacky surface. These leak if reused - usually round the screen where it is sandwiched between the gasket material.

The little bolts are 2BA as far as I remember.

Chris at Octarine Services

Thank's Chris. I did see that ball inside the bullet. I didn't test for movement. I will now.

I do have a new screen gasket for the sump.

Do you think I should build up the sunken parts of the label and sump with some black silicone? IE build it up and use flat washers to cap it with a bolt in the hole until it dries?

I'll putt both the label gasket and sump gasket on dry.

Yes, I confirmed they are 2BA. If that means the thread pitch is also different then I'll have to order some up.
Max71

The OD oil pump cover is completely stuck.

I tried:

Mondo heavy duty needle nose

This:
https://www.harborfreight.com/adjustable-pin-wrench-36554.html

The needle nose vice grips locked tight and tried big adj wrench, then a large screwdriver between the jaws. I get a lot of force until finally the grips come out of the holes.

Any suggestions? Someone really wrenched that down solid...
Max71

As soon as the new 2BA screws come I'll put the gaskets in dry and not over tighten. Alan, if it still leaks I'll get some of those very cool Dowty washers and see if they help. Thanks for the education.

Chris - hopefully it will act smoother. I'll give a final update when assembled. Again, thanks all.
Max71

Held my breath a bit and finally was able to take it out for run. At first no OD. Then it came on (maybe oil needed to get back there).

Wow. Chris was right. It's the smoothest I've ever experience the OD. No more slamming out of overdrive. Smooth engage and disengage.

As John Twist showed I carefully polished bits that weren't mating smoothly. Took my time, cleaned maniacally and assembled. Also ordered new 2BA screws.

No idea if the leak has been cured. I did manage to get a new grommet onto the solenoid. The old one was a whisper of itself.

Even if it still leaks a little the performance is sweet. I'll top off the trans after oil got back to the OD.

Thanks to everyone - as always - for all your wise help!
Max71

Spoke too soon, unfortunately....

Went for a long run flipping the OD on/off at proper speeds. Went in and out like butter.

Then.

It engaged a little slowly. No problem disengaging. Then more and more slowly until it would engage partially then jump out of OD.

Suddenly flipping the stalk did nothing. Occasionally it would come on but jump out.

When I got it home I hoped maybe there wasn't enough oil getting back there. To my surprise when I pulled the side bolt oil came rushing out with the tranny being overfilled. Odd since it did it slowly until it started to drip and let it for a while before I put the plug back.

So what does this sound like to all of you? Too much oil? Solenoid not functioning right? One of the other ones I rebuilt ie pump or low pressure?

I don't understand why it worked perfectly then stopped. Sucks. I was very proud of the job.

Aside from the leak it worked fine (although not as smooth) previously.
Max71

This thread was discussed between 07/04/2017 and 24/08/2017

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now