Auto Gearbox leak

[TR5convalescent]

Afternoon learned ones. My recently acquired mark 1 auto (BW 35) had a small transmission leak when I bought it in June but this has now reached epic levels (i.e. about a pint over 8 weeks when standing. Looking at the Rimmers catalogue I can see that the dipstick tube is mounted almost in the sump using a banjo bolt? Is it probable that this might be the cause? The PO said that as far as he could determine it only leaked while standing and the increased loss would seem to be due to a fastening working loose, while I assume that in driving the ATF is forced up from the sump thus leading to reduced leakage? (Please don't laugh at my ignorance, I'm happy to admit that I regard all transmissions as sorcery!)

If this is the cause is it safe to give the fixing a good tweak or am I likely to strip threads? If I do have to dismantle the dipstick tube, presumably I should drain first? If so does it make sense to whip the sump off the Autobox and renew its gasket. How hard can it be? (With apologies to Top Gear,)

Any thoughts would be welcome.

David

[richardthestag]

You may find that when standing the torque converter is draining back into the box which then overflows up the dipstick tube. Wedge some paper into the top of the dipsick tube and see if it gets soaked with atf.

If it does overflow by this method then it dribbles back down the outside of the tube and drips off the banjo bolt, which is probably why you think it is leaking from the banjo bolt itself.

If it is overflowing up the dipstick tube i am afraid that they all do that sir, invest in comma shares.

[milothedog]

David, Richard has probably hit the nail on the head with the T/C leaking back into the box. Mine has done it about 5 or 6 times now in 5 years of ownership.

To quote Russ (Kyrten) Stags don't leak they mark their territory

What I have done in the past is remove the dip stick if I have left it for any period of time somewhere where it might embarrass me. I have also pondered the merits of making a better seal for the dip stick when in it's tube and extending the breather tube in to a container hidden behind the aperture of the inner wing adjacent the battery.

I also find a better seal can be achieved using dowty washers as the banjo bolt can stretch due to the holes in the side of it and also become distorted

Ian.

[Nauts]

Hi, had the same problem with mine (before the gearbox gave up completely, now time for a re-build ) the po had used copper washers and it would never seal, I also invested in a new sump gasket because I had fluid running down the sides of the sump and running off the bolts, drained my box and got out about 8/9 litres of atf, removed sump to find metal shavings etc, the original gasket had gone hard so was not sealing to box/sump. Box now on garage floor waiting to go to Robsport for a re-build, and whilst off might as well have diff done as well as that also leaks from everywhere and whilst that's off might as well re-con the diff extension and add strengthening pieces. reminder to me buy lottery ticket !

paul

[marshman]

As others have said its a common problem with the BW35. The solution is to use the car. If mine is moved/used/started every couple of weeks or so there are only a few drops of ATF on the floor, but if I leave it for more than 3 or 4 weeks then an epic puddle develops. Driven all through the summer the ATF level doesn't drop at all, it only actually loses any fluid when left for a few weeks. Mine has been like it for the last 6 years or so. Not totally convinced about bothering to change the sump gasket or dowty washers, I did both on mine and it made no difference at all. As Richard said invest in some Comma shares or just use the car more regularly.

Roger

[David Lloyd]

Hi
I posted an issue identical to yours. I found that the company that I bought it from had omitted to connect the breather tube to the gearbox. I had another thread on how I fixed this without jacking the car up. Hope this helps and good luck.
another David with a leak!

[TR5convalescent]

Thanks for the speedy replies, gentlemen. Apologies for the delayed response, but I am busy earning the weekly envelope. Assuming it is forcing its way up the dipstick tube, is the answer to stuff a long rubber bung in instead of the dipstick?

How long does it take, when parked, for the fluid to climb up the dipstick tube? If it's fairly instant, then I guess I would leave the bung in the tube and only use the dipstick to check the oil level. But I don't want to pressurise the box while in use if that is a bad thing to follow?

[Lingen]

As David suggests, have a look at that breather tube. The oil will drain back from the torque converter, but cannot possibly reach the level of the top of the dipstick tube, and the gearbox should otherwise be oil tight.. The breather fitting is above the level of the oil in the box when in use, so if the tube is loose/missing, it is only after standing for some time that fluid will escape.
The plastic breather spigot is fitted above where the dipstick/filler tube enters the box, pointing upwards above the sump pan. It is a bit of a fiddle to get at, but not impossible. There should be a rubber tube attached to it, that runs up the outside of dipstick tube to which it is attached loosely by cable ties. From there it should run across the top of the brake servo, and the open end should pass through the inner wing and just hang in there. I think you will find that the end of the rubber tube that presses on to the spigot has simply hardened with age, and from the heat of the fluid, and is simply loose. If the open end is still soft, then fitting the whole tube the other way round will make it fluid-tight again. Or you could even buy a new length. It is probably original, so has lasted well enough.
Mike.

[richardthestag]

there is a breather tube attached to the top tail end of the gearbox, it exits in the engine bay and curls around the top of the brake servo.

with that in mind you shouldnt be able to pressurise the box but also by bunging the dipstick tube you may well force the overflow up the breather. maybe a nescafe catch tank on the end of the pipe.

Mine used to start overflowing after at least 2 days standing. i resorted to a cat litter tray and kitty litter to catch the drips. i rarely lost more that about a 1/4 of a pint but it was a messy pita

It is worth checking that you have checked the fluid level correctly and not overfilled the box! not all bw35s overflow. Do you bother topping up again after it has leaked? maybe let it find a natural level and then check using the dipstick and method

[richardthestag]

The oil will drain back from the torque converter, but cannot possibly reach the level of the top of the dipstick tube, .

Hi Mike

I can assure you (as will others no doubt) that a correctly filled BW35 with a failed non return valve on the TQ will most definitely fill the dipstick tube and overflow if the car is ignored for a day or so.

Can only assume that you don't have a BW35 or are most fortunate

That said other tips are useful and it is always easy to check the cheap and easy stuff first. This is why i suggested slicking some paper in the top of the dipstick tube when parking up for an extended period of time. evidence of atf on the paper would suggest that the box is overflowing

My stag when first bought had a rough change and started to overflow while running. hmmm Found after investigation that DPO had blocked the breather by clamping it back on itself. fluid was then pushed out by excess pressure until the box ran low. I unblocked the breather and although it didnt over flow any more while running it did become most incontinent if left for a couple of days. Then a decade or so later the front pump started growling and i threw in the towel for a man o/d.

[milothedog]

Hi Mike

I can assure you (as will others no doubt) that a correctly filled BW35 with a failed non return valve on the TQ will most definitely fill the dipstick tube and overflow if the car is ignored for a day or so.

Can only assume that you don't have a BW35 or are most fortunate

That said other tips are useful and it is always easy to check the cheap and easy stuff first. This is why i suggested slicking some paper in the top of the dipstick tube when parking up for an extended period of time. evidence of atf on the paper would suggest that the box is overflowing

My stag when first bought had a rough change and started to overflow while running. hmmm Found after investigation that DPO had blocked the breather by clamping it back on itself. fluid was then pushed out by excess pressure until the box ran low. I unblocked the breather and although it didnt over flow any more while running it did become most incontinent if left for a couple of days. Then a decade or so later the front pump started growling and i threw in the towel for a man o/d.

Absolutely, without question. and when the car is restarted if you check the oil level it will not register on the dipstick. it chucks out well over a pint

[Lingen]

Richard. It is some time since I had a Stag with a 35 box, but I do remember having a leaking breather pipe, but once I had re-fitted it the problem was solved. What confuses me about your assertion is, how does the oil get up to the top of the tube? It is well above the height of the torque converter, so gravity won't do it. If the breather was blocked, it might rise up there as the air/oil in the box expanded as it heated up during use, but this appears to be happening after a period of inactivity. Perhaps the cars with the problem have the wrong dipstick, and simply have far too much oil in them. What do you think?
Mike.

[milothedog]

It does happen. My thoughts are a correctly routed breather pipe (over the top of the servo) is higher than the top of the filler tube. the seal on this (on the dip stick) is only a felt, so really only there to keep out airborne contamination. As the T/C drains back it also fills the breather pipe and once above a certain height in the gearbox air will be trapped in the casing but the weight of the extra oil draining down through the NRV in the valve block which hasn't sealed properly pushes it up the filler tube and breather pipe but as the filler tube is about 6 to 8 inches lower than the breather it make a bloody big red mess on the floor

I know one thing, after nearly 40 years in the motor trade, it's that sometimes S**T Happens despite trying to understand why

Ian

[TR5convalescent]

Hello, chaps. Just got back in after a night out. Most grateful for all your thoughts & tips and will try and have look this weekend and report back. That said, grandparenting duties have conspired to keep be out of the garage for the last year or so!

[richardthestag]

hope you are spoiling the little treasure(s) rotten then then handing back to parents when they become a little too noisy

good luck with the box though