Mystery oil loss in BW35

mikecoombs

Active Member
some of you are aware i started my P6b for the first time in about ten years a few weeks back. I checked the Trans oil level then and it was at the top line and nice and clean. Later i did a few three point turn type maneuvers around the workshop and the gearbox behaved as it always did. yesterday i started it up to drive it home and it wouldn't engage gear. after a minute or two it did and i drove off but with very high revs. 90% of the trip is downhill about two miles with a big climb in the middle (down up down) the down bit was ok but next to no uphill drive, felt like no oil in trans so I checked at the bottom of the first down and not a drop on the dipstick, dry as a bone. i put three litres in it and it registered at the bottom of the stick so I finished the trip. Mystery is that between first starting it up and yesterday i lost at least four litres of oil but there is no puddle, not even a drop on the floor! Anyone got any clever ideas where it went. Drive was completely normal when I first started it up.
 
I seem to have a vague recollection of it being possible to lose fluid into the torque converter if there is a failure in the 'box?
 
The converter should be full all the time once the engine has been run. If it drains back into the box that's another matter, but that normally causes external leaks, and the converter refills as soon as the engine is started.
 
The converter should be full all the time once the engine has been run. If it drains back into the box that's another matter, but that normally causes external leaks, and the converter refills as soon as the engine is started.

Harvey, Have pumps been known to intermittently fail and not fill the torque converter and so give false positive level check on the dipstick?

Colin
 
I've known pumps that need replacement when dismantled but they still work in service, and I've seen the drive tangs broken on the converter so the pump doesn't get driven, but that won't cure itself, as well as the seal failing on the input pipe, but that draws air and aerates the fluid making it all pink and frothy, and you can't really miss that, but I've not seen intermittant pump faults, come to that, although I've heard lots of people suggesting pumps as the cause of noise and various other things I can't say I remember coming across it. All I can remember is very early boxes with rear pumps can, when facing steeply downhill, uncover the rear filter and draw air that way.
In fact I'd say that the pumps were one of the most reliable bits of the box, in the recent boxes I've been involved with I've only sold one pump, and IIRC that was only because the box had been left outside uncovered and the nose and splines had got all rusty.
 
PS: I've lost count of the number of blocked filters that have been diagnosed elsewhere as a failing pump.
 
Hi, Fair enough Harvey, I was just sort of thinking out loud, if you can on a forum. I was wondering if the pump had failed the first time and worked again later leaving not enough oil for the operation of the bands and clutches. Having said that putting 3 litres in and still only on the bottom of the dipstick seems curious, that's a fair amount of oil. Unless it wasn't checked with the engine running the first time.

Colin
 
PS: I've lost count of the number of blocked filters that have been diagnosed elsewhere as a failing pump.

That's a good point, all the sediment being picked up and blocking filter the first time, but that produces a whining noise from the cavitated fluid.

Colin
 
you were right Harvey, I checked the fluid engine running both hot and cold. didn't think of the radiator though i'll go have a look. That isa very ugly thought as it'd mean water in the box I presume.
 
No oil floating on top in Radiator. Plenty of Glycol in it though. Car is currently downhill on a 15 degree slope and cold. it's where I left it last night, Trans oil level isn't on the dipstick...Maybe the glycol is working as a soap to dissolve the ATF in the radiator water so nothing on top. Doesn't smell like ATF though, smells like glycol? doesn't leave an oily residue either.
 
If the car is facing nose-down and there's nothing on the dipstick then iot sounds like more has gone missing. I'd suggest getting the car on level ground and setting the trans fluid level again, and then see what happens. If it loses the same amount of fluid again, 8 litres should be twice as easy to spot as 4......

ATF and coolant cross contamination isn't good, as the clutches and bands used a water soluble adhesive, but if the coolant never got up to temperature, and hence, pressure, then as the box comes up to pressure instantly, in theory the a ATF should go into the rad before the coolant gets up enough pressure to go back the other way.
 
The good news is: Harvey you were right! the bad news is; Harvey your were right! I drained what was left in the pan and it came our rather runny and thin, but no seperation as such. I disconnected the pigtail flexible lines and collected what ran out there as well. It all ran out as one but settled into distinct water - oil layers when left a minute which is ominous. Plan now is to connect the two pigtail pipes together refill the transmission with new fluid and let it warm up. Idea is to turn the water to vapour and have it exit via the filler pipe. I have almost all the bits for the ZF conversion so I'm avoiding a transmission swap just to move the car in and out of the driveway until I'm ready for the Big One.
 
I've connected the cooler pipes together now. then I realised that there is now a leak in the radiator as the pipe ends are open. Oddly ther is no water coming out? I suspect the hole is therefore very small and closes up when cold and not under pressure. I'll make a pipe up between the two radiator fittings to seal it up for now
 
Yes, I'll need one for the ZF anyway, but I am waiting till I get the air con condensor back in so I know what shape and size to fit. Car will only be shuffling places in and out of the garage and driveway so It should be ok for that.
 
Started putting the fluid back it today and lo, found another leak... looks like the filler pipe may have rubbed a hole in itself against the transmission tunnel. Which is a big pain on my car as I have a two inch exhaust pipe running next to either side of the pan making access to the big nut that holds the tube impossible without removing the exhaust first....Mind you I can't actually see the point the fluid is coming out. It is running down the side of the transmission tunnel but not down the transmission....I'll try again tomorrow with a better light. Rear mount has collapsed again too.
 
Just after i finished writing the previous blurb U realised that I didn't see the air breather pipe anywhere... checked to day and no breather pipe so I made a new one up and fitted it and no more leak. I also forgot that the eight litres of oil includes whats in the torque converter, which doesn't fill till you run the engine. So I just need to replace that rear engine mount...
 
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