Gearbox oil: G052171A2 vs G052527A2

[veteran]

Combattant,

Yes, I already had the torque settings for the fill and drainplugs. What I didn't have, and what you'll not have had either, are the recommended torques for those three screws/bolts. At the time, and as I've stated this was around 5 years ago, I did go along to my VW dealer and buy a brand new drainplug, but more to determine whether it had a tapered thread than anything else. I still have that drainplug and could, if I wanted to, fit it to see whether the oil leak disappears. However, it's not as simple as it sounds because clearly if I undo and remove the existing drainplug, the majority of the oil will pour out, and I'll be faced with a second fill operation, with all that that entails. I'd not long replaced that oil. So, I didn't try the new drainplug. I still have the option of doing that of course but it's unlikely that I will because my physical health is now such that doing such work has become all but impossible.

Amer6R,

At the time, I did indeed try using some thread sealant. I bought and tried one or two sealants, one of which actually was a Permatex product, so may have been the one you've shown. The exact type of sealant had to be chosen carefully, because it needed to set in the presence of the oil (I cleaned the orifice as best as was possible with alcohol), but on the other hand it needed to set as hard as possible without making it absolutely impossible thereafter to ever undo the plug. All the sealants I tried failed miserably.

As I stated earlier, I'm not even 100% convinced anyway that the drainplug is the source of the leak. Degreasing the exterior of the gearbox's casing on several separate occasions hasn't yielded any clues either. The oil leak might not be coming from that drainplug at all; it could be coming from the gasketing between gearbox and engine, or from inside the clutch's bellhousing, but all my attempts to track it down over these last 4 or 5 years have been unsuccessful. Each year, when I've done an engine oil change and have therefore been under the car, I've continued to look for clues but am now resigned to having to clean up the plastic undercover each time and ignoring the problem. Where the oil shows on the undercover isn't much of a help either, because over a year's driving the dripped oil moves around on the undercover. As for identifying the oil itself, in trace amounts it's all but impossible to tell the difference between the Polo's gearbox oil, the engine oil and the brake/clutch fluid, as they're all of similar viscocities and colourations. But it's definitely not engine oil, and I've found nothing at all that suggests it's brake/clutch fluid.

undertray.jpg (975.19 KiB) Viewed 467 times

[Le_Combattant]

I have the same amount of oil leak but just over the little hole on the plastic cover.

[veteran]

" ...... but just over the little hole on the plastic cover".

Only over one hole, then? As you can see, in my situation there are two small holes in the cover around which the oil collects and then drops to the ground. Mind you, it may initially collect around one hole but then as more of the oil accumulates and gets sloshed around on the cover due to movement of the vehicle, it's likely that the oil surges over that raised rib in the cover and then collects around the second hole. If your cover has those two holes also it'd be interesting to know around which hole (of those two) your leak is currently collecting, as then I could work out the precise lower point on the gearbox's casing from which the droplets drip.

This however would still not prove whether the source of the leak is the drainplug. For example, in your case it could be leakage from one of those three screws at the bottom of the gearbox that you undid and then retightened. The leak will always accumulate on the gearbox at the lowest point on the casing, and then drip from there. Clearly, that rectangular cap and those screws were originally fitted dry in the factory where the gearbox was built, and a special sealant was used on the cap and those screws to ensure that, when the gearbox was later filled with oil, there was no chance that they could become a source of persistent leaks. Well, at least that was the theory!

As you probably realise, these sorts of leaks, whether from low down on the gearbox or further up, can be quite small in themselves and indeed at any one interval of inspection practically imperceptible, but over a full year can amount to several tens of millilitres of oil, making the kind of mess that you can see in my pic.

When properly filled, the static level of oil in the gearbox is above where the drainplug is situated and so unless that drainplug fits absolutely perfectly there's always a chance that oil will gradually leak from it. Incidentally, one thing I do recall is that I found no evidence of any thread sealant having been used on that drainplug when the gearbox was built. So obviously, reliance is placed on the thread being specifically tapered and then the plug being accurately torqued. But it might be that, at the factory, the gearbox's casing (and hence the thread in the orifice) was formed by the manufacturer of the casing but the drainplug itself came from a different supplier, making the probability of a thread mismatch higher than it needed have been. Maybe the difficulty of fully sealing that plug is one of the reasons why VW themselves never advocate that the gearbox's oil be changed, once the original lot has been put in by the factory?