BW35 Inhibitor Switch Leak

keynsham1

Active Member
I recently had my inhibitor switch seemingly come loose and leak a lot of gearbox fluid onto my garage floor! I have since replaced it with a new one. I have adjusted it and tightened the locknut carefully as not to damage the aluminium thread. I just looked under my car and there is another puddle of oil still coming from the switch. It is still coming from out of the threaded hole and dripping off the switch onto the housing, then onto the exhaust and finally onto my floor! The attached picture shows the leak. And when I say leak, it is actually dripping once every 30 seconds or so!

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There doesn't seem to be any sort of oil seal or sealing washer in this location although the one I took off had a copper washer under the nut; something I believe I may have added the last time it was removed some years ago.

Does anyone have any experience of this leak and what I can do about it? Short of draining the gearbox (hole is below the oil level...typical!) and trying to install the switch with some sort of sealant, I am not sure what to do next.
 
Just found that Rimmers sell a fibre sealing washer, part WF510, for this switch which oddly isn't shown in the Rover parts catalogue or mentioned in the maintenance manual, and didn't come with my new switch. I guess that is what I am missing?

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So I have fitted my new inhibitor switch with a proper fibre washer. I also put RTV sealant on the threads and a thin bead on either side of the washer to do a belt and braces job. I refilled the gearbox and all was good for about a week. The car is still in my garage on ramps and hasn't been off. The engine has been started to get the oil around the 'box while filling it. Yesterday I had a quick look underneath and you've guessed it.... a large puddle of gearbox oil on the floor. On the face of it, the leak looked the same but this time it doesn't seem to be coming from the threads of the inhibitor switch but leaking out of the back between the switch housing and the black plastic back plate. So I can only assume the switch is a dud and the oil is leaking past the plunger seal and into the switch.

Questions then, are...

Am I just unlucky to get a dud repalcement part or is it common for them to be rubbish?
Has anyone known this to happen with a brand new switch before (I bought this one from Rimmers but it is of dubious quality!)
Does anyone know of a supplier of a quality replacement part? All the ones I see online look to be the same cheap copy.

Any other ideas would be greatly appreciated as it is not the easiest part to get to and the fun of fitting new parts to my Rover is rapidly fading!!
 
Am I just unlucky to get a dud repalcement part or is it common for them to be rubbish?

It is probably just a rubbish part. My transmission was fitted with a NOS inhibitor switch that I acquired some year 20 years earlier, and it has never leaked.

Unless you can source a NOS item, you will likely need to live with it leaking, which I can appreciate would be very annoying.

Ron
 
The bloke that overhauled my BW35 a year back advised me to remove the switch before pulling the gearbox to avoid damaging the unit. Hens teeth he reckoned
 
I contacted the guy who refurbished my gearbox and he said to find a new old stock switch too. He said pretty much all the 'new' ones leak to some level. They are certainly not cheap but I think I will have to bite the bullet ad go for it!!
 
So now for an update. I got a NOS inhibitor switch and fitted it. All was well. No leaks. I have driven the car once for around 25 miles since it was fitted. I looked under the car last week to find yet another pool of gearbox oil on the floor. On closer investigation, this is an entirely different leak path. The isolator switch is fine and there is no sign of a leak on that side of the gearbox. It seems to be coming from the other side now. It is difficult to see but it looks like it is coming from the rear brake band adjustor. It certainly had gearbox fluid on it. I am pretty sure it isn't coming from the breather pipe (NADA car so breather where the dipstick usually goes) so it is either the rear brake band adjustor or the screw above and forward of it. I am surprised though because the oil level in the box would need to be very high for it to come from there.

Has anyone experienced a leak here before?
 
I wonder if you covered the unit in mastic -{except the threaded part} that would fix the problem with these leaky units.
 
I found a picture of my gearbox after it was cleaned and removed, and before it was refurbished. Interestingly it is very wet directly below the rear brake band adjustor, so I wonder whether it has always leaked from there. Anyway, I removed the locking nut earlier and sealed around the thread and nut with silicone sealant so I will know in a few days' time whether that has cures it?


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Well it didn't! I looked under the car and there was another oil patch on the floor. Good news is that the rear brake band adjustor is dry and is not the culprit! On even more close inspection, I noticed that the speedo angle drive is leaking It is always difficult to tell where the oil is leaking from as it tracks all over the place and I also have the front of the car up on ramps so that changes the angle too. Oddly it wasn't a leak path as I remember when the car is on it's wheels so I am assuming that the oil level in the box now it is up at the front, is high at the back and allowing the leak. There is an oil seal which is readily available so that is my next, and hopefully last, port of call!
 
Quick update! I got the speedo drive out of the gearbox this morning and changed the oil seal. I am waiting for an O ring so it isn't back together yet, but you can see why the old oil seal might have been leaking!! You can guess which is which!!
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