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Andyww

Gearbox Oil Leak

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I am investigating a quite large oil leak. It seems I might have the usual leak from the back cover as there is dripping from the drain plug.

 

But that does not seem to be the complete story. There is also a drip on the location I have marked with an arrow on the right. The vertical surface of the rear section (left hand arrow) is also wet with oil. These areas are above the level of the rear cover so I am not sure where the oil is leaking from to end up here. It almost seems that there is a leak at the joint between the main section and the rear section. Do they ever leak here?

post-16906-0-43313800-1423347780.jpg

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Hi, yes indeed. They often leak at that point. you have to remove front cover, 5 th gear on primairy shaft with synchrohub and fork. Than you can remove casing. Clean and add with new sealant.

 

cheers,

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OK thanks

 

Not sure if its possible to do this with it still in the car? Suspect not.

 

Or maybe it is, if I remove the rear valance.

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All done. No need to remove anything else, this is the first time I have come across a job on these cars thats easier than it looks!

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Silencer off and simply remove and refit? Been on my list of things to do for a while!

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This is what I did:

 

Silencer off

Drain gearbox oil from both drain plugs

Remove silencer mounting bracket

Remove rear cover. Various size bolts so need to avoid mixing them up. On mine the cover just fell off, no sign of any sealant at all.

Pull out speedo drive

Put into 5th and drop the car back on the ground and handbrake on

Use a BIG bar and 21mm socket to unscrew the bolt securing the 5th synchro assembly

Jack up again for access

Remove lock-wired bolt securing 5th selector fork

Pull off synchro and fork

Remove all bolts and rear housing. Different bolt lengths again.

Cleaned mating surfaces with acetone and used Loctite 518

Reassemble with new lock wire on fork screw. Torque synchro bolt to 110 lb ft

Refill oil.

 

Regards the sealant the "book" says silicone. I dont agree this is best for metal-metal flange close-tolerance joints at all. 518 is designed for this and is the more modern product.

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Posted 08 February 2015 - 10:46 AM

 

...

 

Posted 08 February 2015 - 01:39 PM

 

You did all of that in ~3 hours?

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Posted 08 February 2015 - 10:46 AM

 

...

 

Posted 08 February 2015 - 01:39 PM

 

You did all of that in ~3 hours?

 

Yes except for putting the speedo drive back in and exhaust on.

In fact the speedo drive turned out to be rather tricky. The O-ring got sliced up when pushing it in. In the end I used plumbers tape around the brass inner bush and also around the nylon bush where the O-ring should go. Seems to be tight now so should be OK.

 

Need to get some nice brass bolts for putting the exhaust back. I did get sidetracked by noticing that two exhaust manifold studs had fallen out! One was lying in the chassis near the engine mounting. Rather strange. 

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You got the two studs back OK, I presume ? I ask as the first time I took my engine apart the head had rotted away and several of the studs just fell out, the threads surrounded by corroded alloy. Had to get a load of alloy welding and remachining done...this was in the late 80s when there were still loads of little engineering workshops with the sort of old guys who could do that stuff. Ah. Probably younger than I am now....(!) Thought it could have been due to exposure to road salt? Nice job on the gearbox....

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You got the two studs back OK, I presume ? I ask as the first time I took my engine apart the head had rotted away and several of the studs just fell out, the threads surrounded by corroded alloy. Had to get a load of alloy welding and remachining done...this was in the late 80s when there were still loads of little engineering workshops with the sort of old guys who could do that stuff. Ah. Probably younger than I am now....(!) Thought it could have been due to exposure to road salt? Nice job on the gearbox....

 

Yes the studs went back in OK. Some of the others were loose also. This head has already been worked on in this area when the PO had the exhaust manifold replaced.

Looks like when the manifold was refitted by a certain Lotus specialist in Hammersmith they didnt use any threadlock on the studs and they simply vibrated out.

I will ache tomorrow after contorting into all kinds of impossible positions to get at all those nuts! 

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Looks like when the manifold was refitted by a certain Lotus specialist in Hammersmith they didnt use any threadlock on the studs and they simply vibrated out.

Even with threadlock on them the studs will often vibrate out & is why on the later cars they fit lock tabs. :o

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Well this is annoying.

I am having to re-do the job of refitting the rear gearbox housing as it started to leak oil again. 

I was completely bemused as to why it started to leak, I was very careful to clean all mating surfaces completely, with acetone and re-assembling with Loctite 518.

I took it all apart again and could not find any problem with the assembly. But when I did a trial re-fit of the rear housing I found out what had gone wrong. So, in case anyone else falls into the trap:

The problem is, even with the gearbox completely drained, oil still emanates from the hole indicated in the picture. It builds up in the hole.

There is a brass tube which looks like its an oil tube to dump oil onto 5th gear, located in the housing, which protrudes 2-3 mm and fits into this hole when the housing is fitted. So all of the oil built up in the hole is pushed out and dribbles down the mating face and all,over the carefully applied sealant.

The oil is still coming out this hole after several hours so I am going to need to put it back together tomorrow after its hopefully all come out. 

gbox.jpg

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Hi Andy

going to try the same job on my brothers S2 as its leaking. I was thinking easier to do it when the car is on rear ramps rather than jacked up. Any thoughts?

ta

Christian

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26 minutes ago, C43 said:

Hi Andy

going to try the same job on my brothers S2 as its leaking. I was thinking easier to do it when the car is on rear ramps rather than jacked up. Any thoughts?

ta

Christian

Yes that would likely be easier.

 

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thanks

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Hello Andy (and Christian, if you have gotten around to this operation): How did this turn out for you? Did you stop the oil from leaking this time, by allowing it to drain out completely?

Cheers,

Scott

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4 hours ago, greentengu said:

Hello Andy (and Christian, if you have gotten around to this operation): How did this turn out for you? Did you stop the oil from leaking this time, by allowing it to drain out completely?

Cheers,

Scott

I have not driven the car enough to tell as I am working on leaks in the cooling system but I dont expect any problems.

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Hi Scott

I am still trying to pin down exactly where the leaks are in the oil system. Gave everything a really good clean under the car at the weekend so hopefully it should be easier to work out now...

cheers

Christian

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On 06/02/2015 at 22:23, Andyww said:

I am investigating a quite large oil leak. It seems I might have the usual leak from the back cover as there is dripping from the drain plug.

 

But that does not seem to be the complete story. There is also a drip on the location I have marked with an arrow on the right. The vertical surface of the rear section (left hand arrow) is also wet with oil. These areas are above the level of the rear cover so I am not sure where the oil is leaking from to end up here. It almost seems that there is a leak at the joint between the main section and the rear section. Do they ever leak here?

leak.jpg

Mine leaks from the end plate im sure it's caused by the exhaust bracket being bolted to it.

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Edge,

Do you mean bolted instead of studs? or just the fact its hanging on the back of it?

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Having done this twice, annoyingly I still have a slight leak.

But what seems to be happening is the synthetic gear oil (Redline MTL) is melting the Loctite 518. On the garage floor I have a spot of sticky stuff which is a mixture of gear oil and dissolved Loctite 518. Interestingly I also used 518 on the gearbox pan on the Ferrari and that also leaks! I am 100% certain that mating surfaces were totally clean on both cars. 

On the gearbox output shaft seal carriers on the Ferrari I used a Permatex sealant which is specifically made for use on gearboxes with synthetic oil, and thats not leaking. I always thought that was a marketing ploy but it seems that some sealants genuinely are not compatible with synthetic gear oil.

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That must be really annoying! Harry Martens rebuilt my gearbox at the beginning of the year and it's had Redline MT-90 in since then and no leaks. Not sure what sealant he used ( it's blue I know that at least) but he has posted on this thread and if he spots this he may reply to let you know what he uses.

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Harry did my box also,  filled it up with redline MT-90 and it leaked eversince....

Gearbox is fine though.

Edited by gvy

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Hi

Andy, do you have any news about  the Permatec sealant. Did you used it and did it stop the oil leak?

Harry , can you give me the name of the blue sealant you using for the gearbox?

Hugues

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