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POSSIBLE REAR MAIN BEARING CAP OIL LEAK


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My restoration project engine was rebuilt at great expense byt the previous owner using a reputable engine builder. All is good except for a significant oil leak from the rear of the engine. After I run the engine I get a pool of oil under the back of the engine and the leak will continue for a day or two before it stops. It is too big a leak to ignore. 

I have had the gearbox off a couple of times, most recently when I had the clutch issue a month or so back. The oil is NOT coming from the main seal or the welsh plugs on the back of the engine nor the gearbox front seal. The bellhousing is dry as is the back of the engine including under the flywheel. But as I didn't suspect the bearing cap I didn't check it closely while I had it apart. After discussing it with our most knowledgeable TR engine engineer the culprit is probably the main bearing cap, which can be tricky to seal on the sides.

I am going away next week for 6 weeks so will tackle this when I get back. The first thing will be to use a mirror and peer into the area under the flywheel to confirm the oil is coming from there.

The manual says to pack the sides of the seal with felt packing however this has not been the best method as the packing goes hard and I believe rebuilders often use Silastic after cleaning all surfaces with carbie or brake cleaner.

My mate says while tricky it can be done with the engine and box in situ.

Has anybody done this and what process is used?

 

 

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The felt packing allows the sealing agent to be carried in it and then compressed squeezing it into the joints and then out which then goes sticky at the edge where it emerges and finally seals the rear mains against oil passing around and through it. Whatever you use (the factory and I use Wellseal which has been proved over 50 years and does seal excellently) the existing oil leak contaminates the machined sides of the mains bearing block and you'll find it difficult to achieve a satisfactory seal by trying with it in place.

Imagine lying upside down under the open sump with 2" or thereabouts lengths of felt soaked in Wellseal which is like treacle squeezing them into the seal channel either side of the rear mains block (which then dumps it's Wellseal over you), and the final felt fitment strip either side needs to be left proud of the sump surface by about 3mm so that the Wellsealed block has a continued pressure when the sump is immediately refitted and sealed in place...not easy.

Also it's like pushing water uphill, if the rear seal mains is leaking then the machined surfaces up to the crank (it's upside down) is contaminated and you will be trying to drive the Wellseal into the machined seal surfaces uphill and then displacing the oil from between the block mains surfaces and out the end. All this presupposes the alloy rear oil seal scroll is fitted the correct amount up to, but away from the crank by a couple of thou by being fitted with a machined mandrill prior to the crank being fitted. Also is the reputable engine builder aware that the dimensions shown in the workshop manual for machining the mandrill is incorrect, did he even use one  ? can you ask him ? and has he made a new mandrill to the correct dimensions to allow the oil scroll fitment before the crank was fitted. If this seal is incorrectly fitted, in use you will get significant oil leaks from the rear mains as the oil passes along the crank rear main surface by rotation and is screwed out of the end of the crank, when the engine is stopped  it will continue for some hours afterwards as the oil drops onto the crank from the interior surfaces and is pushed along and out of the crank past the seal.

Give the in situ sealing a go if you wish it's the least labour intensive, but I fear it will not work and you will end pulling the engine and gearbox, splitting them, dropping the sump and crankshaft and refitting the rear scroll oil seal in the correct manner. Be advised the oil scroll works when the engine spins but not when the engine is stood, so there is normally a small weep from the crank and rear of the engine when stood (they were a lot more relaxed about a spot of oil on the floor in the 50s and 60s). If you wish to stop that a Christian Marx additional rear of crank seal can be fitted (whilst the crank is out) behind the original scroll and will do a good job.

Mick Richards 

 

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Mick,

I have always cut the felt into handy 1/2"-3/4" lengths, soaked them in Wellseal and thumped them into the slots of the fitted main bearing cap using a square ended punch and 1/2lb hammer.  As you say leaving 1/16" - 1/8" proud.

Cheers

Peter W

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17 minutes ago, Motorsport Mickey said:

The felt packing allows the sealing agent to be carried in it and then compressed squeezing it into the joints and then out which then goes sticky at the edge where it emerges and finally seals the rear mains against oil passing around and through it. Whatever you use (the factory and I use Wellseal which has been proved over 50 years and does seal excellently) the existing oil leak contaminates the machined sides of the mains bearing block and you'll find it difficult to achieve a satisfactory seal by trying with it in place.

Imagine lying upside down under the open sump with 2" or thereabouts lengths of felt soaked in Wellseal which is like treacle squeezing them into the seal channel either side of the rear mains block (which then dumps it's Wellseal over you), and the final felt fitment strip either side needs to be left proud of the sump surface by about 3mm so that the Wellsealed block has a continued pressure when the sump is immediately refitted and sealed in place...not easy.

Also it's like pushing water uphill, if the rear seal mains is leaking then the machined surfaces up to the crank (it's upside down) is contaminated and you will be trying to drive the Wellseal into the machined seal surfaces uphill and then displacing the oil from between the block mains surfaces and out the end. All this presupposes the alloy rear oil seal scroll is fitted the correct amount up to, but away from the crank by a couple of thou by being fitted with a machined mandrill prior to the crank being fitted. Also is the reputable engine builder aware that the dimensions shown in the workshop manual for machining the mandrill is incorrect, did he even use one  ? can you ask him ? and has he made a new mandrill to the correct dimensions to allow the oil scroll fitment before the crank was fitted. If this seal is incorrectly fitted, in use you will get significant oil leaks from the rear mains as the oil passes along the crank rear main surface by rotation and is screwed out of the end of the crank, when the engine is stopped  it will continue for some hours afterwards as the oil drops onto the crank from the interior surfaces and is pushed along and out of the crank past the seal.

Give the in situ sealing a go if you wish it's the least labour intensive, but I fear it will not work and you will end pulling the engine and gearbox, splitting them, dropping the sump and crankshaft and refitting the rear scroll oil seal in the correct manner. Be advised the oil scroll works when the engine spins but not when the engine is stood, so there is normally a small weep from the crank and rear of the engine when stood (they were a lot more relaxed about a spot of oil on the floor in the 50s and 60s). If you wish to stop that a Christian Marx additional rear of crank seal can be fitted (whilst the crank is out) behind the original scroll and will do a good job.

Mick Richards 

 

Thanks Mick. My apologies, the engine doesn't have an original scroll seal but a dripless seal. I'm not sure which type is fitted but the seal itself isn't leaking.

Does that affect your advice?

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John,  I have the drip less rear oil (Land Rover adaption) and no scroll on the crank and mine dripped from installation.  The issue was the machine shop had not made the seal area the correct size for the intended seal. - That meant crank out and re machine.

I ran the engine with the gearbox out and flywheel removed and could see the oil coming out - Thank heavens for a starting handle.

Peter W

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9 minutes ago, John McCormack said:

Thanks Mick. My apologies, the engine doesn't have an original scroll seal but a dripless seal. I'm not sure which type is fitted but the seal itself isn't leaking.

Does that affect your advice?

Not really. If you are sure the seal itself isn't leaking (hhmmmm) then what's so difficult with the experienced original engine builder having to seal the rear mains block with numerous felt strips dipped into Wellseal ? If he couldn't do it with the engine out and on a bench why is an upside down attempt trying to displace oil from sealed surfaces likely to succeed ?

I would stick with the engine out process unless with the engine in place you can remove the gearbox, radiator and spark plugs and spin the crank over with an impact driver on the end of the crank dog bolt to check where the oil is puthering out from. If it is the seal area around the block and not the crank seal itself then I'd go the engine out method, at least it's halfway there with no gearbox on it !...oh and refit with gearbox fitted it's easier.

Mick Richards 

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22 minutes ago, BlueTR3A-5EKT said:

Mick,

I have always cut the felt into handy 1/2"-3/4" lengths, soaked them in Wellseal and thumped them into the slots of the fitted main bearing cap using a square ended punch and 1/2lb hammer.  As you say leaving 1/16" - 1/8" proud.

Cheers

Peter W

This is quite a clear video of the process. This chap shares a lot of TR information. 

 

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42 minutes ago, BlueTR3A-5EKT said:

Mick,

I have always cut the felt into handy 1/2"-3/4" lengths, soaked them in Wellseal and thumped them into the slots of the fitted main bearing cap using a square ended punch and 1/2lb hammer.  As you say leaving 1/16" - 1/8" proud.

Cheers

Peter W

Thanks for the correction Pete, the shorter lengths are far easier to get into the slots and that's what I do, I think the idea of doing it upside down thru me in my description ! Likewise I cut a wooden peg to fit the felt seal hole (square, I'm not a pedant !) and lightly hammer the Wellsealed felts in which squeezes the Wellseal through the machined edges on the mains.

Mick Richards

Edited by Motorsport Mickey
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16 minutes ago, Motorsport Mickey said:

Not really. If you are sure the seal itself isn't leaking (hhmmmm) then what's so difficult with the experienced original engine builder having to seal the rear mains block with numerous felt strips dipped into Wellseal ? If he couldn't do it with the engine out and on a bench why is an upside down attempt trying to displace oil from sealed surfaces likely to succeed ?

I would stick with the engine out process unless with the engine in place you can remove the gearbox, radiator and spark plugs and spin the crank over with an impact driver on the end of the crank dog bolt to check where the oil is puthering out from. If it is the seal area around the block and not the crank seal itself then I'd go the engine out method, at least it's halfway there with no gearbox on it !...oh and refit with gearbox fitted it's easier.

Mick Richards 

Unfortunately the engine was done too long ago (possibly 8-12 years ago) and too far away for me to refer to the rebuilder. While they are a reputable engine business they aren't TR specialists. We just don't have them in Australia.

I have no idea how he sealed it, hopefully it will all come clear when I get the sump off. It might be he used felt strips but didn't leave any excess to keep it in compression.

As it appears pretty straight forward to get the sump off and try to reseal it from underneath I'll give that a try. If it doesn't work I will have to wrap the engine bay in cotton wool, be very careful taking the apron off and lift the engine/box out.

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33 minutes ago, Hamish said:

This is quite a clear video of the process. This chap shares a lot of TR information. 

 

Excellent video, thank you. I reckon it should be doable from underneath, if messy. As I said previously there is no oil coming from the seal itself, that area is bone dry. The mess is at the bottom of the engine.

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Hi John,

you have to remove the gearbox. You are considering removing the sump. With a little more time and effort take the engine out and do it properly.

Clearly the Pro builder has done something not quite right - laying on your back with oil dripping on you will not equal his efforts.

Take the engine out, examine the issue and get it sorted - a weeks work.

 

If you have the standard crank with scroll then consider the Christian Marx oil seal.

 

Roger 

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32 minutes ago, RogerH said:

Hi John,

you have to remove the gearbox. You are considering removing the sump. With a little more time and effort take the engine out and do it properly.

Clearly the Pro builder has done something not quite right - laying on your back with oil dripping on you will not equal his efforts.

Take the engine out, examine the issue and get it sorted - a weeks work.

 

If you have the standard crank with scroll then consider the Christian Marx oil seal.

 

Roger 

Thanks Roger. I want to avoid taking the engine out if at all possible. While I have a good size garage I have limited resources (help) so have a real risk of incurring damage to the apron/engine bay etc.  

I will see what I can get to with the sump off. Taking the box out isn't too big a job so I'll take it off to loosen the two bolts that intrude into the groove. I'll let it drip into a tray for a bit and it should be ok. I mean we do oil pumps and big/little ends with the engine in place.

I can accept a minor drip occasionally, the leak now is excessive.

Edited by John McCormack
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Hi John

Having seen your engine bay and standard of finish I can sympathise with your chosen option to try the repair from underneath, best of luck. Removing the apron and  engine then refitting will most certainly leave a trail.

All bye best

Paul

Now back home and continuing with the TR6 resto.

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I'd go for dropping the sump in the first place -  Provided you have the car jacked up well, it's a half hour job to drop the sump and try ramming some more felt in the holes. With wellseal all over it, the stuff isn't going to fall out.

Rgds Ian

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55 minutes ago, Ian Vincent said:

I'd go for dropping the sump in the first place -  Provided you have the car jacked up well, it's a half hour job to drop the sump and try ramming some more felt in the holes. With wellseal all over it, the stuff isn't going to fall out.

Rgds Ian

+1

Peter W

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11 hours ago, Paul J said:

Hi John

Having seen your engine bay and standard of finish I can sympathise with your chosen option to try the repair from underneath, best of luck. Removing the apron and  engine then refitting will most certainly leave a trail.

All bye best

Paul

Now back home and continuing with the TR6 resto.

Hi Paul,

Glad you are back home in one piece. It was my pleasure to have you around during your visit down under. I was particularly grateful that you bought the 11/2" SUs out for me.

Having studied the manual and discussed it with some good TR engineers, sealing the bearing cap from underneath isný too difficult. Whether I do it well is another question.

Take the sump and box off, remove the main bearing cap, clean it all up with carbie cleaner etc, put it back together and punch the Wellseal or Permatex soaked seal in. Refit the sump and box. Hopefully a days work.

Cheers

 

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23 minutes ago, Fireman049 said:

This is the 'Mad Marx' oil seal.

The extra oil drain holes in the rear main cap will reduce the oil pressure on the oil seal.

Tom.

DSCF0095 - Copy.JPG

DSCF0232 - Copy.JPG

TR2-4 CRANKSHAFT OIL SEAL CONV  INS P2 - Copy - Copy.JPG

Does the Mad Marx seal kit instructions call for the extra drain holes?  I thought they were only required with single lip seal type. Not that extra drainage will be a backward step.

Peter W

Edited by BlueTR3A-5EKT
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