2ZZ-GE Rear main seal leak

[JB21]

So after fitting my new (used) 2ZZ engine the car developed a leak between the gearbox and engine whilst out on track. Oil was being flung out of the gaps between the box and engine by the flywheel so thinking its the rear main seal, given I couldn't smell gear oil (input shaft seal leak), plus I was losing oil when checking the dipstick and not losing gear oil. Around half a litre in 150 track miles.

One thing I do need to check is the sump is not leaking before pulling the box, but I'm pretty sure its not the sump because its not dripping much on the ground and the sump seems clean.

All in all though I'm happy with the new engine, its defo stronger than the old high mileage unit. I'm just annoyed I didn't change the rear main seal before fitting. I did check it and there was no sign of leaking when removing the old clutch so left it alone.

Ahh well, it will give me something to do over Christmas as the track day season is over for me now.

[mr2garageswindon]

Are you running the stock crank case breather or a catch can? A restricted breather system can also lead to leaks from the rear main oil seal.. Just a thought.

[JB21]

Are you running the stock crank case breather or a catch can? A restricted breather system can also lead to leaks from the rear main oil seal.. Just a thought.

Stock breather. Never really had an issue with previous 2ZZ engines with the stock breather, worth a look though, thanks.

[Joesson]

Hindsight is the most useless of the senses, it is always too late with it's bright ideas!

[JB21]

Just thinking about this some more, and could the leak be coming from the flywheel bolts. I re-used my ARP bolts and also the recommended 242 loctite, but didn't use APR ultra torque fastener lube under the heads. Instead I used moly grease. Surly this wouldn't cause a bolt to loosen?

[Joesson]

Just thinking about this some more, and could the leak be coming from the flywheel bolts. I re-used my ARP bolts and also the recommended 242 loctite, but didn't use APR ultra torque fastener lube under the heads. Instead I used moly grease. Surly this wouldn't cause a bolt to loosen?

My understanding is that a lubricant will affect the tension / torque in a fixing.  A specific torque fastener lube will not have that effect.
There are charts showing the effect of various lubricants on tension/ torque figures. Graphite reduces the figure by around 50%. Molybdenum I would think is in the same order.
If that is the case those bolts would not be as tight as you thought they were.
All things are possible but my money would be on the seal being worn.
Whichever it is, inspection is the way forward.
NB
Contentiously I use copper-slip on the wheel nuts of my cars, but this is not classified as a lubricant but an anti seize compound. 

[JB21]

Just thinking about this some more, and could the leak be coming from the flywheel bolts. I re-used my ARP bolts and also the recommended 242 loctite, but didn't use APR ultra torque fastener lube under the heads. Instead I used moly grease. Surly this wouldn't cause a bolt to loosen?

My understanding is that a lubricant will affect the tension / torque in a fixing. Application of a specific torque fastener lubewill not have this affect.
There are charts showing the effect of various lubricants on tension/ torque figures. Graphite reduces the figure by around 50%. Molybdenum I would think is in the same order.
If that is the case those bolts would not be as tight as you thought they were.
All things are possible but my money would be on the seal being worn.
Whichever it is, inspection is the way forward.
NB
I have always used a copperslip

Would oil even escape from a lose bolt? Looking through the holes on the crank of the old engine and they seem closed threaded.

[Joesson]

Just thinking about this some more, and could the leak be coming from the flywheel bolts. I re-used my ARP bolts and also the recommended 242 loctite, but didn't use APR ultra torque fastener lube under the heads. Instead I used moly grease. Surly this wouldn't cause a bolt to loosen?

My understanding is that a lubricant will affect the tension / torque in a fixing. Application of a specific torque fastener lubewill not have this affect.
There are charts showing the effect of various lubricants on tension/ torque figures. Graphite reduces the figure by around 50%. Molybdenum I would think is in the same order.
If that is the case those bolts would not be as tight as you thought they were.
All things are possible but my money would be on the seal being worn.
Whichever it is, inspection is the way forward.
NB
I have always used a copperslip

Would oil even escape from a lose bolt? Looking through the holes on the crank of the old engine and they seem closed threaded.

Oh yes! If under pressure oil will find its way out of the tightest of places. How do I know that?

[AJRFulton]

Are you running non OEM main bolts? or a non OEM Sump?

I ran ARP main bolts on mine.... they protruded very slightly..... this caused the Elise Parts sump to nearly seal.... but not quite. The main bolts overlap the lip of the sump, at the flywheel.

I had symptoms that looked exactly like a rear seal leak.... but it wasn't, it was a tiny gap in the sump right at the flywheel and only when the engine was at power.

After removing the gearbox.... I quickly seen it wasn't the rear seal, and a lot of work could easily have been prevented with pillar drill and removing a tiny bit of material from the sump.

Just sharing some opex.

Just to reiterate - Absolutely no leakage when the engine was not running, but a significant drip when it was.

[Dev]

A few months ago a local member overfilled his aftermarket sump and had a leak at the rear main seal. He filled it based on the capacity of from the sump manufacture but it was wrong. Once we drained and refilled the oil it was about a liter less to where it shows full on the dip stick. It completely solved the problem. I hope you are filling it based on the dip stick and not the known capacity.

[JB21]

Are you running non OEM main bolts? or a non OEM Sump?

I ran ARP main bolts on mine.... they protruded very slightly..... this caused the Elise Parts sump to nearly seal.... but not quite. The main bolts overlap the lip of the sump, at the flywheel.

I had symptoms that looked exactly like a rear seal leak.... but it wasn't, it was a tiny gap in the sump right at the flywheel and only when the engine was at power.

After removing the gearbox.... I quickly seen it wasn't the rear seal, and a lot of work could easily have been prevented with pillar drill and removing a tiny bit of material from the sump.

Just sharing some opex.

Just to reiterate - Absolutely no leakage when the engine was not running, but a significant drip when it was.

OEM main bolts, and EP baffled sump. Never had an issue with the sump on previous engines. Its something I'll be checking before removing the box though, but I can't see it being the sump the way oil is being thrown around inside the bell housing. If it was a sump leak, that much oil wouldn't get past the flywheel into the bell housing, most of it would drip backwards over the rear of the engine.

[JB21]

A few months ago a local member overfilled his aftermarket sump and had a leak at the rear main seal. He filled it based on the capacity of from the sump manufacture but it was wrong. Once we drained and refilled the oil it was about a liter less to where it shows full on the dip stick. It completely solved the problem. I hope you are filling it based on the dip stick and not the known capacity.

5L goes in, EP sump can hold 5.7 but I stay clear of this much.

[AJRFulton]

Thought this as well, even had same symptom, even after putting a fibre optic inspection camera up - was utterly convinced it was main seal.

Deffo check the EP sump, as the lips wider than the OEM sump and does run over the main bolts.

As said I had to use the pillar drill to remove some material from the inner lip, fixed the issue

[JB21]

Thought this as well, even had same symptom, even after putting a fibre optic inspection camera up - was utterly convinced it was main seal.

Deffo check the EP sump, as the lips wider than the OEM sump and does run over the main bolts.

As said I had to use the pillar drill to remove some material from the inner lip, fixed the issue

I'll check that mate, nice one. I'll clean all the shite up, then place a piece of cardboard between the sump and flywheel opening to separate them and hopefully its just the sump leaking.

[Gaz2405]

Thought this as well, even had same symptom, even after putting a fibre optic inspection camera up - was utterly convinced it was main seal.

Deffo check the EP sump, as the lips wider than the OEM sump and does run over the main bolts.

As said I had to use the pillar drill to remove some material from the inner lip, fixed the issue

I'll check that mate, nice one. I'll clean all the shite up, then place a piece of cardboard between the sump and flywheel opening to separate them and hopefully its just the sump leaking.

Another vote here for Elise sump.

Mine leaked on its first track day and I was in sure it was the main seal. But should use of sealant by me was the cause....

[JB21]

95% sure its the sump 🙃

Fitted the flywheel cover that slots in behind the narrowest part of the sump, then stuffed paper towel up around the sump join, and...



That was after just 10 miles road driving, oil only up to 92°c. Zero oil coming out of the bell housing like before.

[Gaz2405]

95% sure its the sump 🙃

Fitted the flywheel cover that slots in behind the narrowest part of the sump, then stuffed paper towel up around the sump join, and...



That was after just 10 miles road driving, oil only up to 92°c. Zero oil coming out of the bell housing like before.

A much easier fix!

[AJRFulton]

As said, just check those main bolts on the new engine are flush.

As Gaz said, a much easier fix!

[JB21]

What sealant are you guys using? I've always used black RTV without issue until now.

[AJRFulton]

What sealant are you guys using? I've always used black RTV without issue until now.

Nothing particularly special. Usually use the Wynn's stuff. Never had any issues with it.

Not teaching you to suck eggs but rough the surfaces up a bit. The aluminium doesn't bond too well.

[Alex Knight]

Hondabond has never let me down.
Used on my EP sump.

[Dev]

There is a specific Toyota oil pan sealant that other hobbyists of other makes recommend because it is better than most of the off the shelf sealants. It can be bought from the dealer and it is not cheap. I have used it and it is very good but you need to set it up by not squeezing it out by threading the pan bolts half way for 4 hours until it is rubbery and then tighten. This way there is some thickness between the matting surfaces so it doesn't leak.
  If you ever wondered why Toyota has the reputation it does for not leaking oil this is why.