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The mkiv Supra Owners Club

oil leak front seal ?


TT Paul

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just had the single fitted low boost,oil pressure is good, now i have a oil leak from crank seal i know its not above it had a good clean and look.

 

the seal is only a few months old, on idle takes about 10 mins to start leaking a little. but a 1 mile drive on wot puts out alot more, its going into garage on thurs for new seal worth doing pump to? your thoughts

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It may just be that the seal is incorrectly fitted. If it is anything but flush, it will seep oil.

 

Often people don't fit them in far enough, or too far (easily done) and it only has to be half a mm, and it will leak.

 

I'd just go with a replacement seal for now, and keep an eye on it. Possibly save yourself circa £200.

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It may just be that the seal is incorrectly fitted. If it is anything but flush, it will seep oil.

 

Often people don't fit them in far enough, or too far (easily done) and it only has to be half a mm, and it will leak.

 

I'd just go with a replacement seal for now, and keep an eye on it. Possibly save yourself circa £200.

 

This is more likely the cause, fitted to far in or not enough.

 

I'd consider getting one of Chris Wilson's modified seals with the extended lip if your going to replace it (if he has any left!) :)

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Its to do with the crankcase pressure on a big single. The stock breathing system is inadequate to deal with that pressure. You need to modify the stock breathers with -AN fittings and hoses into a catch can to breath the crankcase sufficiently. Its blowing the seal out

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Afaik you have to remove the factor breathers and weld in the AN fittings and do the hoses etc. That was a very useful piece if advice given to me by Mark Luney of SATS Cosworth in regards to my own car when i fitted the BL S366HF. Those guys really know their stuff!

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Its to do with the crankcase pressure on a big single. The stock breathing system is inadequate to deal with that pressure. You need to modify the stock breathers with -AN fittings and hoses into a catch can to breath the crankcase sufficiently. Its blowing the seal out

 

Afaik you have to remove the factor breathers and weld in the AN fittings and do the hoses etc. That was a very useful piece if advice given to me by Mark Luney of SATS Cosworth in regards to my own car when i fitted the BL S366HF. Those guys really know their stuff!

 

 

 

Totally disagree, the US guys seem to go with this theory, but having disproved it myself its not down to crankcase pressure.

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Totally disagree, the US guys seem to go with this theory, but having disproved it myself its not down to crankcase pressure.

 

Ok, fair enough and you are entitled to your opinion, I was just stating what I was told by a team that is running a 1000bhp+ drift car and build engines for people up and down the country. Be interested in how you have disproved this theory though?

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Ok, fair enough and you are entitled to your opinion, I was just stating what I was told by a team that is running a 1000bhp+ drift car and build engines for people up and down the country. Be interested in how you have disproved this theory though?

 

Without going into a complete monologue on the subject, I did loads of reading and discussion on the US forums, and after I suffered FMS failure twice, and found that my oil pump was worn and allowing escaping oil to pressurise the seal, even though I had a modded pump with the drain hole enlarged, I started to investigate further,

I then ran several experiment's using accurate vacuum/pressure gauge attached to the crankcase, with std breathers in place, catch can both recirc and open,

this was done at several different boost pressures and loads, and the result was that at no time did I get positive crankcase pressure.

The was with a GT4088 turbo.

 

Now I dare say that there could be a a slight build up of crankcase pressure on a highly tuned 1000bhp + running high boost pressures, however I have yet to see any proof that this is the case, given that most high output engines have modified breather systems and as boost increases so does ring seal.

also the internal pressure would need to be very high to force the seal out, however if the force is hydraulic as in pressurised oil it is capable of exerting a much grater force.

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well after a few hours work oil leak sorted, appears the spring had some how come off and was not fitted correctly, thanks to my mechanic and good friend, anyone else in hants area with a supra and needs work doing i would go to him all done in a day and good price too:d

 

https://www.facebook.com/pages/Pages-autos/292376094256351?fref=ts

Edited by TT Paul (see edit history)
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All rotary pumps leak some oil from the rotors as they need clearance to run at all. this oil that is not fed to the oiling system drains through a very small hole in FRONT of the pump, and BEHIND the front seal. A pump in good order leaks not much oil at all and the drain hole copes just fine. A worn pump can leak a lot of oil and if the drain hole is overwhelmed pressure builds. The pump can build enough pressure to cause the seal to leak or even be ejected against the back of the timing star wheel. having dealt with more of these things than i care to recall i can say with certainty they leak either due to worn oil pumps, or due to the nose of the crank having a wear ridge worn into it by the seal lips. My high tension seal will often help with a wear ridge if it's not too extreme. A worn pump needs replacing and in my opinion it's an engine out job to do satisfactorily due to oil dripping down and general lack of access. The RB series of engines in Skylines has a FAR, FAR bigger drain passage, and never suffers this issue. The (hugely expensive) Tomei race pumps for the RB's have three large drain holes! As Tricky-Ricky so rightly says, an engine in good order will never pressurise the crankcase enough to cause seal issues. I too have measured crankcase pressure on both good and leaking engines and seen no issues. A "1000 BHP" engine if it really makes anything like that power, will flex the block and bores so much anything could happen. I do not attempt 1000 BHP 2JZ-GTE engines as I know such boost will just give grief.

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