Front crank oil seal...

at some point yesterday eve it looks at first glance like the front crank oil seal has gone .... first search it seems to be common on modded cars....whats the latest info on a fix for this prob?

cheeers

Dave

from what I remember reading, there didn't seem to be a fix.

Looks like one of those dreaded problems that happens to some people and not others.

How 'modded' is your car?

I don't think its perculiar to modded cars only, when my SZ went in for its 60K mile service they found the front crank shaft oil seal weeping, they replaced it after informing me (and I'd been down there to have a look) which wasn't too big of a problem as the cambelt was being done anyway so the front of the engine was mostly stripped. Its possibly a weakness of the 2JZ design.

As for the fix I'm pretty sure the only way is to replace it, unless there's some product that "guarantee's to stop oil leaks" and personally I don't think I could trust one of them.

....... first search it seems to be common on modded cars......

have you modified anything around the crankcase ventilation?

(a catch tank venting to the atmosphere would be a 'YES' for example)

ive had nothing but bloody hassel with this seal ive had three new ones fitted and today ive noticed it is leaking again

im getting fed up with taking it back to the garage and i thinl he is also getting fed up with seeing it.

im only running 0.7-0.8 boost,occasionally 1.1 boost so nothing rediculous

any help will be appreciated

i have the little k&n type filters on the breathers....this is a recent rebuild...and unfortunately I did it ( 1st attempt).... so I cant complain to anyone....i wasnt 100% sure it was ok at the time....I hope all the new engine internals survived though.....

i have the little k&n type filters on the breathers....this is a recent rebuild...and unfortunately I did it ( 1st attempt).... so I cant complain to anyone....i wasnt 100% sure it was ok at the time....I hope all the new engine internals survived though.....

Both breathers or just the one on the one on the exhaust side?

I'd consider reconnecting it to the intake. By venting the WOT breather to atmosphere you will be raising the crankcase pressure when you boot it (because you aren't recirculating the breather system to a vacuum).

The altarnative scenario is that the sealing surface on the crankshaft is worn (bizarre as is may sound, the floppy rubber lip seal will eventually wear a permanent groove in the crankshaft!)

both breathers...but isnt the one inlet side for the idle control valve? or is there another breather somewhere.....I'm going to reconnect the exh side one back to the intake....

both breathers...but isnt the one inlet side for the idle control valve? or is there another breather somewhere.....I'm going to reconnect the exh side one back to the intake....

There is a dedicated breather connection on the intake side. Its a short, s-shaped hose from the cam cover to the plenum. Not sure where you have put your other filter. A pic of the engine bay would be handy.

aaah...that ones connected as stock...

ok ...got down to the oil seal...now how can you tell if its the culprit ....it looks still in place,I'm going to replace it anyway....poss pump faults??

cheers

Dave

i have the little k&n type filters on the breathers.......

...there ya go...

where there is meant to be a vacuum you have substituted it for atmospheric pressure.

Not good for the lifespan of turbos either.

[quote name=JohnA

Not good for the lifespan of turbos either. [/quote]

good job I only put one on then!!

cheers

Dave

TBH I'd be surprised if there was sufficient crankcase pressure to push a lot of oil out of the front crank seal if the WOT breather was venting to atmosphere provided that you are only getting normal amounts of blow-by and that the front crank seal was seated properly. The part throttle breather is still connected as stock and that will be operating more than the WOT breather while cruising.

There are other problems that can cause a leaky front crank seal: Excessive leakage from the oil pump, and just plain old worn surfaces. Unfortunately there's no way of telling unless you start seriously taking things apart.

As for crankcase pressure stopping adequate oil flow through the turbos, I wouldn't worry too much at this stage. IIRC oil has the consistence of shaving foam when it exits a turbo centre section, plus it still has a pressurised feed on the other side.

How much oil appears and how quickly?

chucked ALL my fresh ProS out...

all apart....just debating whether or not to remove the oil pump...cant tell yet if the seal is at fault

Can you see where the seal runs on the crankshaft? If you can see some grooving (very unlikely on a young-ish engine) then the sealing surface is fooked. The only thing to do in that case is to make sure tha ta replacement seal if fitted so that it runs forward or rearwards of that area.

If you take the oil pump off, look for a little hole just behind the front seal and just in front of the pump rotors. I've never actually seen a Supra oil pump, but one of these holes is a common feature on pumps and is there to relieve any pressure that builds up due to leakage from the oil pump. It is specifically there to stop the front seal popping out or leaking. If you can find the hole, make sure it is clear. Check the seal housing for nicks or scratches or cracks.

Failing that, put it all back together and re-connect the breather system up as stock.

...There are other problems that can cause a leaky front crank seal: Excessive leakage from the oil pump, and just plain old worn surfaces. Unfortunately there's no way of telling unless you start seriously taking things apart.

there is an interesting theory on to4r.com regarding the crank seal.

Don't know how accurate it is, but worth reading anyway

As for crankcase pressure stopping adequate oil flow through the turbos, I wouldn't worry too much at this stage. IIRC oil has the consistence of shaving foam when it exits a turbo centre section, plus it still has a pressurised feed on the other side.

I would strongly disagree, as I've done my own measurements on these.

The oil return is gravity-driven, not pressurised. Even the smallest amount of crank pressurisation can disrupt it.

Some turbocharger manufacturers only allow a small fraction of a psi as the max allowed sump pressurisation.

I've seen several psi in people's cars though, just fit a gauge on the dipstick and see where you stand.

I find venting the crankcase into the atmosphere as distinctly unwise.

just read the article on to4r.com.....thats why I was debating taking off the oil pump now and modifying it rather than having to do the job twice....someone must have done the pump mod before now....

have a chat to Leon, he's done a few of these now and knows of a possible fix for the problem. Cant guarantee it works as Foodfreak on here has lost 3 front crank oil seals before he went single but may be worth checking with Leon what he recommends now.

JB

I remember Leon enlarging that oilpump relief hole when he was blowing seals.

they do that mod a lot in US ,just trying to find a pic to make sure I do the right one......

I remember Leon enlarging that oilpump relief hole when he was blowing seals.

theres also some sort of trick with the spring but thats as much detail as I know on it...

JB

spring?

If you mean the seal spring, the final verdict was that it wasn't worth the risk of modifying, and it still pops off anyway...

The article on t04r.com is talking about modding the PRV recirc (or dump) hole so tha the pump can control the oil pressure at higher than stock RPM. Whether or not enlarging that hole in that situation helps or not, I don't know, but that isn't the hole I was talking about.

Many modern oil pumps have a hole just behind the front seal to dump excess oil straight back to the sump - specifically to stop a build up of pressure behind the front seal. As I said above, I don't even know whether the Supra oil pump has one or not.

Even if there is no hole, if the pump rotors are sealing properly then there should be minimal leakage into the space behind the front seal. If the rotors are worn then there is a risk of pressure building up there, but modding the PRV is a risky solution. The t04r article is specifically talking about higher than stock RPM, at which the pump is flowing more oil, so the that stock hole isn't large enough to dump it all when the PRV is fully open - hence it ceases to control pressure propery above a certain RPM.

Note that if you enlarge the PRV vent hole, you may also make the PRV open at a slightly lower pressure (because the piston will start to uncover the hole slightly sooner).

If there was a design fault with the Supra oil pump PRV at stock PRM, then there would be oil seals popping out left, right and centre on cars with stock breather systems and stock boost pressure.

It may be effective to stop problems if you want to run the stock pump at high PRM, but as a fix for the front seal popping out, I'm not convinced.

Incidentally, there is a gaffe in that article.

It suggestes that the cause of the front crank seal popping out is because the PRV can get swamped so that oil pressure continues to rise even when it is fully open, but it also says that "when the front seal goes the other three seals in the engine have been stressed too" (camshafts and rear crank seals.

If excess pressure from the oil pump is the cause, then there is no way that this can happen. The front crank seal is the only seal that can see pump pressure - and then only if the rotors are worn.

The other seals could pop out of you run a high crankcase pressure - but not from an oil pump problem. That article kind of mixes the two possible causes up.

I'd still say investigate the breather before you pull the pump apart and start enlarging holes in the PRV, but it looks like the engine is already in bits