yet another theory for the crank seal issue

Go here and click on 'oiling bypass'

Hadn't heard that one before. What do the techies here think?

If the link doesn't work, below is a rough cut'n'paste:

MKIV Supra Streamlined Oiling Upgrade

The idea behind this is to remove and therefore bypass the stock oil filter bracket, and oil cooler, and also allow the use of larger, higher flowing oil filters.

Stock Problems:

The inside of the stock oil cooler is not a free flowing design, rather the oil must flow through some very small passages. The oil must pass through two separate hollow bolts, with only a few 1/8” holes to pass through. The stock oil filter is rather small, being only about 3” diameter and 3” tall. The oil has to make several abrupt turns within the bracket and cooler.

See the parts here: Stock oil filter bracket and cooler

FMS Failures:

The MKIV Supra has a problem with blowing the FMS (front main seal). Consider that the oil at that point in the system is after the oil pump, but before the oil filter bracket, cooler, and filter. Therefore, any pressure drop from resistance at the bracket, cooler, and filter will result in two things. Oil pressure in the main galleys that supply the crankshaft and rods will be less. Oil pressure at the FMS will be raised, possibly significantly. This is a main contributor to FMS failures. So far the approach has been to strengthen the seal with a aftermarket replacement. Why not treat the problem directly? Remove the backpressure from the system (bracket, cooler, small filter), and the tendency for FMS failures will be drastically reduced, AND you will have more oil pressure where you want it.

What the Upgrade Is:

A threaded adapter that screws directly into the side of the engine block, after the stock bracket and cooler are removed. You can then use any number of much larger than stock oil filters (any in the most common 3/4x16 thread), and screw right onto the engine block. It looks like this: Installed Filter

I found this on TO4R concerning the same problem:

2JZ CRANK SEAL

Lance M Wolrab

December 29th '04

 

BACKGROUND

All oil pumps build increasing flow with increasing rpm. It is inherent in the design. The Supra oil pump has (as most OEM oil pumps do) a piston type valve with a spring behind the piston. When the pump pressurizes, the piston compresses in its bore against the spring. The spring determines the ultimate pressure the pump will create, because the piston's bore has a hole drilled in the side of it to relieve the pressure once the piston compresses enough. In the Supra's case, the hole that is bored in the side of the piston's bore isn't large enough to flow the amount of oil necessary to control pressure at higher than stock rpm, so the pressure just keeps rising. Eventually something has to give, and it is usually the oil pump seal (which is technically what members are calling the crankcase seal).

 

The oil pump is concentric with the crank, so there are only four seals for the engine: the two cam seals, the oil pump seal, and the rear main seal. When the oil pump seal goes, the other seals have also been stressed, but not as hard, and the oil pump seal is right at the heart of the problem, so it sees a higher pressure than any other part of the engine. It fails, and typically dumps a LOT of oil very quickly.

 

SOLUTION

Forget the oil being "dirty", at 1400 miles it has hardly had a chance to suffer any damage at all. What needs to happen to resolve the problem, is the oil pump needs to have the pressure relief valve return hole enlarged to flow enough oil to keep the pressure under control. A superior seal will only cause one of the other seals to fail, and you will end up chasing your tail until all the seals are super tight (not good for seal life, very bad for horsepower, and pressurizing the oil excessively only leads to even more power loss. You shouldn't see more than 80 psi ever, and I would set it up to run 75 psi.

 

I would also run a temperature sensor on the oil sump to know when the oil is up to temperature. Cold oil makes a LOT more pressure than hot oil, so even properly modified, it is possible to make too much pressure and blow a seal if you run an engine with cold oil up to redline. The BMW M5 has a variable redline for just this reason. As the engine warms up, the redline goes up. The same is true for 2JZs that have altered the stock redline (even a stock engine with heavy oil jeopardizes the oil pump seal when revved hard while cold). As I recall, Jason Chien blew his oil pump seal on a basically stock TT Supra while racing a bike on the freeway, so this isn't unique to high power Supras, but it is certainly a LOT more common.

 

Lance

yeah, I've seen it before. Different theory on the subject.

I normally find the T04R site entertaining, but they've got a couple of good tech articles by Lance (I don't agree 100% but they're good)

Just for information, this passage is incorrect:

 

The oil pump is concentric with the crank, so there are only four seals for the engine: the two cam seals, the oil pump seal, and the rear main seal. When the oil pump seal goes, the other seals have also been stressed, but not as hard, and the oil pump seal is right at the heart of the problem, so it sees a higher pressure than any other part of the engine. It fails, and typically dumps a LOT of oil very quickly.

 

 

 

SOLUTION

 

Forget the oil being "dirty", at 1400 miles it has hardly had a chance to suffer any damage at all. What needs to happen to resolve the problem, is the oil pump needs to have the pressure relief valve return hole enlarged to flow enough oil to keep the pressure under control. A superior seal will only cause one of the other seals to fail, and you will end up chasing your tail until all the seals are super tight

 

Yes, the filter is after the pump, so if it got blocked then you could over-stress the pump and oil seal, but don't most filters have a safety bypass for ultra-cold starts and such, anway?

GIven the reliability of the 2JZ engine, I would assume that the Engineers at Toyota were at least capable of specifying an adequate oil filter and lube system, and the pump will have been tested for something like the dyno equivalent of 100,000 miles.

I'd still put the oil seal issues down to breather problems.

Deficient crank ventilation and/or use of too thick oil would be my first suspects.

It's surprising how many people hack the crank ventilation system and fit those funny little filters instead, losing the intake vacuum. But hey, whatever floats their boat...

managed to replace the oil seal and mod the pump last week, and reconnected the breather back to the intake.....no issues with it so far after 300 miles... quite a challenging job for a novice mechanic with engine left in situ....

My own theory on this, is a failed 'one way valve' fitted in the exit pipe of the nearside camcover to the plenum.

If this fails, boost is fed into the camcover.

Charlie, whereabouts is this one-way valve?

Is it easy to see from the top of the engine? I can't see anything similar on mine.

It's not this one, is it?

http://www.max-boost.co.uk/stuff/breather_hose.jpg

Is it not Cam side rather than intake side, John.

Thanks Digsy for a breath of fresh air and facts. I have never read such a load of tosh as the yanks seem to create with regard to cars. There is no way the front seal blow outs are anything whatsoever to do with oil pressure, the oil filetr or holes in banjo bolts. More like the idiots run silly boost, det without even realisimng, suffer massive crankcase blow by that overcoemes the breathers and the weakest link is the front seal that comes out of its outer bore. I have neber, ever, seen a MKIV blow a front seal where the engine isn't, frankly, shot, with ring or piston / bore wear to make you cry.

Thanks Digsy for a breath of fresh air and facts. I have never read such a load of tosh as the yanks seem to create with regard to cars. There is no way the front seal blow outs are anything whatsoever to do with oil pressure, the oil filetr or holes in banjo bolts. More like the idiots run silly boost, det without even realisimng, suffer massive crankcase blow by that overcoemes the breathers and the weakest link is the front seal that comes out of its outer bore. I have neber, ever, seen a MKIV blow a front seal where the engine isn't, frankly, shot, with ring or piston / bore wear to make you cry.

This was the cause of my front oil seal problems, I had 3 blow in just over a month! I had bore/ring wear which was determined to be pressurising crank case. A new short block and rebuilt head courtesy of Chris, completely cured the problem

crankase pressurisation also kills the turbo slowly

Charlie, whereabouts is this one-way valve?

Is it easy to see from the top of the engine? I can't see anything similar on mine.

 

It's not this one, is it?

 

http://www.max-boost.co.uk/stuff/breather_hose.jpg

Don't have a pic, but its the breather between the nearside camcover and the plenum. Edit:yeah that one.

The valve is in the camcover. You cannot see it unless you take the hose off, and even then its not obvious what it is, as it just looks like a stub pipe.

And its a PCV valve (positve crankcase ventilation valve), which is a bit more clever than a one way valve, but in one sense that is what it does and yes, if the "one way" part of its action fails then a small proportion of boost pressure can enter the camcover.

...and thanks for the vote of confidence, Chris

Chris,

while on the subject of valves and breather type things, did you have a chance to see if there was one on the V160 and if so where?

Thanks, Paul.

The valve is in the camcover. You cannot see it unless you take the hose off, and even then its not obvious what it is, as it just looks like a stub pipe.

 

And its a PCV valve (positve crankcase ventilation valve), which is a bit more clever than a one way valve, but in one sense that is what it does and yes, if the "one way" part of its action fails then a small proportion of boost pressure can enter the camcover.

 

 

Hmm, why is it a bit more clever than a one way valve? When i checked mine, I could suck but not blow (as the actoress said...) what else does it do?

Thanks a lot guys.

I'll investigate this pronto.

On other makes this sort of valves tend to block or fail regularly on higher-mileage engines. It's definately worth checking on the 2JZGTE perhaps, the last thing I'd want would be to pressurise the crankcase under boost...

Looking into my hard disks I found this relevant doc

OK, quick check and the PCV appears to be behaving itself

http://www.max-boost.co.uk/stuff/PCV_test_sm.jpg

It holds 1.5bar one way (no need to push it further), flows fine the other way. Job done.

Hmm' date=' why is it a bit more clever than a one way valve? When i checked mine, I could suck but not blow (as the actoress said...) what else does it do?[/quote']

I think John has covered that in the Toyota document on his site.

 

For information, I'm in the middle of doing a big write up on breather systems at the request of a couple of members on here.

Chris,

while on the subject of valves and breather type things, did you have a chance to see if there was one on the V160 and if so where?

 

Thanks, Paul.

There's a breather on the rear diff too, as i would expect. On top, on rear alloy cover.

Another great thread you guys, I must admit I was a little sceptical about the article I posted at the begining of this thread. Some really useful info from you guys again.

JohnA - cheers for the link

Digsy - Would be very interested in your article on breather systems, are you going to upload it to the technical downloads section?

Chris Wilson - those photos will come in handy too

I dont think in my case the engine is 'shot'....and only ran max 17psi boost,will check the pcv valve also.....also the seal was found to be solidly in place but the spring was off, the centre seal to the crank had failed....

Digsy - Would be very interested in your article on breather systems, are you going to upload it to the technical downloads section?

Well I'll post it up on here in Technical and if it's well recieved I guess it'll end up in the FAQ or downloads section. I think it'll be a three-parter, just to get some information out in the open sooner rather than later (the people who asked me to write it are probably getting fed up waiting for it!).

Chris: Surprised to learn there are breathers on the tranny and diff. Just thinking aloud, is this because the little helical grooves on the shaft seals actually create a pressure difference across the seals, which needs to be equalised, or just to stop condensation?

I hope they work better than the ones on the headlights

.. Surprised to learn there are breathers on the tranny and diff.

why are you surprised? there is gear oil sloshing around, surely there must be some form of pressure relief.

Sometimes the breather is not obvious, perhaps part of the filler plug.