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The mkiv Supra Owners Club

Oil pump (crankshaft front) oil seal failures


Chris Wilson
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Dip stick is 9mm dia, but still a fair bit of pressure required, and yes it may explain 50% of seal failure's,

i do know that mine is not due to this as i have said before that i have run a peak hold pressure gauge on my dip stick tube and got zero reading.

 

In fact it would be an easy check for most people to carry out, if they have a peak hold boost gauge, it would only take a couple of bits of tube to adapt to the dip stick tube, give the car a good welly and report the readings you get, is anyone up for this?

it would certainly give a lot more insight on crankcase pressure than testing seals and dip sticks;)

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What about the stress of a 5 Ft scaffold pole used to release the crank bolt that we keep hearing about?

 

I think this would just cause a twisting torsional strain on crank nose.........

 

........ Hammer and chisel on the other hand! and if that didn't cause any probs for Soonto, I'd imagine would take a lot of force to upset the crank nose.

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9mm would drop the pressure require to push the dipstick out to 3 bar, and the load on the seal to 61lbs

 

If the breather system is working there sould not be ANY crankcase pressure. I'd still like to see a proper crankcase depression measurement usng a sensitive sensor or a manometer. Excessive vacuum could still be a cause.

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9mm would drop the pressure require to push the dipstick out to 3 bar, and the load on the seal to 61lbs

 

If the breather system is working there sould not be ANY crankcase pressure. I'd still like to see a proper crankcase depression measurement usng a sensitive sensor or a manometer. Excessive vacuum could still be a cause.

 

Fair enough, but we have been talking pressures of 3 to 7 BAR to theoretically eject dip stick and/or seal, so using a sensitive gauge to measure crankcase pressure/depression is a bit overkill to me, at least my suggestion would also show up malfunctioning breather systems as well;)

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IF!!! this problem is down to cc pressure ,it may not be a continuous fault ,only a transient thing that pops the seal and then is no longer apparent and any cc px measuring would have to have the fault present-which it might not be.

why does the dipstick never seem to be affected? perhaps some sort of pressure delay ,allowing the seal to be moved first?

certainly there is a lot of air moving through the engine especially on high boost,is this more common on larger turbos or those engines running higher boost?.

is it more common on engines with different cams? or do the bone stock engine have this also? if so is it mileage related?

is it both autos and manuals have the problem?

has any vvti ever had the problem?

sorry for all the questions ,but it is the way to find if the fault is ramdom or specific ,system or component,inherent or introduced

 

it is correct that the n/a does not have this failure ?...... vvti?

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So if it were possible for the crank nose to marginally bend from damper separation, could this cause it to run eccentrically around seal contact face, guess this could be checked with a dial guage i situ with sump and pump removed, or a set of Vee blocks with crank removed.

 

:think:

 

As I said, garsping straws, but a possibility. Yes and yes to the questions :)

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A couple more questions,

First question: out of all the people who have had seal failure and also have an oil pressure gauge fitted, what is your highest pressure when hot? and where is your sensor? and what oil grade?

 

Second question: out all who have experienced seal failure, who had either a rebuild or at least the sump off? and who s engine had never been apart?

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Sorry yet another one, but bare with me as this is all aimed at getting to the bottom of this problem;)

Had a log chat with Greg earlier today, throwing ideas around, and something he said got me thinking! we where talking about the PRV and the idea that it may be possible that its staying open far more and longer than it was intended to, and as it dumps excess pressure straight back to the low pressure /pick up side of the pump, could it be causing a kind of overpressure feedback cycle, which in turn could be forcing the excess oil past the pump rotors, and in turn overwhelming the seal??

Now next we need a reason for the overpressure, which got me thinking about what the US guys say about the std oil cooler being restrictive! so could this be deteriorating with age or dirt? causing back pressure in the system?

Has anyone ever measured the difference in oil pressure between say a sandwich plate take off/or modded bolt, and the std oil pressure switch? which i believe is after the oil cooler??

 

Yes there is more to this, but if anyone can answer any of these questions, it could shead some light:)

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Some more dipstick pullout figures:

 

Non vvti 4.4-5.5 lbf (3-3.8bar crankcase pressure)

vvti 15.5 lbf on first pull (10.7bar crankcase pressure)

vvti 6.6 lbf on repeated pulls (4.6bar crankcase pressure)

 

Pressures are based on 9mm dipstick tube bore but I didn't check this.

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If it is related to oil pressure increase/flow restriction,as I previously mentioned the na/TT differences should be looked at

like the oil squirters.and pressure relief on them ?

clutching at straws = free thinking:)

 

 

 

I have been looking into the differences between the two oil systems and there are only small differences,

Oil pump is exactly the same, so is the PRV springs, but the N/A has a different nut/cap for the PRV,

The oil pump rotor Clearance figures are slightly larger on the N/A

They run the same oil pressure, but the N/A achieves the pressure at 3,000 RPM and the TT at 4,000 RPM, so N/A runs slightly higher pressure.

Can't see the piston squirter's or there internal oil galleries having a bearing on things as the feed is split for crank, head/cams and turbo, so i don't think the squirter's PRV being stuck would have that much effect on system back pressure,

but however if the cooler PRV was stuck or the filter PRV was stuck this would, which is why i was asking for the figures in my previous post.

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Cars home now, gave it some stick on the way home and all seems good, last couple oil seals never lasted the journey home so this looks promising, oil return has couple drips, im waiting for it to cool down so i can have a look at that.

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I, with your permission Peter, will await what Tricky-Ricky finds when he splits his leaky pump open, then button your engine up. When a good pal of mine returns from holiday I have an idea for modding the drain back on a stock pump, but it would be experimental, and would not be a proper fix if there ARE a batch of new faulty pumps around.

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