Blown Front Crankshaft Seal

[GetawayDriver]

Hello...

 

I've blown the front crankshaft seal on the supra. Funny thing is it's the second time in as many weeks. The old one had a small leak for some time after the car was stood for months during repairs. It was replaced last week and went within hours, this was replaced again and last night it failed again second time out in it; Lots of oil all over exhaust and plenty of expensive looking smoke.

 

I have every faith in my mechanic and his skills; something else is causing the seal to fail.

 

I did a search on the BBS and some other forums and found lots of reasons this may be happening and lots of potential ways to fix it depending on the cause.

 

My UK spec TT is 'mature' with 130,000 miles on the clock on original turbos. I’ve had a boost controller fitted for about 6 months now; I also have the True Twin turbo Mod. I haven’t been running crazy boost, usually around 1 – 1.1 bar depending on the ambient temp and whether in twin turbo or sequential mode.

 

I’ve recently tweaked the settings on the boost controller to give me a max of 1.2 bar.

 

Because my engine is older and worn, could the additional boost be pressurising the crankcase causing the seal to blow out? What else can I look for to give me a clue as to what is causing this? Any ideas would be greatly appreciated.

[Chris Wilson]

In my experience these blow out due to excess crankcase pressure caused by very worn rings or detonation induced piston / bore damage. Having recently "tweaked" the boost controller the prognosis doesn't sound good I'm afraid.

[foodfreak]

I had 4 go in 5 months.

Make sure the housing is scrupulously(sp) clean & dry.

Don't push the new oil seal back too much, it can cover the small oilway.

you can also mod the spring, but there's lots of argument on supraforums about this.

edited to say, this was on a new built bottom end

[Winston Wolf]

your crank case is designed to run with some negative pressure under normal driving conditions.Toyota designed the engine that way so as to not blow seals etc.On the n/a there is a crank breather on both the vacum and positive pressure sides if the throttle body so the harder you rev the more it sucks and ensures displaced crank air is under suction when it matters most.

It has been known for people to mod these breathers (not just on the sup) to exit to atmostphere as they double up as recirculation for the crank gasses for emission purposes.The effect of the mod stops hot dirty gasses from the crank being sucked back into the combustion cycle but the down side is you no longer have negative pressure in the crankcase which can cause pressure to blow seals.

it would be worth measuring your crank pressue and comparing it to a friends car as this may well not be an issue with the milage on your sup.

It may also be worth considering a small shim when you replace your seal this time as dirty oil at some point in your cars life may have created a wear lip on the crank that will cause future seals to fail.a shim stye spacer will allow a new seal to sit on previously untouched area of crank.

Food for thought ,do't know how the crack gasses are displaced on the Turbo but well worth checking for carbon deposits etc on yours.

[GetawayDriver]

Just spoke to my mechanic... mechanical oil pressure gauge is being fitted tomorrow - i'll let you know the results... my wallet is shitting itself.