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capeyorker

increasing turbo boost

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has anyone experienced  a leaking rear main seal in a gu 4.2TD after increasing their turbo boost pressure. I went from 12pd to 18pd and suddenly got a leaking rear main , could be just a coincidence or maybe more internal sump pressure. running 2871 garret turbo with ultimate cross country intercooler. cheers phil.

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Edited by capeyorker

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G'day mate,

 

IMHO 18 psi is too much for TD42.....

 

In any case increased crankcase pressure can cause oil leaks through rear main or harmonic balancer end or rocker cover seal especially if those seals are well worn already.

One way to know for sure is to measure crankcase pressure. If it is 5 KPa above ambient/atmospheric pressure then you have a problem.

 

Do you have crankcase breather still connected or is it open to atmosphere? If it open it should be spewing a lot more oil out if the excessive boost cause extra pressure.

 

You are reducing the reliability of the engine big time with higher boost.

 

Regards

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thanks for the advice, when I fitted the garret turbo and cross country intercooler I took the vehicle to On off road 4x4 in brisbane to have it tuned as they own 4.2 patrols them selves and one of the their patrols is used for competition so they should know there stuff. they told me that their com trucks run 25pd boost with no problem but to be on the safe side 18pd is ok. I did question this and they assure me that the 4.2TD  is a very strong motor and will handle 18 ok. you now have me confused. why in your experience are these motors not able to handle 18pd boost. the breather pipe from on top of the tappet cover is free from any obstruction  as I can blow through it quite easily so would not that allow any crank pressure to just circulate through to the inlet pipe to the turbo how does crank pressure exist when there is a breather pipe out of the top of the turbo? thanks for your reply appreciate any advice. cheers.

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That your rear main started leaking after the boost was upped could purely be just a coincidence.....or if yours is ventilation recirculated back in to intake there is a valve which controls the flow of blow by gases and it is possible that is not operating correctly.....

 

That's why I had mentioned to know for sure you'll need to measure crankcase back pressure, if everything works as it should  the back pressure should be equal or less then atmospheric pressure at the time of measuring with engine running of course best during the road test..

 

If it is positive pressure or more then ambient the you have possibly PCV not working correctly or compression leak and crankcase ventilation can't keep up. Compression leaks can be piston rings, engine wear, piston failure related etc. I'm not saying that's what is happening on yours but the only way knowing is to check/measure. I wouldn't have thought that going up by 4-6  psi is drastic increase but everything needs to be considered, the condition of the motor, the load etc.

 

 

Is yours genuine factory TD42T or TD42Ti? Or is yours modded from NA?

 

Factory TD42T starts opening its waste gate actuator at 76 kPA (11 psi) to its max 96 kPa (~14 psi). It is also suppose to have intake bypass valve set to 92 kPa (13.4 psi).

 

I don't really have an experience with TD42 and what exactly they are they able to handle but this is general wisdom: higher boost pressure the higher the stresses on the engine, higher the stresses the quicker something has to give.....

 

High boost is not magic puding for the power needs. TD42s are strong motors but the old design shows its limitations so don't get sucked in to false believe they handle anything you throw at them.

 

I also suspect that 4x4 mob aren't exactly using factory specced engine at 25 psi all day long racing and hammering it. And if they do they don't do 100,000 kays with it in 2 years and I bet ya if they're serious about their race result the engine is pulled down more often the you would ever do!

 

I'm not saying they're not correct but this isn't first time these aftermarket people were promising results and it went "pear shaped".

 

Did you have issues with it when it was running at 12 psi? Personally I'd give it max 14-16 psi and nothing else. My POV is that raising boost above certain levels might not be so smart. Its the lag which matter because that's what affect the tractive effort, slow spool up affects the output,

 

Anyway, see the attachment about PCV description and how to test.

 

Cheers

 

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Edited by Rumcajs

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thanks for the diagram and spending the time to help me out. I will check the air control valve as you mentioned and probably reduce the boost pressure , hope the seal stops leaking. I forgot to mention that the rear main seal has only done about 35,000klms. so I don't think it is a seal problem. thanks again. cheers.

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Keep us posted on how thing pan out. Maybe I must check my control valve..... never thought of checking it.

If one put a clean piece of piping on the valve ( to avoid a black oily ring on my mouth....hahaha ), could one just by blowing or sucking get that valve to move, or will one have to use a vacuum pump? I don't have one of those things in my garage.

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Well, if you are "a good sucker" (pun not intended) then you should see the valve moving. This applies to ZD30 vacuum applied actuator. For TD42 good luck blowing in to get the waste gate valve to move.....

You could use spare tyre pressure and rig up temporary source of pressure at certain level.

Cheers

 

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hahahaha..... I thought my post might sound a bit....ummmm how should a say it.....hahaha

But I think my TD42's waste gate is working just fine... especially with the amount of black smoke bellowing out the back side when I floor it !!

I need to up the boost on mine a little bit. Mines only boosting at 0.7 bar ( 10 psi ). I think me and my Patrol have a date on Saturday .....hahaha

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