4JG2 Blow-by

[Dave]

Are Isuzu motors known to pressurize the sump?
I have been told by my mechanic that the motors are well known for blow-by.
Ever since replacing the head on the Bighorn I have noticed that there is oil coming from the dip stick.
On idle with the dipstick removed there is a small amount of smoke and a bit of oil, but if the dipstick isnt in properly while driving oil sprays out.
It seems worse with the new head and now seems to use oil.
Is this common?

Cheers,
Dave

[oleg]

I think you have a problem . My Wizard got 4JG2 and I donthave anything like you sad. Sounds bad . How is driving? Any los of power?

[geeves]

Is this as well as the hiss you mentioned on NZ4wd
If it wasnt doing this before then I would be looking at the crankcase venilation system very closly. There are 2 pipes that attach to the inlet system one either side of the turbo (unsure exact location) The one that attaches engine side of the turbo connects to the tappet cover via a flap valve inside the cover This could be damaged causing boost pressure to pressurise the sump.
Isuzus are known to have more blowby than some other engines but not anything like what your describing also this applies more to the 4jx1 than the earlier engines.
Did you just get the head done or was other stuff done at the same time? last year one of our aussi members had a timing belt done incorrectly resulting in it being one tooth out It ran fine apart from more intake noise for about 200km. Eventualy the mechanic bought him a new motor.

[Dave]

Alan, I still have the hissing noise at the moment, just havent had a chance to find out what it is yet. Only seems to happen when on boost, but when I turn the truck off I can here what seems to be an air leak from under the bonnet somewhere, which lasts a few seconds before stopping.
Had a new cambelt put on at the same time, could it be something to do with timing?
I havent noticed a drop in performance, more the opposite as it ran like a pig before getting the head replaced.

Dave

[Dave]

Have found what the "hissing noise" was. Found a small vacum hose was off, the mechanic has blocked it off, saying it was part of the EGR setup, which they removed when doing the head, and the hoses are of no use anymore.
Could anything relating to the EGR's be the cause of my blow-by problem?

[James W]

Blow-by due to EGR; no.... but problems with the crankcase ventilation system could. It's quite common it seems. I have a simular problem, with oil leaks from various places due to positive crankcase pressure while under turbo boost. There is a guy in Christchurch who makes Isuzu breather kit's. I've been meaning to go and see what they are like and maybe fit one.

Have you checked the valve on the inlet manifold connecting to the rocker cover isn't open/blocked?

[mudgrip4]

Hi guys - I have similar problem and have gone down the road noted by James. The company who makes/sells the 'engine breather modification kit' is Church Corner Auto Parts - 353 Riccarton Rd, Chch, phone [phone]. Mine was blowing a bit of blue on start up but not otherwise, also sweating oil out of seals, dipstick, on top of turbo area etc. Haven't yet got round to fitting unit yet but it costs $225 club price and he's sold 300 to Isuzu owners. Helps stop pressure, oil use, runs them at slight vacuum, run cleaner etc. Good luck - Mike A.

[Dave]

Cheers guys, will give this breather kit a try. Looks like I wont need to trade the old girl in so soon after all....and I get to keep the Bighorn ;D ;

[James W]

Thanks Mike, I was going to have to dig out the details, you saved me a search.
I would love to see the kit. Any chance of seeing it? Need help fitting it? Maybe it's a good excuse for a beer 'n' Isuzu garage meeting for the Christchurch/Canterbury group.

[Dave]

James, I will be coming down to pick one up in the next couple of weeks so if you dont get to see the kit before then I'll get in touch so you can have a look.
Price was 240+ and around 2 hrs labour to fit (bit of welding etc involved).

[Dave]

Well, after not being completely convinced that my oil "leak" was coming from the dipstick, I taped the top up and found that the oil was still escaping....but from somewhere else.
Took the truck back to the mechanics today and they have found the oil is coming from the inlet manifold , (which may also explain the noisey intake under boost) so they will be getting it back next week to seal up and try to find the source of the oil.
Hopefully it is the turbo, as they are non-servicable and will be covered by the warranty ;D

[James W]

I had lots of oil in my intake, with it I am assuming breathing from the rocker cover. It too showed oil at the turbo inlet, but since I have let it breathe to amtosphere (temporarly) all those issues have disapeared.
I was thinking turbo problems too, but seem to have avoided it. Disconnect the hose of the rocker cover for a while and see what that does. Long term you will need the breather kit to keep the mud, dust and water out.