1HD-T - lots of oil from rocker cover breather

Joined
Feb 15, 2011
Messages
8
[Cross posting from 80 series tech forum on inkpot's suggestion]

Hi all,

My 4.2L 1HD-T 80 series is experiencing some serious oil usage. I've narrowed it down to the rocker cover breather outlet; temporary catch can collected 250-300mL of oil on a ~50km test run.

There is some variability in the amount of oil collected. Driving at ~80km/h (about 5 PSI turbo boost - peaking at no more than 10 PSI) for 10km resulted in a very much drier catch can. Oil was only a thin film in the bottom. I drove the remaining 40km at highway speed and threw in some heavy acceleration to get boost and RPM right up there. That gave me the few hundred mLs of oil in the can... I've closed the baffles in the rocker cover as much as possible but that didn't make a difference.

Block, head and turbo (Gturbo) were reconditioned and self-installed no more than 5,000km ago. Fuel pump and injectors were done no more than 10-15,000km ago.

I've spoken to a couple of diesel mechanics about the symptoms. They reckon the little oil restrictor at the back of the block is the most likely culprit. Part number 11448 on this diagram: Cylinder block for Toyota LAND CRUISER/LAND CRUISER PRADO HDJ80 1990...1995 | MegaZip online shop. With the restrictor missing, oil supply to the head is apparently much more than needed. As I said, some mates and I installed the block and head ourselves. It's possible the oil restrictor wasn't supplied or fell out somewhere along the line.

What do you think? Have you heard of this happening before?
 
Joined
Dec 17, 2007
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Location
Sydney, Australia
Yes, there should definitely be an oil restrictor between the block and the head.
When I replaced a head on my 1HZ, the restrictor went missing when I took the head off. Thankfully I noticed it before putting the new head on.

Have you done a leak down test to check for excessive blow by?

I don't think closing the flaps inside the rocker cover really helps. I tried this on mine. Regardless of the gap here, the same amount of crank case pressure has to escape, closing the gap might actually work against you

Screenshot_2017-09-14-13-16-57.png
 

IanB

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Jan 23, 2010
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Winnipeg, MB
I don't think closing the flaps inside the rocker cover really helps. I tried this on mine. Regardless of the gap here, the same amount of crank case pressure has to escape, closing the gap might actually work against you
I think the point of closing the flaps is to cut down on flung oil from exiting the rocker cover, if you close it enough that it restricts air movement in any way, you've closed it way too far.

@jylan Have you tried loosening the oil fill cap on the valve cover and setting it over the fill hole with the engine running? The pressure will cause the cap to "dance" as the air escapes. Take a video of this, and others can compare to their own and see if you have excessive pressure in the top end.
 
Joined
Feb 15, 2011
Messages
8
Thanks for your replies guys.

I've spent the last couple of days pulling the head and reinstalling. Great news is that the oil restrictor was missing. Even better news is that installing the thing seems to have completely fixed my problem! Better oil pressure to boot too. I repeated the ~40km test drive that gave me 500mL previously and this time ended up with a completely empty bottle. I'm very pleased :D

@jylan Have you tried loosening the oil fill cap on the valve cover and setting it over the fill hole with the engine running? The pressure will cause the cap to "dance" as the air escapes. Take a video of this, and others can compare to their own and see if you have excessive pressure in the top end.
I did try that before embarking on the job Ian - there was no cap dancing at all.

I don't think closing the flaps inside the rocker cover really helps. I tried this on mine. Regardless of the gap here, the same amount of crank case pressure has to escape, closing the gap might actually work against you
Certainly didn't with the restrictor missing mate! Before installing the rocker cover again I opened the baffles to just under 1cm, and that didn't stop me from getting a dry bottle.

Anyway, photos of the pull-down and oil restrictor to help anyone else with this problem:

IMG20170919143214-5.jpg
IMG20170919143214-0.jpg
IMG20170919143214-4.jpg
IMG20170919143214-2.jpg
 
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